A dual-field quantum key distribution system and method

Abstract

This invention discloses a dual-field quantum key distribution system, including a Charlie end, an Alice end, and a Bob end; it also discloses a dual-field quantum key distribution method based on the aforementioned dual-field quantum key distribution system. This invention discloses a dual-field quantum key distribution system and method that interferes with the unencoded signal light transmitted back from the Alice and Bob ends at the Charlie end, and feeds back the phase drift based on the interference result to compensate for the phase drift of the encoded signal light during transmission in the optical fiber, achieving phase stability. This allows it to adapt to the operating environment of drastic phase changes in long-distance transmission, improving the stability and efficiency of quantum networks and transmission links.

Description

Technical Field

[0001] This invention relates to the field of quantum information and optical communication technology, specifically to a dual-field quantum key distribution system and method. Background Technology

[0002] Quantum networks and quantum computing are rapidly expanding into hundreds and thousands of industries. Twin-Field Quantum Key Distribution (TF-QKD) utilizes the coherent interference of two remote, independent laser sources to achieve key distribution rates exceeding the limits of direct transmission without relays, even over long distances, providing crucial technological support for building a global quantum-secure communication network.

[0003] Traditional quantum key distribution systems, such as the BB84 protocol, are mainly limited by qubit error rate and transmission distance. TF-QKD, however, greatly extends the distance range of key distribution by introducing additional light sources and complex phase correlation mechanisms. However, TF-QKD places extremely high demands on phase stability, as even a tiny phase drift or noise can corrupt the quantum state, affecting key generation efficiency and security.

[0004] Phase stability issues mainly stem from two aspects: first, external environmental factors, such as temperature fluctuations and mechanical vibrations, can cause slight changes in the position of optical components, thereby affecting the phase relationship in the optical path; second, internal system factors, including laser frequency jitter and changes in the propagation delay of optical signals in the link.

[0005] Therefore, in complex and ever-changing real-world environments, existing TF-QKD schemes are ill-suited to adapting to drastic phase changes during long-distance transmission, resulting in a failure to guarantee the efficiency and security of key generation. Summary of the Invention

[0006] To address the problem that existing TF-QKD schemes are unable to adapt to drastic phase changes during long-distance transmission, this invention proposes a dual-field quantum key distribution system and method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A dual-field quantum key distribution system, comprising a Charlie end, an Alice end, and a Bob end;

[0009] The Charlie end is used to generate a first signal light and a second signal light and multiplex them into an optical fiber for transmission; then the multiplexed signal light is split into signal light A and signal light B; signal light A and signal light B are transmitted to the Alice end and the Bob end, respectively.

[0010] The Alice end is used to demultiplex signal light A to obtain first signal light A and second signal light A; the first signal light A is phase-locked with the third signal light generated by the Alice end, and the phase-locked signal light is encoded. Then, the encoded signal light is multiplexed with the second signal light A and transmitted back to the Charlie end.

[0011] The Bob end is used to demultiplex the signal light B to obtain the first signal light B and the second signal light B; the first signal light B is phase-locked with the fourth signal light generated by the Bob end, and the phase-locked signal light is encoded. Then the encoded signal light is multiplexed with the second signal light B and transmitted back to the Charlie end.

[0012] The Charlie end is also used to demultiplex the signal light transmitted and returned from the Alice end and the Bob end respectively, interfere with the unencoded signal light, and feed back the phase drift amount based on the interference result to compensate for the phase drift of the encoded signal light when it is transmitted in the optical fiber, thereby achieving phase stability.

[0013] In the above scheme, the uncoded signal light transmitted back from Alice and Bob ends is interfered at Charlie end, and the phase drift is fed back based on the interference result to compensate for the phase drift of the coded signal light when it is transmitted in the optical fiber, thereby achieving phase stability. This not only adapts to drastic phase changes in long-distance transmission, but also achieves high stability and high efficiency in practical deployments.

[0014] Preferably, the Charlie end includes a first laser, a second laser, a first beam splitter, a second beam splitter, a third beam splitter, a first fan-in module, a first fan-out module, a second fan-out module, a single-photon detector, a phase modulator, and a signal detection module;

[0015] The output ends of the first laser and the second laser are respectively connected to the input end of the first beam splitter via fan-in modules. The output end of the first beam splitter is connected to the input ends of the Alice and Bob ends, respectively. The output end of the Alice end is connected to one input end of the second beam splitter and one input end of the third beam splitter via the first fan-out module. The output end of the Bob end is connected to the other input end of the second beam splitter and the other input end of the third beam splitter via the second fan-out module. The output end of the second beam splitter is connected to the input end of the single-photon detector. The output end of the single-photon detector is connected to the input end of the phase modulator. The output end of the Bob end is connected to the input end of the second fan-out module via the phase modulator. The output end of the third beam splitter is connected to the signal detection module.

