Synchronization Method and Apparatus for Quantum Key Distribution System

Abstract

This disclosure provides a synchronization method and apparatus for a quantum key distribution system, relating to the field of quantum communication technology. The method includes: a probe node simultaneously transmitting a first synchronization signal and a second synchronization signal to a first node and a second node, respectively, such that the first node receives the first synchronization signal and transmits a third synchronization signal, and the second node receives second synchronization information and transmits a fourth synchronization signal; in response to the third synchronization signal from the first node, the probe node transmits a fifth synchronization signal to the second node, such that the second node receives the fifth synchronization information and transmits a first quantum signal; in response to the fourth synchronization signal from the second node, the probe node transmits a sixth synchronization signal to the first node, such that the first node receives the sixth synchronization signal and transmits a second quantum signal; the probe node simultaneously receives the first quantum signal from the second node and the second quantum signal from the first node.

Description

Technical Field

[0001] This disclosure relates to the field of quantum communication technology, and more specifically, to a synchronization method and apparatus for a quantum key distribution system. Background Technology

[0002] Measurement-device-independent protocols involve users sending quantum states to untrusted intermediary user nodes. These intermediary nodes then jointly measure the quantum states and publish the results. Users generate keys based on these measurements and their local preparation records. Examples include measurement-device-independent quantum key distribution, twin-field quantum key distribution, and mode-pairing quantum key distribution. Because these protocols require simultaneous measurement of quantum states from multiple users, they place high demands on time synchronization.

[0003] Current synchronization schemes in related technologies suffer from the following technical problems: they lack effective scalability in multi-user network environments, making it difficult to adapt to the construction requirements of large-scale quantum networks; when applied to mobile devices, the difficulty of time synchronization increases, resulting in insufficient stability of time synchronization and affecting the accuracy of time synchronization. Summary of the Invention

[0004] In view of this, the present disclosure provides a synchronization method and apparatus for a quantum key distribution system.

[0005] One aspect of this disclosure provides a synchronization method for a quantum key distribution system, comprising: a probe node simultaneously transmitting a first synchronization signal and a second synchronization signal to a first node and a second node, respectively, such that the first node receives the first synchronization signal and transmits a third synchronization signal, and the second node receives the second synchronization information and transmits a fourth synchronization signal; the probe node, in response to the third synchronization signal from the first node, transmits a fifth synchronization signal to the second node, such that the second node receives the fifth synchronization information and transmits a first quantum signal; the probe node, in response to the fourth synchronization signal from the second node, transmits a sixth synchronization signal to the first node, such that the first node receives the sixth synchronization signal and transmits a second quantum signal; the probe node simultaneously receives the first quantum signal and the second quantum signal from the second node; wherein the probe node is connected to the first node via a first channel; the probe node is connected to the second node via a second channel; the optical path sum of the first synchronization signal, the third synchronization signal, the fifth synchronization signal, and the first quantum signal is 2L. A +2L B The optical path sum of the aforementioned second synchronization signal, fourth synchronization signal, sixth synchronization signal, and second quantum signal is 2L. A +2L B ; among which, L A L is the optical path length of the first channel mentioned above. B It is the optical path length of the second channel mentioned above.

[0006] According to embodiments of this disclosure, the method further includes: the first quantum signal and the second quantum signal interfering at the detection node to complete communication.

[0007] According to an embodiment of this disclosure, the detection node simultaneously transmitting a first synchronization signal and a second synchronization signal to a first node and a second node respectively includes: the detection node simultaneously transmitting the first synchronization signal and the second synchronization signal through the first channel and the second channel respectively, so that the first node obtains the first synchronization signal from the first channel and the second node obtains the second synchronization signal from the second channel.

[0008] According to an embodiment of the present disclosure, the detection node, in response to the third synchronization signal from the first node, transmits a fifth synchronization signal to the second node, comprising: the detection node obtaining the third synchronization signal from the first channel, transmitting the fifth synchronization signal through the second channel, so that the second node obtains the fifth synchronization signal from the second channel, and couples the first quantum signal into the second channel.

[0009] According to an embodiment of the present disclosure, the detection node, in response to the fourth synchronization signal from the second node, transmits a sixth synchronization signal to the first node, comprising: the detection node obtaining the fourth synchronization signal from the second channel, transmitting the sixth synchronization signal through the first channel, so that the first node obtains the sixth synchronization signal from the first channel, and couples the second quantum signal into the first channel.

