CN105676559A - Generating device for entanglement of continuous variable atom ensemble - Google Patents

Abstract

The invention relates to a generating device for entanglement of continuous variable atom ensemble and belongs to the generating device for the entanglement of atom ensemble applied to a quantum information network. The generating device is used for solving the technical problem that probability preparation exists in the present preparation for the entanglement of atom ensemble of variables separation. According to the technical scheme provided by the invention, the generating device for entanglement of continuous variable atom ensemble comprises a light source unit, a plurality of beam coupling systems, two sets of atom ensembles, an entanglement measuring system and a feedback unit. The orthogonal component of a light field in the continuous variable quantum information and the collective spin wave of the atom ensemble are utilized to generate the entanglement of two sets of stokes light and spin wave of atom ensemble in a spontaneous raman scattering process, and then interference signals of the two beams of stokes light are fed back to a first atom ensemble through the quantum entanglement exchange, the entanglements of the first atom ensemble and the second atom ensemble are certainly prepared, and the generated stokes light is utilized to measure and analyze the entanglement of the atom ensemble.

Description

A device for generating entanglement of continuous variable atomic ensemble

technical field

The invention relates to a device for generating continuous variable atomic ensemble entanglement, which belongs to a device for generating atomic ensemble entanglement applicable to quantum information networks.

Background technique

Quantum entanglement is not only one of the important contents of quantum mechanics, but also an important resource for quantum information transmission and processing. With the development of quantum information network, the quantum information network composed of light and atoms is the key to the development and application. Due to the advantages of fast transmission speed and weak interaction with the surrounding environment, light is applied to the transmission of quantum information. Atoms can efficiently interact with light, serving as nodes for quantum information processing and storage. Atomic ensembles are one of the effective candidates for implementing quantum network nodes. Therefore, the construction of entanglement between atomic ensembles is the key to the development of quantum information networks, especially the transmission of arbitrary quantum states between atomic ensembles.

In 2005, Professor Kimble's research group at the California Institute of Technology used the spontaneous Raman scattering process to prepare entanglement between atomic ensembles of separated variables, and published a paper entitled "Measurement-induced entanglement for excitation stored in remote atomic ensembles" in Nature 438, 828 (2005). In 2008, the research group of Professor Pan Jianwei of the University of Science and Technology of China used the spontaneous Raman scattering process to prepare the entanglement between the separated variable light and the atomic ensemble, and then established the entanglement between the atomic ensemble through entanglement exchange, in Nature454 , 1098 (2008) published a paper entitled "Experimental demonstration of a BDCZquantum repeater node".

The above two research works used the spontaneous Raman scattering process to probabilistically prepare atomic entanglement of separated variables, which solved the technical problem of atomic ensemble entanglement preparation, but the above methods still have the problem of probabilistic preparation.

Contents of the invention

The purpose of the present invention is to solve the technical problem of probabilistic preparation of the existing entanglement of atomic ensembles of separated variables, and provide a compact and reliable atomic ensemble entanglement of continuous variables that can be applied to quantum information networks. Deterministic generating device.

In order to solve the above technical problems, the technical solution adopted by the present invention is: using the orthogonal component of the light field in the continuous variable quantum information and the collective spin wave of the atomic ensemble to generate two sets of Stokes light through the process of spontaneous Raman scattering Entanglement with the spin wave of the atomic ensemble, and then through quantum entanglement exchange, the feedback of the interference signal of the two beams of Stokes light to the first atomic ensemble, and the deterministic preparation of the first atomic ensemble and the second atomic system ensemble entanglement, and use the generated anti-Stokes light to measure and analyze atomic ensemble entanglement.

