Double-field quantum key distribution system and method

Abstract

The invention discloses a double-field quantum key distribution system. The double-field quantum key distribution system comprises a Charlie end, an Alice end and a Bob end, the invention also discloses a double-field quantum key distribution method which is realized based on the double-field quantum key distribution system. The invention discloses a double-field quantum key distribution system and method, and the method comprises the steps: carrying out the interference of uncoded signal light transmitted and returned by an Alice end and a Bob end at a Charlie end, and feeding back a phase drift distance according to an interference result to compensate the phase drift of the coded signal light during the transmission in an optical fiber, thereby achieving the stable phase, and achieving the high-precision transmission of the coded signal light. The method can adapt to an operation environment with dramatic phase change in long-distance transmission, and the stability and the high efficiency of a quantum network and a transmission link are improved.

Description

Technical Field

[0001] The present invention relates to the field of quantum information and optical communication technology, and in particular to a dual-field quantum key distribution system and method. Background Art

[0002] Quantum networks and quantum computing are trending towards hundreds of industries. Twin-Field Quantum Key Distribution (TF-QKD) uses the coherent interference of two remote independent laser sources to achieve a key distribution rate that exceeds the limit of direct transmission without relays even at long distances, providing key technical support for building a global quantum secure communication network.

[0003] Traditional quantum key distribution systems, such as the BB84 protocol, are mainly limited by the quantum bit error rate and transmission distance, while TF-QKD greatly expands 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, because any slight phase drift or noise may lead to the destruction of the quantum state, affecting the efficiency and security of key generation.

[0004] Phase stability issues mainly come from two aspects: one is external environmental factors, such as temperature fluctuations, mechanical vibrations, etc., which can cause slight changes in the position of optical components and thus affect the phase relationship in the optical path; the other is internal system factors, including frequency jitter of the laser, changes in the propagation delay of the optical signal in the link, etc.

[0005] Therefore, in the complex and changeable real environment, the existing TF-QKD scheme is difficult to adapt to the drastic phase changes in long-distance transmission, resulting in the inability to guarantee the efficiency and security of key generation. Summary of the invention

[0006] In order to solve the problem that the existing TF-QKD scheme is difficult to adapt to the drastic phase change in long-distance transmission, the present invention proposes a dual-field quantum key distribution system and method.

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

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

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

[0010] The Alice end is used to demultiplex the signal light A to obtain the first signal light A and the second signal light A; phase-lock the first signal light A with the third signal light generated by the Alice end, encode the phase-locked signal light, and then multiplex the encoded signal light with the second signal light A and transmit it 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; phase-lock the first signal light B with the fourth signal light generated by the Bob end, encode the phase-locked signal light, and then multiplex the encoded signal light with the second signal light B and transmit it back to the Charlie end;

[0012] The Charlie end is also used to demultiplex the signal lights transmitted back from the Alice end and the Bob end respectively, interfere with the uncoded signal lights, and feed back the phase drift amount according to 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.

[0013] In the above scheme, the uncoded signal light transmitted and returned by Alice and Bob is interfered at Charlie, and the phase drift is fed back according to the interference result to compensate for the phase drift of the coded signal light during transmission in the optical fiber, thereby achieving phase stability. This can not only adapt to the drastic phase changes in long-distance transmission, but also achieve high stability and high efficiency in actual deployment.

[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 end of the first laser and the output end of the second laser are respectively connected to the input end of the first beam splitter through the fan-in module, and the output end of the first beam splitter is respectively connected to the input end of Alice and the input end of Bob; the output end of Alice is respectively connected to one of the input ends of the second beam splitter and one of the input ends of the third beam splitter through the first fan-out module, the output end of Bob is respectively connected to the other input end of the second beam splitter and the other input end of the third beam splitter through 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 Bob is connected to the input end of the second fan-out module through the phase modulator, and the output end of the third beam splitter is connected to the signal detection module.

[0016] Preferably, the Alice end 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 of the output ends of the first beam splitter is connected to one of the input ends of the first phase-locked loop and one of the input ends of the second fan-in module through the third fan-out module, the output end of the first phase-locked loop is connected to the input end of the third laser, the output end of the third laser is connected to the other input end of the first phase-locked loop and the input end of the first encoding module through the fourth beam splitter, the output end of the first encoding module is connected to the other input end of the second fan-in module, and the output end of the second fan-in module is connected to the input end 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 end of the first beam splitter is connected to one of the input ends of the second phase-locked loop and one of the input ends of the third fan-in module respectively through the fourth fan-out module, the output end of the second phase-locked loop is connected to the input end of the fourth laser, the output end of the fourth laser is connected to the other input end of the second phase-locked loop and the input end of the second encoding module respectively through the fifth beam splitter, the output end of the second encoding module is connected to the other input end of the third fan-in module, and the output end of the third fan-in module is connected to the input end of the second fan-out module through the 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 intensities.

