CN112630882A

CN112630882A - Multi-core ring optical fiber and quantum system comprising same

Info

Publication number: CN112630882A
Application number: CN202011072326.7A
Authority: CN
Inventors: N·F·博雷利; R·R·赫拉帕孔; D·T·恩古延; T·A·T·恩古延; D·A·诺兰
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2019-10-08
Filing date: 2020-10-09
Publication date: 2021-04-09
Anticipated expiration: 2040-10-09
Also published as: CN112630882B

Abstract

Multicore annular optical fibers and quantum systems incorporating the optical fibers are disclosed. The multicore fiber includes a plurality of waveguide cores disposed in a cladding. A plurality of cores are positioned adjacent to at least one other core and the core center to core center spacing is no more than 10 times the average core radius such that greater than 10% of light will couple from one core to an adjacent core along the length of the fiber within a propagation distance of 1cm, thereby providing coupling between adjacent cores and enabling quantum walking. The plurality of waveguide cores are disposed in the cladding in an annular distribution or at least a portion of an annular distribution.

Description

Multi-core ring optical fiber and quantum system comprising same

Cross Reference to Related Applications

The present application claims priority benefits from U.S. provisional application serial No. 62/912426 filed 2019, 10, 8, 35u.s.c. § 119, 2019, which is incorporated herein by reference in its entirety.

Background

The present disclosure relates to multicore optical fibers suitable for quantum systems, and systems incorporating the multicore optical fibers. More particularly, the present disclosure relates to systems comprising multicore ring fibers, e.g., multicore ring fibers with cores arranged in a periodic or aperiodic sequence, for implementing localized quantum walking. The centers of the cores are spaced from the center of the core by no more than 10 times the average core radius such that more than 10% of the light will couple from one core to an adjacent core over a propagation distance of at least 1cm, thereby enabling quantum walking.

Disclosure of Invention

According to one embodiment of the present disclosure, a multicore optical fiber includes a plurality of optical fiber cores disposed in a fiber cladding. A plurality of waveguide cores disposed in the cladding and positioned adjacent to at least one other core, and the core center to core center spacing is no more than 10 times the average core radius, such that greater than 10% of light will couple from one core to an adjacent core along the length of the fiber within a propagation distance of 1cm, thereby providing coupling between adjacent cores and enabling quantum walking; and the plurality of waveguide cores are disposed in the cladding in an annular distribution or at least a portion of an annular distribution.

A multicore optical fiber, comprising:

a cladding layer is arranged on the surface of the substrate,

a plurality of cores disposed in a cladding, wherein:

the plurality of cores comprises one or more first waveguide cores and one or more second waveguide cores, wherein the cores are positioned adjacent to at least one other core and the core center to core center spacing is no more than 10 times the average core radius such that greater than 10% of light will couple from one core to an adjacent core along the length of the optical fiber within a propagation distance of 1cm, thereby providing coupling between adjacent cores and enabling continuous quantum walking;

the one or more first waveguide cores comprise a first propagation constant, the one or more second waveguide cores comprise a second propagation constant, and the first propagation constant is different from the second propagation constant; and is

The one or more first waveguide cores and the one or more second waveguide cores are disposed in the cladding in an annular distribution, and at least a portion of the annular distribution is arranged based on a non-periodic or quasi-periodic sequence.

According to one embodiment, a multicore optical fiber includes:

a cladding layer is arranged on the surface of the substrate,

a plurality of cores disposed in a cladding, wherein:

the plurality of cores comprises one or more first waveguide cores and one or more second waveguide cores, wherein the cores are positioned adjacent to at least one other core and the core center to core center spacing is no more than 10 times the average core radius to provide coupling between adjacent cores to enable continuous quantum walking such that greater than 10% of light will couple from one core to an adjacent core within a 1cm propagation distance along the length of the optical fiber;

the one or more first waveguide cores comprise a first propagation constant and the one or more second waveguide cores comprise a second propagation constant; and is

The one or more first waveguide cores and the one or more second waveguide cores are disposed in the cladding in an annular distribution, and at least a portion of the annular distribution is arranged based on a periodic sequence.

Although the concepts of the present disclosure are described primarily with reference to quantum walking, it should be understood that these concepts will apply to any quantum system, for example: quantum information systems, quantum communication systems, quantum computing systems, and quantum simulation.

Drawings

The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

FIG. 1 schematically depicts a communication system including a photon generator, a multicore optical fiber, and a photon detector, according to one or more embodiments shown and described herein;

FIGS. 2 and 2A schematically depict cross-sectional views of exemplary multicore optical fibers, according to one or more embodiments shown and described herein;

FIG. 2B schematically depicts a cross-sectional view of another example multicore optical fiber, according to one or more embodiments shown and described herein;

FIG. 2C schematically depicts a cross-sectional view of another example multicore optical fiber, according to one or more embodiments shown and described herein;

FIG. 3A schematically depicts a cross-sectional view of an exemplary multicore optical fiber;

FIG. 3B depicts a cross-sectional view image of a finished multicore fiber corresponding to FIG. 3A;

FIG. 3C illustrates a measured photon probability distribution determined using a communication system including the optical fiber of FIG. 3B, in accordance with one or more embodiments shown and described herein;

FIG. 3D illustrates a modeled photon probability distribution determined using the communication system of one or more embodiments shown and described herein, which utilizes the multicore optical fiber of FIG. 3B;

FIG. 4A schematically depicts a cross-sectional view of another example multicore optical fiber, according to one or more embodiments shown and described herein;

FIG. 4B depicts a cross-sectional view image of a finished multicore fiber corresponding to the fiber of FIG. 4A;

FIG. 4C illustrates a measured photon probability distribution determined using a communication system including the optical fiber of FIG. 4B, in accordance with one or more embodiments shown and described herein;

FIG. 4D illustrates a modeled photon probability distribution determined using a communication system including the optical fiber of FIG. 3A, in accordance with one or more embodiments shown and described herein;

FIG. 5 illustrates the general rules for the recursive construction of a quasiperiodic array of waveguide cores;

FIG. 6 illustrates a configuration of an exemplary Fibonacci (Fibonacci) array sequence (FAWC) of waveguide cores;

FIG. 7A illustrates a configuration of a core annular profile in a 4 th order Fibonacci multicore annular fiber (FMCRF 4);

FIG. 7B illustrates a configuration of a core annular profile in a 5 th order Fibonacci multicore annular fiber (FMCRF 5);

FIG. 7C illustrates a configuration of a core annular profile in a 6 th order Fibonacci multicore annular fiber (FMCRF 6);

fig. 8A to 8C illustrate simulation results of probability distributions of photons in quantum walk in a multicore optical fiber having a core ring distribution in which cores include 15 waveguide cores, 23 waveguide cores, and 39 waveguide cores, respectively.

Fig. 8D illustrates the simulation results of the probability distribution of photons in quantum walking in a system containing a 4 th order fibonacci multicore annular fiber (FMCRF4) and having 15 waveguide cores;

fig. 8E illustrates the simulation results of the probability distribution of photons in quantum walking in a system comprising a 5 th order fibonacci multicore annular fiber (FMCRF5) and having 23 cores;

fig. 8F illustrates the simulation results of the probability distribution of photons in quantum walking in a system containing a 6 th order fibonacci multicore annular fiber (FMCRF6) and having 39 cores;

FIG. 9 schematically depicts a system including a photon generator (light source), a multicore optical fiber, and a photon detector, in accordance with one or more embodiments shown and described herein;

FIG. 10 illustrates an exemplary image provided by an algorithm for detecting the position of a waveguide core, according to one or more embodiments shown and described herein.