A device for generating continuous variable atomic ensemble entanglement, including a light source unit, a beam coupling system, two sets of atomic ensembles, an entanglement measurement system and a feedback unit; the beam coupling system consists of eight Glan Thomson prisms and an optical splitter The entanglement measurement system is composed of four sets of balanced zero-beat detection systems, a power adder and subtractor, and a storable digital oscilloscope; the feedback unit is a variable gain amplifier circuit with band-pass filtering characteristics; the The light source unit is equipped with two beams of pump light pulse signal a _UP , a _DP output end, two beams of write light pulse signal a _UW , a _DW output end, two beams of read light pulse signal a _UR , a _DR output end, four beams Local oscillator optical signal a _UL1 , a _DL1 , a _UL2 , a _DL2 output terminals and four beams of analog optical pulse signals a _UL3 , a _DL3 , a _UL4 , a _DL4 output terminals; among them, the first pumping optical pulse signal a _UP The output end is connected to the first input end of the first atomic ensemble; the output end of the first vertically polarized write optical pulse signal a _UW and the output end of the first horizontally polarized analog optical pulse signal a _UL4 are respectively connected to the first Glan The two input terminals of the Thomson prism, the output terminal of the first Glan-Thomson prism is connected with the second input terminal of the first atomic ensemble; the vertically polarized first read light pulse signal a _UR output terminal and the horizontally polarized The output terminals of the second analog light pulse signal a _UL3 are respectively connected to the two input terminals of the second Glan Thomson prism, and the output terminal of the second Glan Thomson prism is connected to the third input terminal of the first atomic ensemble; The first and second output terminals of the first atomic ensemble are respectively connected to the input terminals of the third and fourth Glan-Thomson prisms; the output terminal of the second pump light pulse signal a _DP is connected to the first The input end is connected; the output end of the second beam of vertically polarized writing optical pulse signal a _DW and the output end of the third beam of analog optical pulse signal a _DL4 of horizontal polarization are respectively connected to the two input ends of the fifth Glan-Thomson prism, the first The output end of the five Glan-Thomson prisms is connected with the second input end of the second atomic ensemble; the output end of the second read light pulse signal a _DR of the vertical polarization and the fourth analog light pulse signal a _DL3 of the horizontal polarization The output ends are respectively connected to the two input ends of the sixth Glan Thomson prism, and the output end of the sixth Glan Thomson prism is connected to the third input end of the second atomic ensemble; The second output end is respectively connected to the input end of the seventh and eighth light Glan Thomson prisms; the output ends of the third and seventh Glan Thomson prisms are connected to the two input ends of the optical beam splitter, and the optical beam splitter The two output terminals of the first and second balanced zero beat detection systems are respectively connected to the first input terminals, and the output terminals of the first and second beams of local oscillation optical signals a _UL1 and a _DL1 are respectively connected to the first and second balanced zero beat detection systems. The second input end of the beat detection system, the output ends of the first and second balanced zero-beat detection systems are connected to the radio frequency coil of the first atomic ensemble through the feedback unit; the output ends of the fourth and eighth Glan Thomson prisms are respectively Connect the third and fourth balance The first input terminal of the zero-beat detection system, the output terminals of the third and fourth beams of local oscillation optical signals a _UL2 and a _DL2 are respectively connected to the second input terminals of the third and fourth balanced zero-beat detection systems, the third and fourth The output end of the balanced zero-beat detection system is connected with a storable digital oscilloscope through a power adder and subtractor.

The light source unit is composed of a tunable laser, a single-mode 1x7 fiber coupler, seven sets of acousto-optic modulators and seven sets of optical beam splitters. The output end of the tunable laser is connected to the input end of the single-mode 1x7 fiber coupler. The output end of the mode 1x7 fiber optic coupler is connected with the input end of seven sets of AOMs, and the output ends of seven sets of AOMs are connected with the input ends of seven sets of optical beam splitters; so that seven sets of AOMs and seven sets The optical beam splitter generates two beams of pumping optical pulse signals a _UP , a _DP , two beams of writing optical pulse signals a _UW , a _DW , two beams of reading optical pulse signals a _UR , a _DR , and four beams of local oscillator optical signals a _UL1 , a _DL1 , a _UL2 , a _DL2 and four analog light pulse signals a _UL3 , a _DL3 , a _UL4 , a _DL4 .

The first atomic ensemble is composed of a cubic atomic gas chamber, a radio frequency coil, a magnetic shielding system and a temperature control system; the magnetic shielding system is composed of a magnetic shielding paper and a metal magnetic shielding cylinder; the cubic atomic gas chamber is filled with atomic gas and a certain amount of buffer inert gas, the light-transmitting surface of the cubic atomic gas chamber is coated with an anti-reflection film corresponding to the wavelength of the laser; the cubic atomic gas chamber is placed in the radio frequency coil; the outer layer of the radio frequency coil is wrapped with magnetic shielding paper, and the It is placed in a metal magnetic shielding cylinder; on the outer layer of the magnetic shielding cylinder, a temperature control system composed of a heating belt, heat preservation material and temperature control equipment is used to heat the rubidium atoms and precisely control the temperature.

