A simplified bidirectional quantum time synchronization reference clock station device, system and method

Abstract

The present invention discloses a simplified bidirectional quantum time synchronization reference clock station device, system, and method. The system includes a reference clock station device and a station device to be synchronized. The reference clock station device includes: a frequency-entangled two-photon source, a first beam splitter, a first circulator, a first polarization beam splitter, a polarization beam combiner, a first single-photon detector, a first event timer, and a reference clock; the station device to be synchronized includes a second circulator, a third circulator, a fiber Faraday rotator, a second polarization beam splitter, a second single-photon detector, a second event timer, a clock to be synchronized, and a data processing terminal. The present invention uses the same entangled two-photon source as the quantum light source to avoid the impact of low frequency consistency of two frequency-entangled two-photon sources on synchronization accuracy in existing solutions. Reducing the number of single-photon detectors also reduces the impact of inherent detector jitter on synchronization error, thereby further improving the accuracy of quantum time synchronization.

Description

Technical Field

[0001] The present invention belongs to the field of time and frequency technology, and in particular relates to a simplified bidirectional quantum time synchronization reference clock station device, system and method. Background Art

[0002] Quantum time synchronization is a new time synchronization technology proposed at the beginning of this century. Leveraging frequency-entangled quantum light pulses and quantum coincidence detection, quantum time synchronization surpasses the classical shot noise limit in time synchronization accuracy while also exhibiting dispersion resistance. A simplified bidirectional quantum time synchronization technology based on a frequency-entangled source has been proposed, which can improve the accuracy of practical timing systems, particularly those based on fiber-optic links, by 2-3 orders of magnitude, reaching sub-picosecond or even femtosecond precision. Furthermore, compared to classical time synchronization, this simplified bidirectional quantum time synchronization technology, combined with the quantum non-cloning property, can also ensure the security of time synchronization.

[0003] Existing simplified bidirectional quantum time synchronization schemes require a frequency-entangled two-photon source and two single-photon detectors at each location to be synchronized. As quantum time synchronization technology continues to advance towards practical applications, there is a need to further simplify the time synchronization system to reduce system size and power consumption. Furthermore, to achieve high quantum time transfer and measurement accuracy, existing simplified bidirectional quantum time synchronization schemes require high frequency consistency between the two two-photon sources and minimal inherent delay between the four detectors. Consequently, existing schemes are complex in structure and have high environmental requirements. Summary of the Invention

[0004] To address the aforementioned issues in the prior art, the present invention provides a simplified bidirectional quantum time synchronization reference clock station device, system, and method. The technical issues addressed by the present invention are achieved through the following technical solutions:

[0005] A simplified bidirectional quantum time synchronization system includes a reference clock site device and a site device to be synchronized, wherein the reference clock site device includes: a frequency entangled two-photon source connected to the input end of a first beam splitter; a first output end of the first beam splitter connected to a first circulator interface a, and a second output end connected to a first polarization beam splitter; the first polarization beam splitter is connected to the first input end of the polarization beam combiner; the first circulator interface b is connected to a remote end device via an optical fiber link, and interface c is connected to the second input end of the polarization beam combiner; the output end of the polarization beam combiner is connected to a first single-photon detector, the first single-photon detector is connected to a first event timer, and the first event timer is connected to a reference clock;

[0006] The site equipment to be synchronized includes a second circulator, wherein the second circulator interface a is connected to the first circulator interface b, and the interface b is connected to the third circulator interface a; the third circulator interface b outputs an optical signal to the fiber Faraday rotator, and the interface c is connected to the input end of the second polarization beam splitter; the first output end of the second polarization beam splitter is connected to the second single-photon detector; the second output end is connected to the second circulator interface c; the second single-photon detector is connected to the second event timer, and the second event timer is connected to the clock to be synchronized; the data processing terminal is connected to the first event timer and the second event timer via a communication link; a programming delay is connected to the data processing terminal, and the clock to be synchronized is connected to the programming delay.

[0007] In a specific embodiment, the splitting ratio of the first beam splitter is 10:90, and 90% of the light beam is output to the first circulator.

