RU2825593C1 - Physical part for clock on optical array - Google Patents

Abstract

FIELD: clocks and other time meters.

SUBSTANCE: physical part (12) comprises: Zeeman retarder (44) with a portion which is a part of a magnetooptical trap, and device (48) which is a part of the MOT, which form a magnetooptical trap (MOT); optical chamber (46) forming an optical array forming section; and vacuum chamber (20) enclosing said components and made substantially in the form of a cylinder. MOT device is located along the axis of atomic beam (42) and catches a group of atoms. Optical grating formation section uses optical grating light entering it to form an optical grating in the resonator, holding a group of atoms trapped by the MOT device, in the optical lattice and moving along the axis X, which is the axis of movement perpendicular to the axis of the beam, said group of atoms into the clock transition space (52), which facilitates the occurrence of the clock transition. Central axis of the cylinder of main housing (22) of vacuum chamber (20) passes through space (52) of the clock transition and is set so that it is substantially parallel to the axis of the beam.

EFFECT: disclosed is a physical part for a clock on an optical lattice, the design of which enables to reduce the size and the possibility of transportation.

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Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

[0001] The invention relates to a physical part for a clock on an optical lattice.

LEVEL OF TECHNOLOGY

[0002] The optical lattice clock is an atomic clock proposed by KATORI Hidetoshi, one of the inventors of the present application. The optical lattice clock holds a population of atoms in an optical lattice formed by laser light and measures the resonant frequency in the visible spectrum. Due to this, the optical lattice clock can provide a measurement accuracy of up to 18 digits, which is higher than the accuracy of the currently existing cesium clock. Active research and development in the field of the optical lattice clock has been carried out not only by the group that includes the inventors of the present invention but also by a number of other groups both in Japan and abroad, as a result of which the optical lattice clock, which is the next-generation atomic clock, has been developed.

[0003] The latest optical lattice clock technology is disclosed in, for example, the following Patent Documents 1 to 3. Patent Document 1 discloses a one-dimensional movable optical lattice formed in a hollow-pass light guide. Patent Document 2 discloses an aspect of adjusting an effective magic frequency. Patent Document 3 discloses a radiation shielding member mitigating the negative effects of blackbody radiation emitted from surrounding walls.

[0004] The optical lattice clock measures time with high precision. Therefore, the optical lattice clock can detect a height difference of 1 cm on the Earth based on the general relativistic effect caused by gravity in the form of a deviation in the development over time. Accordingly, if the optical lattice clock can be transported and used outside the laboratory, it can be used in new geodetic technologies, such as mining, as well as detecting underground voids and magma chambers. The optical lattice clock is mass-produced and installed in many places, and the change in the potential of gravity over time is continuously monitored, which makes it possible to use it, including for detecting diastrophism and for spatial mapping of the gravitational field. Therefore, the optical lattice clock is expected to benefit society as a new fundamental technology beyond high-precision time measurement.

[0005] The following Non-Patent Documents 1 to 5 describe attempts to make the optical lattice clock transportable. For example, Non-Patent Document 4 discloses a physical part of the optical lattice clock housed in a frame with a length of 99 cm, a width of 60 cm and a height of 45 cm. Said physical part includes an atomic furnace, a Zeeman moderator and a vacuum chamber arranged sequentially in the length direction. Outside the vacuum chamber, a pair of square magnetic field correction coils with a side of approximately 30-40 cm are arranged for each of three axes: the length direction, the width direction and the height direction. In order to perform clock transition spectroscopy in atoms in zero magnetic field, the magnetic field correction coils serve to compensate for the distribution of the magnetic field in the area around the atoms during spectrometry.

LIST OF CITED LITERATURE PATENT LITERATURE

[0006] Patent Document 1: JP 6206973 B

Patent document 2: JP 2018-510494 A

Patent Document 3: JP 2019-129166 A

NON-PATENT LITERATURE

[0007] Non-Patent Document 1: Stefan Vogt et al. "A transportable optical lattice clock" Journal of Physics: Conference Series 723 012020, 2016;

Non-patent document 2: S.B. Koller et al. "Transportable optical lattice clock with 7 × ^{10 -17 Uncertainty} " Physical review letters 118 073601, 2017;

Non-Patent Document 3: William Bowden et al. "A Pyramid MOT with Integrated Optical Cavities as a Cold Atom Platform for an Optical Lattice Clock" Scientific Reports 9 11704, 2019;

Non-Patent Document 4: S. Origlia et al. "Towards an Optical Clock for Space: Compact, High-Performance Optical Lattice Clock based on Bosonic Atoms" Physical Review A 98, 053443, 2018;

Non-Patent Document 5: N. Poli et al. "Prospect for a Compact Strontium Optical Lattice Clock" Proceedings of SPIE 6673, 2007.

DISCLOSURE OF THE ESSENCE OF THE INVENTION TECHNICAL PROBLEM

[0008] The optical lattice clock disclosed in the above-mentioned Non-Patent Documents 1 to 5 can be further improved in terms of miniaturization and transportability to facilitate transportation, installation, etc. of the optical lattice clock, and to improve the efficiency of its use.

[0009] Miniaturization and transportability of the physical part for known optical lattice clocks was facilitated by miniaturization of devices or components based on the design of large-sized optical lattice clocks used in laboratory conditions. Therefore, in the said physical part, there is a complex arrangement of many axes, in particular - an atomic beam, laser light and magnetic fields, in the space for trapping atoms or in the space of the clock transition for inducing the atoms to the clock transition. Therefore, difficulties arise with the integration of the necessary devices or components.

[0010] The aim of the present invention is to create a physical part of a clock on an optical lattice, the design of which would allow for its miniaturization or ensure its transportability.

SOLVING THE PROBLEM

[0011] The proposed physical part for an optical lattice clock comprises: a magneto-optical trap (MOT) device located along the axis of an atomic beam and configured to trap a population of atoms; an optical lattice forming section configured to form an optical lattice using incident light from the optical lattice, retaining the population of atoms trapped by the MOT device in the optical lattice, and moving the population of atoms into a clock transition space to excite a clock transition along a displacement axis perpendicular to the beam axis; and a vacuum chamber including a substantially prism-shaped main body enclosing the MOT device and the optical lattice forming section, wherein the central axis of the vacuum chamber passes through the clock transition space and is substantially parallel to the beam axis.

[0012] According to one aspect of the present invention, the vacuum chamber includes a protruding portion that protrudes from the main body along the beam axis, wherein the physical portion further comprises a moderator configured to slow down a population of atoms on the upper side of the MOT device along the beam axis, wherein the moderator is located on both sides of the main body and the protruding portion.

[0013] According to one aspect of the present invention, the MOT device is provided with the ability to emit MOT light in both directions of each of three axes, which include the beam axis and two axes perpendicular to the beam axis and different from the axis of movement.

[0014] According to one aspect of the present invention, the retarder is provided with the possibility of emitting retarding light on the upstream side along the beam axis, wherein the main body includes: a pair of first vacuum-resistant optical windows configured to allow the MOT light and the retarding light to pass through them along the beam axis; and a pair of second vacuum-resistant optical windows configured to allow the MOT light to pass through them along the said two axes.

[0015] One aspect of the present invention further provides a vacuum pump cartridge configured to evacuate the vacuum chamber, wherein the vacuum pump cartridge is arranged in the main body such that it is located in line with the retarder, but offset from the center in a direction different from the direction of the retarder.

[0016] According to one aspect of the present invention, the substantially prism-shaped main body is formed in the shape of a substantially tetrahedral prism, a substantially hexagonal prism, a substantially octagonal prism, or a substantially cylindrical shape.

BENEFICIAL EFFECTS OF THE INVENTION

[0017] The design of the proposed physical part provides the possibility of embedding components, etc., which makes it possible to miniaturize the physical part or ensure its transportability.

BRIEF DESCRIPTION OF DRAWINGS

[0018] [FIG. 1] FIG. 1 schematically illustrates the general configuration of an optical lattice clock according to one embodiment.

[FIG. 2] FIG. 2 illustrates a schematic configuration of the physical portion of the optical lattice clock.

[FIG. 3] FIG. 3 schematically illustrates an external view of the physical part.

[FIG. 4] FIG. 4 is a partial perspective view of the interior of the physical portion of FIG. 3.

[FIG. 5] FIG. 5 illustrates the general shape of a three-axis magnetic field correction coil.

[FIG. 6] FIG. 6 illustrates the shape of the first group of coils of the magnetic field correction coil in the X-axis.

[FIG. 7] FIG. 7 illustrates the shape of the second group of coils of the magnetic field correction coil in the X-axis.

[FIG. 8] FIG. 8 illustrates the shape of the first group of coils of the magnetic field correction coil in the Y axis.

[FIG. 9] FIG. 9 illustrates the shape of the second group of coils of the magnetic field correction coil in the Y axis.

[FIG. 10] FIG. 10 illustrates the shape of the first group of coils of the magnetic field correction coil in the Z-axis.

[FIG. 11] FIG. 11 illustrates the shape of the second group of coils of the magnetic field correction coil in the Z-axis.

[FIG. 12] FIG. 12 illustrates the shape of the holder of the magnetic field correction coil in three axes.

[FIG. 13] FIG. 13 illustrates an example of a correction coil with a flexible printed circuit board.

[FIG. 14] FIG. 14 illustrates an example of a cylindrical correction coil with a flexible printed circuit board.

[FIG. 15] FIG. 15 illustrates an example of currents flowing in a correction coil.

[FIG. 16] FIG. 16 illustrates current flows equivalent to the currents in the correction coil of FIG. 15.

[FIG. 17] FIG. 17 illustrates another example of currents flowing in a correction coil.

[FIG. 18] FIG. 18 illustrates current flows equivalent to the currents in the correction coil of FIG. 17.

[FIG. 19] FIG. 19 illustrates another example of a correction coil with a flexible printed circuit board.

[FIG. 20] FIG. 20 illustrates a physical portion containing a spherical vacuum chamber.

[FIG. 21] FIG. 21 illustrates another example of installing a three-axis magnetic field correction coil.

[FIG. 22] FIG. 22 illustrates an embodiment of supporting the magnetic field correction coil in three axes with FIG. 21.

[FIG. 23A] FIG. 23A schematically illustrates an embodiment of magnetic field correction.

[FIG. 23B] FIG. 23B schematically illustrates an embodiment of magnetic field correction.

[FIG. 24] FIG. 24 is a diagram of the calibration sequence of the magnetic field correction coil in three axes.

[FIG. 25] FIG. 25 is a sequence diagram illustrating correction processes by means of a magnetic field correction coil in three axes.

[FIG. 26] FIG. 26 schematically illustrates another embodiment of magnetic field correction.

[FIG. 27] FIG. 27 illustrates compensation of the parasitic magnetic field in a refrigeration device.

[FIG. 28] FIG. 28 is a sectional view illustrating the structures of a Zeeman moderator and a MOT (Magnetic Optical Trap) device.

[FIG. 29] FIG. 29 is a sectional view illustrating a coil cavity.

[FIG. 30] FIG. 30 depicts a magnetic field distribution corresponding to the configuration of FIG. 28.

[FIG. 31A] FIG. 31A is a sectional view illustrating the structures of a Zeeman moderator and a MOT device.

[FIG. 31B] FIG. 31B is a sectional view illustrating the structures of a Zeeman moderator and a MOT device.

[FIG. 32] FIG. 32 shows a magnetic field distribution corresponding to the configuration in FIGS. 31A and 31B.

[FIG. 33A] FIG. 33A shows the construction of a modified version of FIGS. 31A and 31B.

[FIG. 33B] FIG. 33B shows the construction of a modified version of FIGS. 31A and 31B.

[FIG. 34] FIG. 34 is a sectional view of a Zeeman coil with a constant coil outer diameter.

[FIG. 35A] FIG. 35A is a sectional view illustrating the enclosure of a coil for a Zeeman moderator.

[FIG. 35B] FIG. 35B is a sectional view illustrating the enclosure of a coil for a Zeeman moderator.

IMPLEMENTATION OF THE INVENTION

[0019] (1) Physical part configuration diagram

FIG. 1 schematically illustrates the general configuration of the optical lattice clock 10. The optical lattice clock comprises a physical part 12, an optical system device 14, a control device 16 and a PC (personal computer) 18, all connected to each other.

[0020] As described in detail below, the physical part 12 is a device that captures a population of atoms, holds them in an optical lattice and causes clock transitions. The optical system device 14 is a device that includes optical devices, in particular a laser radiation source, a laser radiation receiver and a laser spectrometer. The optical system device 14 not only emits laser radiation and transmits it to the physical part 12, but also carries out processes of receiving light emitted due to clock transitions in the population of atoms in the physical part 12, converting it into an electrical signal and dividing the signal into frequency bands. The control device 16 is a device that controls the physical part 12 and the optical system device 14. The control device 16 is a computer intended for the clock 10 on the optical lattice, the operation of which consists in the software controlling the hardware of the computer, including processors and memory devices. For example, the control device 16 carries out not only the control of the operation of the physical part 12 and the control of the operation of the device 14 of the optical system, but also the analysis processes, in particular - the analysis of the frequency of the clock transition obtained by measurement. The physical part 12, the device 14 of the optical system and the control device 16 closely interact with each other and form a clock 10 on an optical lattice.

[0021] The PC 18 is a general-purpose computer, the operation of which consists in that software controls the hardware of the computer, including processors and memory devices. An application program for controlling the clock 10 on the optical lattice is installed in the PC 18. The PC 18 is connected to the control device 16 and controls not only the control device 16, but also the clock 10 on the optical lattice as a whole, including the physical part 12 and the device 14 of the optical system. The PC 18 forms the UI (user interface) of the clock 10 on the optical lattice. The user can activate the clock 10 on the optical lattice, measure time and check the correctness of the results by means of the PC 18. In this embodiment, mainly the physical part 12 is disclosed. It should be noted that the physical part 12 and the associated components necessary for controlling this part are in some cases collectively referred to as the "physical part system". The components necessary for control are in some cases included in the composition of the control device 16 or PC 18, as well as in the composition of the physical part 12 itself.

[0022] FIG. 2 is a schematic diagram of a physical portion 12 of the optical lattice according to the embodiment. FIG. 3 is a schematic diagram of an example of the physical portion 12 from the outside. FIG. 4 is a partial perspective view of the internal structure of the physical portion 12 of FIG. 3. FIGS. 2-4 (and subsequent diagrams) illustrate an orthogonal rectilinear coordinate system XYZ with an origin in a target space (clock transition space 52), where atoms, which will be discussed below, can be located during clock transition spectroscopy.

[0023] The physical part 12 includes a vacuum chamber 20, an atomic furnace 40, a coil 44 for a Zeeman moderator, an optical resonator 46, a coil 48 for a MOT (magneto-optical trap) device, a cryostat reservoir 54, a thermal coupling element 56, a refrigeration device 58, a main body 60 of a vacuum pump and a cartridge 62 of a vacuum pump.

[0024] The vacuum chamber 20 is a box that maintains a vacuum in the main part of the physical part 12 and is formed essentially in the shape of a cylinder. In particular, the vacuum chamber 20 comprises a main body 22 formed essentially in the shape of a large cylinder, and a protruding part 30 formed essentially in the shape of a small cylinder and protruding from the main body 22. The main body 22 is a part that contains inside an optical resonator 46, which will be disclosed below, etc. The main body 22 comprises a cylindrical wall 24 that forms the end surface of the cylinder, as well as a front circular wall 26 and a rear circular wall 28 that form circular surfaces of the cylinder. The front circular wall 26 is a wall containing the protruding part 30. The rear circular wall 28 is a wall opposite the protruding part 30 and shaped to have a diameter greater than the diameter of the cylindrical wall 24.

