A bidirectional ring quantum channel multi-user quantum time synchronization system and method

Abstract

The application discloses a kind of two-way annular quantum channel multi-user quantum time synchronization systems, including reference site, first annular quantum channel, second annular quantum channel and multiple user nodes;The application also discloses a kind of two-way annular quantum channel multi-user quantum time synchronization method, based on the two-way annular quantum channel multi-user quantum time synchronization system implementation.The application discloses a kind of two-way annular quantum channel multi-user quantum time synchronization system and method, time synchronization is carried out by setting double annular quantum channel, and each annular quantum channel is used for signal transmission in different directions respectively, avoid the interference of two directions of optical signal to each other, then more accurate synchronization correction is realized by combining the double clock difference under two independent direction transmission path, so as to improve the precision and stability of time synchronization, can be applied to quantum inertial navigation and quantum time synchronization technical field.

Description

Technical Field

[0001] This invention relates to the field of quantum inertial navigation and quantum time synchronization technology, specifically to a two-way ring quantum channel multi-user quantum time synchronization system and method. Background Technology

[0002] The large-scale application of quantum inertial navigation combined with BeiDou is a national strategic initiative. Time synchronization technology is fundamental to modern communication, navigation, distributed computing, and quantum networks. Its core objective is to establish a unified and high-precision time or frequency reference for widely distributed user nodes. Traditional time synchronization methods have been widely used within a certain range of accuracy, but their synchronization accuracy and security face serious bottlenecks in complex environments, high security requirements, or cutting-edge fields such as quantum communication.

[0003] Quantum inertial navigation technology is a high-precision (time and displacement) autonomous navigation system based on quantum mechanical principles (such as atomic interference and cold atom manipulation).

[0004] Quantum time synchronization technology, by utilizing the nonlocal time correlation of entangled photons, can not only break through the classical limit of synchronization accuracy, but also has the inherent advantages of being resistant to eavesdropping and interference, making it a key supporting technology for building a reliable time network in the future.

[0005] In existing quantum time synchronization technologies, the clock difference between two nodes is often obtained through a single path, which may introduce errors and randomness. Ring-structured quantum networks, due to their symmetry, allow signals to propagate in both clockwise and counterclockwise directions, thus providing more paths. However, a single ring structure, due to phase drift and other factors, may experience interference between clockwise and counterclockwise signals, interfering with time measurements and reducing synchronization accuracy. Summary of the Invention

[0006] To address the problem of reduced synchronization accuracy caused by the use of a single ring structure in existing quantum time synchronization technologies, this invention provides a bidirectional ring quantum channel multi-user quantum time synchronization system and method.

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

[0008] A bidirectional ring quantum channel multi-user quantum time synchronization system includes a reference station, a first ring quantum channel, a second ring quantum channel, and multiple user nodes; wherein,

[0009] The reference station is used to generate entangled photon pairs, separate the entangled photon pairs to obtain signal light and idle light; and split the signal light into a first signal light and a second signal light.

[0010] The first signal light and the second signal light are transmitted to the corresponding user nodes along the first ring quantum channel and the second ring quantum channel, respectively, and the transmission direction of the first signal light in the first ring quantum channel is different from that of the second signal light in the second ring quantum channel (i.e., clockwise and counterclockwise).

[0011] The user node is used to split the first signal light and the second signal light into beams, corresponding to first signal light A, first signal light B, second signal light A and second signal light B;

[0012] The first signal light B and the second signal light B are transmitted back to the reference station along the first ring quantum channel and the second ring quantum channel, respectively, and the transmission direction of the first signal light B in the first ring quantum channel is different from the transmission direction of the second signal light B in the second ring quantum channel.

[0013] The reference station is also used to perform time detection on the idle light, the first signal light B, and the second signal light B, respectively.

[0014] The user node is also used to perform time detection on the first signal light A and the second signal light A, respectively;

[0015] The user node's clock to be synchronized is adjusted until the difference between the first clock difference and the second clock difference between the reference station and the user node is 0. Then, the reference station and the user node are time-synchronized according to any clock difference. The first clock difference and the second clock difference are calculated based on the time detection results and the time difference of the signal light transmission in the first ring quantum channel and the second ring quantum channel.

