Automatic compensation quantum key distribution system

Abstract

The utility model discloses a quantum key distribution system with automatic compensation. The quantum key distribution system comprises an optical signal generation module, a polarization coding module, a differential phase generation module, a polarization decoding module and a phase decoding module. The utility model discloses an automatic compensation quantum key distribution system, which realizes automatic polarization compensation by combining differential phase coding and polarization coding, automatically eliminates birefringence effect and polarization loss of a round-trip light path, and automatically tracks and compensates time offset by detecting arrival time of a light signal and feeding back the arrival time. The bit error rate is reduced, the stability and the code rate are improved, and the problem that the bit error rate of an existing quantum key distribution system is high is solved.

Description

TECHNICAL FIELD

[0001] The utility model relates to quantum communication equipment field, concretely relates to a quantum key distribution system of automatic compensation. BACKGROUND

[0002] Quantum Key Distribution (QKD) is to use quantum mechanics to ensure the security of communication. It enables both parties to generate and share a random, secure key to encrypt and decrypt messages.

[0003] The commonly used QKD encoding mode mainly has phase encoding and polarization encoding, transmission medium includes optical fiber and free space, in actual transmission process, polarization encoding is susceptible to the influence of random birefringence existing in optical fiber and polarization mode dispersion effect caused by birefringence, causes the random change of polarization state after long-distance transmission, thereby leading to high error rate, low code rate of system;Phase encoding has strong anti-interference ability in optical fiber transmission process, but due to the influence of optical fiber transmission loss and other factors, leading to high error rate, low stability.

[0004] Therefore, it is necessary to improve the prior art, and a quantum key distribution system with low error rate is proposed. UTILITY MODEL CONTENT

[0005] The utility model discloses in order to solve the problem of high error rate of current quantum key distribution system, and proposes a quantum key distribution system of automatic compensation.

[0006] In order to achieve the above object, the technical scheme adopted by the utility model is as follows:

[0007] A quantum key distribution system of automatic compensation, including optical signal generation module, polarization encoding module, differential phase generation module, polarization decoding module and phase decoding module;

[0008] The optical signal generation module is used for generating optical signal;

[0009] The polarization encoding module is used for polarization encoding to optical signal;

[0010] The differential phase generation module is used for polarization automatic compensation to the polarization encoded optical signal, and generates a plurality of optical signals with time difference;

[0011] The polarization decoding module is used for polarization beam splitting according to polarization measurement base to each optical signal after polarization automatic compensation, and obtains horizontal optical signal and vertical optical signal;

[0012] The phase decoding module is configured to perform polarization automatic compensation and detection response on the horizontal light signal and the vertical light signal, and to detect the time of arrival of the horizontal light signal and the vertical light signal and feed back, so as to automatically track and compensate the time offset.

[0013] Preferably, the light signal generation module comprises a multi-wavelength laser and a wavelength filter; the light signal generated by the multi-wavelength laser enters the polarization encoding module through the wavelength filter.

[0014] Preferably, the polarization encoding module comprises a dynamic polarization modulator, a first circulator and a phase modulator.

[0015] The light signal generated by the multi-wavelength laser enters the dynamic polarization modulator for random polarization modulation through the wavelength filter, and the polarization-modulated light signal is transmitted to the differential phase generation module through the first circulator for polarization automatic compensation, and a plurality of light signals with time difference are generated; each light signal enters the phase modulator through the first circulator for phase modulation and is transmitted to the polarization decoding module.

[0016] Preferably, the differential phase generation module comprises a first Faraday mirror, a second Faraday mirror, a third Faraday mirror and a first coupler.

[0017] The polarization-modulated light signal is transmitted to the first coupler through the first circulator and is divided into three light signals, and the three light signals respectively reach the first Faraday mirror, the second Faraday mirror and the third Faraday mirror along different fiber branches for polarization automatic compensation and time difference generation, generating three light signals with time difference, and the three light signals return to the first coupler after coupling and are transmitted to the phase modulator through the first circulator for phase modulation.