[0025] The protruding portion 30 includes a cylindrical wall 32 forming a lateral surface of the cylinder, and a front circular wall 34. The front circular wall 34 is a surface in the shape of a circle, remote from the main body 22. The section of the protruding portion 30 in the immediate vicinity of the main body 22 has a nearly open shape, is connected to the main body 22 and does not contain a wall portion.

[0026] The vacuum chamber 20 is arranged so that the central axis (called the "Z axis") of the cylinder of the main body 22 extends substantially horizontally. The central axis (this axis forms the beam axis) of the cylinder of the protruding part 30 extends parallel to the Z axis above the Z axis vertically upward.

[0027] It is envisaged that the vacuum chamber 20 can be made in dimensions of, for example, no more than approximately 35 cm in the Z axis direction and no more than approximately 20 cm in the X axis direction and in the Y axis direction. It is also envisaged that further miniaturization to no more than approximately 30 cm, no more than approximately 25 cm, or no more than approximately 20 cm in the Z axis direction is possible. It is also envisaged that miniaturization to no more than approximately 15 cm or no more than approximately 10 cm in the X axis direction and in the Y axis direction is possible. The distance from the beam axis to the Z axis is, for example, approximately 10-20 mm.

[0028] In this embodiment, four legs 38 are located at the four corners of the lower part of the main body 22 of the vacuum chamber 20, on which the vacuum chamber 20 rests. The vacuum chamber 20 is made of metal, for example, stainless steel (SUS, English: Steel Use Stainless) strong enough to withstand the difference in air pressure when a vacuum is formed inside. The vacuum chamber 20 is designed with the possibility of detaching the rear circular wall 28 and the front circular wall 34. These walls are detached when checking the technical condition.

[0029] The atomic furnace 40 is a device installed near the distal end of the protruding part 30. The atomic furnace 40 causes the heater to heat the solid metal placed therein, emits, through the pore, atoms ejected from the metal due to thermal disturbance, and forms an atomic beam 42. The beam axis along which the atomic beam 42 passes is located parallel to the Z axis and with the possibility of intersecting with the X axis at a position at a small distance from the starting point. The intersection point refers to the trapping space 50, which is a tiny space in which the trapping of atoms occurs, which will be discussed below. The atomic furnace 40 is located mainly in the vacuum chamber 20. However, its radiator extends outside the vacuum chamber 20 for cooling. The atomic furnace 40 heats the metal to approximately 750K, for example. The metal can be chosen, for example, from strontium, mercury, cadmium, ytterbium, etc. However, the choice of metal is not limited to them.

[0030] The Zeeman moderator coil 44 is located on the lower side along the beam axis of the atomic furnace 40 from the protruding portion 30 to the main body 22 of the vacuum chamber 20. The Zeeman moderator coil 44 is a device created by making a Zeeman moderator that slows down the atoms of the atomic beam 42 and a MOT device that traps the slowed atoms as a single unit. Both the Zeeman moderator and the MOT device are devices based on laser cooling technology of atoms. The Zeeman moderator coil 44 in FIG. 2 includes a Zeeman coil serving for the Zeeman moderator and one of a pair of magneto-optical trap (MOT) coils serving for the MOT device in the form of a set of coils. It is impossible to establish a precise classification, but the largest part in the order from top to bottom along the path corresponds to the Zeeman coil, generating a magnetic field that facilitates the implementation of the Zeeman deceleration method, and the lowest side along the path corresponds to the MOT coil, generating a gradient magnetic field that facilitates the implementation of the magneto-optical trapping method.

[0031] In the illustrated example, the Zeeman coil is a decreasing-turn coil with a large number of turns on the upstream side and a smaller number of turns on the downstream side. The Zeeman decelerator coil 44 is arranged axially symmetrically around the beam axis with the possibility of the atomic beam 42 passing through the interior of the Zeeman coil and the MOT coil. A magnetic field with a spatial gradient is formed in the Zeeman coil, and the optical beam 82 emitted by the Zeeman decelerator slows down the atoms.

[0032] The optical resonator 46 is a cylindrical component located around the Z axis with the possibility of forming an optical lattice in it. A plurality of optical components are installed in the optical resonator 46. One pair of optical mirrors is installed on the X axis, and another pair of optical mirrors is installed parallel to it, wherein multiple reflection of the optical lattice light occurs between all four mirrors with the formation of an optical lattice resonator in the form of a "bow tie". The population of atoms captured in the capture space 50 is held in the optical lattice. When a shift in the relative frequencies of two beams of optical lattice light (clockwise and counterclockwise) introduced into the optical resonator 46 occurs, the resonator forms a movable optical lattice, which sets in motion a standing wave of the optical lattice. The movable optical lattice moves the population of atoms into the space 52 of the hourly transition. In this embodiment, the optical lattice including the movable optical lattice can be formed on the X axis. It should be noted that in this case, it is possible to use a two-dimensional or three-dimensional optical lattice with the possibility of arranging the lattice not only on the X axis, but also on one of the Y axis and the Z axis or on both of them. Therefore, the optical resonator 46 can be called "an optical lattice forming section forming an optical lattice". The optical resonator 46 is also a device based on laser atom cooling technology.

[0033] The coil 48 for the MOT device generates a gradient magnetic field for the collection space 50. The MOT device emits MOT light beams along three axes X, Y and Z, respectively, in the gradient magnetic field formation space. That is, the MOT device collects atoms in the collection space 50. The collection space 50 is formed on the X axis. The coil 44 for the Zeeman moderator in FIG. 2 comprises a Zeeman coil serving for the Zeeman moderator and one of a pair of MOT coils serving for the MOT device in the form of a set of coils. In this diagram, the gradient magnetic field facilitating the implementation of the magneto-optical collection method is generated jointly with the coil 48 for the MOT device and a part of the coil 44 for the Zeeman moderator.

[0034] The cryostat tank 54 is formed with the possibility of containing the space 52 of the hourly transition and maintaining a low temperature in the inner space. Accordingly, the radiation of the absolute black body is reduced in the inner space. The thermal coupling element 56, which also serves as a supporting structure, is attached to the cryostat tank 54. The thermal coupling element 56 transfers heat from the cryostat tank 54 to the refrigeration device 58. The refrigeration device 58 maintains a low temperature of the cryostat tank 54 by means of the thermal coupling element 56. The refrigeration device 58 includes a Peltier element and cools the cryostat tank 54, for example, to 190K.

[0035] The main body 60 of the vacuum pump and the cartridge 62 of the vacuum pump are devices for evacuating the vacuum chamber 20. The main body 60 of the vacuum pump and the cartridge 62 of the vacuum pump are devices for sequentially evacuating the vacuum chamber 20. The main body 60 of the vacuum pump is located outside the vacuum chamber 20. The cartridge 62 of the vacuum pump is located in the vacuum chamber 20. At the beginning of the start-up, the cartridge 62 of the vacuum pump is heated by a heater located at the main body 60 of the vacuum pump and starts. Accordingly, the cartridge 62 of the vacuum pump will start and will absorb atoms, thereby ensuring the creation of a vacuum.

[0036] The vacuum pump cartridge 62 is installed in the main body 22 so that the cartridge is located parallel to the Zeeman moderator coil 44. The Zeeman moderator coil 44 is located along the beam axis with an offset from the center in the X-axis direction relative to the central axis of the cylinder of the main body 22. Therefore, there is a relatively large space on the side opposite to the direction of the eccentric arrangement of the Zeeman moderator coil 44. The vacuum pump cartridge 62 is installed in this space.

[0037] The physical part 12 includes, as components of the optical system: vacuum-resistant optical windows 64 and 66 for the optical grating light; a vacuum-resistant optical window 68 for the MOT light; vacuum-resistant optical windows 70 and 72 for the Zeeman retarder light and the MOT light; and optical mirrors 74 and 76.

[0038] The vacuum-resistant optical windows 64 and 66 for the optical grating are vacuum-resistant optical windows located on opposite cylindrical walls 24 of the main body 22 of the vacuum chamber 20 so that they face each other. The vacuum-resistant optical windows 64 and 66 for the optical grating light are designed with the possibility of receiving and emitting optical grating light through them.

[0039] The vacuum-resistant optical window 68 for the MOT light is arranged to receive and emit beams of MOT light in two axes from beams of MOT light in three axes used for the MOT device.

[0040] Vacuum-resistant optical windows 70 and 72 for Zeeman moderator light and MOT light are arranged to allow Zeeman moderator light and MOT light to enter and be emitted through them in the same axis.

[0041] Optical mirrors 74 and 76 are arranged with the possibility of changing the directions of the Zeeman moderator light and the MOT light in one axis.

[0042] As cooling components, the physical part includes: a cooler 90 for an atomic furnace; a cooler 92 for a Zeeman moderator; and a cooler 94 for a MOT device.

[0043] The cooler 90 for the nuclear furnace is a water cooling device that cools the nuclear furnace 40. The cooler 90 for the nuclear furnace is located outside the vacuum chamber 20 and cools the radiator of the nuclear furnace 40, wherein the radiator extends outside the vacuum chamber 20. The cooler 90 for the nuclear furnace includes a water cooling tube, which is a tube made of metal and is intended for cooling, and causes cooling water, which is a liquid coolant, to flow in the tube, thereby cooling the vacuum chamber 20.

[0044] The Zeeman moderator cooler 92 is a device mounted on the wall portion of the vacuum chamber 20 and cooling the Zeeman moderator coil 44. The Zeeman moderator cooler 92 includes a tube made of metal, and cooling water flows in the tube, thereby removing the Joule heat generated in the Zeeman moderator coil 44.

[0045] The cooler 94 for the MOT device is a radiator located on the circular wall portion of the vacuum chamber 20. In the coil 48 for the MOT device, Joule heat is generated, although its amount is less (for example, approximately 1/10) than the amount of Joule heat of the cooler 92 for the Zeeman moderator. Therefore, the metal of the cooler 94 for the MOT device extends beyond the vacuum chamber 20 from the coil 48 for the MOT device and radiates heat into the atmosphere.

[0046] As components for correcting the magnetic field, the physical part 12 further comprises: a three-axis magnetic field correction coil 96; a vacuum-resistant electrical connector 98; an individual magnetic field compensation coil 102 for a refrigeration device; and an individual magnetic field compensation coil 104 for an atomic furnace.

[0047] The three-axis magnetic field correction coil 96 is a coil for uniformly reducing the magnetic field to zero in the 52-hour transition space. The three-axis magnetic field correction coil 96 is three-dimensional in shape with the possibility of correcting the magnetic field in three axes - i.e. X, Y and Z. In the example of FIG. 4, the three-axis magnetic field correction coil 96 is substantially generally cylindrical in shape. Each of the coils forming the three-axis magnetic field correction coil 96 is point-symmetrical in shape with a center in the 52-hour transition space in the direction of each of the axes.

[0048] The vacuum-resistant electrical connector 98 is a connector for supplying electrical energy into the vacuum chamber 20 and is located on the circular wall portion of the vacuum chamber 20. Energy from the vacuum-resistant electrical connector 98 is supplied to the coil 44 for the Zeeman moderator, the coil 48 for the MOT device and the coil 96 for correcting the magnetic field in three axes.

[0049] The individual magnetic field compensation coil 102 for the refrigeration device is a coil for compensating the parasitic magnetic field from the refrigeration device 58 cooling the cryostat tank 54. The Peltier element included in the refrigeration device 58 is a powerful current device in which a large current flows and generates a strong magnetic field. The magnetic field around the Peltier element is shielded by a material with high magnetic permeability. However, complete shielding is not ensured, due to which some of the magnetic field is scattered. Therefore, the individual magnetic field compensation coil 102 for the refrigeration device is designed with the possibility of compensating the parasitic magnetic field in the space 52 of the hour transition.

[0050] The individual magnetic field compensation coil 104 for the atomic furnace is a coil for compensating the stray magnetic field from the heater of the atomic furnace 40. The heater of the atomic furnace 40 is also a high-power current device, and in some cases, the stray magnetic field cannot be ignored even if there is shielding with a material with high magnetic permeability. For example, even if the heater circuit is formed from a non-inductive winding, in practice, there is a component induced in the winding through the terminal and the insulating layer. For example, even if the atomic furnace is covered with a material with high magnetic permeability to provide magnetic shielding, in practice, some part may not be covered, for example, an opening for an atomic beam. Therefore, the individual magnetic field compensation coil 104 for the atomic furnace is configured to compensate for the stray magnetic field in the space of the 52 hour transition.

[0051] (2) Work of the physical part

The basic operation of the physical part 12 is disclosed below. In the physical part 12, the vacuum pump cartridge 62 contained in the vacuum chamber 20 absorbs atoms, thereby creating a vacuum inside the vacuum chamber 20. As a result, for example, a vacuum state of approximately 10 ^-8 Pa exists inside the vacuum chamber 20, which eliminates the effect of air components, in particular nitrogen and oxygen. Depending on the type of the vacuum pump to be used, a preliminary treatment is first performed. For example, in the case of a pump with a non-evaporable gas getter (a pump with a non-evaporable gas getter) and an ion pump, before they are put into operation, evacuation to a preliminary vacuum from atmospheric pressure to a certain degree of vacuum must be performed. In this case, a evacuation hole to a preliminary vacuum must be provided for the vacuum chamber, through which evacuation to a sufficient preliminary vacuum is performed using a turbomolecular pump, for example. For example, in the case of using a pump with a NRGP as the main body of the 60 vacuum pump, a stage of starting heating to a high temperature in a vacuum must be performed in advance.

[0052] In the atomic furnace 40, the metal is heated by a heater to a high temperature with the formation of atomic steam. The atomic steam emitted from the metal during this process passes through a pore with subsequent fusion, transformation and formation of an atomic beam 42. The atomic furnace 40 is installed with the possibility of forming an atomic beam 42 on the beam axis parallel to the Z axis. It should be noted that the heating of the main body of the atomic furnace in the atomic furnace 40 is carried out by a heater. In this case, the main body of the atomic furnace and the unit on which the said main body rests are thermally insulated by means of a heat insulator. In addition, the cooler 90 for the atomic furnace cools the unit connected to the physical part, thereby preventing the effect of a high temperature on the physical part 12 or mitigating the negative effect of a high temperature.

[0053] The Zeeman moderator coil 44 is mounted axially symmetrically with respect to the beam axis. The optical beam 82 of the Zeeman moderator and the optical beam 84 of the MOT irradiate the interior of the Zeeman moderator coil 44 along one axis. The optical beam 82 of the Zeeman moderator enters from the vacuum-resistant optical window 70 for the light of the Zeeman moderator and the light of the MOT, and is reflected by the optical mirror 74 mounted downstream of the beam at a distance from the MOT coil 48. As a result, the optical beam 82 of the Zeeman moderator is superimposed on the atomic beam 42 and the optical beam 82 of the Zeeman moderator moves upstream of the beam axis parallel to the beam axis. During this process, under the influence of the Zeeman splitting effect proportional to the magnetic field strength and the Doppler effect, the atoms in the atomic beam 42 absorb the Zeeman moderator light, receive a momentum in the direction of deceleration and decelerate. The Zeeman moderator light is reflected upstream of the Zeeman moderator coil 44 by the optical mirror 76 located away from the beam axis and emitted through the vacuum-resistant optical window 72 for the Zeeman moderator light and the MOT light. It should be noted that the Zeeman moderator coil 44 generates Joule heat. However, the Zeeman moderator cooler 92 performs cooling. This prevents the occurrence of high temperature.