Detailed Description

Quantum walking has various potential applications in quantum communication and quantum computing, for example, in the development of quantum algorithms and quantum simulations. Quantum walking can increase computational speed and facilitate the resolution of problems that are not feasible using classical computers. Furthermore, due to the particle-biphase nature of photons, they can be used for quantum walking. One phenomenon that occurs in quantum migration is localization, which is free of wave diffusion in disordered media. Localized quantum walking can result in symmetric probability distributions and thus allows localized quantum walking to show potential applications in quantum communication, e.g., using localized photonic states for secure transmission of information and using localized photonic states as quantum reservoirs. Localized quantum walking can be achieved using a randomly disordered system of waveguides (e.g., spatial or temporal disorder), but this requires a large number of randomly disordered systems, and the randomness of each system needs to be controlled within a defined range of disorder. In addition, localized quantum walk causing symmetric probability distribution is not available in a spatial random disorder system, and although localized quantum walk having symmetric probability distribution can be realized with a transient random disorder system by using a plurality of quantum coins, the multi-quantum-coin method is difficult to implement in reality. Accordingly, there is a need for improved methods and systems to achieve localized quantum walking.

Reference will now be made in detail to embodiments of a communication system for implementing improved localized quantum walking. The communication system includes a multicore optical fiber including a cladding and a plurality of cores (also referred to herein as waveguide cores) including one or more first waveguide cores and one or more second waveguide cores disposed in the cladding. The one or more first waveguide cores and the one or more second waveguide cores comprise differential propagation constants and are arranged in a quasi-periodic sequence. (the propagation constant of a mode in the waveguide fiber core determines how the amplitude and phase of light of a given frequency varies along the propagation direction z (i.e., along the core axis.) A single mode fiber core has only one mode propagating through the core. the propagation constant depends on the wavelength of the light propagating through the waveguide core. As used herein, "quasi-periodic sequence" refers to a sequence that is arranged in a design pattern and lacks translational symmetry. And a symmetric probability distribution is obtained that is predictable, controllable and repeatable. While not intending to be limited by theory, localized quantum walking, such as that performed in the communication systems described herein, in an unordered system may be used to store information about the initial state of a qubit and thus may be used as part of a secure quantum memory. In addition, the storage time of a quantum memory will be directly related to the number of implementable steps of quantum walking. Without localization, the size of the location space required to store information increases linearly with time, making it difficult to store information for long periods of time.

Further, the communication system 100 includes one or more photon generators 180 optically coupled to the input 114 of at least one of the plurality of cores 110 and one or more photon detectors 190 optically coupled to the output 116 of at least one of the plurality of cores 110. For example, in some embodiments, at least one of the one or more photon detectors 190 is optically coupled to the output 116 of the plurality of cores 110.

In operation, communication system 100 may be used for quantum walking, which may be used to determine a photon probability distribution. For example, quantum walking may include directing a plurality of photons generated using photon generator 180 into input 114 of one or more individual waveguide cores of multicore fiber 101, receiving the plurality of photons using one or more photon detectors 190, and determining a photon probability distribution based on the plurality of photons received by one or more photon detectors 190. As used herein, a "photon probability distribution" is a distribution function representing the probability of a photon being directed into the input end 114 of the multicore fiber 101 and exiting the output end 116 of each individual waveguide core of the plurality of cores 110 of the multicore fiber 101.

Referring now to fig. 2, 2A-2C, 3A, 3B and 4A, 4B, adjacent waveguide cores of the plurality of cores 110 arranged in an annular distribution 140 are spaced apart from one another by a spacing distance D (core center to core center distance D). While not intending to be limited by theory, during quantum walking, each photon "walks" through the multicore fiber 101, moving between adjacent cores via evanescent coupling while propagating from the input end 114 of the multicore fiber 101 to the output end 116 of the multicore fiber 101. Thus, the separation distance D between adjacent cores is sufficiently close for evanescent coupling to occur, for example, the separation distance D may comprise about 40 μm or less, e.g., about 30 microns or less, about 25 μm or less, about 20 μm or less, about 15 μm or less, about 10 μm or less, about 7.5 μm or less, and the like. For example, D can comprise about 30 μm or less, e.g., about 25 μm or less, about 20 μm or less, about 15 μm or less, about 10 μm or less, about 5 μm or less, and the like.

Further, in some embodiments, adjacent cores of the plurality of cores 110 may be evenly spaced in the annular distribution 140. The separation distance D 'between the edges of adjacent cores is also close enough for evanescent coupling to occur, for example, the separation distance D' may be greater than about 2 μm and about 30 μm or less, e.g., about 25 μm or less, about 20 μm or less, about 15 μm or less, about 10 μm or less, about 7.5 μm or less, etc. In some embodiments, the distance D 'is from 3 μm to 30 μm, and in some embodiments, the distance D' is from 5 μm to 30 μm.

Referring to fig. 2, 2A-2C, 4A and 4B, the plurality of cores may include: one or more first waveguide cores 120 comprising a first propagation constant and one or more second waveguide cores 130 comprising a second propagation constant. Without intending to be limited by theory, the propagation constant of the waveguide core determines the propagation in the coreHow the amplitude and phase of light with a given frequency vary along the propagation direction. In these embodiments, the first propagation constant is different from the second propagation constant. The propagation constant depends on a number of factors, such as the refractive index of the core and the diameter of the core. The propagation constant may be determined by the value V, where,

n_WGis the refractive index of a single core of the plurality of cores 110, n_{Cladding layer}Is the refractive index of the cladding 105, a₁Is the radius of a single core of the plurality of cores 110, and λ is the wavelength of one or more photons propagating along the plurality of cores 110. The wavelength λ may for example be in the following wavelength range: 800nm to 900nm, 920nm to 970nm, or 1200nm to 1400nm, 1530nm to 1565nm, or 1.0 μm to 1.1 μm.

In addition, the one or more first waveguide cores 120 include a first value V₁Said one or more second waveguide cores 130 comprising a second value V₂And a first value V₁And a second V value V₂Are not identical. Specifically, the first V value

Wherein,

n_WG1is the refractive index, n, of the one or more first waveguide cores 120_{Cladding layer}Is the refractive index of the cladding 105, a₁Is the radius of the one or more first waveguide cores 120, and λ is the wavelength of one or more photons propagating along the plurality of cores 110, and a second value of V

Wherein,

n_WG2is the refractive index, n, of the one or more second waveguide cores 130_{Cladding layer}Is refraction of the cladding 105Rate, a₂Is the radius of the one or more second waveguide cores 130, and λ is the wavelength of the one or more photons propagating along the plurality of cores 110. In addition, since the one or more first waveguide cores 120 and the one or more second waveguide cores 130 are single-mode cores, the first V value V is₁And a second V value V₂Less than 2.405.

As the value of V mathematically shows, two waveguide cores comprising different refractive indices may comprise different propagation constants, and two waveguide cores comprising different diameters may comprise different propagation constants. For example, the one or more first waveguide cores 120 include a first diameter and a first refractive index, and the one or more second waveguide cores 130 include a second diameter and a second refractive index. To achieve a differentiated propagation constant, the first diameter may be different from the second diameter, the first refractive index may be different from the second refractive index, or the first diameter may be different from the second diameter and the first refractive index may be different from the second refractive index.

