Single-channel multi-entangled photon pair generation method, device, equipment and medium

Abstract

The invention relates to a single-channel multi-entangled photon pair generation method, device and equipment and a medium, and belongs to the technical field of nonlinear optics. According to the method, an existing method for generating entangled light through spontaneous parametric down-conversion in a nonlinear crystal is improved, the quasi-phase matching period of the nonlinear crystal is designed in a targeted mode, based on the spontaneous parametric down-conversion process, high-dimensional polarization entangled photon pairs of two wavelengths are generated at the same time, conversion channels are reduced, and the conversion efficiency is improved. Compared with an existing spontaneous parametric down-conversion generation method, generated entangled photon pairs are doubled, and compared with an existing non-spontaneous parametric down-conversion generation method, a complex optical system is not needed, the multisource of experimental errors is reduced, and the experimental efficiency is improved. Therefore, compared with an existing entangled light generation method, the method has the advantages of being simple, efficient, reliable and flexible in design, the difficulty of preparing the high-dimensional entangled source is greatly reduced, and development of the quantum entangled source and the quantum information technology can be better promoted.

Description

Technical Field

[0001] The present invention relates to the field of nonlinear optical technology, and in particular to a method, device, equipment and medium for generating single-channel multi-entangled photon pairs. Background Art

[0002] Quantum entanglement sources play a vital role in quantum information technology. Their significance is not only reflected in improving communication security, accelerating computing processes, improving sensing accuracy and expanding simulation capabilities, but also in promoting basic scientific research and technological innovation. With the continuous development of quantum technology, quantum entanglement sources play a role in a wide range of fields, promoting the innovation and development of a series of related technologies, including quantum communication protocols, quantum computing algorithms, quantum sensing technology and quantum simulation methods. At the same time, quantum entanglement, as one of the most non-classical features of quantum mechanics, is of great significance for understanding the basic principles and characteristics of quantum mechanics. By studying quantum entanglement sources, scientists can further reveal the mysteries of the quantum world and promote the development of basic science.

[0003] At present, the main methods for generating quantum entangled photon pairs include spontaneous parametric down conversion (SPDC) in nonlinear crystals, atomic cascade radiation, four-wave mixing, and quantum dots. Among them, the realization of generating entangled sources based on nonlinear crystals of SPDC is relatively simple. It mainly uses the nonlinear effect of light to split a photon into two entangled photons with lower energy and longer wavelength, and is used for applications such as quantum communication. However, the current development of nonlinear crystals only stays at the generation of two-photon entangled sources, that is, the existing spontaneous parametric down conversion can only generate one photon pair, the number of photon pairs generated is small, and the efficiency is low. Other methods for generating quantum entangled photon pairs are difficult to implement, such as four-wave mixing technology, which generates entangled photon pairs by mixing four optical signals (usually with different frequencies) in nonlinear elements (such as silicon optical waveguides). Although this method can generate multiple entangled photon pairs at the same time to achieve high-dimensional photon entangled states, and can control the characteristics of entangled photons to a certain extent, the experimental conditions are relatively harsh and require high-precision control and optimization, so it is difficult to implement.

[0004] That is, the current methods of generating quantum entangled photon pairs are either difficult or have low photon generation efficiency. Therefore, there is an urgent need for a simple and efficient method to generate high-dimensional entangled light. Summary of the invention

[0005] In view of this, the embodiments of the present invention provide a single-channel multi-entangled photon pair generation method, device, equipment and medium to solve the current technical problem that it is difficult to simply and efficiently achieve high-dimensional entangled light generation.

[0006] In a first aspect, a method for generating multiple entangled photon pairs in a single channel is provided, the method comprising:

[0007] According to the quasi-phase matching conditions that the nonlinear crystal needs to meet during the optical parameter down-conversion process, determine the first polarization period and the second polarization period of the nonlinear crystal with respect to the wavelength and the refractive index during the type II quasi-phase matching process, wherein the first polarization period represents the polarization period when the signal light is vertically polarized and the idle light is horizontally polarized, and the second polarization period represents the polarization period when the signal light is horizontally polarized and the idle light is vertically polarized;

[0008] Under the constraints that the length of the first polarization period is equal to the length of the second polarization period, and the constraints that the wavelength of the signal light is not equal to the wavelength of the idle light, determine the wavelength of the target signal light and the wavelength of the target idle light corresponding to the target pump light with a known wavelength, as well as the refractive index corresponding to the target pump light, the refractive index corresponding to the target signal light, and the refractive index corresponding to the target idle light;

[0009] The target polarization period length is determined according to the wavelength of the target signal light, the wavelength of the target idle light, the corresponding refractive index of the target pump light, the corresponding refractive index of the target signal light and the corresponding refractive index of the target idle light, and the target pump light is injected into the periodically polarized crystal under the target polarization period length to complete the generation of single-channel multi-entangled photon pairs.

[0010] In a second aspect, a single-channel multi-entangled photon pair generating device is provided, the device comprising:

[0011] A polarization period determination module, for determining a first polarization period and a second polarization period of the nonlinear crystal regarding wavelength and refractive index in a type II quasi-phase matching process according to a quasi-phase matching condition that the nonlinear crystal needs to satisfy in an optical parameter down-conversion process, wherein the first polarization period represents a polarization period when the signal light is vertically polarized and the idle light is horizontally polarized, and the second polarization period represents a polarization period when the signal light is horizontally polarized and the idle light is vertically polarized;

[0012] a wavelength and refractive index determination module, for determining the wavelength of the target signal light and the wavelength of the target idle light corresponding to the target pump light of known wavelength, and the refractive index corresponding to the target pump light, the refractive index corresponding to the target signal light, and the refractive index corresponding to the target idle light, based on the constraint that the length of the first polarization period is equal to the length of the second polarization period, and the constraint that the wavelength of the signal light is not equal to the wavelength of the idle light;

[0013] An entangled light generating module is used to determine a target polarization period length according to the wavelength of the target signal light, the wavelength of the target idle light, the corresponding refractive index of the target pump light, the corresponding refractive index of the target signal light and the corresponding refractive index of the target idle light, and inject the target pump light into a periodically polarized crystal under the target polarization period length to complete the generation of single-channel multiple entangled photon pairs.