[0018] Preferably, the lengths of the three fiber branches in the differential phase generation module are in an arithmetic relationship.

[0019] Preferably, the polarization decoding module comprises a polarization controller and a polarization beam splitter.

[0020] The light signal sequentially passes through the polarization controller and the polarization beam splitter for polarization measurement base selection, and the beam splitting obtains the horizontal light signal and the vertical light signal.

[0021] Preferably, the polarization measurement base is 0°, 90°, or +45°, -45°.

[0022] Preferably, it further comprises an optical attenuator; the phase modulator is connected with the polarization controller through the optical attenuator.

[0023] Preferably, the phase decoding module comprises a second circulator, a third circulator, a second coupler, a third coupler, a fourth coupler, a first beam splitter, a second beam splitter, a fourth Faraday mirror, a fifth Faraday mirror, a sixth Faraday mirror, a seventh Faraday mirror, a first single-photon detector, a second single-photon detector, a third single-photon detector, a fourth single-photon detector, a first standard photon detector and a second standard photon detector.

[0024] The horizontal light signal is divided into two light signals after passing through the second circulator and the second coupler in sequence, and the two light signals reach the fourth Faraday mirror and the fifth Faraday mirror for polarization automatic compensation and reflection along different fiber branches; the lengths of the two fiber branches are in an arithmetic progression and correspond to the arithmetic progression of the fiber branches in the differential phase generation module; the two reflected light signals return to the second coupler along the original paths and are coherent, and then are split by the second coupler, one of which is split again after passing through the second circulator and the first beam splitter and then enters the first single-photon detector and the first standard photon detector for detection response, and the other enters the second single-photon detector for detection response.

[0025] The vertical light signal is divided into two light signals after passing through the third circulator and the third coupler in sequence, and the two light signals reach the sixth Faraday mirror and the seventh Faraday mirror for polarization automatic compensation and reflection along different fiber branches; the lengths of the two fiber branches are in an arithmetic progression and correspond to the arithmetic progression of the fiber branches in the differential phase generation module; the two reflected light signals return to the third coupler along the original paths and are coherent, and then are split by the third coupler, one of which is split again after passing through the third circulator and the second beam splitter and then enters the third single-photon detector and the second standard photon detector for detection response, and the other enters the fourth single-photon detector for detection response.

[0026] The first standard photon detector and the second standard photon detector are used for detecting the arrival times of the horizontal light signal and the vertical light signal respectively, and the detection results are fed back to the phase modulator through the fourth coupler to automatically track and compensate the time offset.

[0027] Preferably, the servo system is further provided; and the fourth coupler is connected with the phase modulator through the servo system.

[0028] The utility model has the beneficial technical effect:

[0029] The utility model provides a quantum key distribution system of automatic compensation, realizes polarization automatic compensation by combining differential phase encoding and polarization encoding, automatically eliminates the birefringence effect and polarization loss of the round-trip light path, detects the arrival time of the detection light signal and feeds back, thereby automatically tracking and compensating the time offset, reduces the error rate, improves the stability and the code rate. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The module connection schematic diagram of one embodiment of the utility model;

[0031] Figure 2 The module connection schematic diagram of another embodiment of the utility model;

[0032] Among them: 1, optical signal generation module; 101, multi-wavelength laser; 102, wavelength filter; 2, polarization encoding module; 201, dynamic polarization modulator; 202, first circulator; 203, phase modulator; 3, differential phase generation module; 301, first Faraday mirror; 302, second Faraday mirror; 303, third Faraday mirror; 304, first coupler; 4, polarization decoding module; 401, polarization controller; 402, polarization beam splitter; 5, phase decoding module; 501, second circulator; 502, third circulator; 503, second coupler; 504, third coupler; 505, fourth coupler; 506, first beam splitter; 507, second beam splitter; 508, fourth Faraday mirror; 509, fifth Faraday mirror; 510, sixth Faraday mirror; 511, seventh Faraday mirror; 512, first single-photon detector; 513, second single-photon detector; 514, third single-photon detector; 515, fourth single-photon detector; 516, first standard photon detector; 517, second standard photon detector; 6, optical attenuator; 7, servo system. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the utility model more clearly, the following will be further detailed with examples, but the scope of the utility model claimed is not limited to the following specific examples.

