Plug-and-play multi-user MDI-TF-QKD device

Abstract

The utility model discloses a plug-and-play multi-user MDI-TF-QKD device, which comprises a plurality of user terminals and an annular quantum channel, and the user terminals are connected through the annular quantum channel. The user side comprises a sending measurement module, a path selection module and a code modulation module; the sending measurement module is connected with the annular quantum channel through the path selection module, and the coding modulation module is connected with the annular quantum channel. The utility model discloses a plug-and-play multi-user MDI-TF-QKD device, which is characterized in that two paths of light pulses are respectively sent to different user terminals through a sending measurement module to prepare quantum state signals, so that a single light source is used for preparing a quantum state between every two users, and the problem of inconsistent quantum state preparation is prevented; and meanwhile, a plug-and-play structure is adopted, so that the system can perform automatic compensation on phase and polarization, the structure is simple, the implementation is easy, and the practicability is high.

Description

Technical Field

[0001] The utility model relates to the technical field of quantum secure communication and optical communication, and in particular to a plug-and-play multi-user MDI-TF-QKD device. Background Art

[0002] The MDI-QKD protocol has not broken through the limits of the coding rate and transmission distance without quantum relays. Therefore, some studies have proposed the TF-QKD protocol, which not only retains the security advantage of the MDI-QKD protocol from being attacked by detection devices, but also breaks through the limit value of point-to-point communication without relays (PLOB boundary), and improves the quantum key rate and coding rate.

[0003] In the TF-QKD protocol, the two parties in legal communication need highly consistent twin light fields to produce stable single-photon interference at the measurement end Charlie. Therefore, for the TF-QKD protocol, the choice of light source is particularly important. However, since the actual system is different from the theoretical one, even if two completely identical light sources are used, there will be differences between them, resulting in inconsistent quantum state preparation and the risk of eavesdropping. Moreover, technically speaking, it is very difficult for two remote parties to prepare highly consistent "twin fields". In addition, the TF-QKD protocol requires the phase coordination of the dual fields, but it is easily affected by the external environment and causes phase drift. Therefore, an additional phase compensation system is required at the receiving end to compensate for the phase drift in real time.

[0004] The large-scale application of quantum networks is becoming more and more complex, and building multi-user quantum networks has become a new research hotspot.

[0005] In the prior art, patent CN213879845U discloses a three-user TF-QKD network system. Although it has a simple structure, it does not address the light source and phase drift. Utility Model Content

[0006] In order to solve the problem that the current TF-QKD scheme adopts dual light sources resulting in inconsistent quantum state preparation, the utility model proposes a plug-and-play multi-user MDI-TF-QKD device.

[0007] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0008] A plug-and-play multi-user MDI-TF-QKD device includes a plurality of user terminals and a ring quantum channel, wherein the user terminals are connected via the ring quantum channel;

[0009] The user terminal includes a sending measurement module, a path selection module and a coding modulation module;

[0010] The sending measurement module is connected to the ring quantum channel through the path selection module, and the coding modulation module is connected to the ring quantum channel.

[0011] In the above scheme, two optical pulses are sent out through a sending and measuring module to prepare quantum state signals in different user terminals respectively, so that a single light source is used to prepare quantum states between two users, thus preventing the problem of inconsistent quantum state preparation. At the same time, a plug-and-play structure is adopted, so that the system can automatically compensate for phase and polarization. The structure is simple, easy to implement, and highly practical.

[0012] Preferably, the user end further includes a first Faraday mirror; the first Faraday mirror is connected to the path selection module.

[0013] Preferably, the sending measurement module includes a laser, a first beam splitter, a second beam splitter, a first single photon detector and a second single photon detector;

[0014] The output end of the laser is connected to the input end of the first beam splitter, and the two output ends of the first beam splitter are respectively connected to the ring quantum channel through the path selection module; the two input ends of the second beam splitter are respectively connected to the ring quantum channel through the path selection module, and the input end of the first single-photon detector and the input end of the second single-photon detector are respectively connected to different output ends of the second beam splitter.