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

[0024] S1: Generate the first signal light and the second signal light at 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 the signal light A to Alice's end and demultiplex it to obtain the first signal light A and the second signal light A;

[0027] Transmit the signal light B to Bob's end and demultiplex it to obtain the first signal light B and the second signal light B;

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

[0029] Phase-locking the first signal light B with the fourth signal light generated by the Bob end, and encoding the phase-locked signal light;

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

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

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

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

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

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

[0036] Beneficial technical effects of the present invention:

[0037] The present invention provides a dual-field quantum key distribution system and method, which interferes with the uncoded signal light transmitted and returned by the Alice and Bob ends at the Charlie end, and feeds back the phase drift amount according to the interference result to compensate for the phase drift of the coded signal light during transmission in the optical fiber, thereby achieving phase stability, adapting to the drastic phase changes in long-distance transmission, and improving the stability and efficiency of network deployment. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0040] Among them: 11, the first laser; 12, the second laser; 21, the first beam splitter; 22, the second beam splitter; 23, the third beam splitter; 31, the first fan-in module; 41, the first fan-out module; 42, the second fan-out module; 51, the single-photon detector; 61, the phase modulator; 71, the signal detection module; 21, the third fan-out module; 22, the first phase-locked loop; 23, the third laser; 24, the fourth beam splitter; 25, the first encoding module; 26, the second fan-in module; 31, the fourth fan-out module; 32, the second phase-locked loop; 33, the fourth laser; 34, the fifth beam splitter; 35, the second encoding module; 36, the third fan-in module. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments, but the scope of protection claimed in the present invention is not limited to the following specific embodiments.

[0042] Example 1

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

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

[0045] The Alice end is used to demultiplex the signal light A to obtain the first signal light A and the second signal light A; phase-lock the first signal light A with the third signal light generated by the Alice end, encode the phase-locked signal light, and then multiplex the encoded signal light with the second signal light A and transmit it 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; phase-lock the first signal light B with the fourth signal light generated by the Bob end, encode the phase-locked signal light, and then multiplex the encoded signal light with the second signal light B and transmit it back to the Charlie end;

[0047] The Charlie end is also used to demultiplex the signal lights transmitted back from the Alice end and the Bob end respectively, interfere with the uncoded signal lights, and feed back the phase drift amount according to 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.

[0048] In the specific implementation process, the uncoded signal light transmitted and returned by Alice and Bob is interfered at the Charlie end, and the phase drift amount is fed back according to the interference result to compensate for the phase drift of the coded signal light during transmission in the optical fiber, thereby achieving phase stability. It can not only adapt to the drastic phase changes in long-distance transmission, but also achieve high stability and high efficiency in actual deployment.

[0049] Example 2

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

[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 end of the first laser 11 and the output end of the second laser 12 are respectively connected to the input end of the first beam splitter 21 through the fan-in module, and the output end of the first beam splitter 21 is respectively connected to the input end of Alice and the input end of Bob; the output end of Alice is respectively connected to one of the input ends of the second beam splitter 22 and one of the input ends of the third beam splitter 23 through the first fan-out module 41, the output end of Bob 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 the 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 Bob is connected to the input end of the second fan-out module 42 through the phase modulator 61, and the output end of the third beam splitter 23 is connected to the signal detection module 71.

[0053] More specifically, the Alice end 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 of the output ends of the first beam splitter 21 is connected to one of the input ends of the first phase-locked loop 22 and one of the input ends of the second fan-in module 26 through the third fan-out module 21, the output end of the first phase-locked loop 22 is connected to the input end of the third laser 23, the output end of the third laser 23 is connected to the other input end of the first phase-locked loop 22 and the input end of the first encoding module 25 through the fourth beam splitter 24, the output end of the first encoding module 25 is connected to the other input end of the second fan-in module 26, and the output end of the second fan-in module 26 is connected to the input end 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 end of the first beam splitter 21 is connected to one of the input ends of the second phase-locked loop 32 and one of the input ends of the third fan-in module 36 through the fourth fan-out module 31, the output end of the second phase-locked loop 32 is connected to the input end of the fourth laser 33, the output end of the fourth laser 33 is connected to the other input end of the second phase-locked loop 32 and the input end of the second encoding module 35 through the fifth beam splitter 34, the output end of the second encoding module 35 is connected to the other input end of the third fan-in module 36, and the output end of the third fan-in module 36 is connected to the input end of the second fan-out module 42 through 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, and the two signal lights are transmitted in different optical fiber cores respectively.