[0034] Example 1

[0035] As Figure 1 shown, an automatic compensation quantum key distribution system includes optical signal generation module 1, polarization encoding module 2, differential phase generation module 3, polarization decoding module 4 and phase decoding module 5.

[0036] The optical signal generation module 1 is used to generate optical signals.

[0037] The polarization encoding module 2 is used to perform polarization encoding on the optical signals.

[0038] The differential phase generation module 3 is used to perform polarization automatic compensation on the polarization-encoded optical signals and generate a plurality of optical signals with time difference.

[0039] The polarization decoding module 4 is used to perform polarization beam splitting on each optical signal after automatic polarization compensation according to the polarization measurement base to obtain horizontal optical signal and vertical optical signal.

[0040] The phase decoding module 5 is used to perform automatic polarization compensation and detection response for horizontal and vertical optical signals, and is also used to detect and feed back the arrival time of horizontal and vertical optical signals, thereby automatically tracking and compensating for time offset.

[0041] Example 2

[0042] like Figure 2 As shown, more specifically, the optical signal generation module 1 includes a multi-wavelength laser 101 and a wavelength filter 102; the optical signal generated by the multi-wavelength laser 101 enters the polarization encoding module 2 through the wavelength filter 102.

[0043] In practical implementation, a single-source multi-wavelength laser 101 satisfies the simultaneous multi-wavelength laser pulses required by multiple users. Wavelength selection is flexible, enabling wavelength changes and user additions / removals in a multi-user network, thus increasing network scalability. This embodiment employs a two-stage arithmetic interval method for wavelength selection, specifically using wavelength intervals of 2λ, 5λ, 10λ, 17λ, 26λ, 37λ… to ensure that the new frequency light generated by four-wave mixing is as far away as possible from the wavelengths of the four pulse signals.

[0044] More specifically, the polarization encoding module 2 includes a dynamic polarization modulator 201, a first circulator 202, and a phase modulator 203;

[0045] The optical signal generated by the multi-wavelength laser 101 passes through the wavelength filter 102 and enters the dynamic polarization modulator 201 for random polarization modulation (0°, ±45°, 90°). The polarization-modulated optical signal is transmitted through the first circulator 202 to the differential phase generation module 3 for automatic polarization compensation and generates multiple optical signals with time differences. Each optical signal passes through the first circulator 202 and enters the phase modulator 203 for phase modulation before being transmitted to the polarization decoding module 4.

[0046] More specifically, the differential phase generation module 3 includes a first Faraday mirror 301, a second Faraday mirror 302, a third Faraday mirror 303, and a first coupler 304;

[0047] The polarization modulated optical signal is transmitted to the first coupler 304 through the first circulator 202 to be divided into three optical signals, which reach the first Faraday mirror 301, the second Faraday mirror 302 and the third Faraday mirror 303 along different optical fiber branches to be automatically compensated in polarization and to generate time difference, thereby generating three optical signals with time difference, which return to the first coupler 304 and are coupled to be transmitted to the phase modulator 203 through the first circulator 202 for phase modulation.

[0048] In the specific implementation process, the Faraday mirror structure is used to automatically compensate the pulses transmitted in the optical fiber, so that the depolarization phenomenon is avoided, and the stability of the system is improved.

[0049] More specifically, the lengths of the three optical fiber branches in the differential phase generation module 3 are in an arithmetic progression.

[0050] In the specific implementation process, the lengths of the three optical fiber branches are in an arithmetic progression, so that the time difference of the three optical signals is also in an arithmetic progression.

[0051] More specifically, the polarization decoding module 4 includes a polarization controller 401 and a polarization beam splitter 402.