[0010] According to embodiments of this disclosure, the detection node separates the first quantum signal from the second channel and the second quantum signal from the first channel.

[0011] Another aspect of this disclosure provides an apparatus for the above-described quantum key distribution system synchronization method, comprising: a probe node, a first node, and a second node.

[0012] The aforementioned detection node includes: a first laser for transmitting a first synchronization signal to the first node, such that the first node responds to the first synchronization signal and transmits a third synchronization signal; a second laser for transmitting a second synchronization signal to the second node, such that the second node responds to the second synchronization signal and transmits a fourth synchronization signal; a first quantum signal detector for receiving a first quantum signal from the second node; and a second quantum signal detector for receiving a second quantum signal from the first node; the detection node receives the third synchronization signal from the first node and transmits a fifth synchronization signal to the second node; the detection node receives the fourth synchronization signal from the second node and transmits a sixth synchronization signal to the first node.

[0013] The first node includes: a first photodetector for receiving the sixth synchronization signal from the detection node and generating a first trigger signal; and a third laser for responding to the first trigger signal and transmitting the second quantum signal to the detection node.

[0014] The second node includes: a second photodetector for receiving the fifth synchronization signal from the detection node and generating a second trigger signal; and a fourth laser for responding to the second trigger signal and transmitting the first quantum signal to the detection node.

[0015] According to an embodiment of this disclosure, the first node further includes a first reflection device for receiving the first synchronization signal from the detection node and reflecting and outputting the third synchronization signal; the second node further includes a second reflection device for receiving the second synchronization signal from the detection node and reflecting and outputting the fourth synchronization signal.

[0016] According to embodiments of this disclosure, the detection node further includes: a third photodetector for receiving the third synchronization signal and generating a third trigger signal; a fifth laser for responding to the third trigger signal and transmitting the fifth synchronization signal to the second node; a fourth photodetector for receiving the fourth synchronization signal and generating a fourth trigger signal; and a sixth laser for responding to the fourth trigger signal and transmitting the sixth synchronization signal to the first node.

[0017] According to embodiments of this disclosure, the first node further includes: a fifth photodetector, configured to receive the first synchronization signal from the detection node and generate a fifth trigger signal; and a seventh laser, configured to respond to the fifth trigger signal and transmit the third synchronization signal to the detection node; the second node further includes: a sixth photodetector, configured to receive the second synchronization signal from the detection node and generate a fifth trigger signal; and an eighth laser, configured to respond to the fifth trigger signal and transmit the fourth synchronization signal to the detection node.

[0018] According to embodiments of this disclosure, by utilizing the characteristic that different communication nodes have a constant total optical path length for transmitted signals, quantum signals from different communication nodes can simultaneously reach the detection node. The detection node, the first node, and the second node are constructed into a closed-loop bidirectional synchronous signal transmission network through the first channel and the second channel, achieving efficient and stable time synchronization. This ensures good scalability and flexibility even in multi-user network environments, making it suitable for the construction of large-scale, high-precision quantum networks. Attached Figure Description

[0019] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0020] Figure 1 A schematic flowchart illustrating the operation of a synchronization method for a quantum key distribution system according to an embodiment of the present disclosure is shown.

[0021] Figure 2 A schematic diagram of a synchronization device for a quantum key distribution system according to an embodiment of the present disclosure is shown.

[0022] Figure 3 A schematic diagram of a synchronization device for a quantum key distribution system according to another embodiment of the present disclosure is shown; and

[0023] Figure 4 A schematic diagram of a synchronization device for a quantum key distribution system according to another embodiment of the present disclosure is shown. Detailed Implementation

[0024] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0025] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0026] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0027] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0028] With the development of social informatization, people have higher demands for information security. Currently, the security of classical cryptography relies on computational complexity; however, with the development of quantum computing, this classical encryption method will become insecure. Quantum key distribution (QKD) technology provides a method for establishing unconditionally secure keys between communicators, which, combined with "one-time pad," can theoretically achieve unconditional security of information. In particular, the proposal of measurement device-independent protocols has promoted the practical application of quantum key distribution.

[0029] After more than 30 years of development, quantum key distribution technology has become very mature. However, the successful implementation of measurement-device-independent protocols is highly dependent on accurate quantum state interference. This requires that the quantum states emitted by the user arrive at the receiver as simultaneously as possible, thus placing extremely stringent requirements on the accuracy of time synchronization. The accuracy of time synchronization is directly related to the accurate identification and decoding of quantum states; any slight time deviation can introduce bit errors and reduce the key generation rate.