Additionally, while not intending to be limited by theory, fields of waves (e.g., optical waves) propagating in the multicore fiber 101 of the first waveguide core 120 and the second waveguide core 130 may be coupled, and the multicore fiber 101 may include a first coupling coefficient κ₁₂(i.e., the coupling coefficient from second waveguide core 130 to first waveguide core 120) and a second coupling coefficient κ₂₁(i.e., the coupling coefficient from first waveguide core 120 to second waveguide core 130), which represents the amount of coupling between the fields in the two cores. In other words, the coupling coefficient measures the mode field Ψ of first waveguide core 120₁(x, y) and mode field Ψ in second waveguide core 130₂The amount of overlap between (x, y). Thus, each coupling coefficient κ is dominated by an overlap integral, which indicates the coupling behavior between the mode fields that causes energy to be transferred from one waveguide core to the other. In addition, the first coupling coefficient κ₁₂And a second coupling coefficient k₂₁Are not identical. In general, the mode field Ψ in the waveguide core₁(x, y) and Ψ₂(x, y) depending on various parameters, e.g. coreWidth (e.g. diameter) of the body, refractive index n of the core₁(x，y)，n₂(x, y), the material of the cladding 105 and the operating wavelength (λ). While not intending to be bound by theory, the coupling coefficient κ₁₂And kappa₂₁Can be mathematically passed through

And

is shown in the specification, wherein b₁Is the propagation constant of first waveguide core 120, b₂Is the propagation constant of the second waveguide core 130,

and is

And wherein n_T(x, y) is the refractive index profile of two waveguide core portions of the multicore fiber 101 including a separate first waveguide core 120 adjacent to a separate second waveguide core 130.

Still referring to fig. 2, 2A-2C and 4A, 4B, in some embodiments, at least a portion of the annular profile 140 is arranged based on a quasi-periodic sequence of one or more first waveguide cores 120 and one or more second waveguide cores 130. In other words, the annular distribution 140 is arranged such that the first and second propagation constants vary quasi-periodically, whereby the annular distribution 140 becomes disordered and the quasi-periodically varying coupling coefficients also cause disorder.

The quasi-periodic sequence includes a plurality of sequence segments. Each sequence segment is determined based on a quasiperiodic function and includes an order (e.g., an order of a quasiperiodic sequence, e.g., first order, second order, third order, etc.). In addition, each sequence section corresponds to an alignment section 145 having one or more first waveguide cores 120, one or more second waveguide cores 130, or both one or more first waveguide cores 120 and one or more second waveguide cores 130. Each alignment section 145 may include a single waveguide core or may include multiple waveguide cores. For example, in the embodiments shown in fig. 2, 2A-2C and 4A, 4B, the ring-shaped distribution 140 includes an arrangement section 145 corresponding to six orders of the sequence section, i.e., a first order arrangement section 145a, a second order arrangement section 145B, a third order arrangement section 145C, a fourth order arrangement section 145d, a fifth order arrangement section 145e, and a sixth order arrangement section 145 f. However, it should be understood that other annular distributions 140 are also contemplated. For example, the circular distribution 140 may include one portion that follows a quasi-periodic sequence and another portion that does not follow a quasi-periodic sequence. Further, the portion of the circular distribution 140 that follows the quasi-periodic sequence may include any one or more sequence segments of the quasi-periodic sequence, not just the initial sequence segments of the quasi-periodic sequence. Exemplary quasi-periodic sequences include fibonacci sequences, charles-Morse (due-Morse) sequences, and luding-sharp (Rudin-Shapiro) sequences. It should be noted that while the exemplary annular distribution 140 shown in fig. 2A-2B follows a fibonacci sequence, other annular distributions are also contemplated.

When the quasiperiodic sequence is a Fibonacci sequence, the quasiperiodic function of the Fibonacci sequence includes S_N+1＝S_N-1S_NIn which S is_NIncludes N-order sequence sections and corresponds to the N-order arrangement sections. S₁A, where a comprises a first order sequence section and corresponds to a first order arrangement section 145a, which comprises a single first waveguide core 120; and S₂B, where B comprises a second order sequence section and corresponds to second order arrangement section 145B, which comprises a single second waveguide core 130. S₃＝S₁S₂AB, wherein AB comprises a third order sequence section and corresponds to a third order permutation section 145c, which comprises a first order permutation section 145a adjacent to a second order permutation section 145 b. Specifically, third order array segment 145c includes a separate first waveguide core 120 disposed directly adjacent to a separate second waveguide core 130. S₄＝S₂S₃The BAB includes a fourth-order sequence section and corresponds to a fourth-order arrangement section 145d, which includes a second-order arrangement section 145b adjacent to a third-order arrangement section 145 c. Specifically, fourth-order alignment section 145d includes a single first waveguide core120 disposed directly between two separate second waveguide cores 130. S₅＝S₃S₄ABBAB, wherein ABBAB includes a fifth order sequence section and corresponds to a fifth order arrangement section 145e, which includes a third order arrangement section 145c adjacent to a fourth order arrangement section 145 d. In addition, S₆＝S₄ S₅Babbab includes a sixth-order sequence section and corresponds to a sixth-order permutation section 145f, which includes a fourth-order permutation section 145d adjacent to a fifth-order permutation section 145 e.

The graph angstrom-morse sequence is a binary sequence (an infinite sequence of 0 and 1) obtained by starting from 0 and successively appending the Boolean (Boolean) complements of the sequences obtained so far. The first few steps of this sequence produce string 0, then 01, 0110, 01101001, 0110100110010110, and so on. The Boolean complements are opposite numbers in a binary system, e.g., 1 has a Boolean complement of 0, 0 has a Boolean complement of 1, and 101 has a Boolean complement of 010. When the quasiperiodic sequence is a graph Angstrom-Morse sequence, the quasiperiodic function of the graph Angstrom-Morse sequence includes

Wherein T is_NIncludes N-order sequence sections and corresponds to the N-order arrangement section 145, and

comprising T_NThe sequence segment of the boolean complement of the sequence segment and corresponds to the boolean complement of the rank N permutation segment 145.

In the scheme Angstrom-Morse sequence, T₁Where a comprises a first order sequence section and corresponds to first order alignment section 145a, which comprises a single first waveguide core 120. T is₂B, where B comprises a second order sequence section and corresponds to second order arrangement section 145B, which comprises a single second waveguide core 130.

Wherein BA comprises a third order sequence section and corresponds to a third order permutation section 145c comprising an arrangement with a second order permutation section 145bComplementary adjacent second order permutation sections 145 b. Specifically, third order array segment 145c includes a separate second waveguide core 130 directly adjacent to a separate first waveguide core 120.

Wherein the BAAB includes a fourth order sequence section and corresponds to a fourth order permutation section 145d, which includes a third order permutation section 145c adjacent to the boolean complement of the third order permutation section 145 c. Specifically, fourth-order alignment section 145d includes a directly adjacent pair of first waveguide cores 120 that is directly between a pair of second waveguide cores 130.

Wherein the ABBAB includes a fifth order sequence section and corresponds to a fifth order permutation section 145e including a fourth order permutation section 145d adjacent to the boolean complement of the fourth order permutation section 145 d. In addition, the first and second substrates are,

wherein baababbabababaab includes a sixth order sequence section and corresponds to a sixth order permutation section 145f including a fifth order permutation section 145e adjacent to the boolean complement of the fifth order permutation section 145 e.