[0052] The optical signal passes through the polarization controller 401 and the polarization beam splitter 402 in turn to select the polarization measurement basis, and the beam splitting obtains the horizontal optical signal and the vertical optical signal.

[0053] More specifically, the polarization measurement basis is 0°, 90°, or +45°, -45°.

[0054] More specifically, it further includes an optical attenuator 6; the phase modulator 203 is connected with the polarization controller 401 through the optical attenuator 6.

[0055] In the specific implementation process, the optical attenuator 6 is used to attenuate the optical signal.

[0056] More specifically, the phase decoding module 5 includes a second circulator 501, a third circulator 502, a second coupler 503, a third coupler 504, a fourth coupler 505, a first beam splitter 506, a second beam splitter 507, a fourth Faraday mirror 508, a fifth Faraday mirror 509, a sixth Faraday mirror 510, a seventh Faraday mirror 511, a first single-photon detector 512, a second single-photon detector 513, a third single-photon detector 514, a fourth single-photon detector 515, a first standard photon detector 516 and a second standard photon detector 517.

[0057] The horizontal light signal is divided into two light signals after passing through the second circulator 501 and the second coupler 503 in turn, and the two light signals reach the fourth Faraday mirror 508 and the fifth Faraday mirror 509 along different fiber branches for polarization automatic compensation and reflection; wherein the lengths of the two fiber branches are in an arithmetic relationship and correspond to the arithmetic relationship of the fiber branches in the differential phase generation module 3; the two reflected light signals return to the second coupler 503 along the original path and interfere, and then one of the beams is divided again after passing through the second circulator 501 and the first beam splitter 506 and enters the first single-photon detector 512 and the first standard photon detector 516 for detection response, and the other beam enters the second single-photon detector 513 for detection response.

[0058] The vertical light signal is divided into two light signals after passing through the third circulator 502 and the third coupler 504 in turn, and the two light signals reach the sixth Faraday mirror 510 and the seventh Faraday mirror 511 along different fiber branches for polarization automatic compensation and reflection; wherein the lengths of the two fiber branches are in an arithmetic relationship and correspond to the arithmetic relationship of the fiber branches in the differential phase generation module 3; the two reflected light signals return to the third coupler 504 along the original path and interfere, and then one of the beams is divided again after passing through the third circulator 502 and the second beam splitter 507 and enters the third single-photon detector 514 and the second standard photon detector 517 for detection response, and the other beam enters the fourth single-photon detector 515 for detection response.

[0059] The first standard photon detector 516 and the second standard photon detector 517 are used for detecting the arrival time of the horizontal light signal and the vertical light signal respectively, and the detection results are fed back to the phase modulator 203 through the fourth coupler 505 for automatic tracking compensation of time offset.

[0060] In the specific implementation process, the Faraday mirror is used to automatically compensate the pulses transmitted in the optical fiber, so as to avoid the phenomenon of depolarization and improve the stability of the system.

[0061] Assuming that the three light signals in the differential phase generation module 3 are T0, T1 and T2, wherein the time difference between T0 and T1 is t, the time difference between T1 and T2 is t, and the time difference between T0 and T2 is 2t; in the phase decoding module 5, T0, T1 and T2 pass through the shorter fiber branch to obtain T1', T2' and T3'; T0, T1 and T2 pass through the longer fiber branch to obtain T2'', T3'' and T4''; therefore, two pairs of (T2' and T2'', T3' and T3'') can return to the coupler at the same time for interference, and the signals after interference are detected by the detector for detection response.

[0062] Phase decoding of the optical signals: when the phase difference between the optical signals is "0", the first single photon detector 512 and the third single photon detector 514 respond, which is defined as the bit value "0"; when the phase difference between the optical signals is "±π", the second single photon detector 513 and the fourth single photon detector 515 respond, which is defined as the bit value "1".

[0063] More specifically, it further comprises a servo system 7; the fourth coupler 505 is connected with the phase modulator 203 through the servo system 7.