[0030] Several solutions for free space time synchronization have been proposed in related technologies, but they still have some key problems in practical applications:

[0031] On the one hand, achieving global time synchronization in a multi-user network environment is a challenge. Existing solutions often lack effective scalability and flexibility, making it difficult to adapt to the construction requirements of large-scale quantum networks;

[0032] On the other hand, in mobile devices (such as vehicles, airplanes, and ships), the time it takes for light pulses to reach the detector is constantly changing, which poses a great challenge to time synchronization. Existing solutions may result in insufficient stability of time synchronization, affecting the accuracy of time synchronization.

[0033] This disclosure provides a synchronization method and apparatus for a quantum key distribution system, which aims to effectively solve the above-mentioned technical problems.

[0034] Figure 1 A schematic flowchart illustrating the operation of a synchronization method for a quantum key distribution system according to an embodiment of the present disclosure is shown.

[0035] like Figure 1 As shown, the synchronization method of the quantum key distribution system includes operations S110-S140.

[0036] In operation S110, the detection node simultaneously transmits a first synchronization signal and a second synchronization signal to the first node and the second node respectively, so that the first node receives the first synchronization signal and transmits a third synchronization signal, so that the second node receives the second synchronization information and transmits a fourth synchronization signal.

[0037] In operation S120, the probe node responds to the third synchronization signal from the first node and transmits a fifth synchronization signal to the second node, so that the second node receives the fifth synchronization information and transmits the first quantum signal.

[0038] In operation S130, the probe node responds to the fourth synchronization signal from the second node by transmitting a sixth synchronization signal to the first node, so that the first node receives the sixth synchronization signal and transmits a second quantum signal.

[0039] During operation S140, the probe node simultaneously receives the first quantum signal from the second node and the second quantum signal from the first node.

[0040] It should be noted that there is no restriction on the order of operation S120 and operation S130.

[0041] According to embodiments of this disclosure, the detection node is connected to the first node via a first channel; the detection node is connected to the second node via a second channel; the optical path sum of the first synchronization signal, the third synchronization signal, the fifth synchronization signal, and the first quantum signal is 2L. A +2L B The sum of the optical path lengths of the second synchronization signal, the fourth synchronization signal, the sixth synchronization signal, and the second quantum signal is 2L. A +2L B ; among which, L A It is the optical path length of the first channel, L B It is the optical path length of the second channel.

[0042] According to embodiments of this disclosure, the sum of the optical path lengths of the first synchronization signal, the third synchronization signal, the fifth synchronization signal, and the first quantum signal represents the total optical path length of the transmitted signal of the second node. The sum of the optical path lengths of the second synchronization signal, the fourth synchronization signal, the sixth synchronization signal, and the second quantum signal represents the total optical path length of the transmitted signal of the first node. The total optical path length of the transmitted signal of the first node is equal to the total optical path length of the transmitted signal of the second node, so that the detection node can simultaneously receive the first quantum signal and the second quantum signal after simultaneously transmitting the first synchronization signal and the second synchronization signal.

[0043] According to embodiments of this disclosure, when the detection node simultaneously sends a first synchronization signal and a second synchronization signal, and the speed of light is c, the time taken for the first quantum signal and the second quantum signal to reach the detection node is the same (2L). A +2L B ) / c.

[0044] This disclosure constructs a closed-loop bidirectional synchronous signal transmission network, ensuring that the first node and the second node, i.e., different communication nodes, have a constant total optical path for the transmitted signals. This allows the detection node to simultaneously receive the first quantum signal and the second quantum signal after simultaneously transmitting the first synchronization signal and the second synchronization signal. This ensures that even when the distance between different communication nodes is different, their respective quantum signals can be simultaneously delivered to the detection node without calibration, thereby achieving precise synchronization of quantum signals.

[0045] According to embodiments of this disclosure, a first quantum signal and a second quantum signal interfere at a detection node to complete communication.

[0046] According to embodiments of this disclosure, a first quantum signal and a second quantum signal simultaneously enter the detection node and interfere with each other at the detection node, enabling precise identification and decoding of the quantum state to complete communication.