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

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

[0061] The signal light transmitted from Charlie to Alice is first demultiplexed by the third fan-out module 21, one of which is phase-locked by the first phase-locked loop 22 and the signal light emitted by the third laser 23, and the other is directly transmitted to the second fan-in module 26; the phase-locked optical signal is encoded in 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 of which is phase-locked by the second phase-locked loop 32 and the signal light emitted by the fourth laser 33, and the other is directly transmitted to the third fan-in module 36; the phase-locked optical signal is encoded in 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, wherein one beam is a non-encoded signal light and is transmitted to the second beam splitter 22, and the other beam is an encoded signal light and 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, wherein one beam is a non-encoded signal light and is transmitted to the second beam splitter 22, and the other beam is an encoded signal light and is transmitted to the third beam splitter 23;

[0064] The two uncoded signal lights interfere in the second beam splitter 22, and the single photon detector 51 detects the result and feeds back the drift amount to the phase modulator 61. The phase modulator 61 performs phase compensation on the signal light transmitted back from the Bob end, so as to compensate for the phase drift of the coded signal light when it is transmitted in the optical fiber.

[0065] Example 3

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

[0067] S1: Generate the first signal light and the second signal light at 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 the signal light A to Alice's end and demultiplex it to obtain the first signal light A and the second signal light A;

[0070] Transmit the signal light B to Bob's end and demultiplex it to obtain the first signal light B and the second signal light B;

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

[0072] Phase-locking the first signal light B with the fourth signal light generated by the Bob end, and encoding the phase-locked signal light;

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

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

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

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

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

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

[0079] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs may also 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 scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A dual-field quantum key distribution system, characterized in that: Including Charlie, Alice and Bob; The Charlie end is used to generate the first signal light and the second signal light and multiplex them into the optical fiber for transmission; then split the multiplexed signal light to obtain signal light A and signal light B; and transmit the signal light A and signal light B to the Alice end and the Bob end respectively; The Alice end is used to demultiplex the signal light A to obtain the first signal light A and the second signal light A; phase-lock the first signal light A with the third signal light generated by the Alice end, encode the phase-locked signal light, and then multiplex the encoded signal light with the second signal light A and transmit it 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; phase-lock the first signal light B with the fourth signal light generated by the Bob end, encode the phase-locked signal light, and then multiplex the encoded signal light with the second signal light B and transmit it back to the Charlie end; The Charlie end is also used to demultiplex the signal lights transmitted back from the Alice end and the Bob end respectively, and interfere the uncoded signal lights, and feed back the phase drift amount according to 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.

2. A 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 end of the first laser and the output end of the second laser are respectively connected to the input end of the first beam splitter through the fan-in module, and the output end of the first beam splitter is respectively connected to the input end of Alice and the input end of Bob; the output end of Alice is respectively connected to one of the input ends of the second beam splitter and one of the input ends of the third beam splitter through the first fan-out module, the output end of Bob is respectively connected to the other input end of the second beam splitter and the other input end of the third beam splitter through 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 Bob is connected to the input end of the second fan-out module through the phase modulator, and the output end of the third beam splitter is connected to the signal detection module.

3. A dual-field quantum key distribution system according to claim 2, characterized in that: The Alice end 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 of the output ends of the first beam splitter is connected to one of the input ends of the first phase-locked loop and one of the input ends of the second fan-in module through the third fan-out module, the output end of the first phase-locked loop is connected to the input end of the third laser, the output end of the third laser is connected to the other input end of the first phase-locked loop and the input end of the first encoding module through the fourth beam splitter, the output end of the first encoding module is connected to the other input end of the second fan-in module, and the output end of the second fan-in module is connected to the input end of the first fan-out module.

4. A dual-field quantum key distribution system according to claim 2, characterized in that: 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; The other output end of the first beam splitter is connected to one of the input ends of the second phase-locked loop and one of the input ends of the third fan-in module respectively through the fourth fan-out module, the output end of the second phase-locked loop is connected to the input end of the fourth laser, the output end of the fourth laser is connected to the other input end of the second phase-locked loop and the input end of the second encoding module respectively through the fifth beam splitter, the output end of the second encoding module is connected to the other input end of the third fan-in module, and the output end of the third fan-in module is connected to the input end of the second fan-out module through the 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 the signal light B have the same intensities.

8. A dual-field quantum key distribution method, characterized in that: The following steps are involved: S1: Generate the first signal light and the second signal light at 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 the signal light A to Alice's end and demultiplex it to obtain the first signal light A and the second signal light A; Transmit the signal light B to Bob's end and demultiplex it to obtain the first signal light B and the second signal light B; S4: Phase-locking the first signal light A with the third signal light generated by Alice, and encoding the phase-locked signal light; Phase-locking the first signal light B with the fourth signal light generated by the Bob end, and encoding the phase-locked signal light; S5: Multiplex the encoded signal light from Alice and the second signal light A and transmit them back to Charlie; The encoded signal light at the Bob end is multiplexed with the second signal light B and then transmitted back to the Charlie end; S6: Demultiplex and interfere the signal light transmitted back from Alice and Bob; S7: Feedback the phase drift amount based on the interference result to perform phase compensation on 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 uncoded signal light is interfered.

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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