[0016] In the above scheme, time synchronization is achieved by setting up dual-ring quantum channels, with each ring quantum channel used for signal transmission in different directions, thus avoiding interference between the optical signals in the two directions. Then, by combining the dual clock differences under the two independent transmission paths, more accurate synchronization correction is achieved, thereby improving the accuracy and stability of time synchronization.

[0017] Preferably, the reference station includes an entangled light source, an entangled light separation module, a first beam splitter, a first single-photon detector, a first event timer, and a reference clock; wherein,

[0018] The entangled light source is used to generate entangled photon pairs;

[0019] The entangled light separation module is used to separate entangled photon pairs to obtain signal light and idle light;

[0020] The first beam splitter is used to split the signal light into a first signal light and a second signal light; and input the first signal light into a first ring quantum channel and the second signal light into a second ring quantum channel;

[0021] The first single-photon detector is used to detect the idle light, the first signal light B, and the second signal light B, respectively.

[0022] The first event timer is used to convert the output of the first single-photon detector into a time signal;

[0023] The reference clock is used as a time reference for user nodes to be synchronized.

[0024] Preferably, the user node includes a first wavelength selection switch, a second wavelength selection switch, a second beam splitter, a third beam splitter, a second single-photon detector, a second event timer, and a clock to be synchronized; wherein,

[0025] The first wavelength selection switch is used to send the first signal light, which is transmitted in the first ring quantum channel and belongs to a specified wavelength, to the second beam splitter, and to allow the first signal light, which does not belong to the specified wavelength, to continue to transmit along the original path.

[0026] The second wavelength selection switch is used to send the second signal light, which is transmitted in the second ring quantum channel and belongs to a specified wavelength, to the third beam splitter, and to allow the second signal light, which does not belong to the specified wavelength, to continue to transmit along the original path.

[0027] The second beam splitter is used to split the first signal light into first signal light A and first signal light B, and input the first signal light B into the first ring quantum channel;

[0028] The third beam splitter is used to split the second signal light into second signal light A and second signal light B, and input the second signal light B into the second ring quantum channel;

[0029] The second single-photon detector is used to detect the first signal light A and the second signal light A, respectively;

[0030] The second event timer is used to convert the output of the second single-photon detector into a time signal;

[0031] The clock to be synchronized is used as the local time reference for user nodes.

[0032] Preferably, the first clock difference between the base station and user node j is calculated using the following formula. :

[0033]

[0034] in, To detect the time of idle light, To determine the time of detection of the first signal light A, To determine the time of detection of the second signal light A, To determine the time of detection of the second signal light B, Let be the arc length traversed by the first signal light as it travels from the reference station to the user node j. Let be the arc length that the second signal light B travels from user node j to the reference station, and c be the speed of light.

[0035] Preferably, the second clock difference between the reference station and user node j is calculated using the following formula. :

[0036]

[0037] in, To detect the time of idle light, To determine the time of detection of the first signal light A, To determine the time of detection of the second signal light A, To determine the time of detection of the first signal light B, Let be the arc length traversed by the second signal light as it travels from the reference station to the user node j. Let be the arc length traversed by the first signal light B from user node j to the reference station, and c be the speed of light.

[0038] Preferably, taking user node j as an example, when the difference between the first clock difference and the second clock difference between the base station and user node j is not 0, the clock to be synchronized for user node j is adjusted to:

[0039] ,or

[0040] Until the difference between the first clock difference and the second clock difference between the base station and user node j is 0;

[0041] in, Let j be the time before the adjustment of user node j. Let j be the first clock difference between the base station and user node j. The second clock difference between the reference station and user node j. This is the difference between the first clock difference and the second clock difference, i.e. .

[0042] A method for multi-user quantum time synchronization via a bidirectional ring quantum channel, implemented based on the aforementioned bidirectional ring quantum channel multi-user quantum time synchronization system, includes the following steps:

[0043] S1: Entangled photon pairs are generated and separated at the reference station to obtain signal light and idle light;

[0044] S2: Split the signal light at the reference station to obtain the first signal light and the second signal light, and perform time detection on the idle light;

[0045] S3: Transmit the first signal light and the second signal light along the first ring quantum channel and the second ring quantum channel respectively to the corresponding user nodes;

[0046] The transmission direction of the first signal light in the first ring quantum channel is different from that of the second signal light in the second ring quantum channel.