[0047] According to embodiments of this disclosure, the detection node simultaneously transmits a first synchronization signal and a second synchronization signal through a first channel and a second channel, respectively, so that the first node obtains the first synchronization signal from the first channel and the second node obtains the second synchronization signal from the second channel.

[0048] According to embodiments of this disclosure, the detection node uses wavelength division multiplexing (WDM) technology to simultaneously transmit a first synchronization signal and a second synchronization signal through a first channel and a second channel, respectively. The first node uses WDM technology to separate the first synchronization signal from the first channel; the second node uses WDM technology to separate the second synchronization signal from the second channel.

[0049] According to an embodiment of this disclosure, the probe node separates a third synchronization signal from the first channel and transmits a fifth synchronization signal through the second channel, so that the second node separates a fifth synchronization signal from the second channel and couples a first quantum signal into the second channel.

[0050] According to embodiments of this disclosure, the detection node uses wavelength division multiplexing (WDM) technology to separate a third synchronization signal from a first channel, and uses WDM technology to transmit a fifth synchronization signal through a second channel, so that the second node uses WDM technology to separate a fifth synchronization signal from the second channel, and uses WDM technology to couple a first quantum signal into the second channel.

[0051] According to an embodiment of this disclosure, the probe node separates a fourth synchronization signal from the second channel and transmits a sixth synchronization signal through the first channel, so that the first node separates a sixth synchronization signal from the first channel and couples a second quantum signal into the first channel.

[0052] According to embodiments of this disclosure, the detection node uses wavelength division multiplexing (WDM) technology to separate a fourth synchronization signal from a second channel, and uses WDM technology to transmit a sixth synchronization signal through a first channel, so that the first node uses WDM technology to separate a sixth synchronization signal from the first channel, and uses WDM technology to couple a second quantum signal into the first channel.

[0053] According to embodiments of this disclosure, the detection node separates a first quantum signal from the second channel; and separates a second quantum signal from the first channel.

[0054] According to embodiments of this disclosure, the detection node uses wavelength division multiplexing (WDM) technology to separate a first quantum signal from a second channel; and uses WDM technology to separate a second quantum signal from the first channel.

[0055] According to embodiments of this disclosure, wavelength division multiplexing (WDM) technology can be used to compress different synchronization signals into the same channel and separate the quantum signal from the same channel. WDM technology ensures that the first, third, sixth, and second synchronization signals all enter the first channel and are separated from it; it also ensures that the second, fourth, fifth, and first synchronization signals all enter the second channel and are separated from it. This makes the equality of the total optical path length of the transmitted signals at the first node more stable with that at the second node, increasing the stability of the synchronization method in the quantum key distribution system.

[0056] Figure 2 A schematic diagram of a synchronization device for a quantum key distribution system according to an embodiment of the present disclosure is shown.

[0057] like Figure 2 As shown, the device includes a probe node Charlie, a first node Alice, and a second node Bob.

[0058] According to embodiments of this disclosure, the detection node Charlie includes: a first laser A1 for transmitting a first synchronization signal to the first node Alice, such that the first node Alice responds to the first synchronization signal and transmits a third synchronization signal; a second laser B1 for transmitting a second synchronization signal to the second node Bob, such that the second node Bob responds to the second synchronization signal and transmits a fourth synchronization signal; a first quantum signal detector 24 for receiving the first quantum signal from the second node Bob; and a second quantum signal detector 14 for receiving the second quantum signal from the first node Alice.

[0059] According to an embodiment of this disclosure, the probe node Charlie receives a third synchronization signal from the first node Alice and transmits a fifth synchronization signal to the second node Bob; the probe node Charlie receives a fourth synchronization signal from the second node Bob and transmits a sixth synchronization signal to the first node Alice.

[0060] According to embodiments of this disclosure, the first node Alice includes: a first photodetector 13, configured to receive a sixth synchronization signal from the detection node Charlie and generate a first trigger signal; and a third laser A. Q It is used to respond to the first trigger signal and transmit the second quantum signal to the probe node Charlie.

[0061] According to embodiments of this disclosure, the second node Bob includes: a second photodetector 23 for receiving a fifth synchronization signal from the detection node Charlie and generating a second trigger signal; and a fourth laser B. Q It is used to respond to the second trigger signal and transmit the first quantum signal to the probe node Charlie.