[0014] In a third aspect, an embodiment of the present invention provides a computer device, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the processor implements the single-channel multi-entangled photon pair generation method as described in the first aspect when executing the computer program.

[0015] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the single-channel multi-entangled photon pair generation method as described in the first aspect is implemented.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The single-channel multi-entangled photon pair generation method of the present invention improves the existing method of generating entangled light by spontaneous parametric down-conversion in nonlinear crystals, and realizes the generation of high-dimensional polarization entangled photon pairs of two wavelengths based on the spontaneous parametric down-conversion process by targeted design of the quasi-phase matching period of the nonlinear crystal, thereby reducing the conversion channels. Compared with the existing spontaneous parametric down-conversion generation method, the entangled photon pairs are doubled, and compared with the existing non-spontaneous parametric down-conversion generation method, no complex optical system is required, thereby reducing the multi-source of experimental errors. Therefore, in general, compared with the existing generation method, the method has the characteristics of simplicity, efficiency, reliability and flexible design, which greatly reduces the difficulty of preparing high-dimensional entangled sources and can better promote the development of quantum entangled sources and quantum information technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 This is a schematic diagram of an application environment of a method for generating multiple entangled photon pairs in a single channel provided in Embodiment 1 of the present invention;

[0020] Figure 2It is a flow chart of a method for generating multiple entangled photon pairs in a single channel provided in Embodiment 1 of the present invention;

[0021] Figure 3 This is a schematic diagram of the principle of generating four-photon entanglement provided by Embodiment 1 of the present invention;

[0022] Figure 4 This is a schematic diagram of an optical path for generating multiple entangled photon pairs in a single channel provided by an embodiment of the present invention;

[0023] Figure 5 It is a schematic diagram of a periodically polarized potassium titanyl phosphate crystal prepared with a target polarization period provided by one embodiment of the present invention;

[0024] Figure 6 An embodiment of the present invention provides a method based on Figure 5 Schematic diagram of the entangled photon counting results generated by periodically poled potassium titanyl phosphate crystal;

[0025] Figure 7 It is a structural schematic diagram of a single-channel multi-entangled photon pair generating device provided in Embodiment 2 of the present invention;

[0026] Figure 8 It is a structural diagram of a computer device provided in Embodiment 3 of the present invention. DETAILED DESCRIPTION

[0027] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0028] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0029] It should also be understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0030] As used in the present specification and the appended claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]", depending on the context.

[0031] In addition, in the description of the present specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0032] References to "one embodiment" or "some embodiments" etc. described in the present specification mean that one or more embodiments of the present invention include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0033] The embodiments of the present invention can acquire and process relevant data based on artificial intelligence technology. Artificial Intelligence (AI) is the theory, method, technology and application system that uses digital computers or machines controlled by digital computers to simulate, extend and expand human intelligence, perceive the environment, acquire knowledge and use knowledge to obtain the best results.

[0034] AI basic technologies generally include sensors, dedicated AI chips, cloud computing, distributed storage, big data processing technology, operation / interaction systems, mechatronics, etc. AI software technologies mainly include computer vision technology, robotics technology, biometrics technology, speech processing technology, natural language processing technology, and machine learning / deep learning.

[0035] It should be understood that the order of execution of the steps in the following embodiments does not imply a precedence of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0036] In order to illustrate the technical solution of the present invention, specific embodiments are provided below for illustration.

[0037] A single-channel multi-entangled photon pair generation method provided in the first embodiment of the present invention can be applied in the following aspects: Figure 1 In the application environment, the client communicates with the server. The client includes but is not limited to PDA, desktop computer, laptop computer, ultra-mobile personal computer (UMPC), netbook, cloud terminal device, personal digital assistant (PDA) and other terminal devices. The server can be implemented by an independent server or a server cluster composed of multiple servers. The above single-channel multi-entangled photon pair generation method can be applied to Figure 1 The server in the server, the computer device corresponding to the server is connected to the corresponding database, rule base, etc. to obtain the corresponding data in the database. The above-mentioned computer device can also be connected to the client to collect data and control instructions sent by the client user. The above-mentioned single-channel multi-entangled photon pair generation method can also be applied to Figure 1 The client in the client, the terminal device corresponding to the client connects to the target database through a preset application programming interface (Application Programming Interface, API). When the target data is driven to execute the corresponding task, a corresponding task log will be generated, and the above task log can be collected through the API.

[0038] See also Figure 2 , is a flow chart of a method for generating multiple entangled photon pairs in a single channel provided in Embodiment 1 of the present invention, such as Figure 2 As shown, the single-channel multi-entangled photon pair generation method may include the following steps:

[0039] S101, according to the quasi-phase matching conditions that the nonlinear crystal needs to meet during the optical parameter down-conversion process, determine the first polarization period and the second polarization period of the nonlinear crystal with respect to the wavelength and the refractive index during the type II quasi-phase matching process, wherein the first polarization period represents the polarization period when the signal light is vertically polarized and the idle light is horizontally polarized, and the second polarization period represents the polarization period when the signal light is horizontally polarized and the idle light is vertically polarized.

[0040] The current methods of generating quantum entangled photon pairs such as atomic cascade radiation, four-wave mixing and quantum dots have implementation principles that determine that it is difficult to significantly reduce the difficulty of implementation. Therefore, the present invention chooses to improve the efficiency of the method for generating quantum entangled photon pairs based on spontaneous parametric down-conversion in nonlinear crystals, and improves the existing single-channel method that can only generate one entangled photon pair to a single-channel method that can generate two entangled photon pairs, thereby increasing the types of entangled light generated from two to four, so as to obtain a method for simply and efficiently generating high-dimensional entangled light.