[0015] Preferably, the path selection module comprises a first wavelength selection switch and a second wavelength selection switch connected to each other; wherein,

[0016] The first wavelength selective switch is provided with a first output end, a first input end and a first bidirectional end;

[0017] The second wavelength selective switch is provided with a second output end, a second input end, a second bidirectional end and a third bidirectional end;

[0018] The first input end and the second input end are respectively connected to different output ends of the first beam splitter, the first output end and the second output end are respectively connected to different input ends of the second beam splitter, the first bidirectional end and the second bidirectional end are respectively connected to the ring quantum channel, and the third bidirectional end is connected to the first Faraday mirror.

[0019] Preferably, the sending measurement module further includes a first circulator and a second circulator;

[0020] The first port of the first circulator and the first port of the second circulator are respectively connected to different output ends of the first beam splitter, the second port of the first circulator and the second port of the second circulator are respectively connected to different ports of the path selection module, and the third port of the first circulator and the third port of the second circulator are respectively connected to different input ends of the second beam splitter.

[0021] Preferably, the path selection module comprises a first wavelength selection switch and a second wavelength selection switch connected to each other; wherein,

[0022] The first wavelength selective switch is provided with a first bidirectional end and a second bidirectional end;

[0023] The second wavelength selective switch is provided with a third bidirectional end, a fourth bidirectional end and a fifth bidirectional end;

[0024] The first bidirectional end is connected to an output end of the first beam splitter and an input end of the second beam splitter through the second circulator, the second bidirectional end and the fourth bidirectional end are connected to the ring quantum channel, the third bidirectional end is connected to the other output end of the first beam splitter and the other input end of the second beam splitter through the first circulator, and the fifth bidirectional end is connected to the first Faraday mirror.

[0025] Preferably, the first circulator is a counterclockwise transmission structure, and the second circulator is a clockwise transmission structure.

[0026] Preferably, the coding modulation module includes a bandpass filter, a third beam splitter, a photodetector, an amplitude modulator, a first phase modulator, a second Faraday mirror, a second phase modulator and a variable optical attenuator;

[0027] The input end of the bandpass filter is connected to the ring quantum channel, the output end of the bandpass filter is connected to the input end of the third beam splitter, the input end of the photodetector and the input end of the amplitude modulator are respectively connected to different output ends of the third beam splitter, the output end of the amplitude modulator is connected to the input end of the first phase modulator, the output end of the first phase modulator is connected to the input end of the second Faraday mirror, the output end of the second Faraday mirror is connected to the input end of the second phase modulator, the output end of the second phase modulator is connected to the input end of the variable optical attenuator, and the output end of the variable optical attenuator is connected to the ring quantum channel.

[0028] Preferably, the ring quantum channel is a bidirectional transmission structure.

[0029] Preferably, there are at least three user terminals.

[0030] Beneficial technical effects of the utility model:

[0031] The utility model provides a plug-and-play multi-user MDI-TF-QKD device, which sends two optical pulses to different user terminals through a transmission measurement module to prepare quantum state signals, thereby realizing the use of a single light source to prepare quantum states between two users, thereby preventing the problem of inconsistent quantum state preparation; at the same time, a plug-and-play structure is adopted, so that the system can automatically compensate for phase and polarization, and the structure is simple, easy to implement, and highly practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the overall framework of the utility model;

[0033] Figure 2 This is a schematic diagram of the module connection between the user end and the ring quantum channel in the utility model;

[0034] Figure 3 This is a schematic diagram of module connection of the sending measurement module in the utility model;

[0035] Figure 4 This is a schematic diagram of the structure of a path selection module in one embodiment of the present utility model;

[0036] Figure 5 This is a schematic diagram of module connection of the coding and modulation module in the utility model;