[0062] like Figure 2 As shown, L A The optical path length of the first channel is represented by [insert optical path length here]. The first channel includes a first end 11 and a second end 12. The detector node Charlie injects a first synchronization signal and a sixth synchronization signal into the first channel from the first end 11 using laser signals of different wavelengths. The detector node Alice separates the first synchronization signal and the sixth synchronization signal from the second end 12 of the first channel according to the different wavelengths of the laser signals. The first node Alice injects a third synchronization signal and a first quantum signal into the first channel from the second end 12 using laser signals of different wavelengths. The detector node Charlie separates the third synchronization signal and the first quantum signal from the first end 11 of the first channel according to the different wavelengths of the laser signals.

[0063] like Figure 2 As shown, L B The optical path length of the second channel is indicated by the terminator. The second channel includes a first end 21 and a second end 22. The detector node Charlie injects a second synchronization signal and a fifth synchronization signal into the second channel from the first end 21 using laser signals of different wavelengths. The detector node Bob separates the second synchronization signal and the fifth synchronization signal from the second end 22 of the second channel based on the different wavelengths of the laser signals. The second node Bob injects a fourth synchronization signal and a second quantum signal into the second channel from the second end 22 using laser signals of different wavelengths. The detector node Charlie separates the fourth synchronization signal and the second quantum signal from the first end 21 of the second channel based on the different wavelengths of the laser signals.

[0064] like Figure 2 As shown, different signal segment formats indicate that the laser signals belong to different wavelength bands. For example, if the first quantum signal and the second quantum signal belong to the same wavelength band, then the third laser A... Q and the fourth laser B Q The emitted signal uses the same signal segment format as the signals received by the first quantum signal detector 24 and the second quantum signal detector 14.

[0065] According to embodiments of this disclosure, the first end 11 of the first channel, the second end 12 of the first channel, the first end 21 of the second channel, and the second end 22 of the second channel may include wavelength division multiplexers to combine or separate laser signals of different wavelength bands. The first end 11 of the first channel and the first end 21 of the second channel may include circulators to separate laser signals of the same wavelength band. According to embodiments of this disclosure, before the detector node Charlie simultaneously transmits the first synchronization signal and the second synchronization signal to the first node Alice and the second node Bob, respectively, the method further includes: initialization and configuration of the quantum key distribution system synchronization device.

[0066] According to embodiments of this disclosure, the hardware installation and debugging of the synchronization device for a quantum key distribution system are performed. Ensure that the first laser A1, the second laser B1, the first quantum signal detector 24, and the second quantum signal detector 14 are correctly installed at the Charlie end of the detection node; ensure that the first photodetector 13 and the third laser A1 are... Q Correctly installed at the first node Alice end; ensure the second photodetector 23 and the fourth laser B are installed correctly. Q Install correctly at the second node (Bob end). Perform basic functional tests on each device, such as stable emission of each laser and sensitivity adjustment of each photodetector, to ensure that each device is in optimal working condition.

[0067] According to embodiments of this disclosure, network connectivity verification is performed on the synchronization device of the quantum key distribution system. The physical links between the probe node Charlie, the first node Alice, and the second node Bob are checked to ensure proper connectivity, such as line connectivity and signal attenuation.

[0068] According to embodiments of this disclosure, the synchronization device of the quantum key distribution system is performed as follows: Figure 1 The operation of the synchronization method in the quantum key distribution system is shown. The probe node Charlie receives the third synchronization signal and transmits the fifth synchronization signal to the second node Bob via a direct fiber optic connection. The probe node Charlie receives the fourth synchronization signal and transmits the sixth synchronization signal to the first node Alice via a direct fiber optic connection.

[0069] According to embodiments of this disclosure, the probe node Charlie uses wavelength division multiplexing (WDM) to separate a first quantum signal from a second channel; the probe node Charlie also uses WDM to separate a second quantum signal from a first channel. The first quantum signal from the second node Bob and the second quantum signal from the first node Alice interfere at the probe node Charlie.

[0070] According to an embodiment of this disclosure, the probe node Charlie simultaneously receives a first quantum signal from the second node Bob and a second quantum signal from the first node Alice. The probe node Charlie performs interferometric measurements and announces the measurement results, thereby achieving time synchronization of the three user nodes.

[0071] like Figure 2 As shown, the first node Alice also includes a first reflection device 15, which is used to receive the first synchronization signal from the probe node Charlie and reflect and output the third synchronization signal; the second node Bob also includes a second reflection device 25, which is used to receive the second synchronization signal from the probe node Charlie and reflect and output the fourth synchronization signal.