[0041] To achieve the above objectives, this embodiment provides a single-channel high-dimensional four-photon entanglement generation scheme, which mainly calculates the period of quasi-phase matching (QPM) of the nonlinear crystal used to generate the quantum entanglement source, and uses a polarization period to simultaneously generate two wavelengths and four different states of polarization entangled photons while ensuring spontaneous parametric down-conversion (SPDC).

[0042] For nonlinear crystals, such as the commonly used potassium titanyl phosphate (KTP), the periodically poled potassium titanyl phosphate (PPKTP) crystal obtained by periodically poling it, and the periodically poled crystal obtained by periodically poling other nonlinear crystals, three types of quasi-phase matching processes can occur:

[0043] 1. When the vertically polarized (S-biased) pump light undergoes optical parametric down-conversion to generate vertically polarized signal light and idle light, the process is a type 0 quasi-phase matching process;

[0044] 2. When the vertically polarized (S-biased) pump light undergoes optical parametric down-conversion to generate horizontally polarized signal light and idle light, the process is a type I quasi-phase matching process;

[0045] 3. When the horizontally polarized (P-biased) pump light undergoes optical parametric down-conversion to generate vertically polarized signal light and horizontally polarized idle light, the process is a type II quasi-phase matching process.

[0046] In this field, the process of generating entangled light when the number of photon types generated is greater than 2 is usually referred to as the generation of high-dimensional entangled light, where the type of photon is determined by the differences in degrees of freedom such as wavelength, frequency, polarization, and spin. Therefore, from the above optical parametric down-conversion (SPDC) process, it can be seen that the photons generated by type 0 and type I may only differ in a single degree of freedom, namely wavelength. The difference in a single degree of freedom can only produce two types of photons at most. The photons generated by type II can be different in both polarization direction and wavelength. The difference in the two degrees of freedom can produce four types of photons at most, thereby generating high-dimensional entangled light.

[0047] Therefore, we need to use the type II quasi-phase matching process of KTP crystal to achieve high-dimensional entanglement generation, that is, Figure 3 As shown in the principle diagram of four-photon entanglement generation, two photon pairs are generated, specifically, entangled light of two wavelengths is generated, and each wavelength has photons in two states of horizontal polarization and vertical polarization, and then Figure 4 As shown in the optical path diagram of the single-channel multi-entangled photon pair generation, the two entangled lights of different wavelengths generated are separated into wavelengths λ by a laser beam splitter. 1 The shorter signal light, and the wavelength λ 2 A longer idle light, and because both the signal light and the idle light contain horizontally polarized and vertically polarized photons, four usable entangled lights are finally obtained.

[0048] Specifically, the spontaneous parametric down-conversion (SPDC) process of pump light in a nonlinear crystal must meet quasi-phase matching conditions. First, energy conservation must be satisfied, and second, momentum conservation must be satisfied. Based on the quasi-phase matching conditions, the relationship between the polarization period and the wavelengths of the signal light and the idle light during the quasi-phase matching process can be determined, as well as the relationship between the polarization period and the refractive index of the pump light, signal light, and idle light in each direction in the crystal can be determined.

[0049] For the type II quasi-phase matching process, the polarization directions of the signal light and the idle light are mainly YZY propagation, and the propagation directions of the signal light and the idle light are perpendicular to each other in the type II quasi-phase matching process. Therefore, if we want to achieve Figure 3 The four-photon entanglement shown in the figure can be assumed that one of the four photons is a vertically polarized signal light λ 1 (S) with horizontally polarized idle light λ 2 (P), and the other group is the horizontally polarized signal light λ 1 (P) with vertically polarized idle light λ 2 (S).

[0050] It is assumed that the polarization period corresponding to one group of signal light and idle light is the first polarization period, and the polarization period corresponding to the other group of signal light and idle light is the second polarization period. Since the polarization squares of the signal light and idle light generated by the two groups are different, different relationships between the wavelengths of the signal light and the idle light, as well as the relationships between the refractive indices of the pump light, signal light and idle light in various directions in the crystal can be obtained.

[0051] S102, with the constraint that the length of the first polarization period is equal to the length of the second polarization period, and the constraint that the wavelength of the signal light is not equal to the wavelength of the idle light, determine the wavelength of the target signal light and the wavelength of the target idle light corresponding to the target pump light of known wavelength, as well as the refractive index corresponding to the target pump light, the refractive index corresponding to the target signal light, and the refractive index corresponding to the target idle light.

[0052] Since the present invention aims to realize the generation of such high-dimensional entangled light with multiple entangled photons in a single polarization period, i.e., a single channel, it is expected that the length of the first polarization period and the second polarization period in the above step S101 are equal, so as to realize the generation of two groups of signal light and idle light with one polarization period. At the same time, since the generation of four entangled lights is to be realized, it is necessary to ensure that the wavelengths of the signal light and the idle light in the two groups are different, otherwise it will result in the signal light λ of one group being 1 (S) and the idle light λ of another group 2 (S) are essentially the same and only two entangled lights are actually produced in the end.

[0053] In summary, this embodiment first selects the wavelength of the pump light input to the crystal, that is, the pump light used to stimulate the generation of signal light and idle light, and records it as the target pump light with a known wavelength. Then, based on the target pump light, the target signal light wavelength and the target idle light wavelength corresponding to the target pump light are determined with the constraint that the length of the first polarization period is equal to the length of the second polarization period, and the signal light wavelength is not equal to the idle light wavelength.