[0047] S4: At the user node, the first signal light and the second signal light are split into beams respectively to obtain the first signal light A, the first signal light B, the second signal light A and the second signal light B;

[0048] S5: The user node performs time detection on the first signal light A and the second signal light A respectively, and sends the first signal light B and the second signal light B back to the reference station along the first ring quantum channel and the second ring quantum channel respectively;

[0049] The transmission direction of the first signal light B in the first ring quantum channel is different from that of the second signal light B in the second ring quantum channel.

[0050] S6: The reference station performs time detection on the first signal light B and the second signal light B respectively;

[0051] S7: Based on the time detection results and the time difference between the transmission of signal light in the first and second ring quantum channels, calculate the first clock difference and the second clock difference between the reference station and the user node;

[0052] S8: Determine whether the difference between the first clock difference and the second clock difference is 0;

[0053] If so, proceed to step S9;

[0054] If not, adjust the user node's clock to be synchronized and return to step S1;

[0055] S9: Synchronize the time between the base station and the user node based on any clock difference.

[0056] Preferably, in step S7, the first clock difference between the reference station and user node j is calculated using the following formula. :

[0057]

[0058] in, To detect the time of idle light, To determine the time of detection of the first signal light A, To determine the time of detection of the second signal light A, To determine the time of detection of the second signal light B, Let be the arc length traversed by the first signal light as it travels from the reference station to the user node j. Let be the arc length that the second signal light B travels from user node j to the reference station, and c be the speed of light.

[0059] Preferably, in step S7, the second clock difference between the reference station and user node j is calculated using the following formula. :

[0060]

[0061] in, To detect the time of idle light, To determine the time of detection of the first signal light A, To determine the time of detection of the second signal light A, To determine the time of detection of the first signal light B, Let be the arc length traversed by the second signal light as it travels from the reference station to the user node j. Let be the arc length traversed by the first signal light B from user node j to the reference station, and c be the speed of light.

[0062] Preferably, in step S8, adjusting the user node's clock to be synchronized specifically involves:

[0063] Taking user node j as an example, the clock to be synchronized for user node j is adjusted as follows:

[0064] ,or

[0065] in, Let j be the time before the adjustment of user node j. Let j be the first clock difference between the base station and user node j. The second clock difference between the reference station and user node j. This is the difference between the first clock difference and the second clock difference, i.e. .

[0066] Beneficial technical effects of the present invention:

[0067] This invention provides a bidirectional ring quantum channel multi-user quantum time synchronization system and method. By setting up dual ring quantum channels for time synchronization, and each ring quantum channel is used for signal transmission in different directions, the interference between the optical signals in the two directions is avoided. Then, by combining the dual clock differences under the two independent transmission paths, more accurate synchronization correction is achieved, thereby improving the accuracy and stability of time synchronization. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of the overall framework of the present invention;

[0069] Figure 2 This is a schematic diagram of the structure of the reference station in this invention;

[0070] Figure 3 This is a schematic diagram of the user node structure in this invention;

[0071] Figure 4 This is a flowchart illustrating the implementation steps of the technical solution of the present invention. Detailed Implementation

[0072] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. However, the scope of protection of this invention is not limited to the specific embodiments described below.

[0073] Example 1

[0074] like Figure 1 As shown, a bidirectional ring quantum channel multi-user quantum time synchronization system includes a reference station, a first ring quantum channel, a second ring quantum channel, and multiple user nodes (including user node 1, user node 2, user node 3, ..., user node ...). ..., user nodes );in,

[0075] The reference station is used to generate entangled photon pairs, separate the entangled photon pairs to obtain signal light and idle light; and split the signal light into a first signal light and a second signal light.

[0076] The first signal light and the second signal light are transmitted along the first ring quantum channel and the second ring quantum channel, respectively, to the corresponding user nodes, and the transmission direction of the first signal light in the first ring quantum channel is different from the transmission direction of the second signal light in the second ring quantum channel.

[0077] The user node is used to split the first signal light and the second signal light into beams, corresponding to first signal light A, first signal light B, second signal light A and second signal light B;

[0078] The first signal light B and the second signal light B are transmitted back to the reference station along the first ring quantum channel and the second ring quantum channel, respectively, and the transmission direction of the first signal light B in the first ring quantum channel is different from the transmission direction of the second signal light B in the second ring quantum channel.

[0079] Figure 1The size difference between the first and second ring quantum channels shown is for illustrative purposes only and is intended to aid understanding. In practice, the first and second ring quantum channels can be set to have the same size, or the first ring quantum channel can be larger or smaller than the second ring quantum channel. Similarly, the clockwise and counterclockwise transmission directions of the first and second ring quantum channels are also for illustrative purposes only and can be interchanged in practice.

