Frequency self-matching frequency domain quantum interference method, system and intermediate node device

Abstract

A frequency-self-matched frequency-domain quantum interference method, system, and intermediate node device are disclosed, relating to the field of optical quantum information technology. The method includes: receiving a first signal group from a first user terminal via a first optical fiber and a second signal group from a second user terminal via a second optical fiber, wherein the first signal group includes a first quantum optical signal and a first reference optical signal, and the second signal group includes a second quantum optical signal and a second reference optical signal, and the first and second signal groups satisfy a preset wavelength condition; splitting the first and second signal groups to obtain a quantum optical signal group and a reference optical signal group; determining a target modulation signal based on the reference optical signal group; and applying the target modulation signal to the first and second quantum optical signals, causing the first and second quantum optical signals to produce frequency-domain non-degenerate quantum interference. This method eliminates the need for complex feedback control devices at the intermediate node.

Description

Technical Field

[0001] This application relates to the field of optical quantum information technology, and more specifically, to a frequency-domain quantum interference method, system, and intermediate node device with frequency self-matching. Background Technology

[0002] To meet the requirement that the modulation signal frequency of the frequency domain beam splitter matches the input two-photon frequency difference, i.e., the laser frequency matching requirement at the user end, a feedback control system needs to be deployed to feed back the frequency difference test results from the intermediate node to the user end in order to calibrate and lock the laser frequency at different user ends.

[0003] The existing physical implementation involves laying a service fiber to remotely transmit laser light from the user end to intermediate nodes. This means building fiber of twice the length, which is costly, structurally complex, and difficult to maintain. Several solutions have been proposed in the industry to avoid the complex structural problems of the service fiber, such as using a high-frequency stable laser or implementing feedback control at intermediate nodes by monitoring the visibility of interference fringes.

[0004] However, the applicant of this application discovered that high-frequency stable lasers suffer from complex manufacturing processes and high costs. Furthermore, feedback control via monitoring interference fringes requires multiple interference fringe visibility tests, feedback, and control steps to complete calibration, necessitating a certain convergence time.

[0005] The content of the background section is merely technology known to the public and does not necessarily represent existing technology in the field. Summary of the Invention

[0006] This application aims to provide a frequency-domain quantum interference method, system, and intermediate node device with frequency self-matching, in order to solve the problems of complex and costly processes using high-frequency stable lasers, as well as the technical problems of feedback control and a certain convergence time required for monitoring interference fringes.

[0007] According to one aspect of this application, a frequency-self-matched frequency-domain quantum interference method is provided. The method includes: receiving a first signal group from a first user terminal via a first optical fiber and receiving a second signal group from a second user terminal via a second optical fiber, wherein the first signal group includes a first quantum optical signal and a first reference optical signal, and the second signal group includes a second quantum optical signal and a second reference optical signal, and the first signal group and the second signal group satisfy a preset wavelength condition; splitting the first signal group and the second signal group to obtain a quantum optical signal group and a reference optical signal group, wherein the quantum optical signal group includes a first quantum optical signal and a second quantum optical signal, and the reference optical signal group includes a first reference optical signal and a second reference optical signal; determining a target modulation signal based on the reference optical signal group; applying the target modulation signal to the first quantum optical signal and the second quantum optical signal, such that the first quantum optical signal and the second quantum optical signal generate frequency-domain non-degenerate quantum interference; wherein the difference between the wavelength of the first quantum optical signal and the wavelength of the first reference optical signal is a first difference, and the difference between the wavelength of the second quantum optical signal and the wavelength of the second reference optical signal is a second difference, and the preset wavelength condition is that the first difference and the second difference are equal.

[0008] According to one aspect of this application, an intermediate node device is provided for a frequency-domain quantum interference system with frequency self-matching. The frequency-domain quantum interference system includes a first user terminal, a second user terminal, and an intermediate node. The intermediate node includes a wave splitting module, a frequency matching module, and a frequency-domain beam splitting module. The wavelength division module receives a first signal group from a first user terminal via a first optical fiber and a second signal group from a second user terminal via a second optical fiber. The first signal group includes a first quantum optical signal and a first reference optical signal, and the second signal group includes a second quantum optical signal and a second reference optical signal. The first and second signal groups satisfy a preset wavelength condition. The wavelength division module further divides the first and second signal groups to obtain a quantum optical signal group and a reference optical signal group. The quantum optical signal group includes a first quantum optical signal and a second quantum optical signal, and the reference optical signal group includes a first reference optical signal and a second reference optical signal. A frequency matching module determines a target modulation signal based on the reference optical signal group. A frequency domain beam splitting module applies the target modulation signal to the first and second quantum optical signals, causing the first and second quantum optical signals to produce frequency-domain non-degenerate quantum interference. The difference between the wavelength of the first quantum optical signal and the wavelength of the first reference optical signal is a first difference, and the difference between the wavelength of the second quantum optical signal and the wavelength of the second reference optical signal is a second difference. The preset wavelength condition is that the first difference and the second difference are equal.

