A method, device and communication system for preparing a quantum entanglement source

Abstract

The present application provides a preparation method, device and communication system for a quantum entanglement source, the method comprising: a first laser and a second laser outputting a first pump light and a second pump light, respectively; a first optical parametric resonator and a second optical parametric resonator respectively receiving the first pump light and the second pump light, and correspondingly outputting a first optical signal and a third signal in a first photon state, wherein the first photon state is a single-mode compressed vacuum state, and the second frequency of the third optical signal is equal to the first frequency of the first optical signal; a first operation module performing a non-Gaussian operation on the first optical signal to output a second optical signal in a second photon state; a second operation module performing a non-Gaussian operation on the third optical signal to output a fourth optical signal in a second photon state, wherein the second photon state is a non-Gaussian state; the second optical signal and the fourth optical signal are entangled after passing through a first optical beam splitter, thereby obtaining a quantum entanglement source with enhanced entanglement, thereby improving the communication performance of the quantum communication system.

Description

Technical Field

[0001] The present application belongs to the field of quantum technology, and in particular relates to a preparation method, device and communication system of a quantum entanglement source. Background Art

[0002] In continuous variable quantum communication systems based on quantum entanglement, such as quantum teleportation and quantum dense coding systems, decoherence occurs due to factors such as loss in the quantum channel, thereby reducing the entanglement between two spatially separated particles. This significantly reduces the fidelity of quantum information in quantum teleportation and the mutual information in quantum dense coding systems, thereby leading to a decline in the performance of the quantum communication system.

[0003] There are currently two main methods for enhancing the entanglement of continuous variable quantum entangled sources: one is the noiseless linear amplification method, and the other is the non-Gaussian operation of adding and subtracting photons from the two modes of the two-mode squeezed vacuum state that has formed a quantum entangled state (Photon-Subtracted Two-Mode Squeezed Vacuum state, abbreviated as PSTMSV).

[0004] The existing technology has the problem that the entanglement degree of the prepared quantum entanglement source cannot meet the effective transmission of long-distance quantum information. Summary of the Invention

[0005] The embodiments of the present application provide a method and device for preparing a quantum entanglement source, which can solve the problem that the entanglement degree of the quantum entanglement source cannot meet the effective transmission of long-distance quantum information.

[0006] In a first aspect, an embodiment of the present application provides a method for preparing a quantum entanglement source, comprising:

[0007] The first laser outputs a first pump light of a preset wavelength;

[0008] The first optical parametric resonator is connected to the first pump light and outputs a first optical signal in a first photon state, wherein the frequency of the first optical signal is a first frequency and the first photon state is a single-mode squeezed vacuum state;

[0009] A first operating module receives the first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state, wherein the second photon state is a non-Gaussian state;

[0010] The second laser outputs a second pump light of the preset wavelength;

[0011] The second optical parametric resonator is connected to the second pump light and outputs a third optical signal in the first photon state, wherein the frequency of the third optical signal is the second frequency, and the first frequency is equal to the second frequency;

[0012] A second operation module receives the third optical signal, performs the non-Gaussian operation on the third optical signal, and outputs a fourth optical signal in the second photon state;

[0013] The first optical beam splitter receives the second optical signal in the second photon state and the fourth optical signal in the second photon state, and the second optical signal and the fourth optical signal pass through the first optical beam splitter to obtain the entangled quantum entanglement source.

[0014] In a second aspect, an embodiment of the present application provides a device for preparing a quantum entanglement source, comprising:

[0015] a first laser, configured to output a first pump light of a preset wavelength;

[0016] a first optical parametric resonator, configured to receive the first pump light and output a first optical signal in a first photon state, wherein the first optical signal has a first frequency and the first photon state is a single-mode squeezed vacuum state;

[0017] a first operating module, configured to receive the first optical signal, perform a non-Gaussian operation on the first optical signal, and output a second optical signal in a second photon state, wherein the second photon state is a non-Gaussian state;

[0018] a second laser, configured to output a second pump light of the preset wavelength;

[0019] a second optical parametric resonator, configured to receive the second pump light and output a third optical signal in the first photon state, wherein a frequency of the third optical signal is a second frequency, and the first frequency is equal to the second frequency;

[0020] a second operating module, configured to receive the third optical signal, perform the non-Gaussian operation on the third optical signal, and output a fourth optical signal in the second photon state;

[0021] The first optical beam splitter is used to receive the second optical signal of the second photon state and the fourth optical signal of the second photon state, and the second optical signal and the fourth optical signal are entangled to obtain the quantum entanglement source through the first optical beam splitter.

[0022] In a third aspect, an embodiment of the present application provides a communication system based on quantum entanglement, including a preparation device for implementing the preparation method of the quantum entanglement source of the first aspect.

[0023] It can be understood that the beneficial effects of the second and third aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0024] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0025] The preparation method of the embodiment of the present application is as follows: a first laser outputs a first pump light of a preset wavelength; a first optical parametric resonator is connected to the first pump light, and outputs a first optical signal in a first photon state, wherein the frequency of the first optical signal is a first frequency and the first photon state is a single-mode squeezed vacuum state; a first operation module is connected to the first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state, wherein the second photon state is a non-Gaussian state; a second laser outputs a second pump light of a preset wavelength; a second optical parametric resonator is connected to the second pump light, and outputs a third optical signal in the first photon state, wherein the frequency of the third optical signal is a second frequency, and the first frequency is equal to the second frequency; a second operation module is connected to the third optical signal, performs a non-Gaussian operation on the third optical signal, and outputs a fourth optical signal in the second photon state; a first optical beam splitter is connected to the second optical signal in the second photon state and the fourth optical signal in the second photon state, and the second optical signal and the fourth optical signal pass through the first optical beam splitter to obtain an entanglement-enhanced quantum entanglement source, thereby improving the robustness of the continuous variable quantum communication system based on the entangled state, thereby improving the communication performance of the quantum communication system.

[0026] In addition, the preparation device of the embodiment of the present application greatly simplifies the optical structure for preparing a quantum entangled source with a high entanglement degree, thereby reducing the cost of preparing a quantum entangled source with a high entanglement degree. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of a method for preparing a quantum entanglement source provided in one embodiment of the present application;

[0028] Figure 2-1 This is a flow chart of a first operation module according to an embodiment of the present application receiving a first optical signal, performing a non-Gaussian operation on the first optical signal, and outputting a second optical signal in a second photon state;

[0029] Figure 2-2 This is a flow chart of another embodiment of the present application, in which a first operating module receives a first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state;

[0030] Figure 3-1 This is a flow chart of a second operation module according to an embodiment of the present application receiving a third optical signal, performing a non-Gaussian operation on the third optical signal, and outputting a fourth optical signal in a second photon state;

[0031] Figure 3-2This is a flow chart of another embodiment of the present application, in which a second operation module receives a third optical signal, performs a non-Gaussian operation on the third optical signal, and outputs a fourth optical signal in a second photon state;

[0032] Figure 4 This is a schematic diagram of the logarithmic negative values ​​of the quantum entangled source prepared by various non-Gaussian operations provided in one embodiment of the present application and the logarithmic negative values ​​of the traditional TMSV and PSTMSV at the same compression parameters;

[0033] Figure 5 This is a flow chart of a preparation method based on a quantum optical frequency comb provided in one embodiment of the present application;

[0034] Figure 6 This is a flow chart of a first light reduction submodule according to an embodiment of the present application receiving a first modulated signal, performing a first non-Gaussian operation on the first modulated signal, and outputting a second optical signal;

[0035] Figure 7 This is a flow chart of a third operation module according to an embodiment of the present application receiving a second optical signal, performing a second modulation and a first non-Gaussian operation on the second optical signal, and outputting a fifth optical signal;

[0036] Figure 8 This is a flow chart of a second light reduction submodule according to an embodiment of the present application performing a first non-Gaussian operation on a second modulated signal to output a fifth optical signal;

[0037] Figure 9 This is a schematic structural diagram of a device for preparing a quantum entanglement source provided in an embodiment of the present application;

[0038] Figure 10 Schematic diagram of another device for preparing a quantum entanglement source provided in an embodiment of the present application;

[0039] Figure 11 This is a schematic structural diagram of another device for preparing a quantum entanglement source provided in an embodiment of the present application;

[0040] Figure 12 It is a structural schematic diagram of a device for preparing a quantum entanglement source based on a quantum frequency comb provided in an embodiment of the present application. DETAILED DESCRIPTION

[0041] In the following description, specific details such as specific system structures and techniques are provided for purposes of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application 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 avoid obscuring the description of the present application with unnecessary detail.

[0042] In addition, in the description of the present application 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.

[0043] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application. The terms "including," "comprising," "having," and their variations all mean "including but not limited to," unless otherwise specifically emphasized.

[0044] In a quantum communication system based on continuous variables of quantum entanglement, the entanglement degree of the quantum entangled source decreases due to factors such as signal loss, thereby reducing the performance of the communication system.

[0045] The traditional method of preparing an entangled quantum entanglement source is to first use two Type I non-critical phase-matched optical parametric resonators to generate single-mode squeezed vacuum state optical signals with orthogonal squeezing dimensions. The two single-mode squeezed vacuum state optical signals with orthogonal squeezing dimensions are then combined through a balanced optical beam splitter to obtain an entangled two-mode squeezed vacuum state (Two-Mode Squeezed Vacuum State, abbreviated as TMSV) optical signal. Among them, the optical parametric oscillator (OPO) can also serve as an optical parametric amplifier (OPA).

[0046] There are currently two main methods to enhance the entanglement of continuous variable quantum entanglement sources:

[0047] The first is the noiseless linear amplification method, which is achieved through quantum scissors, quantum catalysis or measurement-based post-selection. However, the noiseless linear amplification technology based on quantum scissors and quantum catalysis requires auxiliary photons during the implementation process, which increases the complexity of the preparation method. In addition, the enhanced quantum entangled source generated by the measurement-based post-selection noiseless linear amplification technology cannot be transmitted freely, and its application in quantum communication systems is greatly limited.