[0080] The reference station is also used to perform time detection on the idle light, the first signal light B, and the second signal light B, respectively.

[0081] The user node is also used to perform time detection on the first signal light A and the second signal light A, respectively;

[0082] The user node's clock to be synchronized is adjusted until the difference between the first clock difference and the second clock difference between the reference station and the user node is 0. Then, the reference station and the user node are time-synchronized according to any clock difference. The first clock difference and the second clock difference are calculated based on the time detection results and the time difference of the signal light transmission in the first ring quantum channel and the second ring quantum channel.

[0083] In the specific implementation process, time synchronization is achieved by setting up dual-ring quantum channels, with each ring quantum channel used for signal transmission in different directions, thus avoiding interference between the optical signals in the two directions. Then, by combining the dual clock differences under the two independent transmission paths, more accurate synchronization correction is achieved, thereby improving the accuracy and stability of time synchronization.

[0084] Example 2

[0085] A bidirectional ring quantum channel multi-user quantum time synchronization system includes a reference station, a first ring quantum channel, a second ring quantum channel, and multiple user nodes (including user node 1, user node 2, user node 3, ..., user node j, ..., user node N).

[0086] More specifically, such as Figure 2 As shown, the reference station includes an entangled light source, an entangled light separation module, a first beam splitter, a first single-photon detector, a first event timer, and a reference clock; wherein,

[0087] The entangled light source is used to generate entangled photon pairs;

[0088] The entangled light separation module is used to separate entangled photon pairs to obtain signal light and idle light;

[0089] The first beam splitter is used to split the signal light into a first signal light and a second signal light; and input the first signal light into a first ring quantum channel and the second signal light into a second ring quantum channel;

[0090] The first signal light and the second signal light are transmitted along the first ring quantum channel and the second ring quantum channel, respectively, to the corresponding user nodes, and the transmission direction of the first signal light in the first ring quantum channel is different from the transmission direction of the second signal light in the second ring quantum channel.

[0091] The first single-photon detector is used to detect the idle light, the first signal light B, and the second signal light B, respectively.

[0092] The first event timer is used to convert the output of the first single-photon detector into a time signal;

[0093] The reference clock is used as a time reference for user nodes to be synchronized.

[0094] In practice, the entangled light source is used to generate several pairs of entangled photons of different wavelengths, and each wavelength has a unique matching user node.

[0095] More specifically, such as Figure 3 As shown, the user node includes a first wavelength selection switch, a second wavelength selection switch, a second beam splitter, a third beam splitter, a second single-photon detector, a second event timer, and a clock to be synchronized; wherein,

[0096] The first wavelength selection switch is used to send the first signal light, which is transmitted in the first ring quantum channel and belongs to a specified wavelength, to the second beam splitter, and to allow the first signal light, which does not belong to the specified wavelength, to continue to transmit along the original path.

[0097] The second wavelength selection switch is used to send the second signal light, which is transmitted in the second ring quantum channel and belongs to a specified wavelength, to the third beam splitter, and to allow the second signal light, which does not belong to the specified wavelength, to continue to transmit along the original path.

[0098] The second beam splitter is used to split the first signal light into first signal light A and first signal light B, and input the first signal light B into the first ring quantum channel;

[0099] The third beam splitter is used to split the second signal light into second signal light A and second signal light B, and input the second signal light B into the second ring quantum channel;

[0100] The first signal light B and the second signal light B are transmitted back to the reference station along the first ring quantum channel and the second ring quantum channel, respectively, and the transmission direction of the first signal light B in the first ring quantum channel is different from the transmission direction of the second signal light B in the second ring quantum channel.

[0101] The second single-photon detector is used to detect the first signal light A and the second signal light A, respectively;

[0102] The second event timer is used to convert the output of the second single-photon detector into a time signal;

[0103] The clock to be synchronized is used as the local time reference for user nodes;

[0104] The user node's clock to be synchronized is adjusted until the difference between the first clock difference and the second clock difference between the reference station and the user node is 0. Then, the reference station and the user node are time synchronized according to any clock difference. The first clock difference and the second clock difference are calculated based on the time detection results and the time difference between the transmission of signal light in the first ring quantum channel and the second ring quantum channel.