When the quasi-periodic sequence is a luding-sharp sequence, the quasi-periodic function of the luding-sharp sequence includes a four-element replacement sequence having the following rule: p → PQ, Q → PR, R → SQ, and S → SR. Thus, a first order sequence section S₁Second order sequence section S ═ P₂Third order sequence segment S ═ PQ₃PQPR, fourth order sequence section S₄PQPRPQSQ, fifth order sequence segment S₅PQPRPQSQPRSRPR, and so on. In addition, to obtain a sequence of only two elements a and B, a four-element sequence may be mapped onto a two-element sequence, where (P, Q) → a and (R, S) → B. Each case of a corresponds to a separate first waveguide core 120 of the alignment section 145, and each case of B corresponds to a separate second waveguide core 130 of the alignment section 145. Thus, S₁A, wherein S₁Is with a1 containing AThe first order sequence section, S, corresponding to the order arrangement section 145a₂AA, wherein S₂Is a second order sequence segment, S, corresponding to the second order permutation segment 145b containing AA₃AAAB, wherein S₃Is a third order sequence segment, S, corresponding to the third order permutation segment 145c comprising AAAB₄Aaabaababa, wherein S₄Is a fourth order sequence segment corresponding to fourth order permutation segment 145d comprising AAA BAABA, and S₅Aaabaaababbabbabab, wherein S₅Is a fifth order sequence segment corresponding to fifth order sequence segment 145e comprising aaabaabaababbab, and so on.

Referring now to fig. 2, in some embodiments, the annular distribution 140 of the one or more first waveguide cores 120 and the one or more second waveguide cores 130 comprises a quasi-periodic sequence in which a lowest order alignment section 145 is located on the first side 111 of the multicore optical fiber 101 (e.g., first order alignment section 145a is located on the left side of the multicore optical fiber 101 in fig. 2) and a highest order alignment section is located on the second side 113 of the multicore optical fiber 101, opposite the first side 111 (e.g., sixth order alignment section 145f is located on the right side of the multicore optical fiber 101 in fig. 2). As shown in fig. 2A, the arrangement segments 145 of the ring-shaped distribution 140 may be stepped from the first side 111 to the second side 113 (e.g., stepped from the left first-order arrangement segment 145a to the right sixth-order arrangement segment 145 f). Additionally, while fig. 2 depicts the entire annular distribution 140 as including a quasi-periodic sequence extending in both the first direction 141 and the second direction 143, it is understood that the entire annular distribution 140 or only a portion of the annular distribution 140 may include a quasi-periodic sequence. The first side 111 and the second side 113 do not separate by a large distance D_xAnd thus the waveguide cores

adjacent sides

111 and 113 are coupled to each other. That is, in this embodiment, the distance D_XRelatively small to enable evanescent coupling between the end cores and continuous Quantum Walking (QW) within the core distribution 140. That is, the multicore fiber configuration allows "endless" quantum walking, i.e., photons walk around a ring without being terminated by a physical boundary. This creates an open quantum system that is useful in analog systems (e.g., when the analog hasMultiple nuclei of material). This embodiment may use a multicore fiber with fewer waveguide cores, making it extremely efficient and less expensive to produce.

According to some embodiments, a multicore optical fiber includes:

a cladding layer is arranged on the surface of the substrate,

a plurality of cores disposed in a cladding, wherein:

the plurality of cores comprises one or more first waveguide cores and one or more second waveguide cores, wherein the cores are positioned adjacent to at least one other core and the core center to core center spacing is no more than 10 times the average core radius such that greater than 10% of light will couple from one core to an adjacent core along the length of the optical fiber within a propagation distance of 1cm, thereby providing coupling between adjacent cores and enabling quantum walking between cores; and is

The plurality of cores are disposed in the cladding in an annular distribution.

According to some embodiments, the distance Dx is equal to or less than the distance D'. According to some embodiments, the distance Dx < 30 um.

According to some embodiments, a multicore optical fiber includes:

a cladding layer is arranged on the surface of the substrate,

a plurality of cores disposed in a cladding, wherein:

the one or more first waveguide cores comprise a first propagation constant, the one or more second waveguide cores comprise a second propagation constant, and the first propagation constant is different from the second propagation constant;

the one or more first waveguide cores and the one or more second waveguide cores are disposed in the cladding in an annular distribution, and at least a portion of the annular distribution is arranged based on a non-periodic sequence.

According to some embodiments, the separation distance between each adjacent pair of waveguide cores in the plurality of waveguide cores is about 30 μm or less. According to some embodiments, a separation distance D between each adjacent pair of waveguides in the plurality of waveguides is between 5 μm and 30 μm. According to some embodiments, a separation distance D between each adjacent pair of waveguides in the plurality of waveguides is between 7.5 μm and 30 μm. According to some embodiments, a separation distance D between each adjacent pair of waveguides in the plurality of waveguides is between 10 μm and 30 μm. According to some embodiments, the waveguide core is a step index core. According to other embodiments, the waveguide core is a graded-index core. According to some embodiments, the separation distance D' between the edges of each adjacent pair of waveguides in the plurality of waveguides is between 5 μm and 30 μm. According to some embodiments, the separation distance D' between the edges of each adjacent pair of waveguides in the plurality of waveguides is between 7.5 μm and 30 μm. According to some embodiments, the separation distance D' between the edges of each adjacent pair of waveguides in the plurality of waveguides is between 10 μm and 30 μm. According to some embodiments, the waveguide core is a step index core. According to other embodiments, the waveguide core is a graded-index core.

According to some embodiments, a multicore optical fiber includes:

a cladding layer is arranged on the surface of the substrate,

a plurality of cores disposed in a cladding, wherein:

the plurality of cores comprises one or more first waveguide cores and one or more second waveguide cores, wherein the cores are positioned adjacent to at least one other core and the core center to core center spacing is no more than 10 times the average core radius such that greater than 10% of light will couple from one core to an adjacent core along the length of the optical fiber within a propagation distance of 1cm, thereby providing coupling between adjacent cores and enabling quantum walking between cores;

the one or more first waveguide cores comprise a first propagation constant and the one or more second waveguide cores comprise a second propagation constant;

the one or more first waveguide cores and the one or more second waveguide cores are disposed in the cladding in an annular distribution.

According to some embodiments, the one or more first waveguide cores and the one or more second waveguide cores have different diameters. According to some embodiments, the one or more first waveguide cores and the one or more second waveguide cores have different refractive index profiles. According to some embodiments, the one or more first waveguide cores and the one or more second waveguide cores have different refractive indices. According to some embodiments, the first propagation constant is different from the second propagation constant.

However, according to some embodiments, the one or more first waveguide cores and the one or more second waveguide cores have the same diameter and the same refractive index, and the first propagation constant and the second propagation constant are substantially the same. In these embodiments, the core annular distribution is not quasi-periodic as shown in FIG. 2, but periodic, for example, as shown in FIG. 3A.

Referring now to fig. 2A, in some embodiments, the annular distribution 140 of the one or more first waveguide cores 120 and the one or more second waveguide cores 130 comprises a quasi-periodic sequence in which a lowest order alignment section 145 is located on the first side 111 of the multicore optical fiber 101 (e.g., first order alignment section 145a is located on the left side of the multicore optical fiber 101 in fig. 2A) and a highest order alignment section is located on the second side 113 of the multicore optical fiber 101, opposite the first side 111 (e.g., sixth order alignment section 145f is located on the right side of the multicore optical fiber 101 in fig. 2A). As shown in fig. 2A, the arrangement segments 145 of the ring-shaped distribution 140 may be stepped from the first side 111 to the second side 113 (e.g., stepped from the left first-order arrangement segment 145a to the right sixth-order arrangement segment 145 f). In addition, although FIG. 2A depicts the entire annular profile 140 as including quasi-extending in both the first direction 141 and the second direction 143A periodic sequence, but it should be understood that the entire circular distribution 140 or only a portion of the circular distribution 140 may comprise a quasi-periodic sequence. The first side 111 and the second side 113 are separated by a sufficient distance D_xSuch that the waveguide cores

adjacent sides

111 and 113 are not coupled to each other. In this embodiment, D is preferred_xIs larger than D'. According to some embodiments, the distance Dx > 30 μm. Systems comprising such fibers are closed quantum systems with boundary effects and can be modeled, for example, when modeling materials with multiple nuclei.