[0054] The sufficiently slowed down atomic beam 42 reaches the MOT device, which includes the MOT coil on the lowermost side of the Zeeman moderator coil 44 and the MOT device coil 48. In the MOT device, a magnetic field with a linear spatial gradient and with a center in the collection space 50 is formed. The MOT light irradiates the MOT device in the directions of three axes on the positive and negative sides.

[0055] The emission of the optical beam 84 of the MOT in the direction of the Z axis occurs in the negative direction of the Z axis with subsequent reflection outside the vacuum-resistant optical window 72 for the Zeeman retarder light and the MOT light, as a result of which it is also emitted in the positive direction of the Z axis. The emission of the optical beams 86a and 86b of the MOT in the remaining two axes into the MOT device occurs through the vacuum-resistant optical window 68 for the MOT light and by means of an optical mirror that is not shown. In FIG. 4, it is shown that these two axes extend in two directions perpendicular to the Z axis and with an inclination from the X axis and the Y axis, respectively, by 45 degrees; the emission occurs in these two directions. The configuration with the possibility of passing two optical beams 86a and 86b of the MOT perpendicular to the Z axis allows to reduce the distance from the coil 44 for the Zeeman moderator to the coil 48 for the MOT device, which contributes to the miniaturization of the vacuum chamber 20. If the emission directions of the optical beams of the MOT are provided with an inclination from the Z axis and the Y axis by 45 degrees, respectively, the distance along the beam axis should be large in order to avoid unwanted contact of the optical beams of the MOT with the Zeeman moderator and the cryostat reservoir. In this case, the size of the device is larger than in the case of two axes of the MOT light beams perpendicular to the Z axis.

[0056] In the MOT device, a restoring force centered in the collection space 50 is applied to the atomic beam due to the magnetic field gradient, and the atomic beam is slowed down. As a result, a population of atoms is collected in the collection space 50. It should be noted that the location in the collection space 50 can be precisely adjusted by adjusting the values of the magnetic field offset to be generated by the magnetic field correction coil 96 in three axes. The Joule heat generated in the coil 48 for the MOT device is removed outside the vacuum chamber 20 by the cooler 94 for the MOT device.

[0057] The beam 80 of the optical grating light enters in the direction of the X-axis through the vacuum-resistant optical window 64 for the optical grating light to the vacuum-resistant optical window 66 for the optical grating light. An optical resonator 46 is installed on the X-axis, which includes two optical mirrors and causes reflection. As a result, an optical grating potential with a set of standing waves in the direction of the X-axis in the optical resonator 46 arises on the X-axis. The optical grating potential ensures the capture of a population of atoms.

[0058] The optical lattice can be moved along the X-axis, slightly changing the wavelength. By means of movement through the movable optical lattice, the population of atoms is moved into the space of the 52 hour transition. The result is that the space of the 52 hour transition is located away from the beam axis of the atomic beam 42. This makes it possible to eliminate the effects of the radiation of an absolutely black body from the atomic furnace 40 at a high temperature. The space of the 52 hour transition is enclosed in a cryostat reservoir 54 and is shielded from the radiation of an absolutely black body emitted by substances in the environment at ordinary temperatures. As a rule, the radiation of an absolutely black body is proportional to the fourth power of the absolute temperature of the substance. Therefore, the reduction in temperature by the cryostat reservoir 54 provides a significant positive effect, consisting in eliminating the effect of the radiation of an absolutely black body.

[0059] In the space of the 52 hour transition, the atoms are irradiated with laser light of a controlled optical frequency, high-precision spectroscopy of the clock transitions (i.e., the resonant transitions of the atoms that are reference for the clock) is carried out, and the frequency characteristic of the atom and invariant is measured. In this way, a precise atomic clock is obtained. In order to increase the accuracy of the atomic clock, it is necessary to eliminate the disturbance around the atoms and reliably take frequency readings. In particular, it is important to eliminate the frequency shift caused by the Doppler effect due to the thermal disturbance of the atoms. The motion of the atoms in the clock on the optical lattice is blocked by holding the atoms in a space that is sufficiently smaller in size than the wavelength of the laser of the clock, by means of an optical lattice formed as a result of the interference of the laser light. In this case, a shift in the frequencies of the atoms occurs in the optical lattice under the action of the laser light that forms the optical lattice. In relation to the beam 80 of light of the optical lattice, a special wavelength or frequency is selected, called the “magic wavelength” or “magic frequency”, at which there is no effect of the optical lattice on the resonant frequency.

[0060] In addition, the clock transitions are also affected by the magnetic field. Atoms in a magnetic field cause Zeeman splitting, which depends on the strength of the magnetic field. This does not allow accurate measurement of the clock transitions. In the space 52 of the clock transition, the magnetic field is corrected to equalize and reduce the magnetic field to zero. First, the parasitic magnetic field generated by the Peltier element of the refrigeration device 58 is dynamically compensated by an individual magnetic field compensation coil 102 for the refrigeration device, which generates a compensating magnetic field depending on the strength of the parasitic magnetic field. Similarly, the parasitic magnetic field generated by the heater of the atomic furnace 40 can be dynamically compensated by an individual magnetic field compensation coil 104 for the atomic furnace. It should be noted that, during the measurement of the clock transition frequency, the current signal is switched off for the coil 44 for the Zeeman moderator and the coil 48 for the MOT device and no energy is supplied, which prevents the effects of the magnetic field. The magnetic field of the space 52 of the clock transition is also corrected by means of the coil 96 for correcting the magnetic field in three axes. The coil 96 for correcting the magnetic field in three axes includes a plurality of coils on each of the axes and is designed with the possibility of eliminating not only the homogeneous components of the magnetic field, but also the non-uniform components in space.

[0061] In the state with the eliminated disturbances, a clock transition is forced into the population of atoms by means of laser light. The light emitted as a result of the clock transition is received by the device of the optical system in which a spectroscopic process, etc., occurs under the influence of the regulating device, and the frequency value is obtained. The embodiments of the physical part 12 are described in detail below.

[0062] (3) Shape and installation option of the magnetic field correction coil

In the examples of FIGS. 5-11, a three-axis magnetic field correction coil 96 is disclosed in the physical part 12. In this case, it is assumed that the three-axis magnetic field correction coil 96 is made in a predetermined shape by winding a wire with an insulated core, including a current-carrying wire made of copper or a similar substance and having undergone an insulation process with a polyimide resin.

[0063] FIG. 5 is a perspective view showing all of the coils comprising the three-axis magnetic field correction coil 96. FIGS. 6-11 are perspective views showing individual coils forming the three-axis magnetic field correction coil. The three-axis magnetic field correction coil 96 is attached along the perimeter of the inner wall of the main body 22 of the vacuum chamber 20. Thus, the three-axis magnetic field correction coil 96 is formed substantially in the form of a cylinder with a center in the 52 hour transition space. The three-axis magnetic field correction coil 96 includes a first group of coils and a second group of coils in each of the directions of the X-axis, the Y-axis, and the Z-axis.

[0064] FIG. 6 shows a first group 120 of coils in the direction of the X axis (the direction in which the optical lattice is formed in one axis and the movement of the movable optical lattice occurs). The first group 120 of coils includes two coils 122 and 124, installed with an indentation from each other at a distance c in the direction of the X axis with a center in the space of the 52 hour transition. Each of the coils 122 and 124 is made in the form of a rectangle with sides of length a in the direction of the Y axis and of length b in the direction of the Z axis. Each of the coils 122 and 124 is made in shape point-symmetrical relative to the space of the 52 hour transition.

[0065] The first group 120 of coils provides the formation of a square Helmholtz coil by coils 122 and 124 with the possibility of substantially uniform generation of a magnetic field in the central part in the direction of the X-axis. The square Helmholtz coil includes coils 122 and 124 made in the form of squares with a=b and c/2a = approximately 0.5445. When currents of the same magnitude flow in the same direction, coils 122 and 124 operate as a pair of Helmholtz coils, forming a magnetic field of high uniformity in the direction of the X-axis. In this embodiment, the possibility of currents of different magnitudes and directions flowing through coils 122 and 124 is provided. It should be noted that coils 122 and 124 can sufficiently increase the uniformity of the magnetic field, even if a ≠ b. If a>b, the deviation of the magnetic field distribution in the Y-axis direction is usually smaller than the deviation of the magnetic field distribution in the Z-axis direction. If a<b, the deviation of the magnetic field distribution in the Z-axis direction is usually smaller than the deviation of the magnetic field distribution in the Y-axis direction. If a ≠ b, c is optimized by the so-called "rectangular" Helmholtz coil. The first group of 120 coils can be designed as a rectangular Helmholtz coil.

[0066] The first group 120 of coils serves to regulate the value of the component of the magnetic field in the direction of the X axis and its spatial derivative of the first order term in the direction of the X axis. First, 1) if currents of the same magnitude flow in the same direction through coils 122 and 124, a uniform magnetic field with a small gradient in the direction of the X axis is formed in the space of the 52 hour transition. However, 2) if currents of the same magnitude flow in opposite directions through coils 122 and 124, a uniform magnetic field with a substantially uniform gradient in the direction of the X axis is formed in the space of the 52 hour transition. In the case of a corresponding change in the magnitudes and directions of the currents flowing through coils 122 and 124, a magnetic field is formed that is a linear sum of 1) and 2). Thus, the first group of 120 coils can correct the component in the form of a constant term of the component Bx of the magnetic field in the direction of the X axis in the space of the 52 hour transition and its spatial derivative term of the first order in the direction of the X axis.

[0067] FIG. 7 shows a second group 130 of coils in the X-axis direction. The second group 130 of coils includes two coils 132 and 134 installed with an indentation from each other in the X-axis direction with a center in the 52 hour transition space. Coils 132 and 134, each individually, are made in a shape obtained by deforming rectangular coils with the formation of a bend in them to ensure the possibility of laying the coils on the same cylindrical surface with a radius e, and are made so that the central angle is f, and the height in the Z-axis direction is d. The cylindrical surface is made with a radius substantially identical to the radius of the cylindrical surface on which the first group 120 of coils in FIG. 6 is fixedly fixed. Thus, the ratio e ² ≅ (a/2) ² + (c/2) ² is maintained. Each of the coils 132 and 134 is made point-symmetrical in shape relative to the space of the 52-hour transition.

[0068] The second group of coils 130 is not a Helmholtz coil and is different in shape from a Helmholtz coil. The coils 132 and 134 of the second group of coils are electrically connected to each other. Currents of the same magnitude flow through the coils in the same direction. That is, the currents flow in the direction of the arrow 136 or the currents flow in the direction of the arrow 138 through both coils 132 and 134. Since the second group of coils 130 is not a Helmholtz coil, an inhomogeneous component also arises in addition to the uniform component created by the Helmholtz coil in the space of the 52 hour transition in the center. It should be noted that the currents have the same magnitudes and directions. Thus, the inhomogeneous component is mainly a component in the form of a spatial derivative of the second order term. That is, the second group of 130 coils can correct the component in the form of a constant term of the component Bx of the magnetic field in the direction of the X axis in the space of the 52 hour transition and its spatial derivative term of the second order in the direction of the X axis.

[0069] The control of the magnetic field component Bx in the X-axis direction in the three-axis magnetic field correction coil 96 is mainly carried out by the first coil group 120 and the second coil group 130 in the X-axis direction. Therefore, they are collectively called the "X-axis magnetic field correction coil." To carry out the correction, the value of the spatial derivative of the second order term in the X-axis direction is first reduced to zero by the second coil group 130. Then, the reduction to zero of the value of the spatial derivative of the first order term in the X-axis direction and the reduction to zero of the constant term in the X-axis direction are adjusted by the first coil group 120.

[0070] FIG. 8 shows a first group 140 of coils in the Y-axis direction. The first group 140 of coils is formed by deforming rectangular coils to form a bend and is laid on a cylindrical surface of radius h with a center in the 52-hour transition space. The first group of coils includes a composite coil 142 formed by a coil 143 and a coil 144, and a composite coil 145 formed by a coil 146 and a coil 147, wherein the composite coils are installed with an indentation from each other in the Y-axis direction. Coils 143, 144, 146 and 147 are formed such that the central angle is i, and the height in the Z-axis direction is j. Coils 143 and 144 are formed with the possibility of overlapping their edges or adjoining them. Similarly, coils 146 and 147 are formed with the possibility of overlapping their edges or adjoining them. Composite coil 142 and composite coil 145 are formed point-symmetrically with the center in the space of the 52 hour transition. Coil 143 and coil 146, as well as coil 144 and coil 147, are formed point-symmetrically with the center in the space of the 52 hour transition.

[0071] First: 3) a case is considered in which currents of the same magnitude flow in the same direction through coils 143 and 144. In this case, the currents in the superimposed or adjoining configuration cancel each other, and the composite coil 142 as a whole operates as a single large coil. Similarly, if currents of the same magnitude flow in the same direction through coils 146 and 147, the composite coil 145 operates as a single large coil. The first group 140 of coils is configured such that the composite coil 142 and the composite coil 145 operate as a pair of Helmholtz coils. The Helmholtz coil on the cylindrical surface in FIG. 8 (i.e., the Helmholtz coil obtained by bending two rectangular coils and placing them on the same cylindrical surface) has a central angle of approximately 120 degrees. There is no particular limitation on the length in the direction of the Z axis. It is known that the greater the length in the direction of the Z axis compared to the radius of the cylinder, the greater the homogeneity of the magnetic field of the central part. The first group of 140 coils is designed with the possibility of aligning the component of the magnetic field in the direction of the Y axis around the center by adjusting the direction and magnitude of the current allowed to flow.

[0072] Next: 4) the current is slightly changed relative to the current at the time of forming the Helmholtz coil. In particular, only the currents through the coil 143 and the coil 147 are slightly increased in the same direction. In this case, the component of the magnetic field in the direction of the Y axis has the value of the spatial derivative of the first order term in the direction of the X axis. It should be noted that, strictly speaking, the magnetic field generated by the coil 143 and the coil 147 has a component in the direction of the X axis. When the first group 140 of coils is adjusted, the magnetic field correction coil in the X axis must also be adjusted.

[0073] FIG. 9 shows a second group 150 of coils in the Y-axis direction. The second group 150 of coils in FIG. 9 is formed by a pair of coils 152 and 154 facing each other in the Y-axis direction. Each of the coils 152 and 154 is a non-Helmholtz coil formed by creating a bend in a circular coil of radius k and laying the coil on the surface of a cylinder of radius I centered in the 52 hour transition space. The non-Helmholtz coil also creates a component of the magnetic field in the form of a spatial derivative of the second order term. Thus, the second group 150 of coils is also configured to control the spatial derivative of the second order term in the X-axis direction of the By component of the magnetic field in the Y-axis direction.

[0074] The first group 140 of coils in the Y-axis direction in FIG. 8 and the second group 150 of coils in the Y-axis direction in FIG. 9 essentially form a Y-axis magnetic field correction coil that corrects the By component of the magnetic field in the Y-axis direction. The Y-axis magnetic field correction coil can correct a constant term of the By component of the magnetic field in the Y-axis direction, a first-order spatial derivative term in the X-axis direction, and a second-order spatial derivative term in the X-axis direction.

[0075] FIG. 10 shows a first group 160 of coils in the direction of the Z axis. The first group 160 of coils includes circular composite coils 162 and 165 having a radius m, facing each other and located at a distance n from each other. The composite coils 162 and 165 are point-symmetrical with respect to the center. The composite coil 162 includes semicircular coils 163 and 164, the wires of which are arranged with an overlap on each other or adjacent to each other. The semicircular coil 163 is located on the positive side of the X axis, and the semicircular coil 164 is located on the negative side of the X axis. Similarly, the composite coil 165 is formed by creating a combination of a semicircular coil 166 on the positive side of the X axis with a semicircular coil 167 on the negative side of the X axis.