The second atomic ensemble is composed of a cubic atomic gas chamber, a magnetic shielding system and a temperature control system; the magnetic shielding system is composed of a magnetic shielding paper and a metal magnetic shielding cylinder; the cubic atomic gas chamber is filled with atomic gas and a certain amount of The buffer inert gas of the cubic atomic gas chamber is coated with an anti-reflection film corresponding to the wavelength of the laser; the outer layer of the cubic atomic gas chamber is wrapped with magnetic shielding paper and placed in a metal magnetic shielding cylinder; The outer layer of the magnetic shielding tube uses a temperature control system consisting of heating tape, insulation materials and temperature control instruments to heat the rubidium atoms and precisely control the temperature.

The present invention adopts the above-mentioned technical scheme, uses the spontaneous Raman scattering process of the interaction between light and atoms to generate the orthogonal component of Stokes light and the entanglement of atomic ensemble spin waves, and utilizes quantum entanglement exchange to establish a deterministic Entanglement of atomic ensembles. The spontaneous Raman scattering process of the interaction between light and atoms generates anti-Stokes light, which maps the quantum state of the atomic ensemble spin wave to the quantum state of anti-Stokes light, and then by measuring the anti-Stokes light The correlated noise of the quadrature components, verifying the entanglement of the Stokes components of the spin waves of two sets of atomic ensembles. Therefore, compared with the background technology, the present invention has the advantages of compact structure, good reliability, deterministic preparation and measurement. The present invention has the following beneficial effects:

1. The spontaneous Raman scattering process of the interaction between light and atoms used in the present invention produces the entanglement of the orthogonal component of the Stokes light and the Stokes component of the atomic ensemble spin wave.

2. The spontaneous Raman scattering process of the interaction between light and atoms used in the present invention produces anti-Stokes light, and verifies the entanglement of the atomic ensemble spin wave. The amount of photon detuning that enables optimal atomic ensemble entanglement.

3. The continuous variable light and atomic entanglement generated by the spontaneous Raman scattering process utilized in the present invention, through Stokes light interference, measurement, and feedback, the entanglement of the atomic ensemble is deterministically prepared and measured.

4. The cubic atomic gas chamber of the first atomic ensemble used in the present invention is placed in the radio frequency coil for the realization of entanglement exchange feedback.

5. The entanglement exchange feedback unit used in the present invention uses an amplifying circuit with frequency filtering and variable gain factors, and by selecting frequencies and adjusting gain factors, the best atomic ensemble entanglement can be realized.

6. The thermal atomic ensemble system used in the present invention is simple and stable.

The continuous variable atomic ensemble entanglement state produced by the invention is suitable for use in quantum information networks including atoms, especially for establishing entanglement between nodes in the quantum information network.

Description of drawings

Fig. 1 structural representation of the present invention;

Fig. 2 is a schematic structural view of the light source unit of the present invention;

Fig. 3 is the control timing diagram of the optical signal of the present invention;

Fig. 4 is a schematic diagram of the energy level of the atomic ensemble of the present invention;

Fig. 5 is a schematic structural diagram of the first atomic ensemble of the present invention;

Fig. 6 is a schematic structural diagram of the second atomic ensemble of the present invention;