Referring now to fig. 2B, in some embodiments, the plurality of cores 110 includes a central waveguide core 112 that separates a first portion 142 of the annular distribution 140 from a second portion 144 of the annular distribution 140. A first portion 142 of annular distribution 140 extends from central waveguide core 112 in a first direction 141 and comprises a quasi-periodic sequence of first waveguide core 120 and second waveguide core 130. A second portion 144 of annular distribution 140 extends from central waveguide core 112 in a second direction 143 and comprises a quasi-periodic sequence of first waveguide core 120 and second waveguide core 130. In some embodiments, the central waveguide core 112 includes a first order of arrangement sections 145a, the first order of arrangement sections 145a for each quasiperiodic sequence extending in both the first direction 141 and the second direction 143. The quasi-periodic sequences extending in the first direction 141 and the second direction 143 may be mirror images of each other. For example, in fig. 2B, the quasi-periodic sequence extending in both first direction 141 and second direction 143 comprises a fibonacci sequence and includes first order alignment section 145a (i.e., shared central waveguide core 112) through sixth order alignment section 145 f. Additionally, although fig. 2B depicts the plurality of cores 110 as including the central waveguide core 112 and the quasiperiodic sequence extending in both the first direction 141 and the second direction 143, it is understood that the entire annular distribution 140 or only a portion of the annular distribution 140 may include the quasiperiodic sequence.

Referring now to fig. 2C, in some embodiments, the plurality of cores 110 includes a first central waveguide core 112' adjacent to a second central waveguide core 112 ". In the embodiment shown in fig. 2C, annular distribution 140 extends from first central waveguide core 112' in a first direction 141 and includes a quasi-periodic sequence of first waveguide core 120 and second waveguide core 130. Specifically, the first central waveguide core 112' includes a quasi-periodic sequence of first order segments 145a extending in the first direction 141. In addition, annular distribution 140 extends from second central waveguide core 112 ″ in a second direction 143 and includes a quasi-periodic sequence of first waveguide core 120 and second waveguide core 130. Specifically, the second central waveguide core 112 "includes a quasi-periodic sequence of first order segments 145a extending in the second direction 143. The quasi-periodic sequences extending in the first direction 141 and the second direction 143 may be mirror images of each other. For example, in fig. 2C, the quasi-periodic sequence extending in both the first direction 141 and the second direction 143 comprises a fibonacci sequence and includes first order alignment segments 145a (i.e., a first central waveguide core 112 'of the sequence extending in the first direction 141 and a second central waveguide core 112' of the sequence extending in the second direction 143) through sixth order alignment segments 145 f. Additionally, although fig. 2C depicts the plurality of cores 110 as including a first central waveguide core 112' and a second central waveguide core 112 "and a quasi-periodic sequence extending in both the first direction 141 and the second direction 143, it is to be understood that the entire annular distribution 140 or only a portion of the annular distribution 140 may include a quasi-periodic sequence.

Referring again to fig. 2A-2C, it should be understood that the entire circular distribution 140 or only a portion of the circular distribution 140 may include a quasi-periodic sequence. For example, the circular distribution 140 may include adjacent arrangement segments 145 corresponding to a first order sequence segment to a second order sequence segment, a first order sequence segment to a third order sequence segment, a first order sequence segment to a fourth order sequence segment, a first order sequence segment to a fifth order sequence segment, a first order sequence segment to a sixth order sequence segment, a first order sequence segment to a seventh order sequence segment, a first order sequence segment to an eighth order sequence segment, and so on. Thus, it should be understood that the circular distribution 140 may include any number of permutation sections corresponding to any number of sequence sections. In addition, in some embodiments, the ring-shaped distribution 140 includes at least one arrangement section 145 corresponding to a third or higher order sequence section, a fourth or higher order sequence section, a fifth or higher order sequence section, a sixth or higher order sequence section, a seventh or higher order sequence section, and the like. In some embodiments, the circular distribution 140 includes alignment segments 145 corresponding to third order sequence segments and fourth order sequence segments, fourth order sequence segments and fifth order sequence segments, third order sequence segments through fourth order sequence segments, and so forth.

Multi-core optical fiber

Fig. 3A, 3B illustrate an example of a multicore annular optical fiber 101 including 39 cores within a cladding. The multi-core annular fiber shown in fig. 3A, 3B is designed and fabricated to have identical Single Mode (SM) waveguide cores that are regularly periodic and positioned in a circular ring. In this exemplary fiber, all of the cores are single mode cores, and all of the cores have the same Δ n (relative to the cladding) and the same core diameter d. That is, in this exemplary optical fiber, the cores are designed to be identical. The main parameters of the multicore fiber are: the core diameter d is 4.4 μm and the refractive index difference Δ n is n_{Core body}-n_{Cladding layer}0.0035, a ring diameter R (i.e., the distance R from the center of each core to the center of the fiber) of 120 μm, a cladding diameter R of at least 155 μm (e.g., 160 μm to 500 μm), waveguide cores regularly (periodically) placed in a ring with equal spacing between the cores, and an input core in the central core CC. The measurement data showed that the core size varied by less than about 10% and the average core diameter was 4.4 μm. Fig. 3B is a photograph of the manufactured optical fiber corresponding to fig. 3A. Fig. 3C is a photograph of the fabrication of fig. 3B, wherein light having an operating wavelength λ 1550nm propagates through the waveguide core. Other operating wavelengths may also be used. The operating wavelength λ may for example be in the following wavelength range: 800nm to 900nm, 920nm to 970nm, or 1200nm to 1400nm, 1530nm to 1565nm, or 1.0 μm to 1.1 μm.

In our single photon Quantum Walk (QW) experiments, we launched a signal into the central core (input core) of the core ring and a QW process occurred from the central waveguide core (input waveguide core) to the end cores of the two symmetric arms a1, a 2. In this embodiment, the two end cores of the two arms a1, a2 are separated by a large distance DxSeparated by a distance from the remaining cores to avoid coupling between the two end cores and thereby not provide a continuous QW over the continuously curved core profile 140. Among these embodiments, D is preferable_xIs larger than D'. For example, in some embodiments, 2D' < D_x< 10D ', or 2D' < D_x＜30D’。

The separation distance D 'between the edges of adjacent waveguide cores is also close enough for evanescent coupling to occur, for example, the separation distance D' may be greater than about 2 μm, about 30 μm or less, e.g., about 25 μm or less, about 20 μm or less, about 15 μm or less, about 10 μm or less, about 7.5 μm or less, etc. In some embodiments, the distance D 'is from 3 μm to 30 μm, and in some embodiments, the distance D' is from 5 μm to 30 μm.

According to some embodiments, a multicore optical fiber includes:

a cladding layer is arranged on the surface of the substrate,

a plurality of cores disposed in a cladding, wherein:

the plurality of cores comprises one or more first waveguide cores and one or more second waveguide cores, wherein at least some of the cores are positioned adjacent to at least one other core and the core center to core center spacing is no more than 10 times the average core radius such that greater than 10% of light will couple from one core to an adjacent core along the length of the optical fiber within a propagation distance of 1cm, thereby providing coupling between adjacent cores and enabling quantum walking between cores; and is

The plurality of cores are periodically (or substantially periodically) positioned within the annular distribution.