[0076] The composite coils 162 and 165 are configured in size and the like to operate as a Helmholtz coil. The ratio in a circular Helmholtz coil is m=n. The composite coils 162 and 165 are configured in such a way that when currents of the same magnitude flow in the same direction, the homogeneity of the magnetic field in the Z direction around the center is substantially equal in magnitude to the homogeneity of the magnetic field of the Helmholtz coil. It should be noted that the directions and magnitudes of the currents through the coils 163 and 164 that form the composite coil 162 can be arbitrarily changed. Thus, like the first group 140 of coils in the Y direction in FIG. 8, the first group 160 of coils can correct the constant term and the first-order spatial derivative term in the X-axis direction of the Bz component of the magnetic field in the Z direction.

[0077] FIG. 11 shows a second group 170 of coils in the Z-axis direction. The second group 170 of coils includes circular coils 172 and 174 having a radius p, spaced apart from each other by a distance q in the Z-axis direction and facing each other. The second group 170 of coils is a non-Helmholtz coil. The non-Helmholtz coil has a non-uniform component. Thus, the spatial derivative term of the second order in the X-axis direction of the Bz component of the magnetic field in the Z-axis direction can be corrected.

[0078] The first group 160 of coils in the Z-axis direction in FIG. 10 and the second group 170 of coils in the Z-axis direction in FIG. 11 essentially form a Z-axis magnetic field correction coil that corrects the Bz component of the magnetic field in the Z-axis direction. The Z-axis magnetic field correction coil can correct a constant term of the Bz component of the magnetic field in the Z-axis direction, a first-order spatial derivative term in the X-axis direction, and a second-order spatial derivative term in the X-axis direction.

[0079] The three-axis magnetic field correction coil 96 in FIG. 5 is formed by jointly adjusting the X-axis magnetic field correction coil, the Y-axis magnetic field correction coil, and the Z-axis magnetic field correction coil. The three-axis magnetic field correction coil 96 can correct a constant term, a first-order spatial derivative term in the X-axis direction, and a second-order spatial derivative term in the X-axis direction of the Bx magnetic field component in the X-axis direction. It is possible to correct the constant term, the first-order spatial derivative term in the X-axis direction, and the second-order spatial derivative term in the X-axis direction of the By magnetic field component in the Y-axis direction. It is possible to correct the constant term, the first-order spatial derivative term in the X-axis direction, and the second-order spatial derivative term in the X-axis direction of the Bz magnetic field component in the Z-axis direction.

[0080] The three-axis magnetic field correction coil 96 performs correction by uniformly reducing the magnetic field value of the 52 hour transition space to zero. In the case of a one-dimensional optical lattice, the 52 hour transition space is formed so that its dimensions are, in particular: 10 mm in the X-axis direction (lattice direction) and approximately 1-2 mm in the Y-axis and Z-axis directions, for example. In this space, for example, the magnetic field error is adjusted so that it is within 3 μG, within 1 μG, or within 0.3 μG. The Helmholtz coils and non-Helmholtz coils included in the three-axis magnetic field correction coil 96 are designed so that their accuracy indicators allow such a magnetic field to be formed.

[0081] The three-axis magnetic field correction coil 96 in FIG. 4 is shaped as a point-symmetrical coil with a center in the 52-hour transition space and with the ability to accurately correct the magnetic field in the 52-hour transition space. In this case, in the macroscopic view, the collection space 50 is located around the center of the three-axis magnetic field correction coil. This also makes it possible to use it to correct the magnetic field of the collection space 50 created by the MOT device. That is, the current is regulated to correct the magnetic field of the collection space 50 during the period of time when the MOT device is started and collects atoms from the atomic beam 42. Upon completion of the collection, the energy transfer to the Zeeman moderator coil 44 and the MOT device coil 48 is stopped and the magnetic field of the 52-hour transition space is corrected. This ensures highly accurate control of the location of the capture space 50 and the possibility of effectively retaining the population of atoms in the optical lattice.

[0082] FIG. 12 shows a cylindrical holder 180 to which a three-axis magnetic field correction coil 96 is attached. The holder 180 comprises circular annular frames 182 and 184 and eight linear frames 186 connecting the frames 182 and 184. The three-axis magnetic field correction coil 96 is attached to the inner wall and to the outer wall of the holder 180. The holder 180, in turn, is fixedly attached to the rear circular wall 28 of the main body 22 of the vacuum chamber 20. Attaching the three-axis magnetic field correction coil 96 to the holder 180 increases labor productivity during assembly operations and checking the technical condition of the physical part 12.

[0083] The holder 180 is made of a low-permeability substance such as resin, aluminum, or the like, in order to avoid influencing the magnetic field generated by the three-axis magnetic field correction coil 96. The holder 180 is installed in the main body 22 so that its axis coincides with the central axis of the cylinder of the main body 22. The holder 180 is made approximately equal in size to the inner diameter of the main body 22. Therefore, the three-axis magnetic field correction coil 96 and the holder 180 do not take up much space in the main body 22. It should be noted that the coils 122 and 124, which are the first group 120 of coils in the X-axis direction, are attached linearly across the inner space of the main body 22.

[0084] The holder 180 is formed in a sparse structure using frames. The sparse structure is a structure with a plurality of gaps on each surface. The sparse structure of the holder 180 reduces weight and helps prevent interference with laser light entering and emitted from the vacuum chamber 20.

[0085] For example, the three-axis magnetic field correction coil 96 may be attached only to the inner wall of the holder 180 or be attached only to the outer wall of the holder 180, and not be attached to the inner wall and the outer wall of the holder 180. In this case, for example, the attachment can be easily ensured by a round annular fastener pressing the three-axis magnetic field correction coil 96 to the outer wall, or a round annular fastener pressing the coil to the inner wall. The three-axis magnetic field correction coil 96 can be fixedly attached to the inner wall of the main body 22 without using the holder 180.

[0086] It is assumed that the above-disclosed three-axis magnetic field correction coil 96 is formed by single or multiple winding of a wire with an insulated core. In this case, the three-axis magnetic field correction coil 96 can be partially or completely implemented on the basis of a flexible printed circuit board.

[0087] FIG. 13 shows a flexible printed circuit board in a flat pattern. A correction coil 190 is formed on this flexible printed circuit board. The correction coil 190 includes conductive tracks 192, made by printing from an electrically conductive material, for example, copper, and facilitating the creation of a magnetic field, and an insulator 194, made of a flexible resin in the form of a sheet, with the possibility of elastic bending. Each conductive track 192 is connected to an interconnection space 196, concentrated at one end. The interconnection space 196 is made by printing from an electrically conductive material. The interconnection space forms a pair, where currents flow in opposite directions in close proximity to each other and the magnetic fields arising around are extinguished. The interconnection space 196 is connected to an end clamp 198.

[0088] FIG. 14 shows a cylindrically curved correction coil 190 along the main body 22 of the vacuum chamber 20. The correction coil 190 comprises a boundary portion 199, where two edges are connected to each other or are located in close proximity to each other. It should be noted that in FIG. 14, the interconnection space 196 and the end clamp 198 are not shown.

[0089] Similar to the three-axis magnetic field correction coil 96 in which a wire with an insulated core is wound, it is assumed that the three-axis magnetic field correction coil formed with a flexible printed circuit board is attached to the inner wall of the cylindrical main body 22 or to the cylindrical holder 180. It should be noted that the three-axis magnetic field correction coil 96 includes a conductive path disconnected from the cylindrical surface, in addition to the conductive path located on the cylindrical surface. In particular, the side containing a portion of the first group 120 of coils in the X-axis direction in FIG. 6 and the linear portion of the first group 160 of coils in the Z-axis direction in FIG. 10 are disconnected from the cylindrical surface. Next, an example will be disclosed in which the conductive tracks located on the cylindrical surface, from among the conductive tracks forming the coil 96 for correcting the magnetic field in three axes, are formed on a flexible printed circuit board.

[0090] FIGS. 15 and 16 illustrate an example of forming a coil in a circular portion of the first group 160 of coils in the Z-axis direction in FIG. 10 with a flexible printed circuit board. In FIG. 15, it is shown that counterclockwise currents flow along the conductive paths 202 indicated by black lines, while no current flows into the conductive paths 200 indicated by gray lines. At this time, considering that currents that are in close proximity to each other and flow in opposite directions cancel each other, this case is equivalent to the case in which currents flow along the virtual conductive paths 203 in FIG. 16.

[0091] FIGS. 17 and 18 illustrate an example of forming the outermost coil of the first group 140 of coils in the Y-axis direction of FIG. 8 with a flexible printed circuit board. In FIG. 17, it is shown that counterclockwise currents flow along the conductive paths 206 indicated by black lines, while no current flows into the conductive paths 204 indicated by gray lines. At this time, considering that currents that are in close proximity to each other and flow in opposite directions cancel each other, this case is equivalent to the case in which currents flow along the virtual conductive paths 208 in FIG.

[0092] As disclosed above, multiple conductive paths may be formed on the flexible printed circuit board, including a conductive path extending backward along the outer periphery of the cylindrical surface around the central axis of the cylinder, and a conductive path extending backward on the cylindrical surface not around the central axis of the cylinder.

[0093] In the scanning diagram shown in FIG. 13, a pattern formed by rectangular conductive tracks can be printed on the flexible printed circuit board. Similarly, for the correction coil 210 of FIG. 19, a complex pattern including rectangular conductive tracks 211 and round conductive tracks 214 can be printed. In the physical part 12, a laser beam path, a vacuum-resistant optical window, etc. are located along the circumference of the wall surface of the vacuum chamber 20. Therefore, it is expedient to create round conductive tracks 214 and prevent interference. Coils can be formed on the flexible printed circuit board as shown in FIGS. 16 and 18. It is possible to use several flexible printed circuit boards superimposed on each other. Thus, the magnetic field correction coil in three axes can be formed partially or completely using several boards.

[0094] In some cases, it is possible for a small amount of gas to be emitted from the resin of the insulator 194 on the flexible printed circuit board. Therefore, a substance with a small gas emission, in particular, a polyimide resin, is selected for the insulator 194. The manufacturing step may include a heat treatment process at an appropriate temperature in addition to deaeration, defoaming, cleaning, etc.

[0095] The three-axis magnetic field correction coil formed on the basis of the flexible printed circuit board can be installed in the vacuum chamber 20 in various forms. For example, the three-axis magnetic field correction coil can be installed along the perimeter of the inner wall of the main body 22 in a cylindrically curved state, and the three-axis magnetic field correction coil can be fixedly attached to the main body 22 by a fastener pressing the coil to the main body 22. Alternatively, the installation can be performed by attaching to the holder 180. Instead of the holder 180 of a sparse structure, it is possible to use a holder of a dense structure without a large number of voids for supporting the flexible printed circuit board on a plane.

[0096] In turn, the conductive path, disconnected from the cylindrical surface, can be formed separately using a wire with an insulated core. Alternatively, by changing the design of the holder, it is possible to create a conductive path, disconnected from the cylindrical surface, using a flexible printed circuit board.

[0097] Compared with the three-axis magnetic field correction coil 96 with a wound wire with an insulated core, the three-axis magnetic field correction coil using a flexible printed circuit board has the advantages of being easier to attach to the vacuum chamber 20, having higher reproducibility in production, and having a higher output.

[0098] It should be noted that the three-axis magnetic field correction coil can also be made in various other forms. For example, for each of the three axes, a large-sized round coil can be located in the middle between two round coils, which makes it possible to form a Maxwell-type coil for correcting the magnetic field in three axes. In the case of a Maxwell-type coil for correcting the magnetic field in three axes, it is possible to correct the magnetic field components in the form of a constant term, a first-order spatial derivative term, and a second-order spatial derivative term.

[0099] In addition, for each of the three axes, small round coils of a predetermined size are installed at predetermined intervals outside the pair of large round coils of a predetermined size installed at predetermined intervals, which makes it possible to form a quadruple type coil for correcting an axial magnetic field. It is possible to correct the components of the magnetic field correction coil in three axes in the form of a constant term, a first-order spatial derivative term, a second-order spatial derivative term, and a third-order spatial derivative term.

[0100] The axial magnetic field correction coil disclosed above is generally formed in the shape of a sphere or a slightly distorted sphere. Therefore, in particular, attachment to the inner wall of a substantially spherical vacuum chamber or along its perimeter makes it possible to effectively use the internal space of the vacuum chamber.

[0101] FIG. 20 is a diagram corresponding to FIG. 4 and is a schematic view of the physical part 218 from the outside and from the inside. Components that are identical or corresponding to the components in FIG. 4 have the same or corresponding designations. The vacuum chamber 220 of the physical part 218 is formed by a substantially spherical main body 222 and a projecting portion 30.

[0102] A three-axis magnetic field correction coil 224 formed by round coils is arranged in the main body 222, with the center in the 52 hour transition space. To simplify the diagram, FIG. 20 shows only a pair of Helmholtz coils in the direction of each of the axes. It is assumed that in practice, one or more non-Helmholtz coils will additionally be arranged on each of the axes. The outer edge of the three-axis magnetic field correction coil 224 can be designed to form a substantially spherical surface. Thus, installing the three-axis magnetic field correction coil 224 in a substantially spherical main body 222 along the perimeter of the inner wall makes it possible to avoid unwanted contact with other components installed in the inner space of the main body 222 and to provide greater freedom in choosing design solutions.

[0103] Similarly, the three-axis magnetic field correction coil can be structurally implemented using square coils. As in the case of round coils, it is possible to use a Helmholtz coil for three-axis magnetic field correction, including each pair of square coils, a Maxwell-type coil for three-axis magnetic field correction, including three square coils, a quadruple-type coil for three-axis magnetic field correction, including two pairs of square coils, etc. The said three-axis magnetic field correction coils are generally implemented in the shape of a cube or a slightly distorted cube. Thus, attaching to the inner wall or to the surface of the inner wall of a substantially cubic or substantially cuboidal vacuum chamber makes it possible to effectively use the inner space of the vacuum chamber.

[0104] The three-axis magnetic field correction coil may be attached at a position located closer to the 52 hour transition space than to the inner wall of the main body 22. FIG. 21 schematically shows the inner space of the optical resonator 46 of FIG. 1 and the space around it. It should be noted that in FIG. 21, instead of the three-axis magnetic field correction coil 96 of FIG. 1, a three-axis magnetic field correction cubic coil 230 is installed in the space between the Zeeman moderator coil 44 and the MOT device coil 48. The three-axis magnetic field correction cubic coil 230 is located with a center in the 52 hour transition space in the cryostat tank 54. The three-axis magnetic field correction cubic coil 230 is formed by two pairs of coil groups consisting of square coils in each of the three axial directions. One of the two pairs of coil groups is a Helmholtz coil, and the other pair is a non-Helmholtz coil. If the magnitudes and directions of the currents are not limited to any particular magnitudes and directions, the cubic three-axis magnetic field correction coil 230 is capable of compensating for a component of the magnetic field up to a spatial derivative of the third order term. Alternatively, if currents of the same magnitude flow in the same direction, as in the case of the non-Helmholtz three-axis magnetic field correction coils 96 in FIG. 5-11, it is possible to simply compensate for a component of the magnetic field up to a spatial derivative of the second order term.