[0009] According to one aspect of this application, a frequency-self-matched frequency-domain quantum interference system is provided. The system includes a first user terminal, a second user terminal, and an intermediate node device as described above. The first user terminal includes a first signal generation module and a first multiplexing module. The first signal generation module generates a first quantum optical signal and a first reference optical signal; the first multiplexing module combines the first quantum optical signal and the first reference optical signal into a first signal group and sends the first signal group to a wavelength division module. The second user terminal includes a second signal generation module and a second multiplexing module. The second signal generation module generates a second quantum optical signal and a second reference optical signal; the second multiplexing module combines the second quantum optical signal and the second reference optical signal into a second signal group and sends the second signal group to the wavelength division module.

[0010] The technical solution provided in this application eliminates the need for feedback control of the first user terminal, the second user terminal, and intermediate nodes. The first and second user terminals do not need to deploy high-frequency stable lasers, the intermediate nodes do not need to deploy complex feedback control devices, and the transmission channel does not need to deploy service optical fibers, thus simplifying the physical implementation of practical applications. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 The diagram shows four possible output scenarios when a frequency-degenerate photon input beamsplitter is used.

[0013] Figure 2 The diagram shows four possible output scenarios when a frequency-degenerate photon input frequency domain beam splitter (FBS) is used.

[0014] Figure 3 This diagram illustrates the physical implementation of quantum interference using frequency-degenerate photons in practical applications.

[0015] Figure 4 A schematic diagram of the intermediate node device and frequency domain quantum interference system according to an embodiment of this application is shown.

[0016] Figure 5 A flowchart illustrating a method 1000 according to an embodiment of this application is shown.

[0017] Figure 6 A flowchart illustrating step S300 according to an embodiment of this application is shown.

[0018] Explanation of reference numerals in the attached figures:

[0019] 10. Intermediate node device.

[0020] 11. Wavelength division module; 12. Frequency matching module; 13. Frequency domain beam splitting module.

[0021] 100. Frequency domain quantum interference system.

[0022] 20. First user terminal; 30. Second user terminal.

[0023] 21. First signal generation module; 22. First multiplexing module.

[0024] 31. Second signal generation module; 32. Second multiplexing module.

[0025] 40. First optical fiber; 50. Second optical fiber. Detailed Implementation

[0026] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0027] The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of these specific details, or other methods, components, materials, devices, etc. In these cases, well-known structures, methods, devices, implementations, materials, or operations will not be shown or described in detail.

[0028] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0029] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, rather than to describe a specific order.

[0030] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0031] The English terms used in this application, their full English names, and their corresponding Chinese definitions are as follows:

[0032] HOM, Hong-Ou-Mandel.

[0033] FBS stands for Frequency-domain beam splitter.

[0034] Quantum interference plays a crucial role in quantum information science, serving as the foundation of quantum manipulation technology and a vital tool for realizing quantum communication. Multiphoton interference is one of the most common phenomena in quantum interference, while two-photon interference is a special case of multiphoton interference.

[0035] HOM (Hohen-Ou-Mandel) interference is a representative two-photon interference method that not only proves the indistinguishability between different photon sources, but also allows the preparation of entangled states using independent single photons. It is mainly used to verify Bell's inequality, Bell state measurement, quantum teleportation, and quantum logic gate operations.

[0036] HOM (Hohen-Ou-Mandel) interferometry is typically implemented using a beamsplitter. One photon is input to each of the two input ports of the beamsplitter, and the output can have four possible outcomes, such as... Figure 1 As shown in (a) to (d) above, the four output scenarios are as follows: Figure 1 In (a), the photon incident at port a is reflected, while the photon incident at port b is transmitted. Figure 1 In (b), photons incident at ports a and b are both transmitted; Figure 1 In (c), photons incident at ports a and b are both reflected; Figure 1 In case (d), photons incident at port a are transmitted, while photons incident at port b are reflected. The probability of any of these four scenarios is equal.