[0048] The second method is to achieve this by performing non-Gaussian operations of adding and subtracting photons from the two modes of the two-mode squeezed vacuum state that has formed a quantum entanglement source (Photon-Subtracted Two-Mode Squeezed Vacuum state, abbreviated as PSTMSV). The method of enhancing quantum entanglement based on PSTMSV can only increase the entanglement to a smaller extent, especially for quantum entanglement with relatively low compression strength. The improvement is limited and cannot meet the requirements for effective transmission of quantum information over long distances.

[0049] The preparation method of the embodiment of the present application is as follows: a first laser outputs a first pump light of a preset wavelength; a first optical parametric resonator is connected to the first pump light, and outputs a first optical signal in a first photon state, wherein the frequency of the first optical signal is a first frequency and the first photon state is a single-mode squeezed vacuum state; a first operation module is connected to the first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state, wherein the second photon state is a non-Gaussian state; a second laser outputs a second pump light of a preset wavelength; a second optical parametric resonator is connected to the second pump light, and outputs a third optical signal in the first photon state, wherein the frequency of the third optical signal is a second frequency, and the first frequency is equal to the second frequency; a second operation module is connected to the third optical signal, performs a non-Gaussian operation on the third optical signal, and outputs a fourth optical signal in the second photon state; a first optical beam splitter is connected to the second optical signal in the second photon state and the fourth optical signal in the second photon state, and the second optical signal and the fourth optical signal pass through the first optical beam splitter to obtain an entanglement-enhanced quantum entanglement source, thereby improving the robustness of the continuous variable quantum communication system based on the entangled state, thereby improving the communication performance of the quantum communication system.

[0050] Some professional terms in the examples of this application are defined as follows:

[0051] The eigenvalue equation of the photon number operator is: n=0, 1, 2, ..., wherein the state |0> when n=0 is called a vacuum state, which is the state with the minimum uncertainty of the orthogonal components.

[0052] Without violating the uncertainty relationship (ΔX)×(ΔY)≧1 / 4, (ΔX)<1 / 2. The quantum state that satisfies the above relationship is called a squeezed state, where ΔX is the deviation of the orthogonal operator X and ΔY is the deviation of the orthogonal operator Y.

[0053] The compressed vacuum state satisfies both the compressed state and the vacuum state requirements, that is,

[0054] |ξ>=S(ξ)|0>

[0055] in, is the compression operator; ξ=re iθ , ξ is the compression parameter; r is the compression amplitude, which describes the strength of the compression, 0≦r<∞; θ is the compression angle (also called phase difference), which describes the direction of compression, 0≦θ≦2π, e is the base of the natural logarithm, and i is the sign of the imaginary part.

[0056] Assume that the states of subsystem A and subsystem B are |ψ A > and |ψ B >, the state vector of the composite system is |ψ AB >, if Then the composite system is said to be in a direct product state, also called a separable state, if |ψAB >≠|ψ A >|ψ B >,|ψ AB >=α|ψ A1 >|ψ B1 >+β|ψ A2 >|ψ B2 >, α≠0, β≠0, then the composite system is said to be in an entangled state, also called an inseparable state.

[0057] A method or device that can enhance the degree of entanglement between entangled particles in a quantum entanglement source is also referred to as a quantum entanglement distillation method or device. Entanglement entropy characterizes the degree of entanglement between entangled particles when the entangled state is pure. When the entangled state is a mixed state, logarithmic negativity is the most commonly used indicator to characterize the degree of entanglement between entangled particles. After partially transposing the density matrix of the entangled state, the eigenvalue of the density matrix is ​​negative, and the logarithm of the sum of the absolute values ​​of all negative eigenvalues ​​is the logarithmic negativity. Therefore, entanglement entropy and logarithmic negativity can both be used as indicators to evaluate the performance of quantum entanglement distillation methods or devices.

[0058] Among them, the calculation formula for the negative logarithm of the quantum entangled source prepared by the traditional method of entangled state is:

[0059]

[0060] Among them, E TMSV is the negative logarithm of the quantum entanglement source prepared by TMSV, λ = tanhξ, tanh is the hyperbolic tangent function, ξ is the compression parameter of the compressed vacuum state, when ξ approaches 0, the negative logarithm E TMSV tends to 0, that is, there is no correlation between the two particles.

[0061] The calculation formula for the logarithmic negative value of the enhanced quantum entanglement degree in the PSTMSV method is:

[0062]

[0063] Among them, E PSTMSV is the negative logarithm of the quantum entanglement source prepared by the PSTMSV method, λ = tanhξ, tanh is the hyperbolic tangent function, ξ is the compression parameter of the compressed vacuum state, T is the transmittance of the optical beam splitter used to add and subtract photons, when ξ approaches 0, the negative logarithm E PSTMSV When it approaches 0, the two particles are separable and there is no correlation between the two particles.

[0064] An optical frequency comb (OFC) is a spectrum consisting of a series of frequency components that are evenly spaced and have relatively stable phase relationships.

[0065] The optical beam splitter includes at least one of an optical energy beam splitter and an optical frequency beam splitter, and the photon number detector includes a single photon detector.

[0066] The technical solution of this application is described below through specific embodiments.

[0067] First, as Figure 1 As shown, the embodiment of the present application provides a method for preparing a quantum entanglement source, comprising:

[0068] S100: A first laser outputs a first pump light of a preset wavelength.

[0069] The first laser outputs laser light of a preset wavelength as a first pump light, and the first laser serves as a light source of pump light input to the first optical parametric resonator.

[0070] In one embodiment, the preset wavelength is 532 nm. In this embodiment, there is no specific limitation on the wavelength range of the preset wavelength, and the preset wavelength is set by the structure of the optical parametric resonator and the requirements of the quantum communication system.

[0071] S200 , a first optical parametric resonator is connected to a first pump light to output a first optical signal in a first photon state.

[0072] In one embodiment, the optical parametric resonator is also called an optical parametric oscillator, and the first optical parametric resonator includes a nonlinear crystal and a reflector, which is used to convert the input first pump light into a first optical signal in a first photon state, wherein the frequency of the first optical signal is a first frequency, and the first photon state is a single-mode squeezed vacuum state.

[0073] In one embodiment, the nonlinear crystal is periodically poled potassium titanium phosphate (PPKTP) to provide better gain for the output photon pairs.

[0074] In one embodiment, the first optical parametric resonator is connected to a pump light with a wavelength of 532 nm, and generates a first optical signal of a photon pair corresponding to an optical frequency of 1064 nm through resonance of a nonlinear crystal gain and an optical reflector.

[0075] S300: A first operating module receives a first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state.

[0076] In one embodiment, the non-Gaussian operation includes a first non-Gaussian operation, a second non-Gaussian operation, and a third non-Gaussian operation. The first non-Gaussian operation is a photon subtraction operation, the second non-Gaussian operation is a photon addition operation and a photon subtraction operation at the same time, and the third non-Gaussian operation is a photon addition operation.

[0077] In one embodiment, the first operation module receives the first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state, wherein the second photon state is a non-Gaussian state.

[0078] In one embodiment, the non-Gaussian operation includes a first non-Gaussian operation, which is a photon subtraction operation. The first operation module includes a second optical beam splitter and a first photon number detector, which is conducive to performing a non-Gaussian operation on the first optical signal and improving the effect after the non-Gaussian operation.

[0079] In one embodiment, Figure 2-1 As shown, the first operation module receives the first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state, including:

[0080] S310 , a second optical beam splitter receives the first optical signal, transmits and outputs a second optical signal in a second photon state, and reflects and outputs a second optical signal in a third photon state.

[0081] In one embodiment, the second optical beam splitter receives the first optical signal in the single-mode compressed vacuum state and separates the first optical signal, transmits and outputs the second optical signal in the second photon state, and reflects and outputs the second optical signal in the third photon state, thereby obtaining the required second optical signal in the second photon state.

[0082] S311 , a first photon number detector receives a second optical signal in a third photon state, and performs a first non-Gaussian operation on the first optical signal.

[0083] In one embodiment, the first photon number detector receives the second light signal of the third photon state reflected and output by the second light beam splitter. When the first photon number detector detects the second light signal of the third photon state, the second light beam splitter transmits and outputs the second light signal of the second photon state, thereby realizing a first non-Gaussian operation on the first light signal.

[0084] In a specific embodiment, when the non-Gaussian operation is the first non-Gaussian operation, l1=1, k1=0 is set, where l1 represents the number of subtracted photons and k1 represents the number of added photons. The second optical beam splitter receives the first optical signal in the first photon state, and when the first photon number detector detects the second optical signal in the third photon state, the second optical beam splitter transmits and outputs the second optical signal in the second photon state, thereby realizing the operation of subtracting one photon from the first optical signal.

[0085] In a specific embodiment, when the non-Gaussian operation is the first non-Gaussian operation, l1>1, k1=0 are set, where l1 represents the number of subtracted photons, k1 represents the number of added photons, the second optical beam splitter receives the first optical signal in the first photon state, and when the first photon number detector detects the second optical signal in the third photon state, the second optical beam splitter transmits and outputs the second optical signal in the second photon state, thereby realizing the operation of subtracting more than two photons from the first optical signal.

[0086] In another embodiment, the non-Gaussian operation further includes a second non-Gaussian operation, the second non-Gaussian operation is a photon addition operation and a photon subtraction operation at the same time, and the first operation module includes a second optical beam splitter, a first photon number detector and a first photon number generator.

[0087] It should be noted that when performing the second non-Gaussian operation, the number of added photons is different from the number of subtracted photons, which is beneficial to improving the entanglement degree of the quantum entanglement source.

[0088] In another embodiment, Figure 2-2 As shown, the first operation module receives the first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state, further comprising:

[0089] S320, the second optical beam splitter receives the first optical signal and the photons output by the first photon number generator, transmits and outputs the second optical signal in the second photon state, and reflects and outputs the second optical signal in the third photon state.