Fig. 7 is a schematic structural diagram of the entanglement measurement system of the present invention.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, a device for generating continuous variable atomic ensemble entanglement in this embodiment includes a light source unit 1, a beam coupling system, two sets of atomic ensembles 3 and 4, an entanglement measurement system and a feedback unit 11; The beam coupling system is composed of eight Glan Thomson prisms 21-28 and an optical beam splitter 29; Composed of a digital oscilloscope 10; the feedback unit 11 is a variable gain amplifier circuit with band-pass filter characteristics; the light source unit 1 is provided with two beams of pumping light pulse signal a _UP , a _DP output end, two beams of writing Optical pulse signal a _UW , a _DW output end, two beams of read optical pulse signal a _UR , a _DR output end, four beams of local oscillator optical signal a _UL1 , a _DL1 , a _UL2 , a _DL2 output end and four beams of analog optical pulse The output terminals of the signal a _UL3 , a _DL3 , a _UL4 , and a _DL4 ; wherein, the output terminal of the first beam of pump light pulse signal a _UP is connected to the first input terminal of the first atomic ensemble 3 ; the vertically polarized first beam writes The output end of the optical pulse signal a _UW and the output end of the first horizontally polarized analog optical pulse signal a _UL4 are respectively connected to the two input ends of the first light beam Glan Thomson prism 21, and the output end of the first Glan Thomson prism 21 It is connected with the second input end of the first atomic ensemble 3; the output end of the first read optical pulse signal a _UR of the vertical polarization and the output end of the second analog optical pulse signal a _UL3 of the horizontal polarization are respectively connected to the second Glan The two input terminals of the Thomson prism 22, the output terminal of the second light Glan-Thomson prism 22 are connected with the third input terminal of the first atomic ensemble 3; the first and second output terminals of the first set of atomic ensemble 3 The terminals are respectively connected to the input terminals of the third and fourth optical Glan-Thomson prisms 23 and 24; the output terminal of the second pump light pulse signal a _DP is connected to the first input terminal of the second atomic ensemble 4; the vertically polarized The output end of the second writing light pulse signal a _DW and the output end of the third horizontally polarized analog light pulse signal a _DL4 are respectively connected to the two input ends of the fifth Glan Thomson prism 25, and the fifth light Glan Thomson prism The output end of 25 is connected with the second input end of the second atomic ensemble 4; the output end of the second beam read pulse signal a _DR of the vertical polarization and the output end of the fourth beam analog optical pulse signal a _DL3 of the horizontal polarization are respectively connected Two input ends of the sixth Glan Thomson prism 26, the output end of the sixth light Glan Thomson prism 26 is connected with the third input end of the second atomic ensemble 4; 1. The second output end is respectively connected to the input ends of the seventh and eighth Glan Thomson prisms 27,28; the output ends of the third and seventh light Glan Thomson prisms 23,27 and two The input terminals are connected, the two output terminals of the optical beam splitter 29 are connected to the first input terminals of the first and second balanced zero-beat detection systems 5 and 6, and the first and second local oscillator optical signals a _UL1 and a _DL1 The output terminals are respectively connected to the 1. The second input terminals of the second balanced zero-beat detection system 5, 6, the output terminals of the first and second balanced zero-beat detection systems 5, 6 are connected to the radio frequency coil of the first atomic ensemble 3 through the feedback unit 11; The output terminals of the fourth and eighth Glan-Thomson prisms 24 and 28 are respectively connected to the first input terminals of the third and fourth balanced zero-beat detection systems 7 and 8, and the third and fourth beams of local oscillator optical signals a _UL2 , a The _DL2 output terminal is respectively connected to the second input terminal of the third and fourth balanced zero-beat detection systems 7 and 8, the output terminals of the third and fourth balanced zero-beat detection systems 7 and 8 and the input of the power adder and subtractor 9 The output terminal of the power adder-subtractor 9 is connected with the digital oscilloscope 10.