[0037] The transformation relationship between the input and output in the beam splitter is shown in formula (1).

[0038] (1)

[0039] in, , , and These are the generation operators corresponding to the spatial modes of the four ports of the beam splitter. It can be seen that when a photon is input from port b and output from port d, a relative phase shift π is introduced. The degrees of freedom that a photon can carry for quantum information include polarization, time, frequency, and space. When two identical photons (indistinguishable in all degrees of freedom) are incident from the two input ports of the beam splitter respectively, and one photon is output from each of the two output ports, the two cases are indistinguishable, resulting in coherent destructive interference. As a result, the two photons cannot be output from the two ports separately; they can only randomly choose one port to output from. This interference phenomenon is known as HOM interference.

[0040] The above describes HOM interference based on linear optics. The quantum interference process on the beam splitter requires that the two photons input to the beam splitter have the same frequency (frequency degeneracy), making HOM interference applications unable to utilize the abundant photon spectrum resources. To overcome this limitation, researchers have proposed quantum interference using frequency-domain linear transformation techniques to achieve non-frequency degenerate photons. This technique can employ a frequency-domain beam splitter (FBS).

[0041] HOM interference between frequency-non-degenerate photons is achieved. The frequency domain beam splitter uses two specific frequency channels as input and output ports to realize a transformation relationship similar to formula (1) in the frequency degree of freedom, specifically formula (2):

[0042] (2)

[0043] in, , , and These are the generation operators corresponding to the frequency modes of the four ports of the frequency domain beamsplitter's input and output. When the two photons input to the frequency domain beamsplitter are indistinguishable in all degrees of freedom except frequency, the output includes four cases, such as... Figure 2 As shown. With Figure 1 The difference lies in the input frequency degenerate photon case: when a photon changes from its original frequency channel to another, it's equivalent to "reflection," and when it remains in its original frequency channel, it's equivalent to "transmission." When two photons are indistinguishable in all degrees of freedom except frequency, the output states corresponding to (b) and (c) in Figure 2 are identical, with equal magnitudes and opposite signs of state coefficients, resulting in coherent destructive interference. Therefore, the two photons will cluster together in the frequency domain and randomly output from one of the two frequency ports, forming a frequency-domain HOM interference.

[0044] Therefore, the key to frequency-domain HOM interferometry is to realize a frequency-domain beamsplitter with a frequency-domain linear transformation relationship as shown in equation (2), requiring the frequency of the modulation signal loaded onto the frequency-domain beamsplitter to match the frequency difference between the two photons input to the frequency-domain beamsplitter. In actual physical implementation, the two photons input to the frequency-domain beamsplitter are generated by the two communicating parties (user A and user B) and transmitted through optical fiber to a third party (intermediate node) for measurement. The user end and the intermediate node are geographically distributed at a certain distance, such as... Figure 3 As shown.

[0045] To meet the requirement of matching the modulation signal frequency of the frequency domain beamsplitter with the input two-photon frequency difference, i.e., the laser frequency matching requirement at the user end, a feedback control system needs to be deployed to feed back the frequency difference test results from the intermediate node to the user end, in order to calibrate and lock the laser frequency at different user ends. The traditional physical implementation involves laying a service fiber to remotely transmit the user-end laser to the intermediate node. This means building a fiber of twice the length, which is costly, structurally complex, and difficult to maintain. Several solutions have been proposed to avoid the complex structure of the service fiber, such as using a high-stability laser or implementing feedback control at the intermediate node by monitoring the visibility of interference fringes. However, high-stability lasers are complex to manufacture and expensive; and feedback control by monitoring interference fringes requires multiple interference fringe visibility tests, feedback, and control cycles to complete calibration, which requires a certain convergence time.

[0046] To achieve frequency matching of light sources at remote user terminals, the following technical solutions are mainly available:

[0047] (1) Service Fiber Solution

[0048] This solution involves laying a service fiber optic cable between the user end and the intermediate node to transmit the laser from the user end to the intermediate node. The intermediate node tests the laser frequency difference at the user end and feeds the results back to the user end, calibrating and locking the laser frequencies at different user ends.