[0105] Figure 2 The transmission directions of the first and second ring quantum channels indicated in the diagram are clockwise and counterclockwise, respectively, for illustrative purposes only and can be interchanged in practice.

[0106] More specifically, the first clock difference between the base station and user node j is calculated using the following formula. :

[0107]

[0108] in, To detect the time of idle light, To determine the time of detection of the first signal light A, To determine the time of detection of the second signal light A, To determine the time of detection of the second signal light B, Let be the arc length traversed by the first signal light as it travels from the reference station to the user node j. Let B be the arc length traversed by the second signal light B from user node j to the reference station. for and The absolute value of the difference, where c is the speed of light.

[0109] More specifically, the second clock difference between the reference station and user node j is calculated using the following formula. :

[0110]

[0111] in, To detect the time of idle light, To determine the time of detection of the first signal light A, To determine the time of detection of the second signal light A, To determine the time of detection of the first signal light B, Let be the arc length traversed by the second signal light as it travels from the reference station to the user node j. Let B be the arc length traversed by the first signal light B from user node j to the reference station. for and The absolute value of the difference, where c is the speed of light.

[0112] In practical implementation, if the reference station and multiple user nodes are uniformly distributed on both the first and second ring quantum channels, then

[0113] The first clock difference between the base station and user node j can be calculated using the following formula. :

[0114]

[0115] The second clock difference between the base station and user node j can be calculated using the following formula. :

[0116]

[0117] in, Let be the radius of the first ring quantum channel. Let N be the radius of the second ring quantum channel, and N be the total number of user nodes.

[0118] More specifically, taking user node j as an example, when the difference between the first clock difference and the second clock difference between the base station and user node j is not zero, the clock to be synchronized for user node j is adjusted each time as follows:

[0119] ,or

[0120] Until the difference between the first clock difference and the second clock difference between the base station and user node j is 0;

[0121] in, Let j be the time before the adjustment of user node j. Let j be the first clock difference between the base station and user node j. The second clock difference between the reference station and user node j. This is the difference between the first clock difference and the second clock difference, i.e. .

[0122] Example 3

[0123] like Figure 4 As shown, a bidirectional ring quantum channel multi-user quantum time synchronization method, implemented based on the aforementioned bidirectional ring quantum channel multi-user quantum time synchronization system, includes the following steps:

[0124] S1: Entangled photon pairs are generated and separated at the reference station to obtain signal light and idle light;

[0125] S2: Split the signal light at the reference station to obtain the first signal light and the second signal light, and perform time detection on the idle light;

[0126] S3: Transmit the first signal light and the second signal light along the first ring quantum channel and the second ring quantum channel respectively to the corresponding user nodes;

[0127] The transmission direction of the first signal light in the first ring quantum channel is different from that of the second signal light in the second ring quantum channel.

[0128] S4: At the user node, the first signal light and the second signal light are split into beams respectively to obtain the first signal light A, the first signal light B, the second signal light A and the second signal light B;

[0129] S5: The user node performs time detection on the first signal light A and the second signal light A respectively, and sends the first signal light B and the second signal light B back to the reference station along the first ring quantum channel and the second ring quantum channel respectively;

[0130] The transmission direction of the first signal light B in the first ring quantum channel is different from that of the second signal light B in the second ring quantum channel.

[0131] S6: The reference station performs time detection on the first signal light B and the second signal light B respectively;

[0132] S7: Based on the time detection results and the time difference between the transmission of signal light in the first and second ring quantum channels, calculate the first clock difference and the second clock difference between the reference station and the user node;

[0133] S8: Determine whether the difference between the first clock difference and the second clock difference is 0;

[0134] If so, proceed to step S9;

[0135] If not, adjust the user node's clock to be synchronized and return to step S1;

[0136] S9: Synchronize the time between the base station and the user node based on any clock difference.

[0137] More specifically, in step S7, the first clock difference between the reference station and user node j is calculated using the following formula. :

[0138]

[0139] in, To detect the time of idle light, To determine the time of detection of the first signal light A, To determine the time of detection of the second signal light A, To determine the time of detection of the second signal light B, Let be the arc length traversed by the first signal light as it travels from the reference station to the user node j. Let be the arc length that the second signal light B travels from user node j to the reference station, and c be the speed of light.