[0016] Preferably, the Alice terminal includes a third fan-out module, a first phase-locked loop, a third laser, a fourth beam splitter, a first encoding module, and a second fan-in module;

[0017] One output of the first beam splitter is connected to one input of the first phase-locked loop and one input of the second fan-in module via the third fan-out module. The output of the first phase-locked loop is connected to the input of the third laser. The output of the third laser is connected to the other input of the first phase-locked loop and the input of the first encoding module via the fourth beam splitter. The output of the first encoding module is connected to the other input of the second fan-in module. The output of the second fan-in module is connected to the input of the first fan-out module.

[0018] Preferably, the Bob end includes a fourth fan-out module, a second phase-locked loop, a fourth laser, a fifth beam splitter, a second encoding module, and a third fan-in module;

[0019] The other output of the first beam splitter is connected to one of the inputs of the second phase-locked loop and one of the inputs of the third fan-in module through the fourth fan-out module. The output of the second phase-locked loop is connected to the input of the fourth laser. The output of the fourth laser is connected to the other input of the second phase-locked loop and the input of the second encoding module through the fifth beam splitter. The output of the second encoding module is connected to the other input of the third fan-in module. The output of the third fan-in module is connected to the input of the second fan-out module through a phase modulator.

[0020] Preferably, the first signal light and the second signal light have the same wavelength.

[0021] Preferably, the Charlie end multiplexes the first signal light and the second signal light into a multi-core optical fiber for transmission.

[0022] Preferably, the signal light A and the signal light B have the same intensity.

[0023] A dual-field quantum key distribution method, implemented based on the aforementioned dual-field quantum key distribution system, includes the following steps:

[0024] S1: Generate the first and second signal lights at the Charlie end and multiplex them into the optical fiber for transmission;

[0025] S2: Split the multiplexed signal light to obtain signal light A and signal light B;

[0026] S3: Transmit signal light A to the Alice end and demultiplex it to obtain the first signal light A and the second signal light A;

[0027] The signal light B is transmitted to Bob's end and demultiplexed to obtain the first signal light B and the second signal light B;

[0028] S4: Phase-lock the first signal light A with the third signal light generated by Alice, and encode the phase-locked signal light;

[0029] The first signal light B is phase-locked with the fourth signal light generated at the Bob end, and the phase-locked signal light is encoded.

[0030] S5: Multiplex the encoded signal light from the Alice end with the second signal light A and transmit it back to the Charlie end;

[0031] The encoded signal light at Bob's end is multiplexed with the second signal light B and then transmitted back to Charlie's end.

[0032] S6: Demultiplex and interfere the signal light transmitted and returned from Alice and Bob ends;

[0033] S7: Feedback the phase drift amount based on the interference result to compensate the phase of the returned signal light, thereby achieving phase stabilization.

[0034] Preferably, in step S6, the unencoded signal light is interfered with.

[0035] Preferably, in step S7, phase compensation is performed on the signal light transmitted back from the Bob end.

[0036] Beneficial technical effects of the present invention:

[0037] This invention provides a dual-field quantum key distribution system and method. By interfering the unencoded signal light transmitted back from Alice and Bob ends at the Charlie end, the phase drift is fed back based on the interference result to compensate for the phase drift of the encoded signal light during transmission in the optical fiber, thereby achieving phase stability. This system can adapt to drastic phase changes in long-distance transmission and improve the stability and efficiency of network deployment. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the overall module connection of the present invention;

[0039] Figure 2 This is a flowchart illustrating the implementation steps of the technical solution of the present invention;

[0040] The components are as follows: 11. First laser; 12. Second laser; 21. First beam splitter; 22. Second beam splitter; 23. Third beam splitter; 31. First fan-in module; 41. First fan-out module; 42. Second fan-out module; 51. Single-photon detector; 61. Phase modulator; 71. Signal detection module; 21. Third fan-out module; 22. First phase-locked loop; 23. Third laser; 24. Fourth beam splitter; 25. First encoding module; 26. Second fan-in module; 31. Fourth fan-out module; 32. Second phase-locked loop; 33. Fourth laser; 34. Fifth beam splitter; 35. Second encoding module; 36. Third fan-in module. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. However, the scope of protection of this invention is not limited to the specific embodiments described below.