As shown in Fig. 2, the light source unit includes a tunable laser 91, a single-mode 1x7 fiber coupler 19, seven sets of acousto-optic modulators 12-18 and seven sets of optical beam splitters 12b-18b. The output end of the tunable laser 91 is connected to the input end of the single-mode 1x7 fiber coupler 19, the output end of the single-mode 1x7 fiber coupler 19 is connected to the input ends of seven sets of acousto-optic modulators 12-18, and the seven sets of acousto-optic modulators The output ends of 12-18 are connected to the input ends of seven sets of optical beam splitters 12b-18b; among them, the tunable laser 91 is a low-noise, narrow-linewidth, tunable Ti:Sapphire laser. The titanium sapphire laser outputs 795nm laser light, which corresponds to the D1 absorption line of rubidium 87 atoms, and the laser light is divided into seven beams through seven sets of acousto-optic modulators 12-18 and seven sets of optical beam splitters 12b-18b, of which the first The light beam is converted into pump light pulse signals a _UP , a _DP by the acousto-optic modulator 12 and the optical beam splitter 12b, which are used for the initial state preparation of the first atomic ensemble 3 and the second atomic ensemble 4 . The second beam of light is converted into write light pulse signals a _UW , a _DW by the acousto-optic modulator 13 and the optical beam splitter 13b, and through the spontaneous Raman scattering process, small-angle Stokes lights a _US , a _DS are generated, Establishment of entanglement between two sets of light and atomic ensembles. The third beam of light is converted into read pulse signals a _UR , a _DR by the acousto-optic modulator 14 and the optical beam splitter 14b, and through the spontaneous Raman scattering process, small-angle anti-Stokes light a _UAS , a _DAS are generated , and map the quantum states of the first and second atomic ensembles 3 and 4 to the quantum states of the anti-Stokes light a _UAS , a _DAS , by measuring the Stokes light a _US , a _DS and the anti-Stokes light Correlation properties of a _UAS and a _DAS of the Kex light, verifying the entanglement characteristics between the two sets of atomic ensembles; at the same time, the write light a _W , the read light a _R , the Stokes light a _S and the anti-Stokes light a _AS satisfies the energy conservation relation ω _W + ω _R ＝ ω _S + ω _AS and the momentum conservation relation The fourth beam of light is converted into local oscillation optical signals a _UL1 , a _DL1 by the acousto-optic modulator 15 and the optical beam splitter 15b. The fifth beam of light is converted into local oscillation optical signals a _UL2 , a _DL2 by the acousto-optic modulator 16 and the optical beam splitter 16b. The sixth beam of light is converted by the acousto-optic modulator 17 and the optical beam splitter 17b into analog optical pulse signals a _UL3 , a _DL3 of Stokes light a _US , a _DS , which are used to simulate Stokes light in a balanced zero-beat detection system. Stokes light a _US , a _DS , and lock the interference phase difference of the measurement signal light and local oscillator light a _UL1 , a _DL1 at 0 and Pi/2 respectively, and then measure the Stokes light a _US , a _DS positive quadrature amplitude and quadrature phase components. The seventh beam of light is converted by the acousto-optic modulator 18 and the optical beam splitter 18b into analog optical pulse signals a _UL4 , a _DL4 of anti-Stokes light a _UAS , a _DAS , which are used to simulate in a balanced zero-beat detection system Anti-Stokes light a _UAS , a _DAS , and lock their interference phase difference with local oscillator light a _UL2 , a _DL2 at 0 and Pi/2 respectively, and then measure the anti-Stokes light a _UAS , a _DAS Quadrature amplitude and quadrature phase components.

As shown in FIG. 3 , the corresponding timing control is realized by using the switching characteristics of the seven sets of AOMs 12 - 18 . The entire control cycle takes one millisecond. The local oscillator light signal of the balanced zero-beat detection system is always on, and outputs strong local oscillator light a _UL1 , a _DL1 and a _UL2 , a _DL2 . The analog lights a _UL3 , a _DL3 and a _UL4 , a _DL4 of the Stokes light and the anti-Stokes light are turned off within ten microseconds of the interaction between the light and the atom, and the rest of the time is turned on and a strong analog light is output, using For the phase locking of Stokes light a _US , a _DS and anti-Stokes light a _UAS , a _DAS in a balanced zero-beat detection system. After the analog lights a _UL3 , a _DL3 and a _UL4 , a _DL4 of Stokes light and anti-Stokes light are turned off, a microsecond strong pulse signal a _UP , a _DP is generated to drive the first atomic ensemble 3 1. The rubidium 87 atom of the second atomic ensemble 4 is prepared to an initial state. After the pump light pulse signal acts, the strong write light pulse signals a _UW , a _DW are turned on for 500 nanoseconds, and two sets of Stokes light a _US , a _DS and the entangled state of the atomic ensemble are obtained. After the entanglement between the light and the atom is maintained for one hundred nanoseconds, the weak read light pulse signals a _UR , a _DR are turned on for five hundred nanoseconds to obtain the anti-Stokes light a _UAS , a _DAS .