[0037] Figure 6 This is a schematic diagram of the structure of a path selection module in another embodiment of the present utility model;

[0038] Figure 7 It is a schematic diagram of the workflow of the utility model;

[0039] Among them: 1. Transmitting measurement module; 11. Laser; 121. First beam splitter; 122. Second beam splitter; 131. First single photon detector; 132. Second single photon detector; 141. First circulator; 142. Second circulator; 2. Path selection module; 21. First wavelength selection switch; 22. Second wavelength selection switch; 3. Coding modulation module; 31. Bandpass filter; 32. Third beam splitter; 33. Photodetector; 34. Amplitude modulator; 35. First phase modulator; 36. Second Faraday mirror; 37. Second phase modulator; 38. Variable optical attenuator; 4. First Faraday mirror. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the utility model more clearly understood, the utility model is further described in detail below in conjunction with embodiments, but the scope of protection claimed in the utility model is not limited to the following specific embodiments. Example

[0041] like Figure 1-2 As shown, a plug-and-play multi-user MDI-TF-QKD device includes multiple user terminals (user terminal User1, user terminal User2, ..., user terminal Usern, n≥3) and a ring quantum channel, and each user terminal is connected through the ring quantum channel;

[0042] The user end includes a transmission measurement module 1, a path selection module 2 and a coding modulation module 3;

[0043] The sending measurement module 1 is connected to the ring quantum channel through the path selection module 2, and the coding modulation module 3 is connected to the ring quantum channel;

[0044] The sending and measuring module 1 sends out two optical pulses, which are respectively transmitted to the coding and modulation modules 3 of different user terminals via the path selection module 2 to prepare two quantum state signals. The two quantum state signals are respectively returned to the same sending and measuring module 1 via the path selection module 2 for interference detection to obtain the original key, and the original key is post-processed to generate a common quantum key.

[0045] In the specific implementation process, two optical pulses are sent to different user terminals through a sending measurement module 1 to prepare quantum state signals, so that a single light source is used to prepare quantum states between two users, thereby preventing the problem of inconsistent quantum state preparation. At the same time, a plug-and-play structure is adopted, so that the system can automatically compensate for phase and polarization, with a simple structure, easy implementation, and strong practicality.

[0046] More specifically, the user end further includes a first Faraday mirror 4 ; the first Faraday mirror 4 is connected to the path selection module 2 .

[0047] More specifically, Figure 3 As shown, the sending measurement module 1 includes a laser 11, a first beam splitter 121, a second beam splitter 122, a first single photon detector 131 and a second single photon detector 132;

[0048] The output end of the laser 11 is connected to the input end of the first beam splitter 121, and the two output ends of the first beam splitter 121 are respectively connected to the ring quantum channel through the path selection module 2; the two input ends of the second beam splitter 122 are respectively connected to the ring quantum channel through the path selection module 2, and the input end of the first single-photon detector 131 and the input end of the second single-photon detector 132 are respectively connected to different output ends of the second beam splitter 122.

[0049] In the specific implementation process, the laser 11 emits a weak coherent light pulse, which is divided into a first light pulse and a second light pulse by the first beam splitter 121; wherein the first light pulse is sent to the coding and modulation module 3 of one user end through the path selection module 2 to prepare a first quantum state signal, and the second light pulse is sent to the coding and modulation module 3 of another user end through the path selection module 2 to prepare a second quantum state signal; the first quantum state signal and the second quantum state signal are respectively returned to the same sending and measuring module 1 through the path selection module 2, and enter the second beam splitter 122 to interfere, and the first single-photon detector 131 and the second single-photon detector 132 detect and respond to the interference result.