[0064] In the specific implementation process, the servo system 7 automatically tracks and compensates the time offset of the optical fiber transmission according to the synchronization signal. In actual implementation, the servo system 7 only automatically tracks and compensates the time offset according to the arrival time of the interfering optical signals. Taking a single optical signal generated by the optical signal generation module 1 as an example, after the optical signal is transmitted to the receiving end, six optical signals T1', T2', T3', T2", T3" and T4" are formed, wherein T1' arrives first, after an interval time difference t, T2' and T2" arrive, after another interval time difference t, T3' and T3" arrive, and finally T4" arrives. Therefore, the servo system 7 only automatically tracks and compensates the time offset of the optical fiber transmission according to the synchronization signal when T2' and T2", T3' and T3" arrive, and does not automatically track and compensate the time offset of the optical fiber transmission when T1', T4" arrives.

[0065] In the implementation process, the output end of the multi-wavelength laser 101 is connected with the input end of the dynamic polarization modulator 201 through the wavelength filter 102, the output end of the dynamic polarization modulator 201 is connected with the first port of the first circulator 202, the second port of the first circulator 202 is bidirectionally connected with the first Faraday mirror 301, the second Faraday mirror 302 and the third Faraday mirror 303 through the first coupler 304 respectively, the third port of the first circulator 202 is connected with an input end of the phase modulator 203, the output end of the phase modulator 203 is connected with the input end of the polarization controller 401 through the optical attenuator 6, the output end of the polarization controller 401 is connected with the input end of the polarization beam splitter 402, the horizontal output end of the polarization beam splitter 402 is connected with the first port of the second circulator 501, the second port of the second circulator 501 is bidirectionally connected with the fourth Faraday mirror 508 and the fifth Faraday mirror 509 through the second coupler 503 respectively, the input end of the first single photon detector 512 and the input end of the first standard photon detector 516 are connected with the third port of the second circulator 501 through the first beam splitter 506 respectively, the second single photon detector 513 is connected with the second coupler 503, the vertical output end of the polarization beam splitter 402 is connected with the first port of the third circulator 502, the second port of the third circulator 502 is bidirectionally connected with the sixth Faraday mirror 510 and the seventh Faraday mirror 511 through the third coupler 504 respectively, the input end of the third single photon detector 514 and the input end of the second standard photon detector 517 are connected with the third port of the third circulator 502 through the second beam splitter 507 respectively, the fourth single photon detector 515 is connected with the third coupler 504, the output end of the first standard photon detector 516 and the output end of the second standard photon detector 517 are connected with the input end of the servo system 7 through the fourth coupler 505 respectively, the output end of the servo system 7 is connected with the other input end of the phase modulator 203.

[0066] According to the disclosure and teaching of the above description, the skilled in the art of the present application can also change and modify the above embodiments. Therefore, the present application is not limited to the specific embodiments disclosed and described above, and some modifications and changes of the present application should fall within the protection scope of the claims of the present application. In addition, although some specific terms are used in the specification, these terms are only for convenience and do not constitute any limitation on the present application.

Claims

1. An automatically compensated quantum key distribution system, characterized by, The light signal generation module, the polarization encoding module, the differential phase generation module, the polarization decoding module and the phase decoding module are included. The light signal generation module is configured to generate a light signal. The polarization encoding module is configured to perform polarization encoding on the light signal. The differential phase generation module is configured to perform polarization automatic compensation on the polarization-encoded light signal and generate a plurality of light signals with time difference. The polarization decoding module is configured to perform polarization beam splitting on each of the polarization automatically compensated light signals according to a polarization measurement base to obtain horizontal light signals and vertical light signals. The phase decoding module is configured to perform polarization automatic compensation and detection response on the horizontal light signals and the vertical light signals, and is further configured to detect the arrival time of the horizontal light signals and the vertical light signals and feed back, so as to automatically track and compensate the time offset.

2. The self-compensating quantum key distribution system of claim 1, wherein, The light signal generation module includes a multi-wavelength laser and a wavelength filter; the light signal generated by the multi-wavelength laser enters the polarization encoding module through the wavelength filter.