[0090] S321 , the first photon number detector receives a second optical signal in a third photon state, and performs a second non-Gaussian operation on the first optical signal.

[0091] In a specific embodiment, when the non-Gaussian operation is the second non-Gaussian operation, l1=2, k1=1 are set, where l1 represents the number of subtracted photons and k1 represents the number of added photons. The second optical beam splitter receives the first optical signal in the first photon state, and when the first photon number detector detects the second optical signal in the third photon state, the second optical beam splitter transmits and outputs the second optical signal in the second photon state, thereby realizing the operation of adding one photon and subtracting two photons on the first optical signal at the same time.

[0092] In yet another embodiment, the non-Gaussian operation further includes a third non-Gaussian operation, the third non-Gaussian operation is a photon addition operation, and the first operation module includes a second optical beam splitter and a first photon number generator.

[0093] The first operation module receives the first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state, further comprising:

[0094] The second optical beam splitter receives the first optical signal and the photons output by the first photon number generator, transmits and outputs the second optical signal in the second photon state, reflects and outputs the second optical signal in the third photon state, and performs a third non-Gaussian operation on the first optical signal.

[0095] In a specific embodiment, when the non-Gaussian operation is the second non-Gaussian operation, l1=0, k1=1 is set, where l1 represents the number of subtracted photons and k1 represents the number of added photons. The second optical beam splitter receives the first optical signal in the first photon state, and when the first photon number detector detects the second optical signal in the third photon state, the second optical beam splitter transmits and outputs the second optical signal in the second photon state, thereby realizing the operation of adding one photon to the first optical signal.

[0096] S400: The second laser outputs a second pump light of a preset wavelength.

[0097] The second laser outputs laser light of a preset wavelength as a second pump light, and the second laser serves as a light source for the pump light of the second optical parametric resonator input light.

[0098] In one embodiment, the preset wavelength is 532 nm. In this embodiment, there is no specific limitation on the wavelength range of the preset wavelength, and the preset wavelength is set by the structure of the optical parametric resonator and the requirements of the quantum communication system.

[0099] S500 , the second optical parametric resonator is connected to the second pump light and outputs a third optical signal in the first photon state.

[0100] In one embodiment, the second optical parametric resonator includes a nonlinear crystal and a reflector, which is used to convert the input second pump light into a third optical signal in the first photon state, wherein the frequency of the third optical signal is the second frequency, the first photon state is a single-mode squeezed vacuum state, and the first frequency is equal to the second frequency.

[0101] S600: The second operating module receives a third optical signal, performs a non-Gaussian operation on the third optical signal, and outputs a fourth optical signal in a second photon state.

[0102] In one embodiment, the second operation module receives the third optical signal, performs a non-Gaussian operation on the third optical signal, and outputs a fourth optical signal in a second photon state, wherein the second photon state is a non-Gaussian state.

[0103] In one embodiment, the second operation module includes a third optical beam splitter and a second photon number detector, which is conducive to performing non-Gaussian operation on the third optical signal and improving the effect after the non-Gaussian operation.

[0104] In one embodiment, Figure 3-1As shown, the second operation module receives the third optical signal, performs a non-Gaussian operation on the third optical signal, and outputs a fourth optical signal in the second photon state, including:

[0105] S610 , the third optical beam splitter receives the third optical signal, transmits and outputs the fourth optical signal in the second photon state, and reflects and outputs the fourth optical signal in the fourth photon state.

[0106] In one embodiment, the third optical beam splitter receives the third optical signal in the single-mode compressed vacuum state and separates the third optical signal, transmits and outputs the fourth optical signal in the second photon state, and reflects and outputs the fourth optical signal in the fourth photon state, thereby obtaining the required fourth optical signal in the second photon state.

[0107] S611, the second photon number detector receives a fourth optical signal in a fourth photon state, and performs a first non-Gaussian operation on the third optical signal.

[0108] In one embodiment, the second photon number detector receives the fourth light signal of the fourth photon state reflected and output by the third light beam splitter. When the second photon number detector detects the fourth light signal of the fourth photon state, the third light beam splitter transmits and outputs the fourth light signal of the second photon state, thereby realizing the first non-Gaussian operation on the third light signal.

[0109] In a specific embodiment, when the non-Gaussian operation is the first non-Gaussian operation, l2=1, k2=0 is set, where l2 represents the number of subtracted photons and k2 represents the number of added photons. The third optical beam splitter receives the third optical signal of the first photon state, and when the second photon number detector detects the fourth optical signal of the fourth photon state, the second optical beam splitter transmits and outputs the fourth optical signal of the second photon state, thereby realizing the operation of subtracting one photon from the third optical signal.

[0110] In a specific embodiment, when the non-Gaussian operation is the first non-Gaussian operation, l2>1, k2=0 is set, where l2 represents the number of subtracted photons, k2 represents the number of added photons, the third optical beam splitter receives the third optical signal of the first photon state, and when the second photon number detector detects the fourth optical signal of the fourth photon state, the second optical beam splitter transmits and outputs the fourth optical signal of the second photon state, thereby realizing the operation of subtracting more than two photons from the third optical signal.

[0111] In another embodiment, the second operating module includes a third optical beam splitter, a second photon number detector and a second photon number generator, such as Figure 3-2 As shown, the second operation module receives the third optical signal, performs a non-Gaussian operation on the third optical signal, and outputs a fourth optical signal in the second photon state, further comprising:

[0112] S620, the third optical beam splitter receives the third optical signal and the photons output by the second photon number generator, transmits and outputs a fourth optical signal in the second photon state, and reflects and outputs a fourth optical signal in the fourth photon state.

[0113] S621: The second photon number detector receives a fourth optical signal in a fourth photon state and performs a second non-Gaussian operation on the third optical signal.

[0114] In a specific embodiment, when the non-Gaussian operation is the second non-Gaussian operation, l2=2, k2=1 are set, where l2 represents the number of subtracted photons and k2 represents the number of added photons. The third optical beam splitter receives the third optical signal of the first photon state, and when the second photon number detector detects the fourth optical signal of the fourth photon state, the second optical beam splitter transmits and outputs the fourth optical signal of the second photon state, thereby realizing the operation of adding one photon and subtracting two photons on the third optical signal at the same time.

[0115] In yet another embodiment, the second operating module includes a third optical beam splitter and a second photon number generator, the second operating module receives the third optical signal, performs a non-Gaussian operation on the third optical signal, and outputs a fourth optical signal in the second photon state, further comprising:

[0116] The third optical beam splitter receives the third optical signal and the photons output by the second photon number generator, transmits and outputs the fourth optical signal in the second photon state, reflects and outputs the fourth optical signal in the fourth photon state, and performs a third non-Gaussian operation on the third optical signal.

[0117] In a specific embodiment, when the non-Gaussian operation is the second non-Gaussian operation, l2=0, k2=1 is set, where l2 represents the number of subtracted photons and k2 represents the number of added photons. The third optical beam splitter receives the third optical signal of the first photon state, and when the second photon number detector detects the fourth optical signal of the fourth photon state, the second optical beam splitter transmits and outputs the fourth optical signal of the second photon state, thereby realizing the operation of adding one photon to the third optical signal.

[0118] S700: The first optical beam splitter receives a second optical signal in a second photon state and a fourth optical signal in a second photon state. The second optical signal and the fourth optical signal pass through the first optical beam splitter to obtain an entangled quantum entanglement source.

[0119] The first optical beam splitter receives the second optical signal in the second photon state after the non-Gaussian operation and the fourth optical signal in the second photon state. The second optical signal and the fourth optical signal interfere with each other in the first optical beam splitter and are separated to obtain a quantum entangled source.

[0120] When the compression parameter is very small, the second optical signal and the fourth optical signal are squeezed single-photon states, which interfere and are separated in the first optical beam splitter. The quantum entangled source obtains the entangled state based on the Hong–Ou–Mandel effect. The quantum entangled source, the entangled state is is a typical entangled state. It is one of the four Bell states with the highest degree of entanglement. When the compression parameter is relatively large, the quantum entangled source prepared by the method of this embodiment still has a strong correlation.

[0121] In some embodiments, as Figure 4 As shown, the traditional TMSV and PSTMSV methods for preparing quantum entangled sources have logarithmic negative values ​​of 0.89 and 1.46, respectively, when the compression parameter ξ = 0.31 (i.e., the compression strength is -2.69 dB); using the preparation method of the quantum entangled source of this embodiment, when l1 = l2 = 1, k1 = k2 = 0, a non-Gaussian operation of subtracting one photon from the second light signal and the fourth light signal is realized, and when the compression parameter ξ = 0.31 (i.e., the compression strength is -2.69 dB) in the single-mode squeezed vacuum state, the logarithmic negative value of the entangled quantum entangled source is 1.90; when l1 = l2 = 0, k1 = k2 = 1, a non-Gaussian operation of adding one photon to the second light signal and the fourth light signal is realized, and when the compression parameter ξ = 0.31 ( That is, when the compression intensity is -2.69dB), the negative logarithm of the entangled quantum entangled source is 1.90; when l1=l2=2, k1=k2=1, the non-Gaussian operation of first adding one photon and then subtracting two photons from the second and fourth optical signals respectively is realized. When the compression parameter ξ=0.31 of the single-mode squeezed vacuum state (that is, the compression intensity is -2.69dB), the negative logarithm of the entangled quantum entangled source is 1.80; in addition, when l1=l2=3, 4, k1=k2=0, the non-Gaussian operation of subtracting 3 and 4 photons from the second and fourth optical signals respectively is realized. When the compression parameter ξ=0.31 of the single-mode squeezed vacuum state (that is, the compression intensity is -2.69dB), the negative logarithm of the entangled quantum entangled source is 2.12 and 2.21 respectively.