[0050] More specifically, Figure 4 As shown, the path selection module 2 includes a first wavelength selection switch 21 and a second wavelength selection switch 22 connected to each other; wherein,

[0051] The first wavelength selective switch 21 is provided with a first output end, a first input end and a first bidirectional end;

[0052] The second wavelength selective switch 22 is provided with a second output end, a second input end, a second bidirectional end and a third bidirectional end;

[0053] Figure 3 BS1 represents the first beam splitter 121, BS2 represents the second beam splitter 122, Circle represents the circular quantum channel, and FM1 represents the first Faraday mirror 4;

[0054] The first input end and the second input end are respectively connected to different output ends of the first beam splitter 121, the first output end and the second output end are respectively connected to different input ends of the second beam splitter 122, the first bidirectional end and the second bidirectional end are respectively connected to the ring quantum channel, and the third bidirectional end is connected to the first Faraday mirror 4.

[0055] In the specific implementation process, the connection function between any two ports is realized through a wavelength selection switch, and the connection function is realized by selecting the same wavelength.

[0056] More specifically, Figure 5 As shown, the coding modulation module 3 includes a bandpass filter 31, a third beam splitter 32, a photodetector 33, an amplitude modulator 34, a first phase modulator 35, a second Faraday mirror 36, a second phase modulator 37 and a variable optical attenuator 38;

[0057] The input end of the bandpass filter 31 is connected to the ring quantum channel, the output end of the bandpass filter 31 is connected to the input end of the third beam splitter 32, the input end of the photodetector 33 and the input end of the amplitude modulator 34 are respectively connected to different output ends of the third beam splitter 32, the output end of the amplitude modulator 34 is connected to the input end of the first phase modulator 35, the output end of the first phase modulator 35 is connected to the input end of the second Faraday mirror 36, the output end of the second Faraday mirror 36 is connected to the input end of the second phase modulator 37, the output end of the second phase modulator 37 is connected to the input end of the variable optical attenuator 38, and the output end of the variable optical attenuator 38 is connected to the ring quantum channel.

[0058] In the specific implementation process, the optical pulse is filtered by the bandpass filter 31 to filter out unnecessary optical pulses, and then is divided into two optical pulses by the third beam splitter 32, one of which enters the photodetector 33 to obtain the photon number distribution of the optical pulse, and the other optical pulse is sequentially intensity modulated by the amplitude modulator 34 and phase randomized by the first phase modulator 35; the phase-randomized optical pulse is reflected back by the second Faraday mirror 36 and enters the second phase modulator 37 for phase encoding, and the information bit is generated by the random number generator. The optical pulse that completes the phase encoding enters the variable optical attenuator 38 to attenuate the photon number to the single photon level or the zero photon level, and the output quantum state signal is returned to the sending measurement module 1 via the path selection module 2.

[0059] More specifically, the ring quantum channel is a bidirectional transmission structure.

[0060] In the specific implementation process, the quantum signal can be transmitted in the ring quantum channel in both the clockwise direction and the counterclockwise direction.

[0061] More specifically, there are at least three user terminals (user terminal User1, user terminal User2, user terminal User3). Example

[0062] A multi-user MDI-TF-QKD system based on plug-and-play is substantially the same as the multi-user MDI-TF-QKD system based on plug-and-play described in Example 1, except that:

[0063] More specifically, the sending measurement module 1 further includes a first circulator 141 and a second circulator 142;

[0064] The first port of the first circulator 141 and the first port of the second circulator 142 are respectively connected to different output ends of the first beam splitter 121, the second port of the first circulator 141 and the second port of the second circulator 142 are respectively connected to different ports of the path selection module 2, and the third port of the first circulator 141 and the third port of the second circulator 142 are respectively connected to different input ends of the second beam splitter 122.

[0065] In a specific implementation process, the first circulator 141 and the second circulator 142 are both three-port circulators and have a unidirectional transmission structure.

[0066] More specifically, the first circulator 141 is a counterclockwise transmission structure, and the second circulator 142 is a clockwise transmission structure.