[0042] Example 1

[0043] A dual-field quantum key distribution system, comprising a Charlie end, an Alice end, and a Bob end;

[0044] The Charlie end is used to generate a first signal light and a second signal light and multiplex them into an optical fiber for transmission; then the multiplexed signal light is split into signal light A and signal light B; signal light A and signal light B are transmitted to the Alice end and the Bob end, respectively.

[0045] The Alice end is used to demultiplex signal light A to obtain first signal light A and second signal light A; the first signal light A is phase-locked with the third signal light generated by the Alice end, and the phase-locked signal light is encoded. Then, the encoded signal light is multiplexed with the second signal light A and transmitted back to the Charlie end.

[0046] The Bob end is used to demultiplex the signal light B to obtain the first signal light B and the second signal light B; the first signal light B is phase-locked with the fourth signal light generated by the Bob end, and the phase-locked signal light is encoded. Then the encoded signal light is multiplexed with the second signal light B and transmitted back to the Charlie end.

[0047] The Charlie end is also used to demultiplex the signal light transmitted and returned from the Alice end and the Bob end respectively, interfere with the unencoded signal light, and feed back the phase drift amount based on the interference result to compensate for the phase drift of the encoded signal light when it is transmitted in the optical fiber, thereby achieving phase stability.

[0048] In the specific implementation process, the uncoded signal light transmitted back from Alice and Bob ends is interfered at the Charlie end. The phase drift is fed back based on the interference result to compensate for the phase drift of the coded signal light when it is transmitted in the optical fiber, thereby achieving phase stability. This not only adapts to drastic phase changes in long-distance transmission, but also achieves high stability and high efficiency in real-world deployments.

[0049] Example 2

[0050] like Figure 1 As shown, a dual-field quantum key distribution system includes a Charlie end, an Alice end, and a Bob end;

[0051] More specifically, the Charlie end includes a first laser 11, a second laser 12, a first beam splitter 21, a second beam splitter 22, a third beam splitter 23, a first fan-in module 31, a first fan-out module 41, a second fan-out module 42, a single-photon detector 51, a phase modulator 61, and a signal detection module 71.

[0052] The output ends of the first laser 11 and the second laser 12 are respectively connected to the input end of the first beam splitter 21 through a fan-in module. The output end of the first beam splitter 21 is respectively connected to the input end of the Alice end and the input end of the Bob end. The output end of the Alice end is respectively connected to one input end of the second beam splitter 22 and one input end of the third beam splitter 23 through a first fan-out module 41. The output end of the Bob end is respectively connected to the other input end of the second beam splitter 22 and the other input end of the third beam splitter 23 through a second fan-out module 42. The output end of the second beam splitter 22 is connected to the input end of the single-photon detector 51. The output end of the single-photon detector 51 is connected to the input end of the phase modulator 61. The output end of the Bob end is connected to the input end of the second fan-out module 42 through the phase modulator 61. The output end of the third beam splitter 23 is connected to the signal detection module 71.

[0053] More specifically, the Alice terminal includes a third fan-out module 21, a first phase-locked loop 22, a third laser 23, a fourth beam splitter 24, a first encoding module 25, and a second fan-in module 26;

[0054] One output of the first beam splitter 21 is connected to one input of the first phase-locked loop 22 and one input of the second fan-in module 26 via the third fan-out module 21. The output of the first phase-locked loop 22 is connected to the input of the third laser 23. The output of the third laser 23 is connected to the other input of the first phase-locked loop 22 and the input of the first encoding module 25 via the fourth beam splitter 24. The output of the first encoding module 25 is connected to the other input of the second fan-in module 26. The output of the second fan-in module 26 is connected to the input of the first fan-out module 41.

[0055] More specifically, the Bob end includes a fourth fan-out module 31, a second phase-locked loop 32, a fourth laser 33, a fifth beam splitter 34, a second encoding module 35, and a third fan-in module 36;

[0056] The other output of the first beam splitter 21 is connected to one of the inputs of the second phase-locked loop 32 and one of the inputs of the third fan-in module 36 via the fourth fan-out module 31. The output of the second phase-locked loop 32 is connected to the input of the fourth laser 33. The output of the fourth laser 33 is connected to the other input of the second phase-locked loop 32 and the input of the second encoding module 35 via the fifth beam splitter 34. The output of the second encoding module 35 is connected to the other input of the third fan-in module 36. The output of the third fan-in module 36 is connected to the input of the second fan-out module 42 via the phase modulator 61.