[0049] The solution requires the installation of service fiber optic cables between the user terminals and intermediate nodes. However, the geographical locations of different user terminals are far apart, and the construction of additional service fiber optic cables increases the difficulty and cost of system deployment, resulting in a complex system structure and difficult operation and maintenance.

[0050] (2) High frequency stability laser scheme

[0051] This approach uses lasers with high frequency stability, such as those locked to molecular absorption lines, to ensure consistent or fixed frequency differences across different user terminals. This method employs specially designed lasers, requiring extremely high laser frequency stability, resulting in complex manufacturing processes and high costs.

[0052] (3) Interference fringe visibility feedback control scheme

[0053] At the intermediate node, the interference fringes of the frequency-domain HOM interference are monitored, and the modulation frequency of the frequency-domain beamsplitter is adjusted. When the visibility of the interference fringes reaches its maximum, the modulation frequency of the frequency-domain beamsplitter matches the frequency difference of the photons transmitted from the two user ends. This scheme involves repeatedly measuring the interference fringes of the HOM interference at the intermediate node and adjusting the modulation frequency of the frequency-domain beamsplitter until the visibility of the interference fringes reaches its maximum, thus achieving the matching of the modulation frequency of the frequency-domain beamsplitter with the frequency difference of the photons at the user ends. Multiple measurements and feedback control incur additional convergence time, and the convergence hysteresis of the feedback control inevitably degrades the effective operating time.

[0054] See Figure 4 The intermediate node device 10 provided in this application may include a wavelength division module 11, a frequency matching module 12, and a frequency domain beam splitting module 13.

[0055] The following is combined Figure 4 This application describes a frequency-self-matching frequency-domain quantum interference method 1000. Method 1000 can be executed by an intermediate node device 10. See also... Figure 5 Method 1000 may include steps S100-S400.

[0056] In step S100, the intermediate node device 10 receives a first signal group from the first user terminal 20 via the first optical fiber 40 and a second signal group from the second user terminal 30 via the second optical fiber 50.

[0057] According to the example embodiment, the first user terminal 20 and the second user terminal 30 can be two communicating parties. The first user terminal 20 generates a first signal group. The first user terminal 20 and the second user terminal 30 are each equipped with an independent signal generation module.

[0058] The first optical fiber 40 can be the optical fiber between the first user terminal 20 and the intermediate node device 10. The first signal group includes a first quantum optical signal and a first reference optical signal. The first quantum optical signal can be a quantum optical signal generated by the signal generation module of the first user terminal 20. The first reference optical signal can be a reference optical signal generated by the signal generation module of the first user terminal 20. The first optical fiber 40 transmits the first signal group.

[0059] The second optical fiber 50 can be the optical fiber between the second user terminal 30 and the intermediate node device 10. The second signal group includes a second quantum optical signal and a second reference optical signal. The second quantum optical signal can be a quantum optical signal generated by the signal generation module of the second user terminal 30. The second reference optical signal can be a reference optical signal generated by the signal generation module of the second user terminal 30. The second optical fiber 50 transmits the second signal group.

[0060] The first signal group and the second signal group satisfy a preset wavelength condition. The difference between the wavelength of the first quantum optical signal and the wavelength of the first reference optical signal is the first difference value, and the difference between the wavelength of the second quantum optical signal and the wavelength of the second reference optical signal is the second difference value. The preset wavelength condition is that the first difference value and the second difference value are equal.

[0061] For example, the signal generation module of the first user terminal 20 uses an independent light source. It can generate a first quantum light source and a first reference light source through an optical frequency comb and a filtering device. The first quantum light source is processed by a quantum light generation device (encoded in degrees of freedom such as polarization, time, frequency, and space) to generate a first quantum light signal. The first reference light source is processed by a reference light generation device (adjusting the optical power) to generate a first reference light signal. The signal generation module of the second user terminal 30 can use an independent light source. It can generate a second quantum light source and a second reference light source through an optical frequency comb and a filtering device. The second quantum light source is processed by a quantum light generation device (encoded in degrees of freedom such as polarization, time, frequency, and space) to generate a second quantum light signal. The second reference light source is processed by a reference light generation device (adjusting the optical power) to generate a second reference light signal. The preset wavelength condition can be expressed as in formula (3):

[0062] (3)

[0063] in, The wavelength of the first quantum optical signal; The wavelength of the first reference optical signal; The wavelength of the second quantum light signal; The wavelength of the second reference optical signal is given.