[0072] According to embodiments of this disclosure, the hardware installation and debugging of the synchronization device for the quantum key distribution system further includes: ensuring that the first reflector 15 is correctly installed at the first node Alice end; and ensuring that the second reflector 25 is correctly installed at the second node Bob end. The angles of each reflector are calibrated to ensure that each device is in optimal working condition.

[0073] Figure 3 A schematic diagram of a synchronization device for a quantum key distribution system according to another embodiment of the present disclosure is shown.

[0074] like Figure 3 As shown, the detection node Charlie also includes: a third photodetector 16 for receiving a third synchronization signal and generating a third trigger signal; a fifth laser B2 for responding to the third trigger signal and transmitting a fifth synchronization signal to the second node Bob; a fourth photodetector 26 for receiving a fourth synchronization signal and generating a fourth trigger signal; and a sixth laser A2 for responding to the fourth trigger signal and transmitting a sixth synchronization signal to the first node Alice.

[0075] According to embodiments of this disclosure, the hardware installation and debugging of the synchronization device for the quantum key distribution system further includes: ensuring that the third photodetector 16, the fifth laser B2, the fourth photodetector 26, and the sixth laser A2 are correctly installed at the Charlie end of the detection node. Basic functional tests are performed on each device, such as stable emission of each laser and sensitivity adjustment of each photodetector, to ensure that each device is in optimal working condition.

[0076] Figure 4 A schematic diagram of a synchronization device for a quantum key distribution system according to another embodiment of the present disclosure is shown.

[0077] like Figure 4As shown, the first node Alice also includes: a fifth photodetector 17, used to receive a first synchronization signal from the probe node Charlie and generate a fifth trigger signal; and a seventh laser A0, used to respond to the fifth trigger signal and transmit a third synchronization signal to the probe node Charlie; the second node Bob also includes: a sixth photodetector 27, used to receive a second synchronization signal from the probe node Charlie and generate a fifth trigger signal; and an eighth laser B0, used to respond to the fifth trigger signal and transmit a fourth synchronization signal to the probe node Charlie.

[0078] According to embodiments of this disclosure, the hardware installation and debugging of the quantum key distribution system synchronization device further includes: ensuring that the fifth photodetector 17 and the seventh laser A0 are correctly installed at the first node Alice; and ensuring that the sixth photodetector 27 and the eighth laser B0 are correctly installed at the second node Bob. Basic functional tests are performed on each device, such as stable emission of each laser and sensitivity adjustment of each photodetector, to ensure that each device is in optimal working condition.

[0079] It should be noted that the quantum key distribution system synchronization device part in the embodiments of this disclosure corresponds to the quantum key distribution system synchronization method part in the embodiments of this disclosure. For a detailed description of the quantum key distribution system synchronization device part, please refer to the quantum key distribution system synchronization method part, which will not be repeated here.

[0080] According to embodiments of this disclosure, by constructing a closed-loop bidirectional synchronization signal transmission network, the total optical path of the synchronization signal and the quantum signal between different communication nodes is always equal, achieving a self-compensating effect of time synchronization. The detection node can simultaneously receive quantum signals from different communication nodes after simultaneously sending synchronization signals to them, achieving efficient and stable interference effects.

[0081] The quantum key distribution system synchronization method disclosed herein is calibration-free and possesses excellent scalability and flexibility, easily meeting the communication needs of multi-communication node quantum networks and mobile devices. Each communication node can perform independent time calibration, while simultaneously achieving global synchronization coordination and optimization, facilitating the construction of large-scale, highly reliable quantum communication networks.

[0082] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A synchronization method for a quantum key distribution system, characterized in that, include: The detection node simultaneously transmits a first synchronization signal and a second synchronization signal to the first node and the second node respectively, so that the first node receives the first synchronization signal and transmits a third synchronization signal, so that the second node receives the second synchronization information and transmits a fourth synchronization signal. In response to the third synchronization signal from the first node, the detection node transmits a fifth synchronization signal to the second node, so that the second node receives the fifth synchronization information and transmits a first quantum signal; in response to the fourth synchronization signal from the second node, the detection node transmits a sixth synchronization signal to the first node, so that the first node receives the sixth synchronization signal and transmits a second quantum signal. The detection node simultaneously receives the first quantum signal from the second node and the second quantum signal from the first node; The detection node is connected to the first node via a first channel; the detection node is connected to the second node via a second channel; the optical path sum of the first synchronization signal, the third synchronization signal, the fifth synchronization signal, and the first quantum signal is 2L. A +2L B The optical path sum of the second synchronization signal, the fourth synchronization signal, the sixth synchronization signal, and the second quantum signal is 2L. A +2L B Among them, L A L is the optical path length of the first channel. B It is the optical path length of the second channel.