[0067] More specifically, Figure 6 As shown, the path selection module 2 includes a first wavelength selection switch 21 and a second wavelength selection switch 22 connected to each other; wherein,

[0068] The first wavelength selective switch 21 is provided with a first bidirectional end and a second bidirectional end;

[0069] The second wavelength selective switch 22 is provided with a third bidirectional end, a fourth bidirectional end and a fifth bidirectional end;

[0070] Figure 5 Wherein cir1 represents the first circulator 141, cir2 represents the second circulator 142, Circle represents a circular quantum channel, and FM1 represents the first Faraday mirror 4;

[0071] The first bidirectional end is connected to an output end of the first beam splitter 121 and an input end of the second beam splitter 122 respectively through the second circulator 142, the second bidirectional end and the fourth bidirectional end are connected to the ring quantum channel respectively, the third bidirectional end is connected to the other output end of the first beam splitter 121 and the other input end of the second beam splitter 122 respectively through the first circulator 141, and the fifth bidirectional end is connected to the first Faraday mirror 4. Example

[0072] like Figure 7 As shown, a multi-user MDI-TF-QKD method based on plug-and-play is implemented based on the multi-user MDI-TF-QKD system based on plug-and-play, assuming that user end User1 and user end User2 communicate, and interference detection is performed at user end User1, including the following steps:

[0073] S1: Sending an optical pulse: the sending and measuring module 1 of the user end User1 sends a first optical pulse and a second optical pulse;

[0074] S2: The optical pulse enters the coding and modulation module 3: The first optical pulse and the second optical pulse enter the ring quantum channel from different ports of the path selection module 2 of the user end User1 respectively, and are transmitted in opposite directions, entering the coding and modulation module 3 of the user end User1 and the coding and modulation module 3 of the user end User2 respectively;

[0075] S3: preparing quantum state signals: encoding and modulating the first optical pulse and the second optical pulse to obtain a first quantum state signal and a second quantum state signal respectively;

[0076] S4: The quantum state signal returns to the sending and measuring module 1: The first quantum state signal returns to the sending and measuring module 1 of the user end User1 through the path selection module 2 of the user end User1;

[0077] The second quantum state signal passes through the path selection module 2 of the user end User2 and reaches the first Faraday mirror 4 of the user end User2 for reflection. The reflected second quantum state signal passes through the path selection module 2 of the user end User2 and the path selection module 2 of the user end User1 in turn and then returns to the sending measurement module 1 of the user end User1.

[0078] S5: Interference detection: The first quantum state signal and the second quantum state signal are subjected to interference detection in the sending measurement module 1 of the user terminal User1 to obtain the original key between the user terminal User1 and the user terminal User2;

[0079] S6: Post-process the original key to generate a quantum key common to user end User1 and user end User2;

[0080] In actual implementation, post-processing includes steps such as error estimation, error correction, and privacy amplification. The specific steps of error estimation are:

[0081] S6.1: QBER estimation: estimate the bit error rate QBER of the original key;

[0082] S6.2: QBER comparison: compare the bit error rate QBER threshold;

[0083] If it is greater than the threshold, it is considered that there is a communication vulnerability, and the process returns to step S1 to re-communicate;

[0084] If it is not greater than the threshold, the bit error rate QBER meets the conditions and the communication is valid.

[0085] According to the disclosure and teaching of the above specification, the technicians in the field of the utility model can also change and modify the above implementation. Therefore, the utility model is not limited to the specific implementation methods disclosed and described above, and some modifications and changes to the utility model should also fall within the scope of protection of the claims of the utility model. In addition, although some specific terms are used in this specification, these terms are only for convenience and do not constitute any limitation to the utility model.

Claims

1. A plug-and-play multi-user MDI-TF-QKD device, characterized in that: It includes multiple user terminals and a ring quantum channel, and each user terminal is connected through the ring quantum channel; The user terminal includes a sending measurement module, a path selection module and a coding modulation module; The sending measurement module is connected to the ring quantum channel through the path selection module, and the coding modulation module is connected to the ring quantum channel.