As shown in Figure 4, the first atomic ensemble 3 and the second atomic ensemble 4 both adopt the F=1 and F=2 of 5 ² S _1/2 and the 5 ² P _1/2 of rubidium 87 atoms The ultra-fine energy levels of F′=1 and F′=2 use the tuning characteristics of the Ti:sapphire laser and the frequency shifting characteristics of the acousto-optic modulators 12-18 to obtain optical signals of corresponding wavelengths. The frequencies of the pump light pulse signals a _UP and a _DP resonate with the transition absorption line from F=2 of 5 ² S _1/2 to F,=1 of 5 ² P _1/2 , and are prepared to the ground state 5 ² P _1/2 F = 1 state; the frequency of write optical pulse signal a _UW , a _DW ^and the transition absorption line of F = _{1 to 5 2 P 1/2} ^F ₌ ² have a certain detuning; The frequencies of the local oscillation light a _UL1 , a _DL1 of the Stokes light and the analog light a _UL3 , a _DL3 are the same as the frequencies of the Stokes light a _US , a _DS are determined by the frequency of the writing light and the corresponding atomic energy levels, and F = ² of 5 ² S _1/2 to F of 5 ² P _1/2 , the transition absorption line of = ₂ has a _{certain detuning} ; F = 2 to 5 ² P _1/2 F, the transition absorption line of = 1 has a certain detuning; the local oscillation light a _UL2 , a _DL2 of the anti-Stokes light and the analog light a _UL4 , a _DL4 The frequency is the same as that of the anti-Stokes light a _UAS and a _DAS , which is determined by the reading frequency and the corresponding atomic energy level, and the frequency and F=1 to 5 ² P _1/2 of 5 ² S _1/2 , = 1 transition absorption line has a certain detuning. By controlling the size of single photon detuning of write optical pulse signal a _UW , a _DW , read optical pulse signal a _UR , a _DR , and local oscillation light a _UL1 , a _DL1 of Stokes light and analog light a _UL3 , a _DL3 , local oscillator light a _UL2 , a _DL2 of anti-Stokes light, and the photon detuning amount of simulated light a _UL4 , a _DL4 , control the interaction strength and associated noise between light and atoms, and the best Optimal entanglement of light and atomic ensembles.

As shown in Figure 1, the beam coupling system is composed of eight Glan Thomson prisms 21-28 with an extinction ratio of 10 ⁵ : 1 and an optical beam splitter 29; the Glan Thomson prisms 21, 25 Coupling vertically polarized write optical pulse signals a _UW , a _DW and horizontally polarized analog optical pulse signals a _UL4 , a _DL4 of anti-Stokes light; Glan Thomson prisms 22, 26 couple vertically polarized Read optical pulse signals a _UR , a _DR and horizontally polarized Stokes light analog optical pulse signals a _UL3 , a _DL3 are coupled together; Glan Thomson prisms 23, 24, 27, 28 combine vertically polarized read pulses The signals a _UR , a _DR , write optical pulse signals a _UW , and a _DW are filtered out when they enter the measurement system, and the optical beam splitter 29 is a 50/50 optical beam splitter, which divides the first atomic ensemble 3 and the second atomic ensemble 4. The Stokes light a _US and a _DS generated by the spontaneous Raman scattering process are interferentially coupled, and the phase difference of the interference is controlled to be 0, and the interferometric optical signals are input into the first and second measurement systems 5 and 6, and used Feedback on entanglement exchange.

As shown in Figure 5, the first atomic ensemble 3 is composed of a cubic atomic gas chamber 31, a radio frequency coil 32, a magnetic shielding system and a temperature control system 35; the magnetic shielding system consists of a magnetic shielding paper 33 and a metal magnetic shielding tube 34 Composition; the cubic atomic gas chamber 31 is filled with rubidium 87 atomic gas and a certain amount of buffer inert gas, and the light-transmitting surface of the cubic atomic gas chamber 31 is coated with an anti-reflection coating corresponding to the wavelength of the laser; the cubic atomic gas chamber 31 is placed on Inside the radio frequency coil 32; the outer layer of the radio frequency coil 32 is wrapped with magnetic shielding paper 33, and it is placed in the metal magnetic shielding tube 34; the outer layer of the magnetic shielding tube 34 is composed of heating tape, heat preservation material and temperature control instrument The unique temperature control system 35 heats the rubidium atoms and precisely controls the temperature.

As shown in Figure 6, the second atomic ensemble 4 is composed of a cubic atomic gas chamber 41, a magnetic shielding system and a temperature control system 45; the magnetic shielding system is composed of a magnetic shielding paper 43 and a metal magnetic shielding tube 44; The cubic atomic gas chamber 41 is filled with rubidium 87 atomic gas and a certain amount of buffer inert gas, and the light-transmitting surface of the cubic atomic gas chamber 41 is coated with an anti-reflection film corresponding to the wavelength of the laser; the outer layer of the cubic atomic gas chamber 41 is magnetically shielded Wrap 43 in paper and place it in a metal magnetic shielding cylinder 44; on the outer layer of the magnetic shielding cylinder 44, a temperature control system 45 composed of a heating belt, thermal insulation material and temperature control equipment is used to heat the rubidium atoms and precisely control the temperature.