[0054] Among them, regarding the determination of the target signal light wavelength and the target idle light wavelength, one method is to first obtain a refractive index data table by experimentally measuring the refractive index corresponding to different wavelengths and different propagation directions, and then substitute the target pump light of known wavelength into the refractive index data table to determine the refractive index of the pump light, and then successively select wavelengths of different lengths from the refractive index data table as the signal light wavelength and determine the idle light wavelength corresponding to the signal light selected each time and the refractive index of the idle light and the signal light, so as to determine the signal light and the idle light that satisfy the constraint that the length of the first polarization period is equal to the length of the second polarization period and the constraint that the signal light wavelength is not equal to the idle light wavelength through cyclic attempts, and use them as the target signal light and the target idle light; another method is to directly derive and calculate the target signal light and the target idle light corresponding to the target pump light based on the existing refractive index equation formula, and the refractive index corresponding to the target signal light and the target idle light respectively.

[0055] S103, determining a target polarization period length according to the wavelength of the target signal light, the wavelength of the target idle light, the refractive index corresponding to the target signal light, and the refractive index corresponding to the target idle light, injecting the target pump light into a periodically polarized crystal under the target polarization period length, and completing the generation of single-channel multi-entangled photon pairs.

[0056] Since the polarization period is related to the wavelength and the refractive index, when the wavelength of the target signal light and the corresponding refractive index of the target signal light, as well as the wavelength of the target idle light and the corresponding refractive index of the target idle light are known, the aforementioned first polarization period or the second polarization period can be calculated. Since the target signal light and the target idle light are obtained under the constraint that the length of the first polarization period is equal to the length of the second polarization period, the first polarization period is equal to the second polarization period, and both are polarization periods that can successfully generate four entangled photons, that is, the required target polarization period.

[0057] After determining the target polarization period, a periodically poled crystal under the target polarization period can be selected, or a nonlinear crystal can be periodically poled to obtain a periodically poled crystal under the target polarization period.

[0058] Taking potassium titanyl phosphate (KTP) as an example, the periodic poling preparation process is as follows: preparing a mask, preparing a periodic electrode by Wiener processing, preparing a periodic poled potassium titanyl phosphate (PPKTP) crystal with a target poling period by periodic poling by an applied electric field method, and polishing and optically coating the crystal. Of course, in other embodiments, any feasible type of nonlinear crystal can be used, and a periodic poled crystal of that type can be selected or prepared.

[0059] After selecting or preparing a periodically polarized crystal under a target polarization period, the periodically polarized crystal under the target polarization period is placed in a Figure 4 The single-channel multi-entangled photon pair is shown in the crystal position in the optical path, and then the target pump light is generated by the laser and input into the periodically polarized crystal under the target polarization period, which can be Figure 3 As shown, four entangled photons with different wavelengths and polarization directions are generated, realizing the generation of single-channel high-dimensional entangled light, that is, realizing the generation of single-channel multiple entangled photon pairs.

[0060] The single-channel multi-entangled photon pair generation method of the present invention breaks the restrictive correlation between polarization and wavelength of photons generated during type II quasi-phase matching in the spontaneous parametric down-conversion process by designing the quasi-phase matching period of the nonlinear crystal, thereby realizing the generation of high-dimensional polarization entangled photon pairs of two wavelengths, reducing the conversion channels, and eliminating the need for a complex optical system to achieve this goal, thereby reducing the multi-source of experimental errors. Therefore, it has the characteristics of simplicity, efficiency, reliability and flexible design, greatly reducing the difficulty of preparing high-dimensional entangled sources, and can better promote the development of quantum entangled sources and quantum information technology.

[0061] In one embodiment, the specific contents of the quasi-phase matching conditions that the nonlinear crystal needs to satisfy during the optical parametric down-conversion process in the above step S101 are given.

[0062] As described in the above embodiment, the quasi-phase matching conditions that the nonlinear crystal needs to meet during the optical parameter down-conversion process include two aspects, one is to satisfy the conservation of energy, and the other is to satisfy the conservation of momentum, which are as follows:

[0063] Conservation of Energy:

[0064] w 0 =w 1 +w 2

[0065] Among them, w 0 represents the frequency of the pump light, w 1 represents the frequency of the generated signal light, w 2 represents the frequency of the idle light produced;

[0066] Conservation of Momentum:

[0067] k 0 =k 1 +k 2 +m*kg

[0068] |k|=2πn / λ

[0069] k g =2π / λ

[0070] Among them, k 0 represents the wave vector of the pump light, k 1 represents the wave vector of the signal light, k 2Represents the wave vector of idle light, kg represents the periodic polarization vector, m represents the order of quasi-phase matching, which is an integer. The value of m determines the effective nonlinear conversion efficiency of the optical parameter conversion process. The larger the m, the lower the nonlinear conversion efficiency, and the corresponding experimentally prepared compressed state and entangled state become lower. k represents the wave vector, |k| represents the absolute value of k, n represents the refractive index of the light beam when propagating in the crystal, and the value direction is consistent with the polarization direction of the wave vector. For type II quasi-phase matching process, the polarization direction is mainly YZY propagation, λ represents the wavelength of the light beam, and Λ represents the polarization period.

[0071] In another embodiment, a specific calculation method of the first polarization period and the second polarization period in the above step S101 is provided.