2. A plug-and-play multi-user MDI-TF-QKD device according to claim 1, characterized in that: The user end also includes a first Faraday mirror; the first Faraday mirror is connected to the path selection module.

3. A plug-and-play multi-user MDI-TF-QKD device according to claim 2, characterized in that: The sending measurement module includes a laser, a first beam splitter, a second beam splitter, a first single photon detector and a second single photon detector; The output end of the laser is connected to the input end of the first beam splitter, and the two output ends of the first beam splitter are respectively connected to the ring quantum channel through the path selection module; the two input ends of the second beam splitter are respectively connected to the ring quantum channel through the path selection module, and the input end of the first single-photon detector and the input end of the second single-photon detector are respectively connected to different output ends of the second beam splitter.

4. A plug-and-play multi-user MDI-TF-QKD device according to claim 3, characterized in that: The path selection module includes a first wavelength selection switch and a second wavelength selection switch connected to each other; wherein, The first wavelength selective switch is provided with a first output end, a first input end and a first bidirectional end; The second wavelength selective switch is provided with a second output end, a second input end, a second bidirectional end and a third bidirectional end; The first input end and the second input end are respectively connected to different output ends of the first beam splitter, the first output end and the second output end are respectively connected to different input ends of the second beam splitter, the first bidirectional end and the second bidirectional end are respectively connected to the ring quantum channel, and the third bidirectional end is connected to the first Faraday mirror.

5. A plug-and-play multi-user MDI-TF-QKD device according to claim 3, characterized in that: The transmission measurement module also includes a first circulator and a second circulator; The first port of the first circulator and the first port of the second circulator are respectively connected to different output ends of the first beam splitter, the second port of the first circulator and the second port of the second circulator are respectively connected to different ports of the path selection module, and the third port of the first circulator and the third port of the second circulator are respectively connected to different input ends of the second beam splitter.

6. A plug-and-play multi-user MDI-TF-QKD device according to claim 5, characterized in that: The path selection module includes a first wavelength selection switch and a second wavelength selection switch connected to each other; wherein, The first wavelength selective switch is provided with a first bidirectional end and a second bidirectional end; The second wavelength selective switch is provided with a third bidirectional end, a fourth bidirectional end and a fifth bidirectional end; The first bidirectional end is connected to an output end of the first beam splitter and an input end of the second beam splitter through the second circulator, the second bidirectional end and the fourth bidirectional end are connected to the ring quantum channel, the third bidirectional end is connected to the other output end of the first beam splitter and the other input end of the second beam splitter through the first circulator, and the fifth bidirectional end is connected to the first Faraday mirror.

7. The plug-and-play multi-user MDI-TF-QKD device according to claim 5, characterized in that: The first circulator has a counterclockwise transmission structure, and the second circulator has a clockwise transmission structure.

8. The plug-and-play multi-user MDI-TF-QKD device according to claim 1, characterized in that: The coding modulation module includes a bandpass filter, a third beam splitter, a photodetector, an amplitude modulator, a first phase modulator, a second Faraday mirror, a second phase modulator and a variable optical attenuator; The input end of the bandpass filter is connected to the ring quantum channel, the output end of the bandpass filter is connected to the input end of the third beam splitter, the input end of the photodetector and the input end of the amplitude modulator are respectively connected to different output ends of the third beam splitter, the output end of the amplitude modulator is connected to the input end of the first phase modulator, the output end of the first phase modulator is connected to the input end of the second Faraday mirror, the output end of the second Faraday mirror is connected to the input end of the second phase modulator, the output end of the second phase modulator is connected to the input end of the variable optical attenuator, and the output end of the variable optical attenuator is connected to the ring quantum channel.

9. The plug-and-play multi-user MDI-TF-QKD device according to claim 1, characterized in that: The ring quantum channel is a bidirectional transmission structure.

10. The plug-and-play multi-user MDI-TF-QKD device according to claim 1, characterized in that: There are at least three user terminals.

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