According to some embodiments, the distance Dx is greater than the distance D'. However, according to some embodiments, the distance Dx is equal to or less than the distance D'. According to some embodiments, the distance Dx > 30 μm.

Fig. 3D and 3C show the calculated photon probability distribution of quantum migration in the multicore fiber and the measured photon distribution of the fiber (experimental data), respectively. Fig. 3C and 3D both show typical patterns of quantum walking, which are characterized by two strong lobes. That is, the experimental measurements and simulations of photon distribution are consistent. Fig. 3C and 3D both clearly show the characteristics of quantum walk with two strong lobes at the end of the walk length.

In some embodiments of the periodically arranged core distribution, the distances Dx and D' are about the same. In such embodiments,

sides

111 and 113 are sufficiently close to enable coupling between the two end cores to provide continuous quantum walking between the waveguide cores. Thus, according to some embodiments, a multicore optical fiber includes:

a cladding layer is arranged on the surface of the substrate,

a plurality of cores disposed in a cladding, wherein:

the plurality of cores comprises one or more first waveguide cores and one or more second waveguide cores, wherein at least some of the cores are positioned adjacent to at least one other core and the core center-to-core center spacing is no more than 10 times the average core radius such that greater than 10% of light will couple from one core to an adjacent core along the length of the optical fiber within a propagation distance of 1cm, thereby providing coupling between adjacent cores and enabling quantum walking (e.g., continuous quantum walking) between waveguide cores;

According to some embodiments, the minimum distance between the edges of adjacent cores is at least equal to one half of the radius of the smaller core (preferably at least the radius of the core). According to some embodiments, the one or more first waveguide cores and the one or more second waveguide cores have the same diameter and the same refractive index.

According to some embodiments, a multicore optical fiber includes:

a cladding layer is arranged on the surface of the substrate,

a plurality of cores disposed in a cladding, wherein:

In some embodiments, the first propagation constant and the second propagation constant are the same. However, in some embodiments, the first propagation constant and the second propagation constant are different. According to some embodiments, the separation distance between each adjacent pair of waveguide cores in the plurality of waveguide cores is about 30 μm or less. According to some embodiments, a separation distance D between each adjacent pair of waveguides in the plurality of waveguides is between 5 μm and 30 μm. According to some embodiments, a separation distance D between each adjacent pair of waveguides in the plurality of waveguides is between 7.5 μm and 30 μm. According to some embodiments, a separation distance D between each adjacent pair of waveguides in the plurality of waveguides is between 10 μm and 30 μm. According to some embodiments, the waveguide core is a step index core. According to other embodiments, the waveguide core is a graded-index core. According to some embodiments, the separation distance D' between the edges of each adjacent pair of waveguides in the plurality of waveguides is between 5 μm and 30 um. According to some embodiments, the separation distance D' between the edges of each adjacent pair of waveguides in the plurality of waveguides is between 7.5 μm and 30 μm. According to some embodiments, the separation distance D' between the edges of each adjacent pair of waveguides in the plurality of waveguides is between 10 μm and 30 μm. According to some embodiments, the waveguide core is a step index core. According to other embodiments, the waveguide core is a graded-index core.

According to some embodiments, a multicore optical fiber includes:

a cladding layer is arranged on the surface of the substrate,

a plurality of cores disposed in a cladding, wherein:

In some embodiments, the first propagation constant and the second propagation constant are the same. However, in some embodiments, the first propagation constant and the second propagation constant are different.

According to some embodiments, the separation distance between each adjacent pair of waveguide cores in the plurality of waveguide cores is about 30 μm or less. According to some embodiments, a separation distance D between centers of each adjacent pair of waveguides in the plurality of waveguides is between 10 μm and 30 μm. According to some embodiments, a separation distance D' between edges of each adjacent pair of waveguide cores of the plurality of waveguide cores is between 7.5 μm and 30 μm, or between 10 μm and 30 μm. According to some embodiments, the waveguide core is a step index core. According to other embodiments, the waveguide core is a graded-index core.

Exemplary embodiments of multicore optical fiber 101

Fig. 4A illustrates a multicore fiber 101 including 39 waveguide cores 110 within a cladding 105. The waveguide cores 110 comprising one or more first waveguide cores are arranged in a ring (e.g., in a broken ring comprising a plurality of arms, such as arm 1 and arm 2) to form an annular distribution 140. More specifically, it is preferable that the core center is spaced from the fiber center by a distance r, as shown in this embodiment. In some embodiments, the core center is spaced from the fiber center by a distance Dc of r ± 0.2Dc, e.g., Dc of r ± 0.15Dc, where Dc is the diameter of the waveguide core. In other embodiments, the edge of the core closest to the center of the fiber may be spaced a distance r' from the center of the fiber. In other embodiments, the edge of the core closest to the center of the outer diameter of the cladding may be spaced a distance r "from the center of the fiber. In the exemplary embodiment, annular distribution 140 includes the one or more first waveguide cores 120 and the one or more second waveguide cores 130 arranged in a quasi-periodic sequence. Fig. 4B is a photograph of the manufactured optical fiber corresponding to fig. 4A.

In this embodiment, the core ring is configured as a fibonacci sequence having two types of Single Mode (SM) cores, namely, core a (waveguide core 120) and core B (waveguide core 130). The optical fiber core A (i.e., the waveguide core 120) has a refractive index difference Δ n₁＝n_{Core 1}-n_{Cladding layer}Wherein, Δ n₁Is the refractive index of waveguide core 120 at the operating wavelength (e.g., λ 1550nm), and n_{Cladding layer}Is the cladding index at the operating wavelength (e.g., λ 1550 nm). The optical fiber core B (i.e., the waveguide core 130) has a refractive index difference Δ n₂＝n_{Core body 2}-n_{Cladding layer}Wherein, Δ n₂Is the refractive index of waveguide core 130 at the operating wavelength (e.g., λ 1550 nm). In this embodiment, all of the waveguide cores 110 have the same diameter d. In some embodiments, however, the core diameter may be different. In general, the sequence of construction of the core annular arrangement 140 is the same as that of a Fibonacci array of waveguide cores, as shown in FIG. 5.The parameters of this embodiment of the optical fiber 101 are as follows. For second waveguide core 120, the refractive index difference (with respect to the cladding) Δ n₁＝n_{Core 1}-n_{Cladding layer}0.0035. In some exemplary embodiments, 0.0025 ≦ Δ n₁Less than or equal to 0.01. For second waveguide core 120, the refractive index difference Δ n₂＝n_{Core body 2}-n_{Cladding layer}0.0045. In some exemplary embodiments, 0.0025 ≦ Δ n₂Less than or equal to 0.01. In some exemplary embodiments, 0.001 ≦ Δ n₂-Δn₁The | is less than or equal to 0.01. The ring diameter (i.e., the distance R from the center of the core to the center of the fiber) is 120 μm, and the outer cladding diameter R is greater than 160 μm (e.g., 500 μm, 300 μm, 250 μm or therebetween). Although the optical fiber core diameters are designed to be the same, the core diameters in the manufactured optical fiber 101 are slightly different. The manufactured optical fiber measurements showed a core diameter variation of 15% or less (compared to the average core diameter) and an average core diameter of 4.55 mm. Thus, in this embodiment, the diameters of the waveguide cores are substantially the same.