[0105] Unlike the three-axis magnetic field correction coils 96 in FIG. 5-11, the three-axis magnetic field correction coil 230 has a very small size and is located close to the 52 hour junction space. Accordingly, the changes in the magnetic field generated in the 52 hour junction space occur on a relatively small spatial scale. In this case, the three-axis magnetic field correction coil 230, by means of a Helmholtz coil, can compensate for the constant term and the first-order spatial derivative term in a relatively wide range. By means of a coil that is not a Helmholtz coil, it is possible to compensate for at least the component of the magnetic field in the form of the second-order spatial derivative term. As a result, the magnetic field of the 52 hour junction space is uniformly reduced to zero with high accuracy. Since the three-axis magnetic field correction coil 230 is located in a position close to the 52-hour transition space, the excited current flow for creating the magnetic field can be very small, which makes it possible to provide excellent energy-saving characteristics.

[0106] FIG. 22 is a side view from the direction A of FIG. 21. FIG. 22 shows that the collection space 50 is irradiated with two optical beams 86a and 86b of the MOT, perpendicular to the Z axis and passing at an inclination of 45 degrees from the X axis and the Y axis. Also, in the direction perpendicular to the sheet, an optical beam 84 of the MOT is emitted. To regulate the gradient magnetic field created in and around the collection space 50, a magnetizing coil 234 is located with a center in the collection space 50. The magnetizing coil 234 includes: a pair of round Helmholtz coils 234a facing each other along the beam axis; a pair of square Helmholtz coils 234b facing each other along the X axis; and a pair of square Helmholtz coils 234 facing each other along the Y axis. The magnetizing coil 234 adjusts the gradient magnetic field to the desired distribution by adjusting the constant term or the first order spatial derivative term component through the coils in each axis.

[0107] In the X axis passing through the collection space 50, the emission of the optical lattice light beam 80 occurs. The cryostat reservoir 54 containing the hourly transition space 52 is located in the path of the optical lattice light beam 80. The three-axis magnetic field correction coil 230 is located with the center in the hourly transition space 52 around the cryostat reservoir 54. The three-axis magnetic field correction coil 230 includes: a group 230b of coils, the plane of which contains a normal parallel to the Z axis; and two groups of coils 230a and 230c, the planes of which contain a normal perpendicular to the Z axis, and which are located with an inclination from the X axis and the Y axis by 45 degrees. That is, the three-axis magnetic field correction coil 230 is in a state in which the cubic shape along the X axis, the Y axis, and the Z axis is rotated around the Z axis by 45 degrees.

[0108] The three-axis magnetic field correction coil 230 is supported by flanges 44a and 48a, which are supporting members on which the MOT device is supported. Therefore, the three-axis magnetic field correction coil 230 must be arranged near the collection space 50 in the center of the MOT device. In this case, the three-axis magnetic field correction coil 230 must be arranged so as to prevent interference with the optical beams 86a and 86b of the MOT passing through the collection space 50. Thus, the three-axis magnetic field correction coil 230 is arranged to form a certain shape along the Z axis and the optical beams 86a and 86b of the MOT.

[0109] The three-axis magnetic field correction coil 230 includes a Helmholtz coil and a non-Helmholtz coil in the direction of each axis. This makes it possible to ensure the alignment of the magnetic field in a large space, including the correction of spatial derivatives of higher-order terms. Accordingly, the magnetic field can also be corrected with high accuracy in the X-axis direction, i.e., in the direction of the light beam 80 of the optical lattice.

[0110] It should be noted that the three-axis magnetic field correction coil 230 does not enclose the collection space 50. This does not allow the magnetic field in the collection space 50 to be corrected. Therefore, as disclosed above, a magnetizing coil 234 correcting the gradient magnetic field is installed in the collection space 50.

[0111] FIGS. 20 and 21 illustrate an example of a three-axis magnetic field correction coil 230 formed by square coils. However, it is possible to use coils of other shapes, such as round coils, instead of square coils. For example, it is possible to use a cylindrical three-axis magnetic field correction coil 96 of FIGS. 5-11.

[0112] The three-axis magnetic field correction coil can be installed either in a position near the 52-hour transition space or in a position along the perimeter of the inner wall of the main body 22. For example, a Helmholtz coil can be installed along the perimeter of the inner wall of the main body 22, and a non-Helmholtz coil can be installed in a position near the 52-hour transition space. Installing a non-Helmholtz coil in a position near the 52-hour transition space makes it possible to easily correct a magnetic field of large curvature.

[0113] (4) Adjusting the magnetic field correction coil

Below is disclosed the regulation of the magnetic field by the magnetic field correction coil in three axes. For the correction of the magnetic field, periodic observation of the magnetic field distribution around the space of the 52 hour transition is carried out and, upon detection of a non-uniform distribution of the magnetic field, control of the currents through the magnetic field correction coil 96 in three axes is carried out to eliminate such a distribution of the magnetic field. Observation of the magnetic field distribution is carried out by moving the population of atoms held in the optical lattice, by means of a movable optical lattice. Due to these operations, a situation is realized in which individual atoms included in a group of atoms are always in a zero magnetic field.

[0114] FIGS. 23A and 23B schematically illustrate the process of adjusting the magnetic field correction coil in three axes. FIG. 23A depicts the state of movement of the population of atoms 240, held in the movable optical lattice, along the X-axis. FIG. 23B illustrates the relationship between the fluorescence transition and the clock transition.

[0115] FIG. 23A shows that the population of atoms 240 is held in lattices sequentially arranged in the direction of the X-axis with a certain spatial extent. In this diagram, the characteristic positions along the X-axis of coordinates where the movement of the population of atoms 240 occurs are represented as position X1, position X2, position X3, position X4 and position X5. These positions in the correction space 242 are set for correcting the magnetic field. The correction space 242 is set with wide limits, including the space 52 of the hour transition, where the actual measurement occurs. This embodiment comprises a one-dimensional lattice, wherein the optical lattice extends in the direction of the X axis, and the population of atoms 240 is located in a region extending in the direction of the X axis. The intention is, in particular, to reduce the magnetic field in the direction of the X axis to zero with high accuracy. The correction space 242 is defined with limits in the direction of the X axis. It should be noted that if the optical lattice is formed in two dimensions, it is desirable that the correction space obtained by expanding the 52 hour transition space in the direction of two dimensions is defined. If the optical lattice is formed in three dimensions, it is desirable that the correction space obtained by expanding the 52 hour transition space in the direction of three dimensions is defined.

[0116] At each of the positions of the moving correction space 242, the population of atoms 240 is irradiated with laser light to excite the clock transition, and the excitation of the clock transition occurs. The frequency of the laser light emission is swept and the frequency of the clock transition is measured at each position. To observe the excitation rate of the clock transition, the "quantum jump" method ("electron shelving") is used. The "quantum jump" method provides for the excitation of the clock transition with the subsequent movement of atoms into the fluorescence observation space 243. As can be seen from FIG. 23B, by emitting fluorescence transition light, the atoms emit fluorescence radiation 244 depending on the excitation rate. The fluorescence radiation is observed using an optical receiver 246. The clock transition is affected by Zeeman splitting, which depends on the intensity of the magnetic field at each position. As a result, the magnetic field distribution at each position is obtained based on the Zeeman splitting information. The frequency distribution obtained in this way is shown in the lower part of FIG. 23A. This method makes it possible to measure the magnetic field even in a place where it is impossible to observe any fluorescent radiation (in a cryo head, etc.). Instead of the "quantum jump" method, a non-destructive measurement method involving the measurement of phase shifts of atoms can be used to measure the excitation rate of the clock transition.

[0117] FIG. 24 and 25 are flow charts illustrating methods for correcting a magnetic field by a three-axis magnetic field correction coil. First, according to the methods in FIG. 24, calibration is performed. The calibration includes the steps of stopping the currents in all coils forming the three-axis magnetic field correction coil (set to 0 A) and measuring the distributions of the magnetic field in three axial directions (S10). A magnetic field, such as magnetic fields in three axial directions, is measured by a magnetic sensor, in particular a small-sized coil or a Hall effect element. The measured magnetic field reflects the background value in a state where the three-axis magnetic field correction coil is not operated. Next, currents of the same magnitude (1 A in FIG. 24) are excited through all coils (n coils) and the magnetic field distributions are measured in three axial directions using a magnetic field sensor or something similar (S12 - S18). By subtracting the background magnetic field from the obtained magnetic field distribution, it is possible to obtain the base magnetic field created by a current of 1 A in each coil.

[0118] Calibration allows the magnetic field of the correction space 242 to be measured. However, the correction space 242 is located in the cryostat tank 54. Therefore, in some cases, difficulties may arise with the installation of the magnetic sensor. Therefore, the magnetic field can be measured in the immediate vicinity of the correction space 242 and the magnetic field can be estimated based on the result of the simulation in combination with the measurement. The magnetic field can be measured in the atmosphere, rather than in a vacuum. In this way, the basic distribution of the magnetic field generated by each coil of the magnetic field correction coil in three axes at a current of 1 A can be estimated. In principle, this is sufficient for performing calibration at the stage of creating the physical part 12.

[0119] Next, according to the methods of FIG. 25, the magnetic field is corrected. First, as described above, the population of atoms 240 is moved by means of a movable optical lattice and the frequency of the clock transition at each position in the correction space 242 (S20) is measured. The effect of Zeeman splitting is estimated and, thereby, the distribution of the magnetic field in the correction space 242 (S22) is obtained. The distribution of the magnetic field is obtained as an absolute value of the magnetic field.

[0120] Then, the current corresponding to the magnetic field to be corrected by each of the coils is determined by some optimization method, for example, the least squares method (S24). That is, a superposition coefficient is obtained at which the magnetic field created in the correction space 242 is uniformly zero in the superposition of the basic magnetic fields created by the corresponding coils. It should be noted that, as disclosed above, in the case of using both a Helmholtz coil and a non-Helmholtz coil, the optimal superposition coefficients for the spatial derivatives of the higher order terms created by the non-Helmholtz coil are first obtained by the least squares method or a similar method. Then, an optimal superposition is obtained for the constant term and the spatial derivative of the first order term created by the Helmholtz coil by the least squares method or a similar method. This simplifies the calculation and increases its accuracy. The obtained superposition coefficients reflect the direction and magnitude of the current that must flow into each of the coils. The flow of the obtained currents is excited into the magnetic field correction coil in three axes, thereby providing the possibility of magnetic field correction in three axes (S26).

[0121] The correction illustrated in FIG. 25 does not have to be performed frequently in the normal mode in which the changes in the magnetic field are small. For example, in the case of repeatedly measuring the clock transition in the 52 clock transition space, it is sufficient to perform the correction illustrated in FIG. 25 every predetermined number of times. It is assumed that, when measuring the clock transition in the 52 clock transition space, the magnitude of the Zeeman splitting can be checked each time, and when the predetermined value of its magnitude is reached or exceeded, the correction illustrated in FIG. 25 can be performed.

[0122] If the magnetic field of the three-axis magnetic field correction coil is corrected within the correction space 242, it is expected that the magnetic field of the 52 hour hop space will be stably and uniformly reduced to zero, unlike the case in which the correction is performed within the 52 hour hop space. For example, it can be assumed that due to small-scale disturbances such as a small fluctuation in the magnetic field, the error in measuring the magnetic field and the error in the basic magnetic field of each coil have an effect in the case where only a narrow space such as the 52 hour hop space is taken as the target. In practice, in one experiment, the correction space 242 was taken as the target and the correction was performed in it, resulting in a result of increased accuracy.

[0123] In the examples of FIGS. 23A and 25, using a movable optical lattice, a population of atoms 240 is moved to each position in the correction space 242. In this case, FIG. 26 schematically illustrates an example of measuring the distribution of a magnetic field in the correction space 242 in one period of time.

[0124] In FIG. 26, a population of 250 atoms is held in an optical lattice over the entire area of the correction space 242. Beams 252a, 252b, 252c, 252d and 252e of fluorescence radiation of the population of 250 atoms with imprinted spatial information are received at one time period by a charge-coupled device (CCD) camera 254 and frequencies are obtained. Thus, the magnetic field distribution of the correction space 242 is obtained immediately.

[0125] (5) Individual magnetic field compensation coil As disclosed above in section (1), for the Peltier element (refrigeration device 58), which is a high-power current device, an individual magnetic field compensation coil 102 for the refrigeration device is installed with the ability to compensate for the magnetic field in the 52-hour transition space. For the heater of the atomic furnace 40, an individual magnetic field compensation coil 104 for the atomic furnace is installed with the ability to compensate for the magnetic field in the 52-hour transition space. If the compensation of the strong parasitic magnetic field from the high-power current device by the magnetic field correction coil in three axes is carried out entirely, it is necessary to increase the multiplicity of the magnetic field correction coil in three axes and the current. Therefore, it is advisable to install individual magnetic field compensation coils to compensate for the said magnetic field. In this case, an example of an individual magnetic field compensation coil 102 for the refrigeration device is disclosed in detail.

[0126] FIG. 27 is a diagram of an example of configurations of a cryostat tank 54, a thermal coupling element 56, a refrigeration device 58, and an individual magnetic field compensation coil 102 for the refrigeration device. The cryostat tank 54 is a hollow component that encloses the hour junction space 52. Although not shown, an opening is formed along the X-axis on the wall portion of the cryostat tank 54 to allow light from the optical array to pass through it. The cryostat tank 54 is made of oxygen-free copper with high thermal conductivity or the like.

[0127] Thermal coupling element 56 is attached to cryostat tank 54. Thermal coupling element 56 is an element that forms a support structure on which cryostat tank 54 is supported, as well as a heat removal path from cryostat tank 54. Thermal coupling element 56 is also made of oxygen-free copper with high thermal conductivity or something similar.

[0128] The refrigeration device 58 includes a Peltier element 58a, a radiator panel 58b, a heat-insulating element 58c, and permalloy magnetic shields 58d and 58e. The Peltier element 58a is connected to the thermal coupling element 56 and conducts heat from the thermal coupling element 56 with a current flowing through it. The radiator panel 58b is an element made of oxygen-free copper with high thermal conductivity or something similar. The radiator panel 58b is located on the outer wall of the vacuum chamber 20 and radiates heat transferred from the Peltier element 58a outside the vacuum chamber 20.

[0129] The heat-insulating element 58 c provides heat insulation between the permalloy magnetic shield 58 d and the thermal connecting element 56. The heat-insulating element 58 c consists of a substance, for example silica, with low thermal conductivity, and is formed in the shape of a sphere to reduce the number of contact points between the permalloy magnetic shield 58 d and the thermal connecting element 56. The permalloy magnetic shield 58 e is a magnetic shield and is formed of permalloy, which has high thermal conductivity and permeability. The permalloy magnetic shield 58 e is located between the Peltier element 58 a and the radiator panel 58 b and transfers heat from the Peltier element 58 a to the radiator panel 58 b.

[0130] Temperature sensor 260, including a thermocouple, thermistor or the like, is mounted in cryostat tank 54 and inputs measured temperature T1 to control device 262. Temperature sensor 264 is mounted on or near radiator panel 58b and inputs measured temperature T2 to control device 262.

[0131] The control device 262 regulates the current to limit the temperature T1 of the cryostat tank 54 to a certain low temperature (for example, 190K). The regulation is carried out, for example, using the PID (proportional-integral-derivative) regulation method, also taking into account the temperature T2 on the side of the radiator panel 58b. A flow of a certain current is excited into the Peltier element 58a along the conductive path 266.

[0132] The Peltier element 58a is a thermoelectric element that moves heat depending on the flow of current. By exciting the flow of current, the Peltier element 58a removes heat from the thermal coupling element 56 (and from the cryostat reservoir 54 connected to the thermal coupling element 56) on the low temperature side and dumps heat onto the permalloy magnetic shield 58e (and the radiator panel 58b connected to the permalloy magnetic shield 58e) on the high temperature side.