[0072] In the process of pump light inputting into the nonlinear crystal to stimulate the generation of signal light and idle light, that is, λ 0 →λ 1 +λ 2 In the process, based on the specific content of the quasi-phase matching condition that the nonlinear crystal needs to satisfy during the optical parametric down-conversion process given in the above embodiment, it can be deduced that:

[0073] K g =2π / λSubstitute into k 0 =k 1 +k 2 + m*kg we get: thereby

[0074] Since |k|=2πn / λ, we have:

[0075] or

[0076] Further deduction yields:

[0077] or where λ 0 represents the wavelength of the pump light, λ 1 Indicates the wavelength of the signal light, λ 2 represents the wavelength of idle light;

[0078] Continue by w 0 =w 1 +w 2 , can be obtained Thus we can get:

[0079] or

[0080] Since we want to use type II SPDC process, the polarization direction is mainly YZY propagation, that is, the refractive index of the pump light n 0 Take the Y propagation direction, denoted as n 0,y ; Refractive index of signal light n 1 Take the Z propagation direction, denoted as n 1,z ; Idle light refractive index n 2 Take the Y propagation direction, denoted as n 2,y . Therefore, we can get:

[0081] or

[0082] In order to make λ 1 With λ 2 To achieve four-photon entanglement with a single-channel period, we must make Λ 1 =|Λ 2 |, then for λ 1 The process produces a wavelength of λ 1 The photon is the signal light, the refractive index is in the Z direction, and the wavelength is λ 2 The photon is idler light, and the refractive index is in the Y direction; 2 The process produces a wavelength of λ 1 The photon is idler light, the refractive index is in the Y direction, and the wavelength is λ 2 The photon is the signal light, and the refractive index is taken in the Z direction of propagation. Therefore, a single channel with multiple entangled photon pairs is realized, and the generated λ 1 With λ 2 There are both vertical and horizontal polarization states, so the first polarization period and the second polarization period can be determined respectively:

[0083] The first polarization period is:

[0084]

[0085] Among them, Λ 1 represents the first polarization period, λ 1 Indicates the wavelength of the signal light, λ 2 represents the wavelength of idle light, n 0,y represents the refractive index of the pump light in the y direction of the nonlinear crystal, n 1,z represents the refractive index of the signal light in the z direction of the nonlinear crystal, n 2,y represents the refractive index of the idle light in the y direction of the nonlinear crystal, and m represents the order of quasi-phase matching.

[0086] The second polarization period is:

[0087]

[0088] Among them, Λ 2 represents the second polarization period, n 1,y represents the refractive index of the signal light in the y direction of the nonlinear crystal, n 2,z represents the refractive index of the idle light in the z direction of the nonlinear crystal.

[0089] This embodiment provides a specific derivation process of the first polarization period and the second polarization period, and clarifies the basis for deriving the first and second polarization periods and their feasibility.

[0090] In one embodiment, a specific method is provided for implementing the constraint that the length of the first polarization period is equal to the length of the second polarization period, and the constraint that the wavelength of the signal light is not equal to the wavelength of the idle light in step S102.

[0091] In order to make λ 1 With λ 2 To achieve four-photon entanglement with a single-channel cycle, it is necessary to make Λ 1 =|Λ 2 |, there are two situations:

[0092] When 1 =Λ 2 hour:

[0093]

[0094] Since n in the nonlinear crystal y -n z is monotonically increasing and less than 0, so only when λ 1 =λ 2 Λ 1 =|Λ 2 |, at this time, four entangled lights with different wavelengths and polarization states cannot be formed, so the high-dimensional entangled state does not exist.

[0095] When 1 =-Λ 2 hour:

[0096]

[0097] At this time, there is a unique solution, and at the same time, λ 1 ≠λ 2 , four entangled lights with different wavelengths and polarization states can be formed, meeting the requirements of high-dimensional entangled states.

[0098] Therefore, by limiting the ratio of the target signal light wavelength to the target idle light wavelength, the above Λ 1 =-Λ 2The proportional formula can be used to ensure the establishment of high-dimensional entangled states by constraining the length of the first polarization period to be equal to the length of the second polarization period, and the wavelength of the signal light to be unequal to the wavelength of the idle light.

[0099] In one embodiment, a specific method is provided for determining the wavelength of the target signal light and the wavelength of the target idle light corresponding to the target pump light with a known wavelength, as well as the refractive index corresponding to the target pump light, the refractive index corresponding to the target signal light, and the refractive index corresponding to the target idle light in step S102.

[0100] The Sellmeier dispersion formula is an empirical equation that describes the relationship between the refractive index and wavelength in a specific transparent medium. This equation is used to determine the dispersion of light in the medium. Based on this empirical formula, the optimal dispersion relation equation for nonlinear crystals can be determined by least squares fitting:

[0101]

[0102] Wherein, n represents the refractive index, λ represents the wavelength, and a, b, c, and d are the Sellmeier coefficients obtained by the least squares fitting process.

[0103] The four Sellmeier coefficients in the optimal dispersion relation equation have different optimal values ​​when the crystal type is different and the light propagates in different directions. Their values ​​need to be determined by least squares fitting based on the actual data. This embodiment takes the nonlinear crystal as potassium titanyl phosphate (KTP) crystal as an example, and considering that the implementation process of the present invention is a single-channel high-dimensional entangled light generation achieved by the selected type II quasi-phase matching process, and the polarization direction of the type II quasi-phase matching process is mainly YZY propagation, it is only necessary to fit and determine the specific values ​​of the four Sellmeier coefficients in the optimal dispersion relation equation when the potassium titanyl phosphate (KTP) crystal is in the y direction and the z direction:

[0104]

[0105] Among them, n y represents the refractive index of light in the y direction of potassium titanyl phosphate crystal, a y 、b y 、c y and y represents the Sellmeier coefficient corresponding to the propagation of light in the y direction of potassium titanyl phosphate crystal, n z represents the refractive index of light in the z direction of potassium titanyl phosphate crystal, a z 、b z 、c z and z It represents the Sellmeier coefficient corresponding to the propagation of light in the z direction of potassium titanyl phosphate crystal.

[0106] After fitting, this embodiment obtains, a y =3.0333, b y =0.04154, c y =0.04547, d y = 0.01408, and a z =3.3134, b z =0.05694, c z =0.05658, d z =0.01682.

[0107] Based on the optimal dispersion relation equation and the target pump light with known wavelength, the refractive index corresponding to the target pump light can be determined first. Assuming that the wavelength of the selected target pump light is λ 0 =532nm, then corresponding to n 0,y =1.790022.