Fig. 4D and 4C show the calculated photon probability distribution of quantum walking in this multicore fiber embodiment and the measured photon distribution (experimental data) of this fiber embodiment, respectively. Fig. 4C and 4D show different behaviors than those exhibited by the multicore ring fiber of fig. 3A, 3B. Unlike the typical pattern of quantum walk characterized by two strong lobes shown in fig. 3C and 3D, fig. 4C and 4D show only one strong lobe. Fig. 4C and 4D both clearly show the atypical features of quantum walk that produce only one strong lobe at the end of the walk length due to the quasi-periodic core distribution within the multicore fiber 101. That is, the experimental measurements and simulations of photon distribution are consistent.

Fig. 5 illustrates the general rules of a recursive construction of a quasiperiodic array of waveguide cores having a fibonacci sequence based on two different waveguide cores. j order Fibonacci element is defined as S_j＝S_j-2S_j- ₁S₁＝A，S₂Where A and B are two different single-mode waveguide cores. The waveguide cores a and B are placed close to each other to ensure evanescent coupling between the two adjacent waveguide cores. More specifically, fig. 5 illustrates an exemplary recursive configuration of a quasiperiodic array (sequence) of waveguide cores having j-order fibonacci sequences of two different waveguide cores a and B, and the elements S of the fibonacci arrays of

waveguide cores

120, 130₁，S₂... S₆Consists of two types of waveguide cores: a single-mode waveguide core a (smaller circle, corresponding to waveguide core 120) and a single-mode waveguide core B (larger circle, corresponding to waveguide core 130).

Fig. 6 illustrates the configuration of an exemplary fibonacci array (sequence) (FAWC) of waveguide cores. To increase the complexity of the waveguide core array, or to make the waveguide core sequence less ordered, the inventors defined a new j-order Fibonacci array for the waveguide core as F_j＝S₁S₂...S_jIn which S is₁，S₂...S_jIs a fibonacci element corresponding to the fiber of fig. 4A above. Fig. 5 schematically illustrates one example of how a sixth order fibonacci array (FAWC6) of waveguide cores may be constructed. Note that the array of waveguide cores may not necessarily be linear, but may be arranged in the same sequence along a curve, i.e., in a circular fashion, as described and illustrated herein, but the sequence of the fiber core arrangement will be similar when the waveguide cores are arranged to form the circular distribution 140.

Fig. 6 is a diagram of a six-order fibonacci array (FAWC6) of waveguide cores composed of two types of

waveguide cores

120, 130. More specifically, in the present embodiment, the plurality of waveguide cores includes single-mode waveguide cores a (smaller circle, corresponding to waveguide core 120) and B (larger circle, corresponding to waveguide core 130).

Fig. 7A and 7B illustrate the configuration of the core annular distribution 140 in a 4 th order fibonacci multicore annular optical fiber 101(FMCRF4) and a 5 th order fibonacci multicore annular optical fiber 101(FMCRF5), respectively. The ring of the core is symmetrical and has two arms, each of which is constructed as described above with respect to fig. 6. Fig. 7C illustrates a core annular profile 140 in a sixth order fibonacci multicore annular fiber 101(FMCRF6) that includes 39 waveguide cores.

It is clear from FIGS. 7A-7C that β is the propagation constant due to_AAnd beta_BThe fibonacci distribution of (a), the core ring constructed using fibonacci sequences of two different SM (single mode) waveguide cores a and B is diagonally quasiperiodic. (e.g., β when waveguide cores A and B correspond to waveguide

cores

120, 130, respectively_A＝b₁And beta is_B＝b₂Wherein b is₁Is the propagation constant of first waveguide core 120, b₂Is the propagation constant of the second waveguide core 130. ) The coupling coefficient between the nearest waveguide cores is a function of the overlap between the modes and the propagation constants of these waveguide cores. Thus, the coupling coefficient in a multicore annular fiber 101, such as the fibonacci multicore annular fiber (FMCRF) disclosed herein, also has a quasi-periodic-or a deterministic, disordered distribution. Thus, FMCRF advantageously provides a platform with diagonal and off-diagonal deterministic disorder for exactly implementing the LQW (e.g., the propagation constant and coupling coefficient are both quasi-periodic). That is, a multicore toroidal fiber (MCRF) having waveguide cores positioned in an annular distribution and configured as a fibonacci sequence with two different waveguide cores is such that both the propagation constant and the coupling coefficient are quasi-periodic or determine a disordered distribution.

Fig. 8A-8C illustrate simulation results of probability distributions of photons in quantum walking in a multicore fiber having a core annular distribution that is periodic (similar to the distribution of the fiber of fig. 3A, but including a)15 waveguide cores (fig. 8A), B)23 cores (fig. 8B), and C)39 cores (fig. 8C). More specifically, fig. 8A-8C show the probability distribution of a QW in a periodic MCRF, where photons are spread over a grating by coupling from one waveguide core to an adjacent waveguide core, the pattern of which is characterized by two strong lobes.

The result of an optical fiber having a waveguide core arranged in a ring profile with a quasi-periodic sequence is structurally different. For example, the LQW is clearly shown in a quasiperiodic Fibonacci multicore annular fiber (FMCRF). In addition, due to the symmetry of the quasi-periodic core rings in the FMCRF, a symmetric distribution of the LQWs can be achieved in the FMCRF. Fig. 8D-8E illustrate simulation results of probability distribution of photons in quantum walking in a fibonacci multicore annular optical fiber 101(FMCRF4, see fig. 8D) having D)15 waveguide cores, E)23 waveguide cores (FMCRF5, see fig. 8E), and F)39 waveguide cores (FMCRF6, see fig. 8F).

Note that the quantum walk of a multicore fiber with a periodic core ring distribution (e.g., the fiber of fig. 3A) has a photon spread of a pattern characterized by two strong lobes on the grating by coupling from one waveguide core to its adjacent waveguide core, as does the normal quantum walk on a straight line. However, the results for an annular multicore fiber 101 with a quasi-periodic core (e.g., a fibonacci multicore annular fiber) are different: localized quantum walking is clearly demonstrated in a fibonacci multicore ring fiber. In addition, due to the symmetry of a quasi-periodic core ring (such as in FMCRF), a symmetric distribution of LQWs can be achieved in FMCRF.

Design of multicore annular optical fiber (MCRF)

The design of an MCRF with a periodic core annular distribution is shown, for example, in FIG. 3A. In this multi-core ring fiber, all single-mode waveguide cores are regularly placed with two identical arms of the ring, and the central waveguide core is the input core for coupling of the input signal. The fiber design shown in FIG. 3a has the following features:

1. the Mode Field Diameter (MFD) of the fiber core (i.e., waveguide core) is close to (e.g., within 10% of) the mode field diameter of a single mode fiber for ease of coupling to a single mode input fiber.

2. The two end cores in the two arms a1, a2 of the core ring are spaced apart by a distance Dx far enough, if necessary, to avoid coupling between the two end cores, which would otherwise distort the distribution of the normal quantum walks in line, which would not have such an interaction.

3. The fiber cladding should not be too close to the core ring to avoid reflections at the interface between the cladding and the fiber jacket or air surrounding the cladding. Although the reflection is minimal, if the cladding is too thin and close to the core ring, it may cause some distortion.

A fiber design of an optical fiber 101 (e.g., FMCRF) having a quasi-periodic core ring distribution (similar to the fiber design of the MCF described above, but with the core ring distribution 140 of the fiber having multiple cores arranged in a quasi-periodic ring distribution, e.g., a ring distribution based on a fibonacci sequence, a ludin-charpy sequence, or a figure angstrom-morse sequence the core ring distribution 140 may include at least two arms (e.g., two symmetric arms a1, a 2.) for example, each arm of the core ring distribution 140 may be configured as a fibonacci sequence with a waveguide core as described and shown herein, e.g., as shown in fig. 2, 2A-C, and 4A-4B and 7.