[0122] In one embodiment, Figure 5 As shown, the preparation method of the quantum entanglement source also includes a preparation method based on a quantum optical frequency comb, wherein the first optical signal includes a first upper sideband frequency component, a first lower sideband frequency component, and a vacuum state, and the first optical parametric resonator is connected to the first pump light to output the first optical signal in the first photon state, and further includes:

[0123] S210 , the first optical parametric resonator is connected to the first pump light, and outputs a first upper sideband frequency component, a first lower sideband frequency component, and a vacuum state of the first photon state, where the frequency component of the vacuum state is the first fundamental frequency signal component.

[0124] In one embodiment, the first optical parametric resonator includes a nonlinear crystal and a reflector, which converts the input first pump light into photon pairs and a vacuum state. The photon pairs include a first upper sideband frequency component and a first lower sideband frequency component, and resonate with the frequency component of the photon pairs. Since the frequency component of the vacuum state is the first fundamental frequency signal component, the first optical signal includes the first upper sideband frequency component, the first lower sideband frequency component, and the first fundamental frequency signal component.

[0125] In a specific embodiment, a first pump light having a preset wavelength of 532 nm is connected to a first optical parametric resonator. After resonance between the nonlinear crystal gain and the optical reflector, at least one photon pair symmetrically distributed around 1064 nm is generated. The photon pair is represented as ω0±nΩ on a quantum optical frequency comb, where n is a positive integer representing the number of photon pairs, ω0 is the central optical frequency corresponding to the 1064 nm photon, and Ω is the frequency of the upper and lower sidebands. For ease of reference, ω0+nΩ is defined as the first upper sideband frequency component of the quantum optical frequency comb, ω0-nΩ is defined as the first lower sideband frequency component of the quantum optical frequency comb, and ω0 is defined as the fundamental frequency signal component. The resonant frequency of the first optical parametric resonator is set at the frequencies of the upper and lower sideband frequency components, rather than at the frequency of ω0, so the fundamental frequency signal component ω0 is in a vacuum state.

[0126] In a specific embodiment, when n=1, the first upper sideband frequency component of the photon pair is ω0+Ω, and the first lower sideband frequency component of the photon pair is ω0-Ω, which is conducive to simplifying the preparation of the quantum entanglement source.

[0127] In one embodiment, the first upper sideband frequency component and the first lower sideband frequency component form a double sideband mode (DBS) and meet the following conditions:

[0128]

[0129]

[0130] Where θ is the phase difference between the first upper sideband frequency component and the first lower sideband frequency component, is the annihilation operator of the first upper sideband frequency component, is the annihilation operator of the first lower sideband frequency component, is the generator of the first upper sideband frequency component, is the generator of the first lower sideband frequency component, is the annihilation operator of the double-side frequency mode, is the double-side frequency mode generation operator, and n is a positive integer.

[0131] In a specific embodiment, when n=1, the first upper sideband frequency component ω0+Ω and the first lower sideband frequency component ω0-Ω form a double-sideband pattern and satisfy the following conditions:

[0132]

[0133]

[0134] in, is the annihilation operator of the double-side frequency mode when n=1, is the generation operator of the double-sideband mode when n=1, θ is the phase difference between the first upper sideband frequency component ω0+Ω and the first lower sideband frequency component ω0-Ω, is the annihilation operator of the first upper sideband frequency component when n=1, is the annihilation operator of the first lower sideband frequency component when n=1, is the generator of the first upper sideband frequency component when n=1, It is the generator of the first lower sideband frequency component when n=1.

[0135] In one embodiment, Figure 5 As shown, the first operating module includes a first electro-optical modulator and a first light reduction submodule. The first operating module receives a first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state. The first operating module also includes:

[0136] S350: A first electro-optical modulator receives a first optical signal and performs a first modulation on the first optical signal to obtain a first modulated signal.

[0137] In one embodiment, a first electro-optical modulator receives a first upper sideband frequency component, a first lower sideband frequency component, and a first baseband signal component, and performs a first modulation of the sum of the amplitudes according to a first modulation depth β1 and a first modulation angle θ1, and outputs a first modulated signal. The first modulated signal includes a second upper sideband frequency component, a second lower sideband frequency component, and a second baseband signal component, wherein a single-mode compressed vacuum state of the sum of the amplitudes is formed between the second upper sideband frequency component and the second lower sideband frequency component.

[0138] In one embodiment, after passing through the first electro-optical modulator, the component with a frequency ω in the first optical signal is distributed at frequencies ω, ω+nΩ, and ω-nΩ. Since the first optical signal includes a first upper sideband frequency component, a first lower sideband frequency component, and a first baseband signal component, the annihilation operator of the modulated first optical signal is:

[0139]

[0140] in, is the annihilation operator of the first modulation signal, β1 is the first modulation depth, θ1 is the first modulation angle, is the annihilation operator of the signal with frequency ω in the first optical signal after being modulated on the frequency component ω, is the annihilation operator of the frequency component of the signal with frequency ω in the first optical signal after modulation at ω+nΩ, is the annihilation operator of the frequency component of the signal with a frequency of ω in the first optical signal after being modulated at ω-nΩ, i is the sign of the imaginary part, e is the base of the natural logarithm, and n is a positive integer;

[0141] It should be noted that, due to the first modulation back The signals obtained at each frequency are superimposed signals. example like The annihilation operator of the second baseband signal includes the annihilation operator on the baseband component after the three frequency components ω=ω0, ω=ω0+nΩ and ω=ω0-nΩ in the first signal input to the first electro-optical modulator are modulated. The annihilation operator of the second upper sideband frequency component includes the annihilation operator on the second sideband frequency component after the three frequency components ω=ω0, ω=ω0+nΩ and ω=ω0-nΩ in the first signal input to the first electro-optical modulator are modulated. The annihilation operator of the second lower sideband frequency component includes the annihilation operator on the second lower sideband frequency component after the three frequency components ω=ω0, ω=ω0+nΩ and ω=ω0-nΩ in the first signal input to the first electro-optical modulator are modulated.

[0142] In one embodiment, when n = 1, after modulation by the first electro-optical modulator, a portion of the first upper sideband frequency component ω0+Ω and the first lower sideband frequency component ω0-Ω are superimposed on the first fundamental frequency signal component ω0, thereby forming a superimposed second upper sideband frequency component ω0+Ω, a superimposed second lower sideband frequency component ω0-Ω, and a superimposed second fundamental frequency signal component ω0, so that the sum of the amplitudes of the second upper sideband frequency component and the second lower sideband frequency component forms a single-mode squeezed vacuum state. When n = 1, the annihilation operator of the first modulated signal in the frequency domain after modulation of the first upper sideband frequency component, the first lower sideband frequency component, and the first fundamental frequency signal component is:

[0143]

[0144] in, is the annihilation operator of the first modulation signal when n=1, β1 is the first modulation depth, θ1 is the first modulation angle, is the annihilation operator of the signal with frequency ω in the first optical signal after being modulated on the frequency component ω, is the annihilation operator of the frequency component of the signal with frequency ω in the first optical signal after modulation at ω+Ω when n=1, is the annihilation operator of the ω-Ω frequency component of the signal with a frequency ω in the first optical signal after modulation when n=1, i is the sign of the imaginary part, e is the base of the natural logarithm, and n is a positive integer.

[0145] In one embodiment, when n is 1 and ω=ω0, the annihilation operator of the signal with a frequency ω in the first optical signal after modulation is:

[0146]

[0147] When n is 1 and ω=ω0+Ω, the annihilation operator of the signal with frequency ω in the first optical signal after modulation is:

[0148]

[0149] When n is 1 and ω=ω0-Ω, the annihilation operator of the signal with frequency ω in the first optical signal after modulation is:

[0150]

[0151] in, is the annihilation operator of the first modulated signal on the second fundamental frequency signal component, is the annihilation operator of the first modulated signal on the second upper sideband frequency component, is the annihilation operator of the first modulated signal at the second lower sideband frequency component

[0152] It should be noted that the annihilation operator of the second baseband signal component includes the following annihilation operators:

[0153]

[0154] The annihilation operators of the second upper sideband frequency component include the following annihilation operators:

[0155]

[0156] The annihilation operators of the second lower sideband frequency component include the following annihilation operators:

[0157]

[0158] It can be understood that the frequency components of ω0+2Ω and ω0-2Ω are filtered out when the first modulated signal passes through the optical frequency divider.

[0159] In one embodiment, the first modulation depth β1 is 0.316; the first modulation angle θ1 is 0, and a single-mode squeezed vacuum state with a sum of amplitudes is formed between the second upper sideband frequency component and the second lower sideband frequency component.

[0160] S360: The first light reduction submodule receives the first modulated signal, performs a first non-Gaussian operation on the first modulated signal, and outputs a second optical signal, where the second optical signal includes a third upper sideband frequency component and a third lower sideband frequency component.

[0161] The first photon subtraction module receives the second upper sideband frequency component, the second lower sideband frequency component and the second baseband signal component of the first modulated signal, performs a photon subtraction operation on the second baseband signal component of the first modulated signal, improves the quantum entanglement of the second upper sideband frequency component and the second lower sideband frequency component, and outputs the third upper sideband frequency component and the third lower sideband frequency component of the second optical signal.

[0162] It should be noted that, unlike the traditional method of increasing the degree of quantum entanglement by performing non-Gaussian operations of adding and subtracting photons on the two modes of a dual-mode squeezed vacuum state that has formed a quantum entanglement source, this embodiment performs a photon subtraction operation before the upper sideband frequency component and the lower sideband frequency component form a quantum entanglement source, thereby increasing the degree of entanglement after the single-mode squeezed vacuum state forms a quantum entanglement source.

[0163] In one embodiment, Figure 6 As shown, the first light reduction submodule includes a fifth optical beam splitter and a third photon number detector. The first light reduction submodule receives the first modulated signal, performs a first non-Gaussian operation on the first modulated signal, and outputs a second optical signal, including:

[0164] S361, the fifth optical beam splitter receives the second upper sideband frequency component, the second lower sideband frequency component and the second baseband signal component of the first modulated signal, transmits and outputs the third baseband signal component, and reflects and outputs the third upper sideband frequency component and the third lower sideband frequency component.