[0133] A high-power current, such as several amperes, is passed through the Peltier element 58a. Therefore, a strong magnetic field is generated. Most of the Peltier element 58a is covered by a permalloy magnetic screen 58d and a permalloy magnetic screen 58e, made of a material with high magnetic permeability. As a result, most of the generated magnetic field flows in these elements and does not leak out. At the same time, taking into account the heat transfer, a magnetic field cannot be generated between the thermal connecting element 56 and the Peltier element 58a. Accordingly, the resulting magnetic field 270 is parasitic. The parasitic magnetic field 270 disturbs the magnetic field in the space 52 of the hourly transition in the cryostat tank 54.

[0134] In this embodiment, the individual magnetic field compensation coil 102 for the refrigeration device is installed at the thermal coupling element 56, forming a passage section in which the magnetic field cannot be shielded. The individual magnetic field compensation coil 102 for the refrigeration device generates a compensating magnetic field 272 during the flow of current.

[0135] The current is directed to the individual magnetic field compensation coil 102 for the refrigeration device via the conductive path 268, which is a branch of the conductive path 266. That is, the Peltier element 58a and the individual magnetic field compensation coil 102 for the refrigeration device are connected in the sense that they are connected in parallel with the same conductive path. It can be assumed that the electrical resistance of the Peltier element 58a and the electrical resistance of the individual magnetic field compensation coil 102 for the refrigeration device have constant values under the temperature conditions where the measurements occur, although these values undergo slight changes. Therefore, the distribution of the current flowing from the control device 262 to the conductive path 266, to the Peltier element 58a and the individual magnetic field compensation coil 102 for the refrigeration device occurs in constant proportions.

[0136] When the current flowing through the Peltier element 58a increases, the current flowing through the individual magnetic field compensation coil 102 for the refrigeration device increases proportionally. Therefore, when the parasitic magnetic field 270 from the Peltier element 58a increases, the compensating magnetic field 272 generated by the individual magnetic field compensation coil 102 for the refrigeration device increases in the same manner. The individual magnetic field compensation coil 102 for the refrigeration device is formed to compensate the parasitic magnetic field 270 in the hour transition space 52 in the cryostat tank 54 (to create a magnetic field of the same magnitude in the opposite direction) when a current of a certain magnitude flows along the conductive path 266. In this way, even if the current changes, the magnetic field can be compensated. It should be noted that currents also flow along the conductive paths 266 and 268. However, currents flow in opposite directions near each other along the conductive paths 266 and 268. Therefore, the resulting magnetic field is weak and does not create any problems.

[0137] The specified arrangement of the conductive paths 266 and 268 can be considered as a means for regulating the compensation current for dynamically changing the current flowing through the individual magnetic field compensation coil 102 for the refrigeration device, depending on the parasitic magnetic field 270. The means for regulating the compensation current can be formed in another way. As an example, a variant can be given in which the control device 262 directs the current flow required according to the calculation through the individual magnetic field compensation coil 102 for the refrigeration device.

[0138] In the example of FIG. 27, it is assumed that the individual magnetic field compensation coil 102 for the refrigeration device is formed by one coil wound on the thermal coupling element 56. In this configuration, the individual magnetic field compensation coil 102 for the refrigeration device is located in close proximity to the wall of the vacuum chamber 20, which makes it possible to avoid creating a complex configuration around the cryostat tank 54. At the same time, there are no particular restrictions regarding the installation location of the individual magnetic field compensation coil 102 for the refrigeration device. For example, it can be installed in close proximity to the cryostat tank 54. Installing the individual magnetic field compensation coil 102 for the refrigeration device in close proximity to the cryostat tank 54 makes it possible to reduce the size of the individual magnetic field compensation coil 102 for the refrigeration device and reduce power consumption.

[0139] The individual magnetic field compensation coil 102 for the refrigeration device may not be formed by one coil, but may be formed by several coils. In the case of a complex distribution of the parasitic magnetic field in the 52 hour transition space, there is a possibility that the use of several coils will make it possible to provide compensation relatively simply.

[0140] The current device, the individual magnetic field compensation coil, and the compensation current adjustment means form a magnetic field compensation module. The magnetic field compensation module can provide accurate magnetic field compensation. Therefore, this module can be used in various devices, including a clock 10 on an optical lattice.

[0141] (6) Zeeman moderator

FIG. 28 shows sectional views of a Zeeman moderator coil 44 and a MOT coil 48. In the illustrated Zeeman moderator coil 44, a coil 282 is wound on an elongated cylindrical core 280 located coaxially with the beam axis. The hollow portion of the core around the center represents a space through which the atomic beam 42 passes along the beam axis.

[0142] From the point of view of functionality, the largest part of the coil 282 is the section 284 forming a decreasing type Zeeman coil, in which the number of turns decreases slightly in the direction from the upper to the lower side along the beam axis. The lowest side of the coil 282 along the beam axis and around it is the section 286 forming a MOT coil with a larger number of turns. The wires with an insulated core of the Zeeman coil-forming section 284 and the MOT coil-forming section 286 are continuously connected to each other, wherein the magnetic field generated by the Zeeman coil-forming section 284 passes in the immediate vicinity of the MOT coil-forming section 286, and the magnetic field generated by the MOT coil-forming section 286 passes downstream of the Zeeman coil-forming section 284. Therefore, it should be noted that the boundary between the Zeeman coil-forming section 284 and the MOT coil-forming section 286 cannot be clearly defined.

[0143] On the side of the frame 280 that is upper along the beam axis, there is a disk-shaped upper flange 288, the radius of which is greater than the radius of the part with the maximum diameter of the section 284 that forms the Zeeman coil. The upper flange 288 is attached to the cylindrical wall 32 of the protruding part 30 of the vacuum chamber 20. A mirror support (not shown) is attached to the front part of the upper flange 288. An optical mirror 76 is attached to the far end of the mirror support.

[0144] On the side of the core 280 downstream of the bundle axis, two circular annular downstream flanges 290 and 292 are formed, the diameter of which is essentially identical to the section 286 forming the MOT coil. The downstream flange 290 is made in the form of a semicircular ring, thickened in the direction along the bundle axis and located along the perimeter of the boundary between the section 284 forming the Zeeman coil and the section 286 forming the MOT coil. The downstream flange 292 is made in the form of a semicircular ring, relatively thin in the direction along the bundle axis, and is located downstream of the section 286 forming the MOT coil. The upper parts of the downstream flanges 290 and 292 are attached to the upper support element 312, and the lower parts of the flanges are attached to the lower support element 314. The upper support element 312 and the lower the support element 314 is attached to the rear circular wall 28 of the main body 22 of the vacuum chamber 20.

[0145] The coil 48 for the MOT device is located downstream of the coil 44 for the Zeeman moderator at a predetermined distance. The coil 302 of the MOT device in the coil 48 is wound on a short cylindrical core 300 located coaxially with the beam axis. On the upper side of the core 300 along the beam axis, a thin circular annular flange 304 is located, which is substantially identical in diameter to the coil 302 of the MOT. On the lower side of the core 300 along the beam axis, a relatively thick circular annular flange 306 is located, which is substantially identical in diameter to the coil 302 of the MOT. The upper parts of the flanges 304 and 306 are attached to the upper support element 312 and fixed thereto.

[0146] The frame 280, the upstream flange 288 and the downstream flanges 290 and 292 in the coil 44 for the Zeeman moderator are made of copper or a similar substance with high thermal conductivity and low permeability. The frame 280, the upstream flange 288 and the downstream flanges 290 and 292 are connected to each other by welding to ensure high strength and their direct contact.

[0147] In the coil 44 for the Zeeman moderator, the greater part of the coil is wound on the upper side along the beam axis. The upper side along the beam axis is heavier than the lower side along the beam axis. The connection of the upper flange 288 along the beam axis with the cylindrical wall 32 of the protruding part 30 of the vacuum chamber 20 ensures a stable positioning of the coil 44 for the Zeeman moderator in the vacuum chamber 20.

[0148] The heat in the Zeeman moderator coil 44 generates a current flowing through the coil 282. The vacuum chamber 20 is in a vacuum state. Unlike the atmosphere, there is no heat transfer through the gas. Therefore, a weak cooling effect due to the radiation of an absolutely black body takes place in the Zeeman moderator coil 44. In this case, the heat removal from the coil 282 must occur mainly by heat transfer through the solid body. The frame 280 is in contact with the coil 282, and effective heat transfer from the coil 282 occurs. The upstream flange 288 and the downstream flanges 290 and 292 have a large contact area with the coil 282 and conduct heat away from the coil 282. In FIG. 2, it is shown that the upstream flange 288 is connected to the cooler 92 for the Zeeman moderator at the cylindrical wall 32 of the protruding part 30. In the cooler 92 for the Zeeman moderator, cooling water circulates in a water cooling tube made of copper or a similar substance, and, thereby, the upstream flange 288 is cooled. This prevents an excessive increase in the temperature of the coil 44 for the Zeeman moderator.

[0149] The frame 300 and the flanges 304 and 306 of the coil 48 for the MOT device also have high thermal conductivity and are made of copper or a similar substance with low permeability. The frame 300 and the flanges 304 and 306 are connected to each other by welding to ensure high strength and their direct contact. The MOT coil 302 of the coil 48 for the MOT device is smaller in size and lighter in weight than the coil 282 of the coil 44 for the Zeeman moderator. The coil 48 for the MOT device as a whole also has a low weight. Accordingly, the coil 48 for the MOT device is firmly attached to the rear circular wall 28 by means of the upper support member 312, to which the flanges 304 and 306 are fixedly attached.

[0150] The current directed to flow in the MOL coil 302 of the MOL coil 48 is weaker, and the amount of heat generated in it is less than in the coil 282 of the Zeeman moderator coil 44. The peripheral sections of the MOL coil 302 in three directions of the MOL coil 48 are enclosed within the frame 300 and the flanges 304 and 306. Therefore, the transfer of heat generated by the MOL coil 302 to the MOL cooler 94 occurs through the upper support element 312. It is assumed that a cooling circuit is provided for the MOL cooler 94. In this case, if the amount of heat to be removed is small, an air cooling circuit can be used.

[0151] In the example of FIG. 28, the number of turns of the coil 282 decreases generally monotonically. In this case, in particular, irregularities are created in the direction of the beam axis. One of the purposes of creating such irregularities is to ensure the desired magnetic field strength at a specific position on the beam axis. For example, in the collection space 50, where the atoms are collected, the magnetic field should be zero. Another purpose may be to use a configuration in which no magnetic field arises at positions where a magnetic field is not needed from the standpoint of energy conservation. It is sufficient that the coil 44 for the Zeeman moderator generates the magnetic field necessary for slowing down the atoms or holding the atoms. One of the reasons for creating irregularities may be the need for mechanical support or thermal radiation. The weight of the coil is greater, the greater the number of turns. Therefore, difficulties arise with its support. In addition, the heat emission from the coil increases. In this connection, the number of turns of the coil in a section convenient for support or a section with high efficiency of thermal radiation can be increased. In the example in FIG. 28, the coil 282 of the coil 44 for the Zeeman moderator is made in a relatively convex shape with a large number of turns in a section in contact with the upstream flange 288, and in a relatively concave shape with a relatively small number of turns on the downstream side. Accordingly, the barycenter of the coil 44 for the Zeeman moderator moves toward the upstream flange 288, wherein the upstream flange 288 provides a strong fixation. The contact area between the coil 282 and the upstream flange 288 is large, wherein effective heat transfer from the coil 282 to the upstream flange 288 is ensured.

[0152] Next, using FIG. 29 as an example, a cavity in a coil is described. FIG. 29 shows sectional views of the upper portions of two Zeeman coils 320 and 330. In the Zeeman coil 320, the number of turns decreases monotonically in the direction of the beam axis, which includes the section 322. In this case, the Zeeman coil 330 contains a locally small number of turns in the section 332, called the "cavity". In this case, the Zeeman coil 330 contains a locally large number of turns before the section 332 and after it in the direction of the beam axis. Thus, the distribution of the magnetic field generated by the Zeeman coil 330 as a whole is substantially equal to the distribution of the magnetic field generated by the Zeeman coil 320.

[0153] The shape to be given to the coil in and around the cavity can be determined theoretically. The distribution of the magnetic field generated by the assembly element obeys the Biot-Savart law. The problem of converting the magnetic field distribution into a current distribution can be solved by the inverse convolution method or as an inverse problem in a general perspective. A method for obtaining a solution with a minimum current-carrying path via an inverse problem is described, for example, in the document by Mansfield P, Grannell RK. "NMR diffraction in solids." J Phys C: Solid State Phys 6:L422-L427, 1973. It is obvious that the presence of several paths is possible only in the absence of a limitation on the minimum current. In FIG. 29 shows that if the solution with the minimum conductive path corresponding to the desired magnetic field distribution is the Zeeman coil 320, then the Zeeman coil 330 with an increased current density around the cavity could also create the desired magnetic field distribution.

[0154] In the case of the coil 282 in FIG. 28, the downstream flange 290 is located in the middle of the coil 282. This means that the downstream flange 290 is located at a large cavity. The number of turns made before and after the downstream flange 290 in the direction of the bundle in this configuration is greater than in the case without the downstream flange 290, which eliminates or mitigates the negative effects of the downstream flange 290.

[0155] FIG. 30 shows the distribution of the magnetic field at the Zeeman moderator coil 44 and the MOT coil 48. The x-axis indicates the position on the beam axis. The origin corresponds to the collection space 50. The y-axis indicates the intensity of the magnetic field at the beam axis. The Zeeman moderator coil 44 and the MOT coil 48 are formed symmetrically with respect to the beam axis. Therefore, the magnetic field at the beam axis has only a component in the direction of the beam axis. The position of the coil 282 of the Zeeman moderator coil 44 and the position of the MOT coil 302 of the MOT coil 48 are indicated on the beam axis. The dots on the graph indicate the calculated values of the magnetic field. The thin lines indicate the value of the magnetic field ideal for slowing down the atoms toward the collection space 50 of the Zeeman moderator.

[0156] The magnetic field becomes maximum slightly downstream from the end of the coil 282 on the upstream side. On the side slightly upstream from the position of the maximum value, a sharp decrease in the value of the magnetic field occurs. On an even further upstream side, the value gradually approaches zero. An ideal magnetic field has a distribution in which the magnetic field outside the coil 282 becomes zero and there is no leakage of the magnetic field outward. In this case, the process of the emergence of a magnetic field under the action of current has a spatial extent. For example, in the absence of an oppositely directed coil compensating (quenching) the external magnetic field, the magnetic field outside the coil 282 cannot be zero.

[0157] On the downstream side of the position with the magnetic field of maximum value, the magnetic field decreases monotonically. There are cases of small non-uniformity of the number of turns of the coil, as disclosed above. The monotonically decreasing magnetic field for the Zeeman moderator arises under the action of the surrounding coil. The magnetic field with a gradient essentially coincides with the ideal magnetic field distribution for the Zeeman moderator and indicates a stable deceleration of the atoms in the direction of the trapping space 50.

[0158] Before the end of the downstream side of the coil 282, a sharp decrease in the magnetic field occurs. The section 286 forming the MOT coil near it has a large number of turns. There is no coil located on the downstream side. Accordingly, the value of the magnetic field decreases rapidly.

[0159] The magnetic field decreases with a substantially constant slope and becomes zero in the collection space 50. In addition, the magnetic field decreases with the same slope and acquires a minimum value (the negative value has become the most persistent) near the MOL coil 302 of the MOL device coil 48. This is due to the fact that the MOL coil 302 induces a current to flow in a direction opposite to the coil 282. A section within the range from a section near the MOL coil-forming section 286 of the coil 282 to a section approximately near the MOL coil 302 forms a Helmholtz coil. Thus, the direction of the current flow through the MOL coil 302 in the opposite direction makes it possible to create a magnetic field with a constant slope. Although not shown, a magnetic field with a constant slope is also created in a direction perpendicular to the beam axis. The gradient magnetic field formed by the MOT device irradiates the optical beams of the MOT in the corresponding three axes. This ensures the possibility of trapping atoms in the space 50 of trapping at the initial point. The magnetic field on the lower side of the MOT coil 302 gradually approaches zero.