As shown in Figure 7, the entanglement measurement system is composed of four sets of balanced zero-beat detection systems 5-8, power adder and subtractor 9, and a storable digital oscilloscope 10, using an optical beam splitter and a balanced zero-beat detector 41U , 42U, 41D, 42D and power subtractors 45U, 45D measure the quadrature components of the optical pulse a' _US , a' _DS after Stokes light interference, so as to use the feedback signal for entanglement exchange, and utilize The analog light a _UL3 and a _DL3 of Stokes light lock its interference phase difference; utilize optical beam splitters, balanced zero-beat detectors 43U, 44U, 43D, 44D and power subtractors 46U, 46D to adjust the Stokes The orthogonal components of light a _UAS and a _DAS are measured, and the interference phase difference is locked by using the analog light a _UL4 and a _DL4 of Stokes light; finally, through the power adder and subtractor 9 and the storable digital oscilloscope 10 The correlation noise of Stokes light a _UAS and anti-Stokes light a _DAS is measured, stored and analyzed to verify the entanglement between continuously variable atomic ensembles.

As shown in Figure 1, the feedback unit 11 is a variable gain amplifier circuit with band-pass filter characteristics, which amplifies the signal of a specific frequency in the measurement signal, and by selecting an appropriate frequency and gain factor, the best Entangled states of atomic ensembles.

According to the inseparability criterion proposed by Duan Luming et al., the entanglement of atomic ensembles of two components can be judged. If the correlated noise of two atomic ensembles satisfies the following inequality:

<Δ ² (X ₁ -X ₂ )>+<Δ ² (Y ₁ +Y ₂ )>≤4

Well, there is entanglement between them. where X and Y denote the quadrature amplitude and phase components of the anti-Stokes light, respectively, corresponding to the Stokes components describing the spin waves of the atomic ensemble. <Δ ² (X ₁ −X ₂ )> and <Δ ² (Y ₁ +Y ₂ )> represent the associated variances of the quadrature amplitude component and the quadrature phase component, respectively.

The generating device of the present invention generates the entangled states of the first atomic ensemble 3 and the second atomic ensemble 4 of continuous variables, and by measuring the associated noise of the anti-Stokes light a _UAS and the anti-Stokes light a _UAS , the two The entanglement of the rubidium atomic ensemble is measured and verified.

Other embodiments of the present invention:

On the basis of the above embodiments, a tunable laser with a wavelength of 852nm is used as a light source to interact with cesium atoms to obtain an ensemble of entangled cesium atoms.

Claims (4)

1. A generation device for entanglement of continuous variable atom ensemble, characterized by: the device comprises a light source unit, a light beam coupling system, two sets of atomic ensembles, an entanglement measurement system and a feedback unit; the light beam coupling system consists of eight Glan Thomson prisms and an optical beam splitter; the entanglement measuring system consists of four sets of balanced homodyne detecting systems, a power adder-subtractor and a storable digital oscilloscope; the feedback unit is a variable gain amplifying circuit with a band-pass filtering characteristic;