[0064] The preset wavelength conditions can set an error within a certain range, and the error can be related to the frequency stability of the light source and the frequency stability of the optical frequency comb device.

[0065] Other degrees of freedom (e.g., polarization, time, space, etc.) of the first quantum optical signal, the first reference optical signal, the second quantum optical signal, and the second reference optical signal can be determined according to the quantum information to be carried.

[0066] For example, in step S100, the wavelength division module 11 can receive a first signal group from the first user terminal 20 through the first optical fiber 40 and a second signal group from the second user terminal 30 through the second optical fiber 50.

[0067] In step S200, the intermediate node device divides the first signal group and the second signal group into 10 groups to obtain the quantum optical signal group and the reference optical signal group.

[0068] According to an example embodiment, the quantum optical signal group includes a first quantum optical signal and a second quantum optical signal, and the reference optical signal group includes a first reference optical signal and a second reference optical signal.

[0069] For example, in step S200, the wavelength division module 11 can perform wavelength demultiplexing on the first signal group and the second signal group to obtain the quantum optical signal group and the reference optical signal group.

[0070] In step S300, the intermediate node device 10 determines the target modulation signal based on the reference optical signal group.

[0071] According to an example embodiment, the target modulation signal can be a control signal that enables the first quantum optical signal and the second quantum optical signal to generate frequency-domain non-degenerate quantum interference.

[0072] For example, in step S300, the frequency matching module 12 can receive the reference optical signal group (i.e., the first reference optical signal and the second reference optical signal) output by the wavelength division module 11. For example, the frequency matching module 12 can determine the beat frequency signal based on the reference optical signal group; the frequency matching module 12 can convert the beat frequency signal into a corresponding electrical signal; the frequency matching module 12 can amplify the electrical signal to obtain the target modulation signal.

[0073] In step S400, the intermediate node device 10 applies the target modulation signal to the first quantum optical signal and the second quantum optical signal, causing the first quantum optical signal and the second quantum optical signal to generate frequency domain non-degenerate quantum interference.

[0074] For example, in step S400, the frequency domain beam splitting module 13 can receive the first quantum signal, the second quantum signal, and the target modulation signal. The frequency domain beam splitting module 13 applies the target modulation signal to the first quantum optical signal and the second quantum optical signal, causing the first quantum optical signal and the second quantum optical signal to produce frequency domain non-degenerate quantum interference.

[0075] Frequency domain beam splitting module 13 can be a frequency domain beam splitter. The first quantum signal and the second quantum signal are combined at the frequency domain beam splitter, and the phase modulation of the frequency domain beam splitter can be the target modulation signal (i.e., the target modulation signal). The phase modulation of the first and second quantum optical signals will match the frequency difference between the first and second quantum optical signals with the target modulation signal, resulting in frequency-domain non-degenerate quantum interference.

[0076] Through the above embodiments, the technical solution of this application can introduce a reference optical signal group into the transmission optical fiber, determine the target modulation signal according to the reference optical signal group, so that the frequency of the quantum optical signal group is automatically matched with the frequency of the target modulation signal, thereby generating frequency domain non-degenerate quantum interference.

[0077] The technical solution provided in this application eliminates the need for feedback control of the first user terminal, the second user terminal, and intermediate nodes. The first and second user terminals do not need to deploy high-frequency stable lasers, the intermediate nodes do not need to deploy complex feedback control devices, and the transmission channel does not need to deploy service optical fibers, thus simplifying the physical implementation of practical applications.

[0078] Optionally, the frequency matching module 12 may include a photodetector and an amplifier. See also Figure 6 Step S300 may include steps S310-S330.

[0079] In step S310, the intermediate node device 10 determines the beat frequency signal based on the reference optical signal group.

[0080] According to the example embodiment, the beat frequency signal can be the optical signal generated by the meeting of the first reference optical signal and the second reference optical signal. For example, in step S310, the photodetector can determine the beat frequency signal based on the group of reference optical signals.

[0081] In step S320, the intermediate node device 10 converts the beat frequency signal into a corresponding electrical signal.

[0082] For example, in step S320, the photodetector can convert the beat frequency signal into a corresponding electrical signal.

[0083] In step S330, the intermediate node device 10 amplifies the electrical signal to obtain the target modulation signal.

[0084] For example, in step S330, the amplifier can amplify the electrical signal to obtain the target modulation signal.