[0165] According to the annihilation operator of the modulation signal after the first electro-optical modulator, the amplitude reflectivity of the fifth optical beam splitter is The amplitude transmittance is When β1=0.316, the amplitude transmittance of the fifth beam splitter is 0.99.

[0166] The fifth optical beam splitter receives the second baseband signal component and transmits the third baseband signal component. It also receives the second upper sideband frequency component and the second lower sideband frequency component and reflects the third upper and third lower sideband frequency components. It should be noted that the intensity of the transmitted third baseband signal component is weaker than the intensity of the second baseband signal component before input, but the frequency remains unchanged. The intensity of the reflected third upper and third lower sideband frequency components is somewhat weaker than the intensity of the second upper and second lower sideband frequency components before input, but the frequency remains unchanged.

[0167] S362: The third photon number detector is connected to the third baseband signal component and performs a photon subtraction operation on the second baseband signal component.

[0168] Since the second fundamental frequency signal component is a signal modulated by superimposing a portion of the second upper sideband frequency component and the second lower sideband frequency component on the second fundamental frequency signal component in a vacuum state, when the third photon number detector is connected to the third fundamental frequency signal component, the photons detected are all from the second upper sideband frequency component and the second lower sideband frequency component, thereby achieving the sum of the amplitudes of the second fundamental frequency signal component and the third upper sideband frequency component and the third lower sideband frequency component output after modulation and reflection X DBS If the third upper sideband frequency component and the third lower sideband frequency component of the reflected output are measured, an amplitude single-mode squeezed vacuum state with one photon l1 minus can be obtained.

[0169] The amplitude and phase of the frequency components in the quantum optical frequency comb are:

[0170]

[0171]

[0172] Where ω represents the frequency, X ω is the amplitude of the frequency ω, Y ω is the phase at frequency ω, is the annihilation operator with frequency ω, is a generating operator with frequency ω.

[0173] In one embodiment, the sum of the amplitudes of the second upper sideband frequency component and the second lower sideband frequency component is X DBS for:

[0174]

[0175] Among them, X DBS is the sum of the amplitudes of the second upper sideband frequency component and the second lower sideband frequency component, is the annihilation operator of the second upper sideband frequency component, is the annihilation operator of the second lower sideband frequency component, is the generator of the second upper sideband frequency component, is the generator of the second lower sideband frequency component, i is the sign of the imaginary part, e is the base of the natural logarithm, and n is a positive integer.

[0176] In a specific embodiment, when n=1, the sum of the amplitudes of the second upper sideband frequency component ω0+Ω and the second lower sideband frequency component ω0+Ω is X DBS for:

[0177]

[0178] Among them, X′ DBS is the sum of the amplitudes of the second upper sideband frequency component and the second lower sideband frequency component for n=1, is the annihilation operator of the second upper sideband frequency component of n=1, is the annihilation operator of the second lower sideband frequency component of n=1, is the generator of the second upper sideband frequency component for n=1, is the generation operator of the second lower sideband frequency component for n=1, i is the sign of the imaginary part, and e is the base of the natural logarithm.

[0179] In one embodiment, when n=1, the second upper sideband frequency component is ω0+Ω, the second lower sideband frequency component is ω0-Ω, and the second upper sideband frequency component and the second lower sideband frequency component after the first modulation satisfy the following first condition:

[0180]

[0181] Where ξ is the compression parameter of the squeezed vacuum state, ω0 is the fundamental frequency signal component, and Ω is the sideband frequency component. is the amplitude deviation at frequency ω0+Ω, is the amplitude deviation at frequency ω0-Ω, and e is the logarithmic base.

[0182] In one embodiment, Figure 5 As shown, after the step of the first operating module receiving the first optical signal, performing a non-Gaussian operation on the first optical signal, and outputting a second optical signal in a second photon state, the method further includes:

[0183] S800: The third operating module receives the second optical signal, performs a second modulation and a first non-Gaussian operation on the second optical signal, and outputs a fifth optical signal, wherein the fifth optical signal includes a fifth upper sideband frequency component and a fifth lower sideband frequency component.

[0184] In one embodiment, the third operation module includes a second electro-optical modulator and a second photon subtraction module, which is conducive to performing a second modulation and a first non-Gaussian operation on the second optical signal, further improving the quantum entanglement after the non-Gaussian operation.

[0185] In one embodiment, Figure 7 As shown, the third operating module receives the second optical signal, performs a second modulation and a first non-Gaussian operation on the second optical signal, and outputs a fifth optical signal, including:

[0186] S810: A second electro-optical modulator receives a second optical signal and performs a second modulation on the second optical signal to obtain a second modulated signal, where the second modulated signal includes a fourth upper sideband frequency component, a fourth lower sideband frequency component, and a fourth baseband signal component.

[0187] It should be noted that although the fifth optical beam splitter transmits and outputs the second fundamental frequency signal component which is the superposition of part of the second upper sideband frequency component and part of the second lower sideband frequency component in the first modulated signal, since the reflected output signal still includes the third upper sideband frequency component, the third lower sideband frequency component and the first fundamental frequency signal component in a vacuum state, the second electro-optical modulator accesses the third upper sideband frequency component, the third lower sideband frequency component and the first fundamental frequency signal component, and performs a second modulation according to the second modulation depth β2 and the second modulation angle θ2, and outputs a second modulated signal, wherein the second modulated signal includes the fourth upper sideband frequency component, the fourth lower sideband frequency component and the fourth fundamental frequency signal component, wherein the phase difference between the fourth upper sideband frequency component and the fourth lower sideband frequency component forms a single-mode compressed vacuum state.

[0188] In one embodiment, since the second optical signal includes a third upper sideband frequency component and a third lower sideband frequency component, the annihilation operator of the modulated second optical signal is:

[0189]

[0190] in, is the annihilation operator of the second modulation signal, β2 is the second modulation depth, θ2 is the second modulation angle, is the annihilation operator of the frequency ω component of the second optical signal after the signal with frequency ω is modulated, is the annihilation operator of the frequency component of the second optical signal with a frequency of ω after modulation at ω+nΩ, is the annihilation operator of the frequency component of the signal with a frequency of ω in the second optical signal after modulation at ω-nΩ, i is the sign of the imaginary part, e is the base of the natural logarithm, and n is a positive integer.

[0191] In one embodiment, when n=1, after modulation by the second electro-optical modulator, a portion of the third upper sideband frequency component ω0+Ω and the third lower sideband frequency component ω0-Ω input to the second electro-optical modulator will be superimposed on the first baseband signal component ω0 after passing through the second electro-optical modulator, thereby forming a superimposed fourth upper sideband frequency component ω0+Ω, a superimposed fourth lower sideband frequency component ω0-Ω, and a superimposed fourth baseband signal component ω0, so that the sum of the amplitudes and the phase difference of the fourth upper sideband frequency component and the fourth lower sideband frequency component can respectively form a single-mode squeezed vacuum state. When n=1, the annihilation operator of the second modulated signal in the frequency domain after modulation of the third upper sideband frequency component, the third lower sideband frequency component, and the first baseband signal component is:

[0192]

[0193] in, is the annihilation operator of the second modulation signal when n=1, β1 is the second modulation depth, θ1 is the second modulation angle, is the annihilation operator of the frequency ω component of the second optical signal after the signal with frequency ω is modulated, is the annihilation operator of the frequency component of the second optical signal with a frequency of ω after modulation at ω+Ω when n=1, is the annihilation operator of the ω-Ω frequency component of the signal with a frequency ω in the second optical signal after modulation when n=1, i is the sign of the imaginary part, e is the base of the natural logarithm, and n is a positive integer.

[0194] It should be noted that, after the second modulation, the annihilation operator of the fourth baseband signal actually includes the annihilation operator of the signal superimposed on ω after the three frequency components ω=ω0, ω=ω0+nΩ and ω=ω0-nΩ in the second optical signal of the second electro-optical modulator are modulated; the annihilation operator of the fourth upper sideband frequency component includes the annihilation operator of the signal superimposed on ω+nΩ after the three frequency components ω=ω0, ω=ω0+nΩ and ω=ω0-nΩ in the second optical signal of the first electro-optical modulator are modulated; the annihilation operator of the fourth lower sideband frequency component includes the annihilation operator of the signal superimposed on ω+nΩ after the three frequency components ω=ω0, ω=ω0+nΩ and ω=ω0-nΩ in the second optical signal of the first electro-optical modulator are modulated.

[0195] In one embodiment, when n is 1 and ω=ω0, the annihilation operator of the signal with a frequency ω in the second optical signal after modulation is:

[0196]

[0197] When n is 1 and ω=ω0+Ω, the annihilation operator of the signal with frequency ω in the second optical signal after modulation is:

[0198]

[0199] When n is 1 and ω=ω0-Ω, the annihilation operator of the signal with frequency ω in the second optical signal after modulation is:

[0200]

[0201] The annihilation operator of the fourth upper sideband frequency component and the annihilation operator of the fourth lower sideband frequency component can be derived in the same way.

[0202] in, is the annihilation operator of the second modulated signal on the second fundamental frequency signal component, is the annihilation operator of the second modulated signal at the second upper sideband frequency component, is the annihilation operator of the second modulated signal at the second lower sideband frequency component

[0203] It should be noted that the annihilation operator of the fourth baseband signal component includes the following annihilation operators:

[0204]

[0205] The annihilation operators of the fourth upper sideband frequency component include the following annihilation operators:

[0206]

[0207] The annihilation operators of the fourth lower sideband frequency component include the following annihilation operators:

[0208]

[0209] It can be understood that the frequency components of ω0+2Ω and ω0-2Ω are filtered out when the second modulated signal passes through the optical frequency divider.

[0210] In one embodiment, when n=1, the second electro-optical modulator sets the second modulation depth β2=0.316 and the second modulation angle θ2=π / 2. After modulation by the second electro-optical modulator, a portion of the third upper sideband frequency component ω0+Ω and the third lower sideband frequency component ω0-Ω will be superimposed on the first baseband signal component ω0, forming a superimposed fourth upper sideband frequency component ω0+Ω, a superimposed fourth lower sideband frequency component ω0-Ω and a superimposed fourth baseband signal component ω0, thereby obtaining the phase difference between the fourth upper sideband frequency component and the fourth lower sideband frequency component, thereby forming a phase-compressed single-mode compressed vacuum state.