Manufacture of MCRF

One exemplary method of manufacturing an MCRF (e.g., FMCRF) includes: the method includes the steps of fabricating a cylindrical rod of clad glass having a top (flat) surface, drilling a hole in a direction normal to the flat surface, and inserting a continuous core rod into the drilled hole to form a multi-core preform, and then drawing the multi-core preform into a multi-core optical fiber. Another exemplary method of manufacturing an MCRF (e.g., FMCRF) includes: a clad glass preform is manufactured having an elongated hole capable of receiving a core rod, the core rod is inserted into the hole, clad glass is consolidated around the core rod to form a multi-core preform, and then the multi-core preform is drawn into a multi-core optical fiber. Other methods of forming multi-core optical fibers may also be employed.

Setting up and measuring

The MCRF (periodic and FMCRF) with 39 single mode cores was characterized using orthogonal polarization microscopy. The microscope system is a Nikon (Nikon) high-power optical microscope, and the error is +/-0.5 um. The measured average core diameters of MCF and FMCF were 4.40 μm and 4.55 μm, respectively. For periodic MCRF (similar to that of FIG. 3A) and FMCRF, the average center-to-center distances of adjacent cores are 16.89 μm and 16.80 μm, respectively. The refractive indices observed from orthogonal polarizations indicate that periodic MCFs have the same refractive index for all cores, while FMCFs have different core refractive indices, grouped as described in the previous section. The core ring radius r is about-120 μm and the fiber cladding outer radius is about-158 μm.

Demonstration of quantum migration in MCRF and FMCF was performed with about 4cm length of stripped fiber. The optical fiber is placed on a V-groove in the imaging system shown in fig. 9. The tunable light source of 1510-1590nm laser was made to illuminate the multicore annular fiber 101. The steps of identifying the central (20 th) core and measuring the quantum walking distribution are as follows:

1.) illuminating a sub-portion of the target optical Fiber (FOI) so as to illuminate the waveguide core.

2.) combine the illumination images to identify the position of each waveguide core using the Matlab/Labview algorithm to identify a circular object, e.g., drawing a circle around the object as shown in fig. 10. More specifically, FIG. 10 illustrates a sample of the algorithm detecting the position of each core. A circle is drawn around the position of each waveguide core.

3.) find the position of the central core (20 th core).

4.) illuminate the central core by butt coupling with a single mode optical fiber that is mode matched to the MCRF core.

5.) capture a signal image.

6.) for wavelength scan from 1530-1559nm, steps 4-5 are repeated to account for fiber length variation.

7.) the total intensity in the MFD of each waveguide core is calculated, for example, by using the Matlab algorithm or another available software.

Experimentally, the inventors have demonstrated quantum walking in at least two types of quantum systems: quantum systems employing a plurality of waveguide cores arranged in an ordered periodic manner include ordered and quasi-periodic arrays of cores or quantum systems of defined disordered arrays of waveguide cores. The ordered system MCRF shows the expected distribution of the quantum walking distribution. On the other hand, FMCRF as a quasi-periodic or deterministic chaotic system shows localization as predicted by the inventors' simulations. However, the system can be further improved, especially for FMCRF, because of the very strong tolerance for misalignment, surface roughness, and reflection at the air/cladding interface. Misalignment, roughness, air/cladding interfaces can cause distortion and undesirable localization and interference in the fiber. These problems can be solved by using an index matching oil to reduce reflection at the interface between the cladding and air. In order to obtain an optical fiber with a short length and a minimal roughness of the end face to prevent undesired back reflection due to poor cracking or flat end faces, a containment unit is made for the optical fiber, which is made of an angled jacket (ferule) and/or rod completely or partially filled with an index matching oil and a high index adhesive. Depending on the tolerance to back reflection, the ferrule is polished at an angle or flat.

For the purposes of describing and defining the present technology, it is noted that reference herein to a variable being a "function" of a parameter or another variable does not mean that the variable is merely a function of the listed parameter or variable. Rather, references herein to a variable being a "function" of a listed parameter are intended to be open ended, and thus a variable may be a single parameter or a function of multiple parameters.

It should also be noted that the recitation of "at least one" element, such as "a," "an," etc., herein should not be taken to limit the recitation of "a" or "an" alternative usage to a single element, etc.

It should be noted that the description herein of components of the present disclosure being "configured" in a particular manner is intended to embody a particular property, or function in a particular manner, and such description is intended to be structural rather than descriptive of the intended use. More specifically, the manner in which a component is "configured" as described herein refers to existing physical conditions of the component and thus can be considered a limiting description of the structural characteristics of the component.

For the purposes of describing and defining the present technology it is noted that the terms "substantially" and "about" are utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The terms "substantially" and "about" are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

Having described the subject matter of the present disclosure in detail and by reference to specific embodiments thereof, it should be noted that the various details disclosed herein are not to be considered as implying that such details relate to elements that are essential components of the various embodiments described herein, even though specific elements are shown in each of the detailed description figures. Further, it will be apparent that modifications and variations are possible without departing from the scope of the disclosure, including but not limited to the embodiments defined in the appended claims. More specifically, although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these aspects.

It is to be noticed that the appended claim(s) used the term 'wherein' as a conjunctive term. For the purposes of defining the technology of the present invention, it is noted that this term is introduced as an open ended claim used to introduce a description of the series of features of the structure and is to be understood in a manner similar to the more commonly used open ended introductory term "comprising".

Claims

1. A multicore optical fiber, comprising:

a cladding layer is arranged on the surface of the substrate,

a plurality of waveguide cores disposed in a cladding, wherein:

a plurality of cores are positioned adjacent to at least one other core, and the core center to core center spacing is no more than 10 times the average core radius, such that greater than 10% of light will couple from one core to an adjacent core along the length of the fiber within a 1cm propagation distance, thereby providing coupling between adjacent cores and enabling quantum walking; and is

The plurality of waveguide cores are disposed in the cladding in an annular distribution or at least a portion of an annular distribution.

2. The multicore optical fiber of claim 1, wherein the plurality of waveguide cores have the same propagation constant.

3. The multicore optical fiber of claim 1, wherein the plurality of waveguide cores comprises at least two waveguide cores having different propagation constants.

4. A multicore optical fiber, comprising:

a cladding layer is arranged on the surface of the substrate,

a plurality of cores disposed in a cladding, wherein:

5. The multicore optical fiber of claim 4, wherein the first and second propagation constants are the same.

6. The multicore optical fiber of claim 4, wherein the first and second propagation constants are not the same.

7. A multicore optical fiber, comprising:

a cladding layer is arranged on the surface of the substrate,

a plurality of cores disposed in a cladding, wherein:

8. The multicore optical fiber of claim 7, wherein the first and second propagation constants are the same.

9. The multicore optical fiber of claim 7, wherein the first and second propagation constants are not the same.

10. The multicore optical fiber of claims 1-9, wherein the separation distance D between each adjacent pair of waveguide cores in the plurality of waveguide cores comprises about 30 μ ι η or less.

11. The multicore optical fiber of claims 1-9, wherein the separation distance D between each adjacent pair of waveguide cores in the plurality of waveguide cores is between 10 μ ι η and 30 μ ι η.

12. A system, comprising:

the multicore optical fiber of any one of claims 1-9;

a photon generator optically coupled to an input of at least one of the plurality of waveguide cores; and

one or more photon detectors optically coupled to an output of at least one waveguide core of the plurality of cores.

13. The system of claim 12, wherein the system is a quantum communication system.

14. The system of claim 12, wherein the system is a quantum computer system.