[0057] More specifically, the first signal light and the second signal light have the same wavelength.

[0058] More specifically, the Charlie end multiplexes the first signal light and the second signal light into a multi-core optical fiber for transmission, with the two signal lights being transmitted in different fiber cores respectively.

[0059] More specifically, the signal light A and the signal light B have the same intensity.

[0060] In the specific implementation process, the first laser 11 and the second laser 12 emit signal light with the same wavelength, which is multiplexed into the multi-core optical fiber through the first fan-in module 31 for transmission. The two signal lights are transmitted in different fiber cores, and then split into two signal lights with the same intensity by the first beam splitter 21. One beam is transmitted to the Alice end and the other is transmitted to the Bob end.

[0061] The signal light transmitted from Charlie to Alice is first demultiplexed by the third fan-out module 21. One beam is phase-locked by the signal light emitted by the first phase-locked loop 22 and the third laser 23, and the other beam is directly transmitted to the second fan-in module 26. The phase-locked optical signal is encoded by the first encoding module 25 and then enters the second fan-in module 26 for multiplexing.

[0062] The signal light transmitted from Charlie to Bob is first demultiplexed by the fourth fan-out module 31. One beam is phase-locked by the signal light emitted by the second phase-locked loop 32 and the fourth laser 33, while the other beam is directly transmitted to the third fan-in module 36. The phase-locked optical signal is encoded by the second encoding module 35 and then enters the third fan-in module 36 for multiplexing.

[0063] The signal light from Alice is transmitted back to Charlie and demultiplexed through the first fan-out module 41. One beam of unencoded signal light is transmitted to the second beam splitter 22, and the other beam of encoded signal light is transmitted to the third beam splitter 23. The signal light from Bob is transmitted back to Charlie and demultiplexed through the second fan-out module 42. One beam of unencoded signal light is transmitted to the second beam splitter 22, and the other beam of encoded signal light is transmitted to the third beam splitter 23.

[0064] Two uncoded signal beams interfere with each other at the second beam splitter 22. The result is detected by the single-photon detector 51, and the drift amount is fed back to the phase modulator 61. The phase modulator 61 performs phase compensation on the signal beam transmitted back from the Bob end, so as to compensate for the phase drift of the coded signal beam when it is transmitted in the optical fiber.

[0065] Example 3

[0066] like Figure 2 As shown, a dual-field quantum key distribution method, implemented based on the aforementioned dual-field quantum key distribution system, includes the following steps:

[0067] S1: Generate the first and second signal lights at the Charlie end and multiplex them into the optical fiber for transmission;

[0068] S2: Split the multiplexed signal light to obtain signal light A and signal light B;

[0069] S3: Transmit signal light A to the Alice end and demultiplex it to obtain the first signal light A and the second signal light A;

[0070] The signal light B is transmitted to Bob's end and demultiplexed to obtain the first signal light B and the second signal light B;

[0071] S4: Phase-lock the first signal light A with the third signal light generated by Alice, and encode the phase-locked signal light;

[0072] The first signal light B is phase-locked with the fourth signal light generated at the Bob end, and the phase-locked signal light is encoded.

[0073] S5: Multiplex the encoded signal light from the Alice end with the second signal light A and transmit it back to the Charlie end;

[0074] The encoded signal light at Bob's end is multiplexed with the second signal light B and then transmitted back to Charlie's end.

[0075] S6: Demultiplex and interfere the signal light transmitted and returned from Alice and Bob ends;

[0076] S7: Feedback the phase drift amount based on the interference result to compensate the phase of the returned signal light, thereby achieving phase stabilization.

[0077] More specifically, in step S6, the unencoded signal light is interfered with.

[0078] More specifically, in step S7, phase compensation is performed on the signal light transmitted back from the Bob end.

[0079] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A dual-field quantum key distribution system, characterized in that, Including the Charlie end, the Alice end, and the Bob end; The Charlie end is used to generate a first signal light and a second signal light and multiplex them into an optical fiber for transmission; then the multiplexed signal light is split into signal light A and signal light B; signal light A and signal light B are transmitted to the Alice end and the Bob end, respectively. The Alice end is used to demultiplex signal light A to obtain first signal light A and second signal light A; the first signal light A is phase-locked with the third signal light generated by the Alice end, and the phase-locked signal light is encoded. Then, the encoded signal light is multiplexed with the second signal light A and transmitted back to the Charlie end. The Bob end is used to demultiplex the signal light B to obtain the first signal light B and the second signal light B; the first signal light B is phase-locked with the fourth signal light generated by the Bob end, and the phase-locked signal light is encoded. Then the encoded signal light is multiplexed with the second signal light B and transmitted back to the Charlie end. The Charlie end is also used to demultiplex the signal light transmitted and returned from the Alice end and the Bob end respectively, and to interfere with the uncoded signal light. Based on the interference result, the phase drift is fed back to compensate for the phase drift of the coded signal light when it is transmitted in the optical fiber, thereby achieving phase stability.