2. The synchronization method for a quantum key distribution system according to claim 1, characterized in that, Also includes: The first quantum signal and the second quantum signal interfere at the detection node to complete communication.

3. The synchronization method for a quantum key distribution system according to claim 1, characterized in that, The simultaneous transmission of a first synchronization signal and a second synchronization signal from the detection node to the first node and the second node respectively includes: The detection node simultaneously transmits the first synchronization signal and the second synchronization signal through the first channel and the second channel respectively, so that the first node obtains the first synchronization signal from the first channel and the second node obtains the second synchronization signal from the second channel.

4. The synchronization method for a quantum key distribution system according to claim 1, characterized in that, The detection node, in response to the third synchronization signal from the first node, transmits a fifth synchronization signal to the second node, including: The detection node separates the third synchronization signal from the first channel and transmits the fifth synchronization signal through the second channel, so that the second node separates the fifth synchronization signal from the second channel and couples the first quantum signal into the second channel.

5. The synchronization method for a quantum key distribution system according to claim 1, characterized in that, The detection node, in response to the fourth synchronization signal from the second node, transmits a sixth synchronization signal to the first node, including: The detection node separates the fourth synchronization signal from the second channel and transmits the sixth synchronization signal through the first channel, so that the first node separates the sixth synchronization signal from the first channel and couples the second quantum signal into the first channel.

6. The synchronization method for a quantum key distribution system according to claim 1, characterized in that, include: The detection node obtains the first quantum signal from the second channel; and obtains the second quantum signal from the first channel.

7. An apparatus for a synchronization method of a quantum key distribution system according to any one of claims 1-6, characterized in that, include: Detection node, first node, and second node; The detection nodes include: A first laser is used to transmit a first synchronization signal to the first node, so that the first node responds to the first synchronization signal and transmits a third synchronization signal; A second laser is used to transmit a second synchronization signal to the second node, so that the second node responds to the second synchronization signal and transmits a fourth synchronization signal; A first quantum signal detector is used to receive a first quantum signal from the second node; and A second quantum signal detector is used to receive a second quantum signal from the first node; The detection node receives the third synchronization signal from the first node and transmits the fifth synchronization signal to the second node; the detection node receives the fourth synchronization signal from the second node and transmits the sixth synchronization signal to the first node. The first node includes: A first photodetector is configured to receive the sixth synchronization signal from the detection node and generate a first trigger signal; and A third laser is used to respond to the first trigger signal and emit the second quantum signal to the detection node; The second node includes: A second photodetector is used to receive the fifth synchronization signal from the detection node and generate a second trigger signal; and A fourth laser is used to respond to the second trigger signal and emit the first quantum signal to the detection node.

8. The apparatus according to claim 7, characterized in that: The first node further includes a first reflection device for receiving the first synchronization signal from the detection node and reflecting and outputting the third synchronization signal; The second node further includes a second reflection device for receiving the second synchronization signal from the detection node and reflecting and outputting the fourth synchronization signal.

9. The apparatus according to claim 7, characterized in that, The detection nodes also include: A third photodetector is used to receive the third synchronization signal and generate a third trigger signal; A fifth laser is used to respond to the third trigger signal and transmit the fifth synchronization signal to the second node; A fourth photodetector is used to receive the fourth synchronization signal and generate a fourth trigger signal; and A sixth laser is used to respond to the fourth trigger signal and to transmit the sixth synchronization signal to the first node.

10. The apparatus according to claim 7, characterized in that: The first node also includes: A fifth photodetector is configured to receive the first synchronization signal from the detection node and generate a fifth trigger signal; and A seventh laser is used to respond to the fifth trigger signal and to transmit the third synchronization signal to the detection node; The second node also includes: A sixth photodetector is used to receive the second synchronization signal from the detection node and generate a fifth trigger signal; and The eighth laser is used to respond to the fifth trigger signal and to transmit the fourth synchronization signal to the detection node.

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