[0160] As disclosed above, the coil 44 for the Zeeman moderator and the coil 48 for the MOT device are installed in combination with each other, which makes it possible to shorten the length in the beam axis direction compared with the case in which the Zeeman moderator and the MOT device are installed separately. The length of the coil as a whole can also be shortened, which can contribute to energy conservation and reduction of heat generation.

[0161] It should be noted that, in the case of the presence of a background magnetic field, there is a deviation of the position in which the magnetic field is zero from the collection space 50. Therefore, in the process of collecting atoms, the three-axis magnetic field correction coil 96 or the bias coil for correcting the gradient magnetic field is adjusted, thereby making it possible to generate a compensating magnetic field that cancels the background magnetic field around the collection space 50.

[0162] Next, with reference to FIGS. 31A and 32B, an example of a Zeeman moderator coil 340 of an incremental type is disclosed. FIG. 31A is a sectional view illustrating a state before the Zeeman moderator coil 340 is attached inside the vacuum vessel 20. FIG. 31B is a sectional view illustrating a state after said attachment. The coil 342 of the Zeeman moderator coil 340 in FIG. 31A is formed by a Zeeman coil-forming portion 344 in which a large portion on the upper side along the beam axis performs the function of a Zeeman coil. The lowermost side along the beam axis of the coil 342 is formed by a MOT coil-forming portion 346 in which the function of a Zeeman coil and the function of a MOT coil are combined. In the section 344 forming the Zeeman coil, the number of turns increases monotonically from the end of the upper downstream side to the lower downstream side. Near the end on the lower downstream side, there are again non-uniformities, and then the number of turns becomes maximum on the lowest downstream side. For convenience, the section with the maximum number of turns and its surroundings are called "section 346 forming the MOT coil". As disclosed above, from the point of view of functionality, this section also performs the function of the Zeeman coil.

[0163] The coil 340 for the Zeeman moderator contains a frame inside it. At the end on the upstream side, a flange 350 is located. In the middle part of the coil 342 near the end on the downstream side, a flange 352 is located. At the end on the downstream side, a flange 354 is located. Flanges 350, 352 and 354 are welded to the frame.

[0164] A mirror support (not shown) is attached to the uppermost flange 350. An optical mirror 76 is fixedly attached to the mirror support.

[0165] The lower flanges 352 and 354 are connected to each other in areas that do not coincide with the frame and increase strength. The flange 352 is a large disk, thin and with a large radius. The flange 352 is attached to a circular annular support 370, made in the shape of a ring. The ring of the circular annular support 370 contains inside itself a water cooling tube 372, through which the cooling water flows and cools the coil 342 through the flange 352. The right and left beams 374 are attached to the upper part of the circular annular support 370. The right and left beams 376, which also form water cooling tubes, are attached to the lower part of the circular annular support 370. The beams 374 and 376 are attached to the rear circular wall 28 of the main body 22 of the vacuum chamber 20 and provide support for the entire part containing the coil 340 for the Zeeman moderator. The beams 374 and 376 form a waste heat path for transferring heat from the coil 342 to the rear circular wall 28. It should be noted that it is possible for the cooling water flowing through the beams 376 to circulate into the panel 58b of the radiator of the refrigeration device 58.

[0166] This configuration assumes that the coil 380 for the MOT device is attached to the rear circular wall 28 using a separate support element. It is assumed that the coil 340 for the Zeeman moderator is positioned together with the coil 380 for the MOT device using a positioning mechanism.

[0167] FIG. 32 is a diagram related to FIG. 30 and shows the distribution of the magnetic field in the case of using a coil 340 of the increasing type for the Zeeman moderator and a coil 380 for the MOT device. The magnetization gradually increases from the downstream side of the coil 342 of the coil 340 for the Zeeman moderator and acquires a maximum value in front of the section 346 forming the MOT coil. This increase in magnetization is quite consistent with the target curve necessary for creating a Zeeman moderator. On the downstream side from the position with the maximum value, the magnetization drops sharply. Before and after the collection space 50, which forms the starting point, the magnetization drops from positive to negative with a substantially constant slope and becomes zero in the collection space 50. The magnetic field reaches a minimum near the 380 coil for the MOL device and then gradually approaches zero.

[0168] In the section forming the MOT device before and after the collection space 50, the slope of the magnetic field curve becomes steep compared to the case of the decreasing type in FIG. 30. This is due to the fact that the number of turns of the MOT coil 346 in the coil 342 is large, while the number of turns of the coil 380 facing it for the MOT device is also large. The steep slope of the magnetic field curve makes it possible to collect atoms at a short distance in the beam axis direction.

[0169] The length of the increasing type coil 340 for the Zeeman moderator in FIG. 32 may be shorter than the length of the decreasing type coil 44 for the Zeeman moderator in FIG. 30. This is because the increasing type coil can effectively slow down atoms. The increasing type coil provides the ability to suppress the magnetic field, which is necessary for slowing down atoms and saving energy compared to the decreasing type coil.

[0170] In this case, in the coil 340 of the increasing type for the Zeeman moderator, the side of the collection space 50 is heavier. Therefore, it is difficult to ensure that the coil is supported in the vacuum chamber 20. The coil of the increasing type has a greater number of turns on the side of the collection space 50. As a result, problems arise in that a large amount of heat is generated around the center of the vacuum chamber 20 and is difficult to cool. In this case, as disclosed above, the coil 340 for the Zeeman moderator is supported around the center of the vacuum chamber 20 on a circular annular support 370 with a cooling function. Therefore, these problems do not arise.

[0171] The embodiment of attaching the coil 340 of the increasing type for the Zeeman moderator in FIGS. 31A and 31B is given solely for example. It is possible to use another embodiment. A modified example is disclosed with reference to FIGS. 33A and 33B.

[0172] FIG. 33A is a perspective view showing a state before attaching the Zeeman moderator coil 390 inside the vacuum chamber 20. FIG. 33B is a perspective view showing a state after attaching. The coil 392 of the Zeeman moderator coil 390 is wound similarly to the Zeeman moderator coil 340. The configuration including the core and the flanges 394, 396 and 398 is also almost similar. Here, in the Zeeman moderator coil 390, the flange 396 located near the lower end in the beam direction has a semicircular shape corresponding substantially approximately to the lower half. The section on which the flange 396 is supported functions as essentially a U-shaped semicircular annular support 400 obtained by dividing a circular ring in half. The semicircular annular support 400 is provided with a water cooling tube 402.

[0173] In the embodiment of FIGS. 33A and 33B, the flange 396 has a semicircular shape. The cooling efficiency in the case of a similar circulation of cooling water is slightly lower. At the same time, in the Zeeman moderator coil 390, there is a space above the flange 396. This facilitates access in the vacuum chamber 20 from the optical resonator 46 towards the atomic furnace 40. The presence of a space above the semicircular annular support 400 facilitates the removal of the optical resonator 46. In addition, since the length of the water cooling tube in the vertical direction is reduced, flow disturbance due to convection in the water cooling tube can be easily prevented. It should be noted that corresponding pores can be created in the surface of the flange 396 in FIGS. 33A and 33B. In the case of creating pores, the heat transfer efficiency decreases, but a reduction in mass can be ensured. Similarly, corresponding pores may be formed in the surface of flange 352 in FIGS. 31A and 31B.

[0174] FIG. 34 is a sectional view of a coil 410 for a Zeeman moderator of an increasing type according to another embodiment. The coil 410 for a Zeeman moderator comprises a core 412 with a thickness that varies in the beam direction. The cylindrical core 412 has a constant inner diameter, but its outer diameter gradually decreases in steps in the direction from top to bottom along the beam path. The coil 414 wound on the core 412 comprises a greater number of turns on the downstream side in the beam axis direction. Therefore, the outer diameter of the coil 414 is substantially constant in the beam axis direction.

[0175] In the configuration of FIG. 34, increasing the outer diameter of the core 412 increases the contact area of the core 412 with the coil 414. This increases the efficiency of heat transfer from the coil 414 to the core 412. The steps 12 of the core 4 provide the possibility of winding a wire with an insulated core, which facilitates the installation of the coil 414.

[0176] It should be noted that this embodiment may not be limiting; instead of a round wire of a round cross-section, it is possible to use a rectangular flat wire of a rectangular cross-section as a wire with an insulated core in the composition of the coil 414, which can further improve the efficiency of heat transfer to the body 412 and the like. As disclosed below, if the peripheral portion of the coil 414 is covered with a heat-conducting casing, and the outer diameter of the coil 414 is constant, this facilitates bringing the casing into direct contact with the coil 414 and dissipating heat through the casing.

[0177] An example of installing a Zeeman moderator in a vacuum chamber 20 was disclosed above. A cooling circuit was created by removing the Joule heat generated by the coil, which makes it possible to install the Zeeman moderator in a thermally stable manner in the vacuum chamber 20. Next, as another example, an example of sealing the coil, partially or completely, with a casing (i.e., enclosing it in a shell) will be disclosed.

[0178] FIGS. 35A and 35B are side cross-sectional views showing the Zeeman moderator coil 420 and the housing 440. FIG. 35A shows a state before the housing 440 is attached to the Zeeman moderator coil 420. FIG. 35B shows a state after the attachment. The Zeeman moderator coil 420 is a decreasing type coil in which the number of turns of the coil gradually decreases in the beam axis direction.

[0179] The frame 422 of the coil 420 for the Zeeman moderator is provided with a flange 424 at the end of the upper side along the beam axis, and also with a flange 426 in the middle position on the lower side along the beam axis. As in the example disclosed above, the frame 422 and the flanges 424 and 426 are made of copper or a similar substance that provides high thermal conductivity. The outer peripheral sections of the flanges 424 and 426 are provided with sealing elements 428 and 430, respectively, made of indium. The sealing elements 428 and 430 are made in the form of an annular relatively thin plate or a thick ring. Indium has a property that allows for a stable vacuum seal to be provided even with large temperature differences. The flange 426 is provided with a hermetic connector 432, which is a vacuum-resistant connector.

[0180] The coil 434 is wound on the core 422 between the flange 424 and the flange 426. The coil 436 is wound on the downstream side of the flange 426. The coils 434 and 436 are each individually formed from a wire with an insulated core containing copper insulated with resin. The coil 434 and the coil 436 are electrically connected by means of a sealed connector 432.

[0181] The casing 440 is formed in the form of a cylinder. The casing 440 is formed of copper, similar to the frame 422, the flanges 424 and 426, and the coils 434 and 436, which prevents deformation due to thermal expansion.

[0182] The casing 440 is installed with the possibility of creating a cover from the flange 424 to the flange 426. That is, a part of the inner peripheral section of the upper end of the casing 440 contains a part of the outer peripheral section of the flange 424 and is sealed by a sealing element 428. A part of the inner peripheral section of the lower end of the casing 440 contains a part of the outer peripheral section of the flange 426 and is sealed by a sealing element 430. The casing 440 is designed with the possibility of having a plus tolerance along the length from the flange 424 to the flange 426, due to which it can be guaranteed to contain both flanges.

[0183] The unimpeded establishment of atmospheric pressure in the casing 440 is possible only if the sealing elements 428 and 430 can guarantee protection. For example, air under atmospheric pressure can be enclosed in the casing, or evacuation to a pre-vacuum can be used. Evacuation to a pre-vacuum is a state of creating a vacuum using a turbo pump or the like with a set value of approximately 1-0.1 Pa, for example. In the case of evacuating the inner space of the casing 440 to a pre-vacuum, the pressure difference between the spaces inside and outside the casing 440 is small in a situation where the vacuum chamber 20 is in a vacuum state. This makes it possible to reliably prevent the surfaces sealed by the sealing elements 428 and 430 from separating from each other.

[0184] An inert gas, in particular nitrogen or helium, may be enclosed within the casing 440. The inert gas is selected to be a gas with a low ability to react with the resin used for the coil when the temperature of the coil 434 is high. The pressure of the inert gas is not limited to any particular values and may be atmospheric pressure or a pumping pressure to a preliminary vacuum. The interior of the casing 440 may be filled, for example, with a light resin, in particular urethane foam. This makes it possible to increase the strength of the casing 440.

[0185] The temperature of the Zeeman moderator coil 420 becomes high due to the Joule heat when the voltage is applied. The coil 434 with a greater number of turns generates more Joule heat than the coil 436 with a lesser number of turns. Therefore, the coil 434 is prone to generating a high temperature. When the temperature increases, a small amount of gas (called "evolved gas") contained in the resin of the insulated core wire in the coil 434 is ejected. However, in the Zeeman moderator coil 420, the coil 434 is sealed by the core 422, the flanges 424 and 426, and the casing 440. Therefore, no amount of evolved gas leaks into the vacuum chamber 20. This prevents the occurrence of a clock transition error that would otherwise be caused by the evolved gas. Therefore, the Zeeman moderator coil 420 sealed by the housing 440 functions as a vacuum installation coil with high suitability for use in the case of installation in a vacuum.

[0186] The casing 440 also forms a heat transfer medium between the flange 424 and the flange 426. That is, heat transfer between the flange 424 and the flange 426 occurs not only through the frame 422, but also through the casing 440. This also provides a useful effect consisting of cooling the coils 434 and 436.

[0187] In the above description, it is assumed that the casing 440 covers the outer peripheral portions of the flanges 424 and 426, but is not in contact with the coil 434. In this case, the casing 440 may be in contact with a part of the outer peripheral surface of the coil 434 or with the entire surface. In this case, heat is transferred from the coil 434 directly to the casing 440, which improves the efficiency of heat radiation. In particular, if the coil 414 has a constant outer diameter, as in the case of the coil 414 in FIG. 34, it is possible to easily ensure direct contact with the inner peripheral portion of the casing 440. If it is difficult to shape the casing 440 so as to ensure contact with the outer peripheral surface of the coil 434, a heat-conducting member can be inserted between the casing 440 and the coil 434.

[0188] In the embodiment of FIG. 35A and 35B, the coil 434 is not covered by the casing 440. This is due to the fact that the number of turns of the coil 434 is small, and the need to combat the emission of the released gas is insignificant. The coil 434 is a section including the MOT coil in the MOT device, and the optical resonator 46 and the like are located in close proximity to this section. This makes it possible to avoid an increase in diameter due to the covering of the coil 434 by the casing. However, if the coupling with the surrounding devices and components can be avoided, the entire part including the coil 434 can be covered by the casing and enclosed in a shell.

[0189] FIG. 35A and 35B show an example of a decreasing type coil 420 for a Zeeman moderator. However, even in the case of an increasing type coil, the part including the section with a large number of turns may be partially or completely enclosed in a shell.

[0190] It should be noted that in the above description it is assumed that the casing 440 is in direct contact with the flanges 424 and 426 provided with indium sealing elements 428 and 430, and its internal space is sealed. Alternatively, it is possible to use sealing elements made of a substance other than indium. In the case of using sealing elements, the casing 440 can be removably attached to the flanges 424 and 426 using fastening screws, for example. Alternatively, for example, the casing 440 and the flanges 424 and 426 can be brought into direct contact with each other by creating a semi-permanent seal, for example, by welding or soldering in a vacuum, and the internal space can be sealed.