3. The self-compensating quantum key distribution system of claim 2, wherein, The polarization encoding module includes a dynamic polarization modulator, a first circulator and a phase modulator. The light signal generated by the multi-wavelength laser enters the dynamic polarization modulator for random polarization modulation through the wavelength filter, and the polarization-modulated light signal is transmitted to the differential phase generation module through the first circulator for polarization automatic compensation and generates a plurality of light signals with time difference; each light signal enters the phase modulator for phase modulation after being transmitted to the polarization decoding module through the first circulator.

4. The self-compensating quantum key distribution system of claim 3, wherein, The differential phase generation module includes a first Faraday mirror, a second Faraday mirror, a third Faraday mirror and a first coupler. The polarization-modulated light signal is transmitted to the first coupler through the first circulator and divided into three light signals, the three light signals respectively reach the first Faraday mirror, the second Faraday mirror and the third Faraday mirror along different fiber branches for polarization automatic compensation and time difference generation, and three light signals with time difference are generated, the three light signals return to the first coupler after coupling and are transmitted to the phase modulator through the first circulator for phase modulation.

5. The self-compensating quantum key distribution system of claim 4, wherein, The lengths of the three fiber branches in the differential phase generation module are in an arithmetic relationship.

6. The self-compensating quantum key distribution system of claim 3, wherein, The polarization decoding module includes a polarization controller and a polarization beam splitter. The light signal passes through the polarization controller and the polarization beam splitter in turn for polarization measurement base selection, and is split into horizontal light signals and vertical light signals.

7. The self-compensating quantum key distribution system of claim 6, wherein, The polarization measurement base is 0°, 90°, or +45°, -45°.

8. The self-compensating quantum key distribution system of claim 6, wherein, It also includes an optical attenuator; the phase modulator is connected with the polarization controller through the optical attenuator.

9. The self-compensating quantum key distribution system of claim 5, wherein, The phase decoding module includes a second circulator, a third circulator, a second coupler, a third coupler, a fourth coupler, a first beam splitter, a second beam splitter, a fourth Faraday mirror, a fifth Faraday mirror, a sixth Faraday mirror, a seventh Faraday mirror, a first single-photon detector, a second single-photon detector, a third single-photon detector, a fourth single-photon detector, a first standard photon detector and a second standard photon detector. The horizontal light signal is divided into two light signals after passing through the second circulator and the second coupler in turn, and the two light signals reach the fourth Faraday mirror and the fifth Faraday mirror along different fiber branches for polarization automatic compensation and reflection; wherein the lengths of the two fiber branches are in an arithmetic relationship and correspond to the arithmetic relationship of the fiber branches in the differential phase generation module; the two reflected light signals return to the second coupler along the original path and are coherent, and then are split by the second coupler, one of which is split again into the first single-photon detector and the first standard photon detector for detection response after passing through the second circulator and the first beam splitter in turn, and the other is split into the second single-photon detector for detection response; The vertical light signal is divided into two light signals after passing through the third circulator and the third coupler in turn, and the two light signals reach the sixth Faraday mirror and the seventh Faraday mirror along different fiber branches for polarization automatic compensation and reflection; wherein the lengths of the two fiber branches are in an arithmetic relationship and correspond to the arithmetic relationship of the fiber branches in the differential phase generation module; the two reflected light signals return to the third coupler along the original path and are coherent, and then are split by the third coupler, one of which is split again into the third single-photon detector and the second standard photon detector for detection response after passing through the third circulator and the second beam splitter in turn, and the other is split into the fourth single-photon detector for detection response; Wherein, the first standard photon detector and the second standard photon detector are used for detecting the arrival time of the horizontal light signal and the vertical light signal respectively, and the detection results are fed back to the phase modulator through the fourth coupler after coupling to automatically track and compensate the time offset.

10. The self-compensating quantum key distribution system of claim 9, wherein, It also includes a servo system; the fourth coupler is connected with the phase modulator through the servo system.

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