[0108] because but λ 2 With λ 1 Substituting the relation into the optimal dispersion relation equation, we have:

[0109]

[0110] The constraint formula obtained by combining the constraint that the length of the first polarization period is equal to the length of the second polarization period and the constraint that the signal light wavelength is not equal to the idle light wavelength is: Finally, the target signal light wavelength λ can be obtained 1 =900.3nm, target idle light wavelength λ 2 =1300.5nm.

[0111] Since the above-mentioned solution process is obtained under the constraint that the length of the first polarization period is equal to the length of the second polarization period, the first polarization period or the second polarization period is calculated according to the wavelength of the target signal light, the wavelength of the target idle light, the corresponding refractive index of the target pump light, the corresponding refractive index of the target signal light and the corresponding refractive index of the target idle light, and the calculated length of the first polarization period or the length of the second polarization period is used as the length of the target polarization period.

[0112] At the same time, since the larger the order m of the quasi-phase matching is, the lower the nonlinear conversion efficiency is, and the corresponding experimentally prepared compressed state and entangled state become lower, so in this embodiment, m is preferably 1, at this time:

[0113]

[0114] Correspondingly, the first polarization period calculation formula at this time can be obtained when the target pump light wavelength is λ 0 =532nm, the target polarization period length is 64.5μm, and the corresponding selection or preparation is as follows Figure 5 As shown, a periodically poled potassium titanyl phosphate (PPKTP) crystal with a target poling period is formed, and a wavelength of λ is set. 0 After the target pump light of 532 nm is injected into the obtained periodically poled potassium titanyl phosphate (PPKTP) crystal, the following can be obtained: Figure 6 Entangled photon counting results shown.

[0115] Depend on Figure 5 and Figure 6 It can be seen that through precise calculation and high-quality preparation of PPKTP crystals, the generation of four-photon entangled photon pairs can be successfully achieved under a single channel without the need for complex experimental equipment and complex micro-ring silicon optical waveguide preparation processes. The complexity and efficiency loss that may be caused by multi-channel systems are avoided, and experimental conditions such as the intensity of laser pumping and the accuracy of optical components can be more effectively controlled, thereby enhancing the stability of the system. By increasing optical components and experimental parameters, entangled states with more photons can be achieved, promoting the development of fields such as quantum computing and quantum communication.

[0116] Corresponding to the method of the above embodiment, Figure 7 The structural block diagram of the single-channel multi-entangled photon pair generating device provided in the second embodiment of the present invention is shown. The above-mentioned entangled light generating device is applied to a computer device, and the computer device is connected to a target database through a preset application program interface. When the target database is driven to execute a corresponding task, a corresponding task log is generated, and the above-mentioned task log can be collected through the API. For the convenience of explanation, only the part related to the embodiment of the present invention is shown.

[0117] See also Figure 7 , the entangled light generating device comprises:

[0118] A polarization period determination module 21 is used to determine the first polarization period and the second polarization period of the nonlinear crystal regarding the wavelength and the refractive index in the type II quasi-phase matching process according to the quasi-phase matching conditions that the nonlinear crystal needs to meet in the optical parameter down-conversion process, wherein the first polarization period represents the polarization period when the signal light is vertically polarized and the idle light is horizontally polarized, and the second polarization period represents the polarization period when the signal light is horizontally polarized and the idle light is vertically polarized;

[0119] a wavelength and refractive index determination module 22, for determining the wavelength of the target signal light and the wavelength of the target idle light corresponding to the target pump light of known wavelength, and the refractive index corresponding to the target pump light, the refractive index corresponding to the target signal light, and the refractive index corresponding to the target idle light, based on the constraint that the length of the first polarization period is equal to the length of the second polarization period, and the constraint that the wavelength of the signal light is not equal to the wavelength of the idle light;

[0120] The entangled light generating module 23 is used to determine the target polarization period length according to the wavelength of the target signal light, the wavelength of the target idle light, the corresponding refractive index of the target pump light, the corresponding refractive index of the target signal light and the corresponding refractive index of the target idle light, and inject the target pump light into the periodically polarized crystal under the target polarization period length to complete the generation of single-channel multiple entangled photon pairs.

[0121] Optionally, the polarization period determining module 21 includes:

[0122] The quasi-phase matching condition limiting unit is used to limit the quasi-phase matching condition to include:

[0123] Conservation of Energy:

[0124] w 0 =w 1 +w 2

[0125] Among them, w 0 represents the frequency of the pump light, w 1 represents the frequency of the generated signal light, w 2 represents the frequency of the idle light produced;

[0126] Conservation of Momentum:

[0127] k 0 =k 1 +k 2 +m*kg

[0128] |k|=2πn / λ

[0129] k g =2π / Λ

[0130] Among them, k 0 represents the wave vector of the pump light, k 1 represents the wave vector of the signal light, k 2 represents the wave vector of idle light, kg represents the periodic polarization vector, m represents the order of quasi-phase matching, k represents the wave vector, |k| represents the absolute value of k, n represents the refractive index of the light beam when it propagates in the crystal, λ represents the wavelength of the light beam, and Λ represents the polarization period.

[0131] Optionally, the polarization period determining module 21 further includes:

[0132] The polarization period limiting unit is used to limit the first polarization period and the second polarization period with respect to the wavelength and the refractive index to be respectively:

[0133] The first polarization period is:

[0134]

[0135] Among them, Λ 1 represents the first polarization period, λ 1 Indicates the wavelength of the signal light, λ 2 represents the wavelength of idle light, n 0,y represents the refractive index of the pump light in the y direction of the nonlinear crystal, n 1,z represents the refractive index of the signal light in the z direction of the nonlinear crystal, n 2,y represents the refractive index of the idle light in the y direction of the nonlinear crystal, and m represents the order of quasi-phase matching;

[0136] The second polarization period is:

[0137]

[0138] Among them, Λ 2 represents the second polarization period, n 1,y represents the refractive index of the signal light in the y direction of the nonlinear crystal, n 2,z represents the refractive index of the idle light in the z direction of the nonlinear crystal.