[0140] More specifically, in step S7, the second clock difference between the reference station and user node j is calculated using the following formula. :

[0141]

[0142] in, To detect the time of idle light, To determine the time of detection of the first signal light A, To determine the time of detection of the second signal light A, To determine the time of detection of the first signal light B, Let be the arc length traversed by the second signal light as it travels from the reference station to the user node j. Let be the arc length traversed by the first signal light B from user node j to the reference station, and c be the speed of light.

[0143] More specifically, in step S8, adjusting the user node's clock to be synchronized involves:

[0144] Taking user node j as an example, the clock to be synchronized for user node j is adjusted as follows:

[0145] ,or

[0146] in, Let j be the time before the adjustment of user node j. Let j be the first clock difference between the base station and user node j. The second clock difference between the reference station and user node j. This is the difference between the first clock difference and the second clock difference, i.e. .

[0147] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A bidirectional ring quantum channel multi-user quantum time synchronization system, characterized in that, It includes a reference station, a first ring quantum channel, a second ring quantum channel, and multiple user nodes; among which, The reference station is used to generate entangled photon pairs, separate the entangled photon pairs to obtain signal light and idle light; and split the signal light into a first signal light and a second signal light. The first signal light and the second signal light are transmitted along the first ring quantum channel and the second ring quantum channel, respectively, to the corresponding user nodes, and the transmission direction of the first signal light in the first ring quantum channel is different from the transmission direction of the second signal light in the second ring quantum channel. The user node is used to split the first signal light and the second signal light into beams, corresponding to first signal light A, first signal light B, second signal light A and second signal light B; The first signal light B and the second signal light B are transmitted back to the reference station along the first ring quantum channel and the second ring quantum channel, respectively, and the transmission direction of the first signal light B in the first ring quantum channel is different from the transmission direction of the second signal light B in the second ring quantum channel. The reference station is also used to perform time detection on the idle light, the first signal light B, and the second signal light B, respectively. The user node is also used to perform time detection on the first signal light A and the second signal light A, respectively; The user node's clock to be synchronized is adjusted until the difference between the first clock difference and the second clock difference between the reference station and the user node is 0. Then, the reference station and the user node are time-synchronized according to any clock difference. The first clock difference and the second clock difference are calculated based on the time detection results and the time difference of the signal light transmission in the first ring quantum channel and the second ring quantum channel.

2. The bidirectional ring quantum channel multi-user quantum time synchronization system according to claim 1, characterized in that, The reference station includes an entangled light source, an entangled light separation module, a first beam splitter, a first single-photon detector, a first event timer, and a reference clock; wherein, The entangled light source is used to generate entangled photon pairs; The entangled light separation module is used to separate entangled photon pairs to obtain signal light and idle light; The first beam splitter is used to split the signal light into a first signal light and a second signal light; and input the first signal light into a first ring quantum channel and the second signal light into a second ring quantum channel; The first single-photon detector is used to detect the idle light, the first signal light B, and the second signal light B, respectively. The first event timer is used to convert the output of the first single-photon detector into a time signal; The reference clock is used as a time reference for user nodes to be synchronized.

3. The bidirectional ring quantum channel multi-user quantum time synchronization system according to claim 1, characterized in that, The user node includes a first wavelength selection switch, a second wavelength selection switch, a second beam splitter, a third beam splitter, a second single-photon detector, a second event timer, and a clock to be synchronized; wherein, The first wavelength selection switch is used to send the first signal light, which is transmitted in the first ring quantum channel and belongs to a specified wavelength, to the second beam splitter, and to allow the first signal light, which does not belong to the specified wavelength, to continue to transmit along the original path. The second wavelength selection switch is used to send the second signal light, which is transmitted in the second ring quantum channel and belongs to a specified wavelength, to the third beam splitter, and to allow the second signal light, which does not belong to the specified wavelength, to continue to transmit along the original path. The second beam splitter is used to split the first signal light into first signal light A and first signal light B, and input the first signal light B into the first ring quantum channel; The third beam splitter is used to split the second signal light into second signal light A and second signal light B, and input the second signal light B into the second ring quantum channel; The second single-photon detector is used to detect the first signal light A and the second signal light A, respectively; The second event timer is used to convert the output of the second single-photon detector into a time signal; The clock to be synchronized is used as the local time reference for user nodes.