[0211] In one embodiment, the phase difference between the fourth upper sideband frequency component and the fourth lower sideband frequency component is:

[0212]

[0213] Among them, Y DBS is the phase difference between the fourth upper sideband frequency component and the fourth lower sideband frequency component, is the annihilation operator of the fourth upper sideband frequency component, is the annihilation operator of the fourth lower sideband frequency component, is the generator of the fourth upper sideband frequency component, is the generator of the fourth lower sideband frequency component, i is the sign of the imaginary part, e is the base of the natural logarithm, and n is a positive integer.

[0214] In a specific embodiment, when n=1, the phase difference between the fourth upper sideband frequency component and the fourth lower sideband frequency component is:

[0215]

[0216] Among them, Y′ DBS is the phase difference between the fourth upper sideband frequency component and the fourth lower sideband frequency component, The annihilation operator of the fourth upper sideband frequency component, is the annihilation operator of the fourth lower sideband frequency component, is the generator of the fourth upper sideband frequency component, is the generator of the fourth lower sideband frequency component, i is the sign of the imaginary part, and e is the base of the natural logarithm.

[0217] In one embodiment, when n=1, the fourth upper sideband frequency component is ω0+Ω, the fourth lower sideband frequency component is ω0-Ω, and the fourth upper sideband frequency component and the fourth lower sideband frequency component after the second modulation satisfy the following second condition:

[0218]

[0219] Where ξ is the compression parameter of the squeezed vacuum state, ω0 is the fundamental frequency signal component, and Ω is the sideband frequency component. is the phase deviation at frequency ω0+Ω, is the phase deviation at frequency ω0-Ω, and e is the logarithmic base.

[0220] When the first and second conditions mentioned above are met, after the first and second modulations, the symmetrical fourth upper sideband frequency component ω0+Ω and the fourth lower sideband frequency component ω0-Ω are entangled with each other, and the variance formed by the sum of their amplitudes X and their phase difference Y is less than the quantum limit. The sum of the amplitudes and the phase difference of the fourth upper sideband frequency component ω0+Ω and the fourth lower sideband frequency component ω0-Ω respectively form two single-mode squeezed vacuum states that are orthogonal in amplitude and phase.

[0221] S820: The second light subtraction submodule performs a light subtraction operation on the second modulated signal to output a fifth optical signal, where the fifth optical signal includes a fifth upper sideband frequency component and a fifth lower sideband frequency component.

[0222] The second photon subtraction module receives the fourth upper sideband frequency component, the fourth lower sideband frequency component and the fourth baseband signal component of the second modulated signal, performs a photon subtraction operation on the fourth baseband signal component, improves the quantum entanglement of the fifth upper sideband frequency component and the fifth lower sideband frequency component, and outputs a fifth optical signal, which includes the fifth upper sideband frequency component and the fifth lower sideband frequency component.

[0223] In one embodiment, the second photon reduction module includes a sixth optical beam splitter and a fourth photon count detector, which can further improve the effect of the photon reduction operation.

[0224] In one embodiment, Figure 8 As shown, the second light reduction submodule performs a first non-Gaussian operation on the second modulated signal to output a fifth optical signal, including:

[0225] S821, the sixth optical beam splitter receives the fourth upper sideband frequency component, the fourth lower sideband frequency component and the fourth baseband signal component, transmits and outputs the fifth baseband signal component, and reflects and outputs the fifth upper sideband frequency component and the fifth lower sideband frequency component.

[0226] The sixth optical beam splitter receives the fourth baseband signal component and transmits and outputs the fifth baseband signal component, receives the fourth upper sideband frequency component and the fourth lower sideband frequency component and reflects and outputs the fifth upper sideband frequency component and the fifth lower sideband frequency component.

[0227] Since the second modulation depth is the same as the first modulation depth, both are 0.316, the transmittance of the second optical frequency splitter is also 0.99. The high transmittance is conducive to transmitting and outputting the fifth fundamental frequency signal component, which is conducive to improving the success probability of the photon subtraction operation.

[0228] S822: The fourth photon number detector is connected to the fifth baseband signal component and performs a photon subtraction operation on the fourth baseband signal component.

[0229] Since the fourth fundamental frequency signal component is modulated by superimposing a portion of the fourth upper sideband frequency component and the fourth lower sideband frequency component on the first fundamental frequency signal component in a vacuum state, when the fourth photon number detector is connected to the fifth fundamental frequency signal component, the detected photons all come from the fourth upper sideband frequency component and the fourth lower sideband frequency component, thereby realizing the phase difference Y between the fourth fundamental frequency signal component and the fourth upper sideband frequency component and the fourth lower sideband frequency component reflected and outputted after the second modulation. DBS The non-Gaussian operation of subtracting photons is performed to obtain a phase-single-mode squeezed vacuum state with one photon subtracted.

[0230] S900: The fourth optical beam splitter separates the fifth upper sideband frequency component and the fifth lower sideband frequency component of the input fifth optical signal to obtain an entangled quantum entanglement source.

[0231] In one embodiment, the fourth optical beam splitter separates the fifth upper sideband frequency component and the fifth lower sideband frequency component of the input fifth optical signal to obtain an entangled source. Figure 4 As shown, the negative logarithm value of the entangled quantum entangled source prepared by the method of this embodiment is higher than the negative logarithm value of the quantum entangled source prepared by the traditional TMSV method and PSTMSV method.

[0232] In one embodiment, the fourth optical beam splitter, the fifth optical beam splitter, and the sixth optical beam splitter are all optical frequency beam splitters, which are more conducive to splitting the frequency components.

[0233] In one embodiment, the fourth optical beam splitter, the fifth optical beam splitter, and the sixth optical beam splitter may be balanced optical beam splitters or unbalanced optical beam splitters.

[0234] Compared with the prior art, this embodiment has the following beneficial effects:

[0235] A first laser outputs a first pump light of a preset wavelength; a first optical parametric resonator receives the first pump light and outputs a first optical signal in a first photon state, wherein the frequency of the first optical signal is a first frequency and the first photon state is a single-mode squeezed vacuum state; a first operating module receives the first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state, wherein the second photon state is a non-Gaussian state; a second laser outputs a second pump light of a preset wavelength; a second optical parametric resonator receives the second pump light and outputs a third optical signal in the first photon state, wherein the frequency of the third optical signal is a second frequency and the first frequency is equal to the second frequency; a second operating module receives the third optical signal, performs a non-Gaussian operation on the third optical signal, and outputs a fourth optical signal in a second photon state; a first optical beam splitter receives the second optical signal in the second photon state and the fourth optical signal in the second photon state, and the second optical signal and the fourth optical signal pass through the first optical beam splitter to obtain an entanglement-enhanced quantum entanglement source, thereby improving the robustness of the continuous variable quantum communication system based on the entangled state, thereby improving the communication performance of the quantum communication system.

[0236] In a second aspect, this embodiment provides a device 100 for preparing a quantum entangled source, comprising:

[0237] The first laser 10 is configured to output a first pump light of a preset wavelength.

[0238] The first optical parametric resonator 20 is used to receive the first pump light and output a first optical signal in a first photon state, wherein the frequency of the first optical signal is a first frequency and the first photon state is a single-mode squeezed vacuum state.

[0239] The first operation module 30 is configured to receive the first optical signal, perform a non-Gaussian operation on the first optical signal, and output a second optical signal in a second photon state, wherein the second photon state is a non-Gaussian state.

[0240] In one embodiment, Figure 9 As shown, the first operation module 30 includes a second optical beam splitter 31 and a first photon number detector 32. The second optical beam splitter 31 is configured to receive the first optical signal, transmit and output the second optical signal in the second photon state, and reflect and output the second optical signal in the third photon state. The first photon number detector 32 is configured to receive the second optical signal in the third photon state and perform a first non-Gaussian operation on the second optical signal.

[0241] In another embodiment, Figure 10 As shown, the first operation module 30 includes a second optical beam splitter 31, a first photon number detector 32, and a first photon number generator 33. The second optical beam splitter 31 is configured to receive the first optical signal and the photons output by the first photon number generator 33, transmit and output the second optical signal in the second photon state, and reflect and output the second optical signal in the third photon state. The first photon number detector 32 is configured to receive the second optical signal in the third photon state and perform a second non-Gaussian operation on the first optical signal.

[0242] In yet another embodiment, Figure 11 As shown, the first operation module 30 includes a second optical beam splitter 31 and a first photon number generator 33. The second optical beam splitter 31 is configured to receive the first optical signal and the photons output by the first photon number generator 33, transmit and output the second optical signal in the second photon state, reflect and output the second optical signal in the third photon state, and perform a third non-Gaussian operation on the first optical signal.

[0243] The second laser 40 is configured to output a second pump light of a preset wavelength.

[0244] The second optical parametric resonator 50 is used to receive the second pump light and output a third optical signal in the first photon state, wherein the frequency of the third optical signal is the second frequency, and the first frequency is equal to the second frequency.

[0245] The second operation module 60 is configured to receive the third optical signal, perform a non-Gaussian operation on the third optical signal, and output a fourth optical signal in a second photon state.

[0246] In one embodiment, Figure 9As shown, the second operation module 60 includes a third optical beam splitter 61 and a second photon number detector 62. The third optical beam splitter 61 is configured to receive the third optical signal, transmit and output a fourth optical signal in the second photon state, and reflect and output a fourth optical signal in the fourth photon state. The second photon number detector 62 is configured to receive the fourth optical signal in the fourth photon state and perform a non-Gaussian operation on the fourth optical signal.