[0139] Optionally, the wavelength and refractive index determination module 22 includes:

[0140] The constraint construction unit is used to limit the method of implementing the constraint that the length of the first polarization period is equal to the length of the second polarization period, and the signal light wavelength is not equal to the idle light wavelength as a constraint:

[0141] Limited Λ 1 =-Λ 2 , and then the following constraint formula is derived based on the expression of the first polarization period and the expression of the second polarization period:

[0142]

[0143] The ratio of the target signal light wavelength and the target idle light wavelength is limited to satisfy the constraint formula, so as to realize the constraint that the length of the first polarization period is equal to the length of the second polarization period, and the constraint that the signal light wavelength is not equal to the idle light wavelength.

[0144] Optionally, the wavelength and refractive index determination module 22 further includes:

[0145] The wavelength and refractive index calculation unit is used to determine the best dispersion relation equation characterizing the wavelength and refractive index in the nonlinear crystal based on the Sellmeier dispersion formula:

[0146]

[0147] Where n represents the refractive index, λ represents the wavelength, and a, b, c, and d are the Sellmeier coefficients obtained by the least squares fitting process;

[0148] The refractive index corresponding to the target pump light is determined according to the optimal dispersion relation equation, and the refractive index corresponding to the target pump light, the refractive index corresponding to the target signal light, and the refractive index corresponding to the target idle light are further determined in combination with the energy conservation condition, and the wavelength of the target signal light and the wavelength of the target idle light are further determined in combination with the constraint formula.

[0149] Optionally, the entangled light generating module 23 includes:

[0150] A target polarization period length determination unit is used to calculate the first polarization period or the second polarization period according to the wavelength of the target signal light, the wavelength of the target idle light, the corresponding refractive index of the target pump light, the corresponding refractive index of the target signal light, and the corresponding refractive index of the target idle light, so as to use the calculated length of the first polarization period or the calculated length of the second polarization period as the length of the target polarization period.

[0151] Optionally, the above device further comprises:

[0152] The crystal type limiting module is used to limit the nonlinear crystal to a potassium titanyl phosphate crystal, and the periodically poled crystal to a periodically poled potassium titanyl phosphate crystal.

[0153] It should be noted that the information interaction, execution process and other contents between the above modules are based on the same concept as the embodiment of the method of the present invention. Their specific functions and technical effects can be found in the method embodiment part and will not be repeated here.

[0154] Figure 8 This is a schematic diagram of the structure of a computer device provided in Embodiment 3 of the present invention. Figure 8 As shown, the computer device of this embodiment includes: at least one processor ( Figure 8 Only one is shown), a memory, and a computer program stored in the memory and executable on at least one processor, wherein when the processor executes the computer program, the steps in any of the above-mentioned health prediction method embodiments are implemented.

[0155] The computer device may include, but is not limited to, a processor and a memory. Those skilled in the art will appreciate that Figure 8 This is merely an example of a computer device and does not constitute a limitation on the computer device. The computer device may include more or fewer components than those shown in the figure, or a combination of certain components, or different components. For example, it may also include a network interface, a display screen, and an input device.

[0156] The processor may be a CPU, or other general-purpose processors, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0157] The memory includes a readable storage medium, an internal memory, etc., wherein the internal memory may be the memory of a computer device, and the internal memory provides an environment for the operation of an operating system and computer-readable instructions in the readable storage medium. The readable storage medium may be a hard disk of a computer device, and in other embodiments may also be an external storage device of a computer device, for example, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc. equipped on a computer device. Further, the memory may also include both an internal storage unit of a computer device and an external storage device. The memory is used to store an operating system, an application program, a boot loader (BootLoader), data, and other programs, such as program codes of computer programs, etc. The memory may also be used to temporarily store data that has been output or is to be output.

[0158] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated into a processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention. The specific working process of the units and modules in the above-mentioned device can refer to the corresponding process in the above-mentioned method embodiment, which will not be repeated here. If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, which can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned method embodiment can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may at least include: any entity or device capable of carrying computer program code, recording medium, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium. For example, a USB flash drive, a mobile hard disk, a magnetic disk or an optical disk. In some jurisdictions, according to legislation and patent practice, computer-readable media cannot be electric carrier signals and telecommunication signals.

[0159] The present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by a computer program product. When the computer program product runs on a computer device, the computer device can implement the steps in the above-mentioned method embodiment when executing.

[0160] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0161] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0162] In the embodiments provided by the present invention, it should be understood that the disclosed devices / computer equipment and methods can be implemented in other ways. For example, the device / computer equipment embodiments described above are only schematic, for example, the division of modules or units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0163] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0164] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A method for generating multiple entangled photon pairs in a single channel, characterized in that: The method comprises: According to the quasi-phase matching conditions that the nonlinear crystal needs to meet during the optical parameter down-conversion process, determine the first polarization period and the second polarization period of the nonlinear crystal with respect to the wavelength and the refractive index during the type II quasi-phase matching process, wherein the first polarization period represents the polarization period when the signal light is vertically polarized and the idle light is horizontally polarized, and the second polarization period represents the polarization period when the signal light is horizontally polarized and the idle light is vertically polarized; Under the constraints that the length of the first polarization period is equal to the length of the second polarization period, and the constraints that the wavelength of the signal light is not equal to the wavelength of the idle light, determine the wavelength of the target signal light and the wavelength of the target idle light corresponding to the target pump light with a known wavelength, as well as the refractive index corresponding to the target pump light, the refractive index corresponding to the target signal light, and the refractive index corresponding to the target idle light; The target polarization period length is determined according to the wavelength of the target signal light, the wavelength of the target idle light, the corresponding refractive index of the target pump light, the corresponding refractive index of the target signal light and the corresponding refractive index of the target idle light, and the target pump light is injected into the periodically polarized crystal under the target polarization period length to complete the generation of single-channel multi-entangled photon pairs.