2. The dual-field quantum key distribution system according to claim 1, characterized in that, The Charlie end includes a first laser, a second laser, a first beam splitter, a second beam splitter, a third beam splitter, a first fan-in module, a first fan-out module, a second fan-out module, a single-photon detector, a phase modulator, and a signal detection module; The output ends of the first laser and the second laser are respectively connected to the input end of the first beam splitter via fan-in modules. The output end of the first beam splitter is connected to the input ends of the Alice and Bob ends, respectively. The output end of the Alice end is connected to one input end of the second beam splitter and one input end of the third beam splitter via the first fan-out module. The output end of the Bob end is connected to the other input end of the second beam splitter and the other input end of the third beam splitter via the second fan-out module. The output end of the second beam splitter is connected to the input end of the single-photon detector. The output end of the single-photon detector is connected to the input end of the phase modulator. The output end of the Bob end is connected to the input end of the second fan-out module via the phase modulator. The output end of the third beam splitter is connected to the signal detection module.

3. The dual-field quantum key distribution system according to claim 2, characterized in that, The Alice terminal includes a third fan-out module, a first phase-locked loop, a third laser, a fourth beam splitter, a first encoding module, and a second fan-in module; One output of the first beam splitter is connected to one input of the first phase-locked loop and one input of the second fan-in module via the third fan-out module. The output of the first phase-locked loop is connected to the input of the third laser. The output of the third laser is connected to the other input of the first phase-locked loop and the input of the first encoding module via the fourth beam splitter. The output of the first encoding module is connected to the other input of the second fan-in module. The output of the second fan-in module is connected to the input of the first fan-out module.

4. A dual-field quantum key distribution system according to claim 2, characterized in that, The Bob terminal includes a fourth fan-out module, a second phase-locked loop, a fourth laser, a fifth beam splitter, a second encoding module, and a third fan-in module; The other output of the first beam splitter is connected to one of the inputs of the second phase-locked loop and one of the inputs of the third fan-in module through the fourth fan-out module. The output of the second phase-locked loop is connected to the input of the fourth laser. The output of the fourth laser is connected to the other input of the second phase-locked loop and the input of the second encoding module through the fifth beam splitter. The output of the second encoding module is connected to the other input of the third fan-in module. The output of the third fan-in module is connected to the input of the second fan-out module through a phase modulator.

5. A dual-field quantum key distribution system according to claim 1, characterized in that, The first signal light and the second signal light have the same wavelength.

6. A dual-field quantum key distribution system according to claim 1, characterized in that, The Charlie end multiplexes the first signal light and the second signal light into a multi-core optical fiber for transmission.

7. A dual-field quantum key distribution system according to claim 1, characterized in that, The signal light A and signal light B have the same intensity.

8. A dual-field quantum key distribution method, characterized in that, Includes the following steps: S1: Generate the first and second signal lights at the Charlie end and multiplex them into the optical fiber for transmission; S2: Split the multiplexed signal light to obtain signal light A and signal light B; S3: Transmit signal light A to the Alice end and demultiplex it to obtain the first signal light A and the second signal light A; The signal light B is transmitted to Bob's end and demultiplexed to obtain the first signal light B and the second signal light B; S4: Phase-lock the first signal light A with the third signal light generated by Alice, and encode the phase-locked signal light; The first signal light B is phase-locked with the fourth signal light generated at the Bob end, and the phase-locked signal light is encoded. S5: Multiplex the encoded signal light from the Alice end with the second signal light A and transmit it back to the Charlie end; The encoded signal light at Bob's end is multiplexed with the second signal light B and then transmitted back to Charlie's end. S6: Demultiplex and interfere the signal light transmitted and returned from Alice and Bob ends; S7: Feedback the phase drift amount based on the interference result to compensate the phase of the returned signal light, thereby achieving phase stabilization.

9. A dual-field quantum key distribution method according to claim 8, characterized in that, In step S6, the unencoded signal light is interfered with.

10. A dual-field quantum key distribution method according to claim 8, characterized in that, In step S7, phase compensation is performed on the signal light transmitted back from Bob's end.

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