[0085] For example, the amplifier can obtain the target modulation signal according to formula (4):

[0086] (4)

[0087] in, Modulated signal for target; The amplitude of the first reference optical signal; The frequency of the first reference optical signal; The phase of the first reference optical signal; The amplitude of the second reference optical signal; The frequency of the second reference optical signal; The phase of the second reference optical signal; It indicates a direct proportion.

[0088] The target modulation signal is used as the modulation signal of the frequency domain beam splitter module 13. Since the first quantum optical signal, the first reference optical signal, the second quantum optical signal, and the second reference optical signal satisfy a preset wavelength condition in wavelength allocation, i.e. ,therefore = .in, The frequency of the first quantum optical signal; The frequency of the second quantum light signal.

[0089] That is, the frequency of the target modulation signal of the frequency domain beam splitter 13 can be realized (the frequency of the target modulation signal is...). ) and the frequency difference between the two input photons (i.e., the difference between the frequency of the first quantum optical signal and the frequency of the second quantum optical signal) Automatic matching.

[0090] The technical solution of this application can achieve the matching of the frequency of the target modulation signal of the frequency domain beam splitter with the frequency difference between the two input photons by controlling the wavelength of the reference optical signal group.

[0091] According to the example embodiments, the technical solution of this application can be applied to frequency-non-degenerate photonic quantum interference and Bell state measurement. For example, it can be used for measurement device-independent quantum key distribution, quantum teleportation, entanglement swapping, etc., to achieve automatic matching between the input two-photon frequency difference and the modulation frequency of the frequency domain beam splitter.

[0092] See Figure 4 The frequency self-matching frequency domain quantum interference system 100 provided in this application includes a first user terminal 20, a second user terminal 30, and an intermediate node device 10.

[0093] See Figure 4 The first user terminal 20 includes a first signal generation module 21 and a first multiplexing module 22.

[0094] According to an example embodiment, the first signal generation module 21 generates a first quantum optical signal and a first reference optical signal.

[0095] For example, the first signal generation module 21 can generate light signals of different wavelengths through a light source and an optical frequency comb device, generate a first quantum light source and a first reference light source through a filtering device, and generate a first quantum light signal and a first reference light signal through a quantum light generation device and a reference light generation device. Other degrees of freedom of the first quantum light signal (e.g., polarization, time, space, etc.) can be determined according to the quantum information to be carried.

[0096] The first combining module 22 combines the first quantum optical signal and the first reference optical signal into a first signal group, and sends the first signal group to the wave splitting module 11.

[0097] For example, the first wavelength multiplexing module 22 multiplexes the first quantum optical signal and the first reference optical signal to form a first signal group, which is then transmitted to the wavelength division module 11 through the first optical fiber 40.

[0098] See Figure 4 The second user terminal 30 includes a second signal generation module 31 and a second multiplexing module 32.

[0099] According to an example embodiment, the second signal generation module 31 generates a second quantum optical signal and a second reference optical signal.

[0100] For example, the second signal generation module 31 can generate light signals of different wavelengths through a light source and an optical frequency comb device, generate a second quantum light source and a third reference light source through a filtering device, and generate a second quantum light signal and a second reference light signal through a quantum light generation device and a reference light generation device. Other degrees of freedom of the second quantum light signal (e.g., polarization, time, space, etc.) can be determined according to the quantum information to be carried.

[0101] The second multiplexing module 32 combines the second quantum optical signal and the second reference optical signal into a second signal group, and sends the second signal group to the wavelength division module 11.

[0102] For example, the second wavelength multiplexing module 32 multiplexes the second quantum optical signal and the second reference optical signal to form a second signal group, which is then transmitted to the wavelength division module 11 through the second optical fiber 50.

[0103] The intermediate node device 10 processes the first signal group and the second signal group through the method 1000 described above, thereby matching the frequency difference between the first quantum optical signal and the second quantum optical signal with the target modulation signal, and generating frequency domain non-degenerate quantum interference.