[0247] In another embodiment, Figure 10 As shown, the second operation module 60 includes a third optical beam splitter 61, a second photon number detector 62, and a second photon number generator 63. The third optical beam splitter 61 is configured to receive the third optical signal and the photons output by the second photon number generator 63, transmit and output a fourth optical signal in the second photon state, and reflect and output a fourth optical signal in the fourth photon state. The second photon number detector 62 is configured to receive the fourth optical signal in the fourth photon state and perform a second non-Gaussian operation on the third optical signal.

[0248] In yet another embodiment, Figure 11 As shown, the second operating module 60 includes a third optical beam splitter 61 and a second photon number generator 63 .

[0249] The third optical beam splitter 61 is used to receive the third optical signal and the photons output by the second photon number generator 63, transmit and output the fourth optical signal in the second photon state, reflect and output the fourth optical signal in the fourth photon state, and perform a third non-Gaussian operation on the third optical signal.

[0250] In another embodiment, Figure 11 As shown, the device for preparing a quantum entangled source further includes a device 200 for preparing a quantum entangled source based on a quantum frequency comb, comprising:

[0251] A first laser 10 is configured to output a first pump light of a preset wavelength;

[0252] The first optical parametric resonator 20 is used to receive the first pump light and output a first optical signal in a first photon state. The first optical signal includes a first upper sideband frequency component, a first lower sideband frequency component, and a vacuum state. The frequency component of the vacuum state is a first fundamental frequency signal component.

[0253] The first operation module 30 is configured to receive the first optical signal, perform a non-Gaussian operation on the first optical signal, and output a second optical signal in a second photon state.

[0254] In one embodiment, the first operation module 30 includes a first electro-optical modulator 33 and a first light reduction submodule 34. The first electro-optical modulator 33 is configured to receive a first optical signal and perform a first modulation on the first optical signal to obtain a first modulated signal, the first modulated signal comprising a second upper sideband frequency component, a second lower sideband frequency component, and a second baseband signal component. The first light reduction submodule 34 is configured to receive the first modulated signal and perform a first non-Gaussian operation on the first modulated signal to output a second optical signal, the second optical signal comprising a third upper sideband frequency component and a third lower sideband frequency component.

[0255] In one embodiment, the first photon subtraction module 34 includes a fifth beam splitter 341 and a third photon count detector 342. The fifth beam splitter 341 is configured to receive the second upper sideband frequency component, the second lower sideband frequency component, and the second baseband signal component, transmit the third baseband signal component, and reflect the third upper sideband frequency component and the third lower sideband frequency component. The third photon count detector 342 is configured to receive the third baseband signal component and perform a photon subtraction operation on the second baseband signal component.

[0256] The third operating module 80 is configured to receive the second optical signal, perform a second modulation and a first non-Gaussian operation on the second optical signal, and output a fifth optical signal, wherein the fifth optical signal includes a fifth upper sideband frequency component and a fifth lower sideband frequency component.

[0257] In one embodiment, the third operation module 80 includes a second electro-optical modulator 83 and a second light-reduction sub-module 84. The second electro-optical modulator 83 is configured to receive a second optical signal and perform a second modulation on the second optical signal to obtain a second modulated signal. The second modulated signal includes a fourth upper sideband frequency component, a fourth lower sideband frequency component, and a fourth baseband signal component. The second light-reduction sub-module 84 is configured to perform a light-reduction sub-operation on the second modulated signal to output a fifth optical signal. The fifth optical signal includes a fifth upper sideband frequency component and a fifth lower sideband frequency component.

[0258] In one embodiment, the second photon subtraction module 84 includes a sixth optical beam splitter 841 and a fourth photon count detector 842. The sixth optical beam splitter 841 is configured to receive the fourth upper sideband frequency component, the fourth lower sideband frequency component, and the fourth baseband signal component, transmit and output the fifth baseband signal component, and reflect and output the fifth upper sideband frequency component and the fifth lower sideband frequency component. The fourth photon count detector 842 is configured to receive the fifth baseband signal component and perform a photon subtraction operation on the fourth baseband signal component.

[0259] The fourth optical beam splitter 90 is used to separate the fifth upper sideband frequency component and the fifth lower sideband frequency component of the input fifth optical signal to obtain an entangled quantum entanglement source.

[0260] The apparatus for preparing a quantum entangled source of this embodiment is used to implement the method for preparing a quantum entangled source of the first aspect. Furthermore, because the apparatus of this embodiment performs non-Gaussian operations in a single-mode compressed vacuum state, that is, before the quantum entanglement source is formed, it enhances the quantum entanglement level. This simplifies the optical structure for preparing a high-entanglement quantum entangled source, thereby reducing the cost of preparing a high-entanglement quantum entangled source.

[0261] The preparation device based on quantum frequency comb only uses one laser and one optical parametric resonator, which further simplifies the optical structure for preparing a high-entanglement quantum entanglement source, thereby reducing the cost of preparing a high-entanglement quantum entanglement source.

[0262] In a third aspect, this embodiment provides a communication system based on quantum entanglement, including a device for implementing the method for preparing a quantum entangled source described in the first aspect. In this embodiment, the communication system also includes a receiving device for receiving and decoding information carried by the quantum entangled source.

[0263] It can be understood that the beneficial effects of the second and third aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0264] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0265] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A method for preparing a quantum entanglement source, characterized in that: include: The first laser outputs a first pump light of a preset wavelength; The first optical parametric resonator is connected to the first pump light and outputs a first optical signal in a first photon state, wherein the frequency of the first optical signal is a first frequency and the first photon state is a single-mode squeezed vacuum state; A first operating module receives the first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state, wherein the second photon state is a non-Gaussian state; The second laser outputs a second pump light of the preset wavelength; The second optical parametric resonator is connected to the second pump light and outputs a third optical signal in the first photon state, wherein the frequency of the third optical signal is the second frequency, and the first frequency is equal to the second frequency; A second operation module receives the third optical signal, performs the non-Gaussian operation on the third optical signal, and outputs a fourth optical signal in the second photon state; The first optical beam splitter receives the second optical signal in the second photon state and the fourth optical signal in the second photon state, and the second optical signal and the fourth optical signal pass through the first optical beam splitter to obtain the entangled quantum entanglement source; The non-Gaussian operation includes a first non-Gaussian operation, which is a photon subtraction operation; the first operation module includes a second optical beam splitter and a first photon number detector, and the second operation module includes a third optical beam splitter and a second photon number detector; the first operation module receives the first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state, including: the second optical beam splitter receives the first optical signal, transmits and outputs the second optical signal in the second photon state, and reflects and outputs the second optical signal in the third photon state; the first photon number detector receives the second optical signal in the third photon state, and performs the non-Gaussian operation on the first optical signal; correspondingly, the second operation module receives the third optical signal, performs a non-Gaussian operation on the third optical signal, and outputs a fourth optical signal in a second photon state, including: the third optical beam splitter receives the third optical signal, transmits and outputs the fourth optical signal in the second photon state, and reflects and outputs the fourth optical signal in the fourth photon state; the second photon number detector receives the fourth optical signal in the fourth photon state, and performs the first non-Gaussian operation on the third optical signal; Alternatively, the non-Gaussian operation also includes a second non-Gaussian operation, and the second non-Gaussian operation is a photon addition operation and a photon subtraction operation at the same time; the first operation module includes a second optical beam splitter, a first photon number detector and a first photon number generator, and the second operation module includes a third optical beam splitter, a second photon number detector and a second photon number generator; the first operation module receives the first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state, and also includes: the second optical beam splitter receives the first optical signal and the photon output by the first photon number generator, transmits and outputs the second optical signal in the second photon state, and reflects and outputs the second optical signal in the second photon state. a second optical signal in a three-photon state; the first photon number detector receives the second optical signal in the third photon state, and performs the second non-Gaussian operation on the first optical signal; correspondingly, the second operation module receives the third optical signal, performs a non-Gaussian operation on the third optical signal, and outputs a fourth optical signal in the second photon state, further comprising: the third optical beam splitter receives the third optical signal and the photons output by the second photon number generator, transmits and outputs a fourth optical signal in the second photon state, and reflects and outputs a fourth optical signal in the fourth photon state; the second photon number detector receives the fourth optical signal in the fourth photon state, and performs the second non-Gaussian operation on the third optical signal; Alternatively, the non-Gaussian operation also includes a third non-Gaussian operation, which is a photon addition operation; the first operation module includes a second optical beam splitter and a first photon number generator, and the second operation module includes a third optical beam splitter and a second photon number generator; the first operation module receives the first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state, and further includes: the second optical beam splitter receives the first optical signal and the photon output by the first photon number generator, transmits and outputs the second optical signal in the second photon state, reflects and outputs the second optical signal in the third photon state, and performs the third non-Gaussian operation on the first optical signal; accordingly, the second operation module receives the third optical signal, performs a non-Gaussian operation on the third optical signal, and outputs a fourth optical signal in a second photon state, and further includes: the third optical beam splitter receives the third optical signal and the photon output by the second photon number generator, transmits and outputs a fourth optical signal in the second photon state, reflects and outputs a fourth optical signal in the fourth photon state, and performs the third non-Gaussian operation on the third optical signal.

2. The preparation method according to claim 1, wherein The preparation method also includes a preparation method of a quantum entangled source based on a quantum optical frequency comb, wherein the non-Gaussian operation includes a first non-Gaussian operation, and the first non-Gaussian operation is a photon subtraction operation; The first operating module includes a first electro-optical modulator and a first light reduction sub-module; The first optical signal includes a vacuum state of a first upper sideband frequency component, a first lower sideband frequency component, and a first fundamental frequency signal component; The first optical parametric resonator is connected to the first pump light to output a first optical signal in a first photon state, further comprising: The first optical parametric resonator is connected to the first pump light, and outputs the first upper sideband frequency component, the first lower sideband frequency component and the vacuum state of the first photon state, where the frequency component of the vacuum state is the first fundamental frequency signal component; The first operation module receives the first optical signal, performs a non-Gaussian operation on the first optical signal, and outputs a second optical signal in a second photon state, further comprising: The first electro-optical modulator receives the first optical signal and performs a first modulation on the first optical signal to obtain a first modulated signal, wherein the first modulated signal includes a second upper sideband frequency component, a second lower sideband frequency component and a second baseband signal component; The first light reduction submodule receives the first modulated signal, performs the first non-Gaussian operation on the first modulated signal, and outputs the second optical signal, where the second optical signal includes a third upper sideband frequency component and a third lower sideband frequency component; After the step of the first operating module receiving the first optical signal, performing a non-Gaussian operation on the first optical signal, and outputting a second optical signal in a second photon state, the method includes: The third operating module receives the second optical signal, performs a second modulation and the first non-Gaussian operation on the second optical signal, and outputs a fifth optical signal, where the fifth optical signal includes a fifth upper sideband frequency component and a fifth lower sideband frequency component; The fourth optical beam splitter separates the fifth upper sideband frequency component and the fifth lower sideband frequency component of the input fifth optical signal to obtain the entangled quantum entanglement source.