2. The single-channel multi-entangled photon pair generation method according to claim 1, characterized in that: The quasi-phase matching condition includes: Conservation of Energy: w0=w1+w2 Wherein, w0 represents the frequency of the pump light, w1 represents the frequency of the generated signal light, and w2 represents the frequency of the generated idle light; Conservation of Momentum: k0=k1+k2+m*kg |k|=2πn / λ k g =2π / Λ Wherein, k0 represents the wave vector of the pump light, k1 represents the wave vector of the signal light, k2 represents the wave vector of the idle light, kg represents the periodic polarization vector, m represents the order of quasi-phase matching, k represents the wave vector, |k| represents the absolute value of k, n represents the refractive index of the light beam when propagating in the crystal, λ represents the wavelength of the light beam, and Λ represents the polarization period.

3. The single-channel multi-entangled photon pair generation method according to claim 2, characterized in that: The first polarization period and the second polarization period with respect to wavelength and refractive index are respectively: The first polarization period is: Wherein, Λ1 represents the first polarization period, λ1 represents the wavelength of the signal light, λ2 represents the wavelength of the idle light, and n 0,y represents the refractive index of the pump light in the y direction of the nonlinear crystal, n 1,z represents the refractive index of the signal light in the z direction of the nonlinear crystal, n 2,y represents the refractive index of the idle light in the y direction of the nonlinear crystal, and m represents the order of quasi-phase matching; The second polarization period is: Wherein, Λ2 represents the second polarization period, n 1,y represents the refractive index of the signal light in the y direction of the nonlinear crystal, n 2,z represents the refractive index of the idle light in the z direction of the nonlinear crystal.

4. The single-channel multi-entangled photon pair generation method according to claim 3, characterized in that: The method for implementing the constraint that the length of the first polarization period is equal to the length of the second polarization period, and the constraint that the signal light wavelength is not equal to the idle light wavelength is: Limit Λ1=-Λ2, and then derive the following constraint formula based on the expression of the first polarization period and the expression of the second polarization period: The ratio of the target signal light wavelength to the target idle light wavelength is limited to satisfy the constraint formula, so as to realize the constraint that the length of the first polarization period is equal to the length of the second polarization period, and the constraint that the signal light wavelength is not equal to the idle light wavelength.

5. The method for generating multiple entangled photon pairs in a single channel according to claim 4, characterized in that: The determining of the wavelength of the target signal light and the wavelength of the target idle light corresponding to the target pump light with a known wavelength, as well as the refractive index corresponding to the target pump light, the refractive index corresponding to the target signal light, and the refractive index corresponding to the target idle light includes: The optimal dispersion relation equation for characterizing wavelength and refractive index in the nonlinear crystal is determined based on the Sellmeier dispersion formula: Where n represents the refractive index, λ represents the wavelength, and a, b, c, and d are the Sellmeier coefficients obtained by the least squares fitting process; The refractive index corresponding to the target pump light is determined according to the optimal dispersion relation equation, and the refractive index corresponding to the target pump light, the refractive index corresponding to the target signal light, and the refractive index corresponding to the target idle light are further determined in combination with the energy conservation condition, and the wavelength of the target signal light and the wavelength of the target idle light are further determined in combination with the constraint formula.

6. The method for generating multiple entangled photon pairs in a single channel according to claim 5, characterized in that: The step of determining a target polarization period length according to the wavelength of the target signal light, the wavelength of the target idle light, the corresponding refractive index of the target pump light, the corresponding refractive index of the target signal light, and the corresponding refractive index of the target idle light comprises: The first polarization period or the second polarization period is calculated according to the wavelength of the target signal light, the wavelength of the target idle light, the corresponding refractive index of the target pump light, the corresponding refractive index of the target signal light and the corresponding refractive index of the target idle light, so as to use the calculated length of the first polarization period or the calculated length of the second polarization period as the length of the target polarization period.

7. The single-channel multi-entangled photon pair generation method according to any one of claims 1 to 6, characterized in that: The nonlinear crystal is a potassium titanyl phosphate crystal, and the periodically poled crystal is a periodically poled potassium titanyl phosphate crystal.

8. A single-channel multi-entangled photon pair generation device, characterized in that: The device comprises: A polarization period determination module, for determining a first polarization period and a second polarization period of the nonlinear crystal regarding wavelength and refractive index in a type II quasi-phase matching process according to a quasi-phase matching condition that the nonlinear crystal needs to satisfy in an optical parameter down-conversion process, wherein the first polarization period represents a polarization period when the signal light is vertically polarized and the idle light is horizontally polarized, and the second polarization period represents a polarization period when the signal light is horizontally polarized and the idle light is vertically polarized; a wavelength and refractive index determination module, for determining the wavelength of the target signal light and the wavelength of the target idle light corresponding to the target pump light of known wavelength, and the refractive index corresponding to the target pump light, the refractive index corresponding to the target signal light, and the refractive index corresponding to the target idle light, based on the constraint that the length of the first polarization period is equal to the length of the second polarization period, and the constraint that the wavelength of the signal light is not equal to the wavelength of the idle light; An entangled light generating module is used to determine a target polarization period length according to the wavelength of the target signal light, the wavelength of the target idle light, the corresponding refractive index of the target pump light, the corresponding refractive index of the target signal light and the corresponding refractive index of the target idle light, and inject the target pump light into a periodically polarized crystal under the target polarization period length to complete the generation of single-channel multiple entangled photon pairs.

9. A computer device, characterized in that: The computer device includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the single-channel multi-entangled photon pair generation method as described in any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the single-channel multi-entangled photon pair generation method according to any one of claims 1 to 7 is implemented.

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