the light source unit is provided with two beams of pumping light pulse signalsa_UP、a_DPOutput end, two writing light pulse signals a_UW、a_DWOutput end, two reading light pulse signals a_UR、a_DROutput end, four beams of local oscillation optical signals a_UL1、a_DL1、a_UL2、a_DL2Output terminal and four beams of analog optical pulse signals a_UL3、a_DL3、a_UL4、a_DL4An output end; wherein the first beam of pump optical pulse signal a_UPThe output end is connected with the first input end of the first atomic ensemble; vertically polarized first beam of write light pulse signal a_UWOutput end and horizontally polarized first beam analog optical pulse signal a_UL4The output end of the first gram Thomson prism is connected with the second input end of the first atomic ensemble; vertically polarized first beam of reading light pulse signal a_UROutput end and horizontally polarized second beam analog optical pulse signal a_UL3The output end of the second Glan Tomson prism is connected with the two input ends of the first atomic ensemble; the first output end and the second output end of the first set of atomic ensembles are respectively connected with the input ends of the third and fourth gram Thomson prisms; second beam of pump optical pulse signal a_DPThe output end is connected with the first input end of the second atomic ensemble; vertically polarized second beam of write light pulse signal a_DWOutput end and horizontally polarized third beam analog optical pulse signal a_DL4The output end of the fifth gram thomson prism is connected with the two input ends of the second atomic ensemble; vertically polarized second beam of reading light pulse signal a_DROutput end and horizontally polarized fourth beam analog optical pulse signal a_DL3The output end of the sixth Glan Tomson prism is connected with the two input ends of the sixth Glan Tomson prism respectively, and the output end of the sixth Glan Tomson prism is connected with the third input end of the second atomic ensemble; the first output end and the second output end of the second set of atom ensemble are respectively connected with the input ends of the seventh optical Glan Thomson prism and the eighth optical Glan Thomson prism; the output ends of the third and seventh gram Thomson prisms are connected with two input ends of the optical beam splitterTwo output ends of the optical beam splitter are respectively connected with first input ends of the first balanced homodyne detection system and the second balanced homodyne detection system, and the first local oscillation optical signal a and the second local oscillation optical signal a are respectively connected with the first input end of the first balanced homodyne detection system and the second balanced homodyne detection system_UL1、a_DL1The output ends of the first and second balanced homodyne detection systems are connected with the radio frequency coil of the first atomic ensemble through a feedback unit; the output ends of the fourth and eighth Glan Tomson prisms are respectively connected with the first input ends of the third and fourth balanced homodyne detection systems, and the third and fourth beams of local oscillation optical signals a_UL2、a_DL2The output end of the third balanced zero-beat detection system is connected with the second input end of the fourth balanced zero-beat detection system, and the output end of the third balanced zero-beat detection system is connected with the storable digital oscilloscope through the power adder-subtractor.

2. The apparatus for generating entanglement of continuous variable atomic ensembles according to claim 1, wherein: the light source unit consists of a tunable laser, a single-mode 1x7 optical fiber coupler, seven sets of acousto-optic modulators and seven sets of optical beam splitters, wherein the output end of the tunable laser is connected with the input end of the single-mode 1x7 optical fiber coupler, the output end of the single-mode 1x7 optical fiber coupler is connected with the input ends of the seven sets of acousto-optic modulators, and the output ends of the seven sets of acousto-optic modulators are connected with the input ends of the seven sets of optical beam splitters; seven sets of acousto-optic modulators and seven sets of optical beam splitters generate two beams of pumping light pulse signals a_UP、a_DPTwo writing light pulse signals a_UW、a_DWTwo reading light pulse signals a_UR、a_DRFour beams of local oscillation optical signals a_UL1、a_DL1、a_UL2、a_DL2And four analog optical pulse signals a_UL3、a_DL3、a_UL4、a_DL4。

3. The apparatus for generating entanglement of continuous variable atomic ensembles according to claim 1, wherein: the first atom ensemble is composed of a cubic atom gas chamber, a radio frequency coil, a magnetic shielding system and a temperature control system; the magnetic shielding system is composed of magnetic shielding paper and a metal magnetic shielding cylinder; the cubic atom gas chamber is filled with atomic gas and a certain amount of buffer inert gas, and the light-passing surface of the cubic atom gas chamber is plated with a reflection reducing film with corresponding laser wavelength; the cubic atom gas chamber is arranged in the radio frequency coil; the outer layer of the radio frequency coil is wrapped by magnetic shielding paper and is placed in a metal magnetic shielding cylinder; the outer layer of the magnetic shielding cylinder adopts a temperature control system consisting of a heating belt, a heat insulation material and a temperature control instrument to heat rubidium atoms and accurately control the temperature.

4. The apparatus for generating entanglement of continuous variable atomic ensembles according to claim 1, wherein: the second atom ensemble consists of a cubic atom gas chamber, a magnetic shielding system and a temperature control system; the magnetic shielding system is composed of magnetic shielding paper and a metal magnetic shielding cylinder; the cubic atom gas chamber is filled with atomic gas and a certain amount of buffer inert gas, and the light-passing surface of the cubic atom gas chamber is plated with a reflection reducing film with corresponding laser wavelength; the outer layer of the cubic atom air chamber is wrapped by magnetic shielding paper and is placed in a metal magnetic shielding cylinder; the outer layer of the magnetic shielding cylinder adopts a temperature control system consisting of a heating belt, a heat insulation material and a temperature control instrument to heat rubidium atoms and accurately control the temperature.