[0104] Finally, it should be noted that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions of the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A frequency self-matching frequency-domain quantum interference method, characterized in that, The method includes: A first signal group is received from a first user terminal via a first optical fiber, and a second signal group is received from a second user terminal via a second optical fiber. The first signal group includes a first quantum optical signal and a first reference optical signal, and the second signal group includes a second quantum optical signal and a second reference optical signal. The first signal group and the second signal group satisfy a preset wavelength condition. The first signal group and the second signal group are split to obtain a quantum optical signal group and a reference optical signal group, wherein the quantum optical signal group includes the first quantum optical signal and the second quantum optical signal, and the reference optical signal group includes the first reference optical signal and the second reference optical signal; The target modulation signal is determined based on the reference optical signal group; The target modulation signal is applied to the first quantum optical signal and the second quantum optical signal, causing the first quantum optical signal and the second quantum optical signal to produce frequency domain non-degenerate quantum interference; Wherein, the difference between the wavelength of the first quantum optical signal and the wavelength of the first reference optical signal is the first difference, the difference between the wavelength of the second quantum optical signal and the wavelength of the second reference optical signal is the second difference, and the preset wavelength condition is that the first difference and the second difference are equal.

2. The method according to claim 1, characterized in that, Determining the target modulation signal based on the reference optical signal group includes: The beat frequency signal is determined based on the reference optical signal group; The beat frequency signal is converted into a corresponding electrical signal; The electrical signal is amplified to obtain the target modulation signal.

3. The method according to claim 2, characterized in that, Amplifying the electrical signal to obtain the target modulated signal includes: The target modulation signal is determined according to the following formula: ； in, The target modulation signal; The amplitude of the first reference optical signal; The frequency of the first reference optical signal; The phase of the first reference optical signal; The amplitude of the second reference optical signal; The frequency of the second reference optical signal; The phase of the second reference optical signal; It indicates a direct proportion.

4. The method according to claim 1, characterized in that, The first signal group is formed by combining the first quantum optical signal and the first reference optical signal; The second signal group is formed by combining the second quantum optical signal and the second reference optical signal.

5. The method according to claim 1, characterized in that, The method is used for frequency-non-degenerate photonic quantum interference and Bell state measurement.

6. An intermediate node device for a frequency-self-matched frequency-domain quantum interference system, the frequency-domain quantum interference system comprising a first user terminal, a second user terminal, and the intermediate node, characterized in that, The intermediate nodes include: The wavelength division module receives a first signal group from the first user terminal through a first optical fiber and a second signal group from the second user terminal through a second optical fiber. The first signal group includes a first quantum optical signal and a first reference optical signal, and the second signal group includes a second quantum optical signal and a second reference optical signal. The first signal group and the second signal group satisfy a preset wavelength condition. The wavelength division module further divides the first signal group and the second signal group to obtain a quantum optical signal group and a reference optical signal group, wherein the quantum optical signal group includes the first quantum optical signal and the second quantum optical signal, and the reference optical signal group includes the first reference optical signal and the second reference optical signal; The frequency matching module determines the target modulation signal based on the reference optical signal group; The frequency domain beam splitting module applies the target modulation signal to the first quantum optical signal and the second quantum optical signal, causing the first quantum optical signal and the second quantum optical signal to produce frequency domain non-degenerate quantum interference; Wherein, the difference between the wavelength of the first quantum optical signal and the wavelength of the first reference optical signal is the first difference, the difference between the wavelength of the second quantum optical signal and the wavelength of the second reference optical signal is the second difference, and the preset wavelength condition is that the first difference and the second difference are equal.

7. The apparatus according to claim 6, characterized in that, The frequency matching module includes: A photodetector determines a beat frequency signal based on the reference optical signal group and converts the beat frequency signal into a corresponding electrical signal. An amplifier amplifies the electrical signal to obtain the target modulation signal.

8. The apparatus according to claim 7, characterized in that, The amplifier determines the target modulation signal according to the following formula: ； in, The target modulation signal; The amplitude of the first reference optical signal; The frequency of the first reference optical signal; The phase of the first reference optical signal; The amplitude of the second reference optical signal; The frequency of the second reference optical signal; The phase of the second reference optical signal; It indicates a direct proportion.

9. A frequency-self-matched frequency-domain quantum interference system, characterized in that, The system includes a first user terminal, a second user terminal, and an intermediate node device as described in any one of claims 6-8, wherein the first user terminal includes: The first signal generation module generates the first quantum optical signal and the first reference optical signal; The first wavelength combining module combines the first quantum optical signal and the first reference optical signal into the first signal group, and sends the first signal group to the wavelength dividing module; The second user terminal includes: The second signal generation module generates the second quantum optical signal and the second reference optical signal; The second combining module combines the second quantum optical signal and the second reference optical signal into the second signal group, and sends the second signal group to the wavelength division module.

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