3. The preparation method according to claim 2, wherein The first photon reduction module includes a fifth optical beam splitter and a third photon number detector; The first light reduction sub-module receives the first modulated signal, performs the first non-Gaussian operation on the first modulated signal, and outputs the second optical signal, including: The fifth optical beam splitter receives the second upper sideband frequency component, the second lower sideband frequency component and the second baseband signal component, transmits and outputs the third baseband signal component, and reflects and outputs the third upper sideband frequency component and the third lower sideband frequency component; The third photon number detector is connected to the third baseband signal component and performs the photon subtraction operation on the second baseband signal component.

4. The preparation method according to claim 2, wherein The third operating module includes a second electro-optical modulator and a second light reduction sub-module; The third operation module receives the second optical signal, performs a second modulation and the first non-Gaussian operation on the second optical signal, and outputs a fifth optical signal, including: The second electro-optical modulator receives the second optical signal and performs a second modulation on the second optical signal to obtain a second modulated signal, wherein the second modulated signal includes a fourth upper sideband frequency component, a fourth lower sideband frequency component and a fourth baseband signal component; The second light reduction submodule performs the light reduction sub-operation on the second modulated signal to output the fifth optical signal; The second light reduction submodule includes a sixth optical beam splitter and a fourth photon number detector, and the second light reduction submodule performs the first non-Gaussian operation on the second modulated signal to output the fifth optical signal, including: The sixth optical beam splitter receives the fourth upper sideband frequency component, the fourth lower sideband frequency component and the fourth baseband signal component, transmits and outputs the fifth baseband signal component, and reflects and outputs the fifth upper sideband frequency component and the fifth lower sideband frequency component; The fourth photon number detector is connected to the fifth baseband signal component and performs the photon subtraction operation on the fourth baseband signal component.

5. The preparation method according to claim 2, wherein The first upper sideband frequency component and the first lower sideband frequency component form a double-sideband pattern and satisfy the following conditions: Wherein, θ is the phase difference between the first upper sideband frequency component and the first lower sideband frequency component, is the annihilation operator of the first upper sideband frequency component, is the annihilation operator of the first lower sideband frequency component, is the generation operator of the first upper sideband frequency component, is the annihilation operator of the first lower sideband frequency component, is the annihilation operator of the double-side frequency mode, is the generating operator of the double-side frequency pattern, and n is a positive integer.

6. The preparation method according to claim 4, wherein The annihilation operator of the frequency component with a frequency ω in the first optical signal after being modulated by the first modulator is: in, is the annihilation operator of the first modulation signal, β1 is the first modulation depth, θ1 is the first modulation angle, is the annihilation operator of the signal with frequency ω in the first optical signal after being modulated on the frequency component ω, is the annihilation operator of the frequency component of the signal with frequency ω in the first optical signal after modulation at ω+nΩ, is the annihilation operator of the ω-nΩ frequency component of the signal with a frequency ω in the first optical signal after modulation, i is the sign of the imaginary part, e is the base of the natural logarithm, and n is a positive integer; The annihilation operator of the second optical signal after being modulated by the second electro-optical modulator is: in, is the annihilation operator of the second modulation signal, β2 is the second modulation depth, θ2 is the second modulation angle, is the annihilation operator of the signal with frequency ω in the second optical signal after being modulated on the frequency component ω, is the annihilation operator of the frequency component of the signal with frequency ω in the second optical signal after modulation at ω+nΩ, is the annihilation operator of the ω-nΩ frequency component of the signal with a frequency ω in the second optical signal after modulation, i is the sign of the imaginary part, e is the base of the natural logarithm, and n is a positive integer.

7. The preparation method according to claim 4, wherein The sum of the amplitudes of the second upper sideband frequency component and the second lower sideband frequency component is: Among them, X DBS is the sum of the amplitudes of the second upper sideband frequency component and the second lower sideband frequency component, is the annihilation operator of the second upper sideband frequency component, is the annihilation operator of the second lower sideband frequency component, is the generator of the second upper sideband frequency component, is the generator of the second lower sideband frequency component, i is the imaginary part sign, e is the base of the natural logarithm, θ1 is the first modulation angle, and n is a positive integer; The phase difference between the fourth upper sideband frequency component and the fourth lower sideband frequency component is: Among them, Y DBS is the phase difference between the fourth upper sideband frequency component and the fourth lower sideband frequency component, is the annihilation operator of the fourth upper sideband frequency component, is the annihilation operator of the fourth lower sideband frequency component, is the generator of the fourth upper sideband frequency component, is the generation operator of the fourth lower sideband frequency component, i is the imaginary part sign, e is the base of the natural logarithm, θ2 is the second modulation angle, and n is a positive integer.

8. A device for preparing a quantum entangled source, characterized in that: include: a first laser, configured to output a first pump light of a preset wavelength; a first optical parametric resonator, configured to receive the first pump light and output a first optical signal in a first photon state, wherein the first optical signal has a first frequency and the first photon state is a single-mode squeezed vacuum state; a first operating module, configured to receive the first optical signal, perform a non-Gaussian operation on the first optical signal, and output a second optical signal in a second photon state, wherein the second photon state is a non-Gaussian state; a second laser, configured to output a second pump light of the preset wavelength; a second optical parametric resonator, configured to receive the second pump light and output a third optical signal in the first photon state, wherein a frequency of the third optical signal is a second frequency, and the first frequency is equal to the second frequency; a second operating module, configured to receive the third optical signal, perform the non-Gaussian operation on the third optical signal, and output a fourth optical signal in the second photon state; a first optical beam splitter, configured to receive a second optical signal in the second photon state and a fourth optical signal in the second photon state, wherein the second optical signal and the fourth optical signal are entangled to obtain the quantum entanglement source through the first optical beam splitter; The non-Gaussian operation includes a first non-Gaussian operation, which is a photon subtraction operation; the first operation module includes a second optical beam splitter and a first photon number detector, and the second operation module includes a third optical beam splitter and a second photon number detector; the receiving the first optical signal, performing the non-Gaussian operation on the first optical signal, and outputting the second optical signal of the second photon state, includes: the second optical beam splitter receives the first optical signal, transmits and outputs the second optical signal of the second photon state, and reflects and outputs the second optical signal of the third photon state; the first photon number detector receives the second optical signal of the third photon state, and performs the non-Gaussian operation on the first optical signal; correspondingly, the receiving the third optical signal, performing the non-Gaussian operation on the third optical signal, and outputting a fourth optical signal of the second photon state, includes: the third optical beam splitter receives the third optical signal, transmits and outputs the fourth optical signal of the second photon state, and reflects and outputs the fourth optical signal of the fourth photon state; the second photon number detector receives the fourth optical signal of the fourth photon state, and performs the first non-Gaussian operation on the third optical signal; Alternatively, the non-Gaussian operation also includes a second non-Gaussian operation, and the second non-Gaussian operation is a photon addition operation and a photon subtraction operation at the same time; the first operation module includes a second optical beam splitter, a first photon number detector and a first photon number generator, and the second operation module includes a third optical beam splitter, a second photon number detector and a second photon number generator; the accessing of the first optical signal, performing a non-Gaussian operation on the first optical signal, and outputting a second optical signal in a second photon state include: the second optical beam splitter accesses the first optical signal and the photons output by the first photon number generator, transmits and outputs the second optical signal in the second photon state, and reflects and outputs the second optical signal in the second photon state. a second optical signal in a three-photon state; the first photon number detector receives the second optical signal in the third photon state, and performs the second non-Gaussian operation on the first optical signal; correspondingly, the receiving of the third optical signal, the performing of the non-Gaussian operation on the third optical signal, and the output of the fourth optical signal in the second photon state, comprising: the third optical beam splitter receives the third optical signal and the photons output by the second photon number generator, transmits and outputs the fourth optical signal in the second photon state, and reflects and outputs the fourth optical signal in the fourth photon state; the second photon number detector receives the fourth optical signal in the fourth photon state, and performs the second non-Gaussian operation on the third optical signal; Alternatively, the non-Gaussian operation also includes a third non-Gaussian operation, which is a photon addition operation; the first operation module includes a second optical beam splitter and a first photon number generator, and the second operation module includes a third optical beam splitter and a second photon number generator; the accessing of the first optical signal, performing a non-Gaussian operation on the first optical signal, and outputting a second optical signal in a second photon state includes: the second optical beam splitter accesses the first optical signal and the photon output by the first photon number generator, transmits and outputs the second optical signal in the second photon state, reflects and outputs the second optical signal in a third photon state, and performs the third non-Gaussian operation on the first optical signal; correspondingly, the accessing of the third optical signal, performing a non-Gaussian operation on the third optical signal, and outputting a fourth optical signal in a second photon state includes: the third optical beam splitter accesses the third optical signal and the photon output by the second photon number generator, transmits and outputs a fourth optical signal in the second photon state, reflects and outputs a fourth optical signal in the fourth photon state, and performs the third non-Gaussian operation on the third optical signal.

9. A communication system based on quantum entanglement, characterized in that: A preparation device comprising a preparation method for implementing the quantum entanglement source of claims 1 to 7.

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