[0191] The above examples are about optical lattice clocks. However, those skilled in the art will be able to apply each of the technical solutions of this embodiment to devices that are not optical lattice clocks. In particular, this technical solution can find application in an atomic clock that is not an optical lattice clock and in an atomic interferometer, which is an interferometer using atoms. In addition, this embodiment can find application in various devices for processing quantum information for atoms (including ionized atoms). In this case, quantum information processing devices are devices that measure, detect and process information based on the quantum states of atoms and light and can be, for example, a magnetic field meter, an electric field meter, a quantum computer, a quantum computer emulator, a quantum repeater, etc., in addition to an atomic clock and an atomic interferometer. The use of the technical solution according to this embodiment allows for miniaturization or transportability of the physical part of the quantum information processing device by analogy with the physical part of the clock on an optical lattice. It should be noted that the clock transition space in such devices in some cases is not a time measurement space, but serves simply as a space for clock transition spectroscopy.

[0192] For example, providing a magnetic field correction coil in three axes according to this embodiment in such a device can improve the accuracy of the device. Providing three axes according to this embodiment in a vacuum chamber can ensure miniaturization, transportability or increase in the accuracy of the physical part. In addition, introducing a magnetic field compensation module can adjust the magnetic field distribution with high accuracy. In the physical part using a vacuum chamber, it is effective to use a vacuum unit coil.

[0193] For ease of understanding, particular aspects have been disclosed above. They are examples of embodiments of the invention, which can be implemented in various other embodiments.

[0194] Supplements to the embodiments are disclosed below.

(Addendum 1)

Magnetic field compensation module containing:

a current device provided in a vacuum chamber containing a clock transition space in which atoms are located, with the possibility of current flowing through it for the device and generating a parasitic magnetic field;

a compensation coil installed in close proximity to the current device with the possibility of current flowing through it for the coil; and

a control means for dynamically changing the current for the coil, which must flow through the compensation coil, and compensating for the parasitic magnetic field in relation to the space of the clock transition.

(Addendum 2)

The magnetic field compensation module according to Supplement 1, in which the current device is a Peltier element cooling an isothermal cryostat reservoir maintaining a predetermined low temperature of the space of the clock transition, and

the control means is designed to change the current for the coil depending on the temperature of the isothermal cryostat tank or the current for the device that must flow through the Peltier element.

(Addendum 3)

A magnetic field compensation module according to Supplement 1, in which a magnetic screen made of a material with high magnetic permeability is installed near the current device, and

The compensation coil compensates for the parasitic magnetic field created by the magnetic shield.

(Addendum 4)

A magnetic field compensation module according to Supplement 1, wherein the control means includes a distribution wire configured to separate the current for the coil from the current for the device and to distribute the current for the coil depending on the current for the device.

(Addendum 5)

A physical part system for an optical lattice clock, comprising a magnetic field compensation module according to Supplement 1.

(Addendum 6)

A physical part system for an atomic clock containing a magnetic field compensation module according to Appendix 1.

(Addendum 7)

Physical part system for an atomic interferometer containing a magnetic field compensation module according to Appendix 1.

(Addendum 8)

A physical part system for a quantum information processing device for atoms or ionized atoms, comprising a magnetic field compensation module according to Supplement 1.

(Addendum 9)

A system of a physical part comprising: a magnetic field compensation module according to Supplement 1; and at least one device based on laser cooling technology of atoms from among a Zeeman moderator, a magneto-optical trap and a trap on an optical lattice, directing atoms into the space of a clock transition.

(Addendum 10)

A physical part comprising: a vacuum chamber; and

a Zeeman moderator comprising a core made in the form of a cylinder with the ability to ensure the flow of an atomic beam along the axis of the beam in the cylinder, and a set of coils wound on the core and made with the ability to form a magnetic field with a spatial gradient in the cylinder,

wherein the frame is provided with a flange on which the outer surface of the cylinder is radially enlarged in an intermediate position in the direction of the beam axis,

and the coils from the set of coils are wound on the frame outside

flange, and

In this case, the Zeeman moderator is installed in a vacuum chamber with the possibility of direct or indirect attachment of the flange to the vacuum chamber.

(Addendum 11)

Physical part according to supplement 10,

in which the set of coils is of an increasing type, in which the number of turns on the side downstream of the atomic beam is greater than on the side upstream of the atomic beam, and

The flange is located on the downstream side of the frame.

(Addendum 12)

Physical part according to Supplement 11,

in which the vacuum chamber is essentially in the form of a cylinder with a central axis parallel to the beam axis, and

The flange is attached to the cylindrical wall on the lower side along the direction of the atomic beam in the vacuum chamber indirectly by means of a support element.

(Addendum 13)

Physical part according to Supplement 12,

in which the flange is made essentially circular in shape,

the support element includes a substantially circular annular support on which the outer edge of the flange rests, and

essentially a circular ring-shaped support equipped with a cooling circuit with the possibility of liquid coolant flowing through the tube and cooling the flange.

(Addendum 14)

Physical part according to Supplement 12,

in which the flange is essentially in the form of a sector and is increased in size along one of the directions, including a vertically downwardly directed component,

the support element includes a substantially U-shaped support on which the outer edge of the flange rests, wherein

In essence, the U-shaped support is equipped with a cooling circuit with

the possibility of liquid refrigerant flowing through the tube and cooling the flange.

(Addendum 15)

Physical part according to supplement 10,

in which the frame and flange are made of metal, and

The physical part is equipped with a cooling circuit with the possibility of direct or indirect cooling of the flange.

(Addendum 16)

The physical part of Appendix 10, additionally containing:

an opposite coil wound around the beam axis in a position located on the lower side of the atomic beam from the Zeeman moderator,

where the set of coils and the opposite coil create a magnetic field MOL between the set of coils and the opposite coil.

(Addendum 17)

Physical part for the optical lattice clock, including the physical part according to supplement 10.

(Addendum 18)

Physical part for atomic clocks, including physical part according to supplement 10.

(Addendum 19)

Physical part for atomic interferometer, including physical part according to Supplement 10.

(Addendum 20)

A physical part for a device for processing quantum information for atoms or ionized atoms, including the physical part according to Supplement 10.

(Addendum 21)

Vacuum installation coil, including:

a coil installed in a vacuum chamber, wound around the beam axis along which the atomic beam flows, and forming a magnetic field with a spatial gradient; and

a sealing element that hermetically encloses the coil

partially or completely.

(Addendum 22)

A vacuum unit coil according to Supplement 21, in which the sealing element is made of metal.

(Addendum 23)

A vacuum unit coil according to Supplement 21, in which the sealing element comprises:

a cylindrical frame located on the inner peripheral side of the coil, on which the coil is wound;

two flanges representing enlarged outer surfaces of the core cylinder and enclosing the end surfaces of the coil in the direction of the beam axis; and

a casing enclosing the outer peripheral side of the coil between two flanges.

(Addendum 24)

A vacuum installation coil according to Supplement 23, wherein the casing comprises at least a portion of the outer peripheral portions of said two flanges.

(Addendum 25)

Vacuum installation coil according to Supplement 23,

in which the casing is in direct contact with a portion of the outer peripheral side of the coil or with the entire outer peripheral side of the coil or in indirect contact with it through a heat-conducting element inserted into a space enclosed within the sealing element.

(Addendum 26)

A coil of a vacuum installation according to Supplement 21, having a variable number of turns in the direction of the beam axis, wherein the length enclosed within the sealing element includes a section with a maximum number of turns in the coil.

(Addendum 27)

A vacuum coil according to Supplement 21, in which a vacuum below atmospheric pressure is maintained in the space enclosed within the sealing element.

(Addendum 28)

A vacuum installation coil according to Supplement 21, in which an inert gas is contained in the space enclosed within the sealing element.

(Addendum 29)

A vacuum installation coil according to Supplement 21, in which the space enclosed within the sealing element is filled with foam resin.

(Addition 30)

A vacuum installation coil for an optical lattice watch according to Supplement 21, wherein the sealing element includes a vacuum-resistant connector,

wherein the section of the coil hermetically enclosed within the sealing element and the section not enclosed within it are electrically connected via a vacuum-resistant connector.

(Addendum 31)

A physical part comprising: a vacuum installation coil according to Supplement 21; and a vacuum chamber.

(Addendum 32)

Physical part according to Supplement 31,

in which the coil is a decreasing type coil with a relatively small number of turns on the lower side along the direction of the atomic beam,

the physical part includes an opposite coil wound around the beam axis in a position located on the lower side of the atomic beam from the descending type coil,

the descending type coil and the counter coil form a gradient magnetic field for the MOT device between the descending type coil and the counter coil, and

the sealing element hermetically encloses the section that includes the uppermost side in the coil along the axis of the bundle, and does not enclose the section that includes the lowermost side along the axis.

(Addendum 33)

Physical part according to Supplement 31,

in which the coil is a rising type coil with a relatively large number of turns on the downstream side of the atomic beam,

wherein the physical part includes an opposite coil wound around the beam axis in a position located on the lower side of the atomic beam from the coil of the increasing type,

wherein the rising coil and the counter coil form a gradient magnetic field for the MOT device between the rising coil and the counter coil, and

In this case, the sealing element hermetically encloses a section that includes the lowest side of the coil along the axis of the bundle.

(Addendum 34)

Physical part for the optical lattice clock, including the physical part according to Supplement 31.

(Addition 35)

Physical part for atomic clocks, including the physical part according to Supplement 31.

(Addendum 36)

Physical part for atomic interferometer, including physical part according to Supplement 31.

(Addendum 37)

A physical part for a device for processing quantum information for atoms or ionized atoms, including the physical part according to Supplement 31.

(Addendum 38)

A sealing element that seals a coil installed in a vacuum chamber, wound around the beam axis along which the atomic beam flows, and forming a magnetic field with a spatial gradient,

in which the area between the sealing element and the side of the coil is sealed with indium formed in the form of an annular plate or a thick ring and hermetically enclosing a part of the coil or the entire coil.

List of reference designations

[0195] 10 - clock on optical lattice, 12 - physical part, 14 - optical system device, 16 - control device, 18 - PC, 20 - vacuum chamber, 22 - main body, 24 - cylindrical wall, 26 - front circular wall, 28 - rear circular wall, 30 - protruding part, 32 - cylindrical wall, 34 - front circular wall, 38 - leg, 40 - atomic furnace, 42 - atomic beam, 44 - coil for Zeeman moderator, 44 - flange, 46 - optical resonator, 48 - coil for MOT device, 48a - flange, 50 - collection space, 52 - clock transition space, 54 - cryostat reservoir, 56 - thermal connecting element, 58 - refrigeration device, 58a - Peltier element, 58b - radiator panel, 58c - heat-insulating element, 58d, 58e - permalloy magnetic shield, 60 - main body of vacuum pump, 62 - vacuum pump cartridge, 64, 66 - vacuum-resistant optical window for optical grating, 68 - vacuum-resistant optical window for MOT light, 70, 72 - vacuum-resistant optical window for MOT light, 74, 76 - optical mirror, 80 - optical grating optical beam, 82 - optical beam of Zeeman moderator, 84, 86a, 86b - MOT optical beam, 90 - cooler for atomic furnace, 92 - cooler for Zeeman moderator, 94 - cooler for MOT device, 96 - three-axis magnetic field correction coil, 98 - vacuum-resistant electrical connector, 102 - individual magnetic field compensation coil for a refrigeration device, 104 - individual magnetic field compensation coil for an atomic furnace, 120 - first group of coils, 122, 124 - coil, 130 - second group of coils, 132, 134 - coil, 136, 138 - pointer, 140 - first group of coils, 142 - composite coil, 143, 144 - coil, 145 - composite coil, 146, 147 - coil, 150 - second group of coils, 152, 154 - coil, 160 - first group of coils, 162 - composite coil, 163, 164 - coil, 165 - composite coil, 166, 167 - coil, 170 - second group of coils, 172, 174 - coil, 180 - holder, 182, 184, 186 - frame, 190 - correction coil, 192 - conductive path, 194 - insulator, 196 - interconnection space, 198 - end clamp, 199 - boundary part, 200, 202, 203, 204, 206, 208 - conductive path, 210 - correction coil, 212, 214 - conductive path, 218 - physical part, 220 - vacuum chamber, 222 - main body, 224, 230 - three-axis magnetic field correction coil, 240 - atomic population, 242 - correction space, 243 - fluorescence observation space, 244 - fluorescence radiation, 246 - optical receiver, 250 - atomic population, 252a, 252b, 252c, 252d, 252e - fluorescence radiation, 254 - CCD camera, 260 - temperature sensor, 262 - control device, 264 - temperature sensor, 266 - conductive path, 268 - conductive path, 270 - parasitic magnetic field, 272 - compensating magnetic field, 280 - frame, 282 - coil, 284 - Zeeman coil-forming section, 286 - MOT coil-forming section, 288 - upstream flange, 290, 292 - downstream flange, 300 - frame, 302 - MOT coil, 304, 306 - flange, 312 - upper support element, 314 - lower support element, 320 - Zeeman coil, 322 - section, 330 - Zeeman coil, 332 - section, 340 - coil for Zeeman moderator, 342 - coil, 344 - section forming Zeeman coil, 346 - section forming MOT coil, 350, 352, 354 - flange, 370 - circular annular support, 372 - water cooling tube, 374, 376 - beam, 380 - coil for MOT device, 390 - coil for Zeeman moderator, 392 - coil, 394, 396, 398 - flange, 400 - semicircular annular support, 402 - water cooling tube, 410 - coil for Zeeman moderator, 412 - frame, 414 - coil, 420 - coil for Zeeman moderator, 422 - frame, 424, 426 - flange, 428, 430 - sealing element, 432 - hermetic connector, 434, 436 - coil, 440 - casing.

Claims (19)

1. A physical part for an optical lattice clock, comprising: a magneto-optical trap (MOT) device located along the axis of the atomic beam and capable of trapping a population of atoms; an optical lattice forming section configured to form an optical lattice using incident light from the optical lattice, retaining the population of atoms captured by the MOT device in the optical lattice, and moving the population of atoms into the clock transition space to excite the clock transition along the axis of movement perpendicular to the beam axis; and a vacuum chamber comprising a substantially prism-shaped main body containing the MOT device and an optical grating formation section, where the central axis of the vacuum chamber passes through the space of the clock transition and is essentially parallel to the beam axis. 2. The physical part for the clock on the optical lattice according to item 1, in which the vacuum chamber includes a protruding portion that projects from the main body along the beam axis, wherein the physical part additionally comprises a moderator, configured to slow down the population of atoms, on the upper side of the MOT device along the beam axis, and The retarder is located on both sides of the main body and the protruding part. 3. The physical part for the clock on the optical lattice according to item 2, in which the MOL device provides the ability to emit MOL light in both directions of each of the three axes, which include the beam axis and two axes perpendicular to the beam axis and different from the axis of movement. 4. A physical part for a clock on an optical lattice according to item 3, in which the retarder: the possibility of emitting retarding light on the upper side along the beam axis is provided, and the main body includes: a pair of first vacuum-resistant optical windows configured to allow the MOT light and the retarding light to pass through them along the beam axis; and a pair of second vacuum-resistant optical windows configured to allow the MOT light to pass through them along the two axes. 5. A physical part for a clock on an optical lattice according to item 2, additionally comprising: a vacuum pump cartridge configured to evacuate a vacuum chamber, wherein the vacuum pump cartridge is placed in the main body so that it is located in line with the retarder, but offset from the center in a direction different from the direction of the retarder. 6. The physical part for the clock on the optical lattice according to item 1, wherein the substantially prism-shaped main body is formed in the form of a substantially tetrahedral prism, a substantially hexagonal prism, a substantially octagonal prism, or a substantially cylindrical shape.