4. The bidirectional ring quantum channel multi-user quantum time synchronization system according to claim 1, characterized in that, The first clock difference between the base station and user node j is calculated using the following formula. : ； in, To detect the time of idle light, To determine the time of detection of the first signal light A, To determine the time of detection of the second signal light A, To determine the time of detection of the second signal light B, Let be the arc length traversed by the first signal light as it travels from the reference station to the user node j. Let be the arc length that the second signal light B travels from user node j to the reference station, and c be the speed of light.

5. A bidirectional ring quantum channel multi-user quantum time synchronization system according to claim 1, characterized in that, The second clock difference between the base station and user node j is calculated using the following formula. : ； in, To detect the time of idle light, To determine the time of detection of the first signal light A, To determine the time of detection of the second signal light A, To determine the time of detection of the first signal light B, Let be the arc length traversed by the second signal light as it travels from the reference station to the user node j. Let be the arc length traversed by the first signal light B from user node j to the reference station, and c be the speed of light.

6. A bidirectional ring quantum channel multi-user quantum time synchronization system according to claim 1, characterized in that, Taking user node j as an example, when the difference between the first clock difference and the second clock difference between the base station and user node j is not 0, the clock to be synchronized for user node j is adjusted to: ,or ; Until the difference between the first clock difference and the second clock difference between the base station and user node j is 0; in, Let j be the time before the adjustment of user node j. Let j be the first clock difference between the base station and user node j. The second clock difference between the reference station and user node j. This is the difference between the first clock difference and the second clock difference, i.e. .

7. A method for multi-user quantum time synchronization via a bidirectional ring quantum channel, characterized in that, Includes the following steps: S1: Entangled photon pairs are generated and separated at the reference station to obtain signal light and idle light; S2: Split the signal light at the reference station to obtain the first signal light and the second signal light, and perform time detection on the idle light; S3: Transmit the first signal light and the second signal light along the first ring quantum channel and the second ring quantum channel respectively to the corresponding user nodes; The transmission direction of the first signal light in the first ring quantum channel is different from that of the second signal light in the second ring quantum channel. S4: At the user node, the first signal light and the second signal light are split into beams respectively to obtain the first signal light A, the first signal light B, the second signal light A and the second signal light B; S5: The user node performs time detection on the first signal light A and the second signal light A respectively, and sends the first signal light B and the second signal light B back to the reference station along the first ring quantum channel and the second ring quantum channel respectively; The transmission direction of the first signal light B in the first ring quantum channel is different from that of the second signal light B in the second ring quantum channel. S6: The reference station performs time detection on the first signal light B and the second signal light B respectively; S7: Based on the time detection results and the time difference between the transmission of signal light in the first and second ring quantum channels, calculate the first clock difference and the second clock difference between the reference station and the user node; S8: Determine whether the difference between the first clock difference and the second clock difference is 0; If so, proceed to step S9; If not, adjust the user node's clock to be synchronized and return to step S1; S9: Synchronize the time between the base station and the user node based on any clock difference.

8. A method for multi-user quantum time synchronization in a bidirectional ring quantum channel according to claim 7, characterized in that, In step S7, the first clock difference between the reference station and user node j is calculated using the following formula. : ； in, To detect the time of idle light, To determine the time of detection of the first signal light A, To determine the time of detection of the second signal light A, To determine the time of detection of the second signal light B, Let be the arc length traversed by the first signal light as it travels from the reference station to the user node j. Let be the arc length that the second signal light B travels from user node j to the reference station, and c be the speed of light.

9. A method for multi-user quantum time synchronization in a bidirectional ring quantum channel according to claim 7, characterized in that, In step S7, the second clock difference between the reference station and user node j is calculated using the following formula. : ； in, To detect the time of idle light, To determine the time of detection of the first signal light A, To determine the time of detection of the second signal light A, To determine the time of detection of the first signal light B, Let be the arc length traversed by the second signal light as it travels from the reference station to the user node j. Let be the arc length traversed by the first signal light B from user node j to the reference station, and c be the speed of light.

10. A method for multi-user quantum time synchronization in a bidirectional ring quantum channel according to claim 7, characterized in that, In step S8, adjusting the user node's clock to be synchronized specifically involves: Taking user node j as an example, the clock to be synchronized for user node j is adjusted as follows: ,or ; in, Let j be the time before the adjustment of user node j. Let j be the first clock difference between the base station and user node j. The second clock difference between the reference station and user node j. This is the difference between the first clock difference and the second clock difference, i.e. .

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