[0008] In a specific embodiment, the data processing terminal calculates the clock error using the formula:

[0009] Among them, t B,1 is the arrival time of the idler photon in the second photon pair measured by the second single-photon detector, t A,1 is the local time of the signal photon in the first photon pair measured by the first single-photon detector, t A,1 ' is the arrival time of the signal photon returned by the device at the site to be synchronized, measured by the first single-photon detector.

[0010] The present invention also provides a simplified bidirectional quantum time synchronization system, including a reference clock site device and a site device to be synchronized, wherein the reference clock site device includes: a frequency entangled two-photon source connected to the input end of a first beam splitter; a first output end of the first beam splitter is connected to a first circulator interface a, and a second output end is connected to a first polarization beam splitter; the first polarization beam splitter is connected to the first input end of the polarization beam combiner; the first circulator interface b is connected to a remote end device via an optical fiber link, and interface c is connected to the second input end of the polarization beam combiner; the output end of the polarization beam combiner is connected to a first single-photon detector, the first single-photon detector is connected to a first event timer, and the first event timer is connected to the reference clock;

[0011] The site equipment to be synchronized includes a second circulator, wherein the second circulator interface a is connected to the first circulator interface b, the interface b is connected to the input end of the optical fiber Faraday rotator mirror, and the output end of the optical fiber Faraday rotator mirror is connected to the input end of the second polarization beam splitter; the first output end of the second polarization beam splitter is connected to the second single-photon detector; the second output end is connected to the second circulator interface c; the second single-photon detector is connected to the second event timer, and the second event timer is connected to the clock to be synchronized; the data processing terminal is connected to the first event timer and the second event timer via a communication link; a programming delay is connected to the data processing terminal, and the clock to be synchronized is connected to the programming delay.

[0012] In a specific embodiment, the fiber optic Faraday rotator mirror is a dual-port Faraday rotator mirror.

[0013] The present invention also provides a simplified bidirectional quantum time synchronization method, which is applied to the simplified bidirectional quantum time synchronization system mentioned above. The method includes:

[0014] S1. The reference clock site equipment records the local time t of the signal photon through the first event timer. A,1 and transmit the entangled photon pair to the equipment at the site to be synchronized;

[0015] S2. The equipment at the site to be synchronized records the arrival time t of the entangled photon pair through the second event timer. B,1 And return the signal photon to the reference clock site equipment;

[0016] S3: The first event timer records the arrival time t of the device at the site to be synchronized and returns to the reference clock site. A,1 ';

[0017] S4. Calculate the clock difference t0, and adjust the output time of the device at the site to be synchronized according to the clock difference t0, so that the time signal of the device at the site to be synchronized is synchronized with the time signal of the reference clock site device, wherein the calculation formula of the clock difference t0 is:

[0018] The present invention also provides a simplified bidirectional quantum time synchronization reference clock station device, comprising:

[0019] A frequency-entangled two-photon source, configured to generate a frequency-entangled entangled photon pair, wherein the entangled photon pair comprises a signal photon and an idler photon;

[0020] a first beam splitter, configured to split the entangled photon pair into a first photon pair and a second photon pair, and send the second photon pair to the to-be-synchronized site device so that the to-be-synchronized site device records the arrival time of the idle photon in the second photon pair, and obtains the signal photon returned by the to-be-synchronized site device;

[0021] The first single-photon detector is used to detect the signal photons returned by the device at the site to be synchronized, so that the first event timer records the local time of the signal photons in the first photon pair and the arrival time of the signal photons returned by the device at the site to be synchronized, so that the device at the site to be synchronized calculates the clock difference according to the arrival time of the idle photons in the second photon pair, the local time of the signal photons in the first photon pair and the arrival time of the signal photons returned by the device at the site to be synchronized, so as to adjust the time signal of the site to be synchronized according to the clock difference, so that the time signal of the site to be synchronized is synchronized with the time signal of the reference clock site.

[0022] In a specific embodiment, the clock error calculation formula is: Among them, t B,1 is the arrival time of the idle photon in the second photon pair, t A,1 is the local time of the signal photon in the first photon pair, t A,1 ' is the arrival time of the signal photon returned by the equipment at the site to be synchronized.

[0023] Beneficial effects of the present invention:

[0024] The simplified bidirectional quantum time synchronization system of the present invention requires only one frequency-entangled two-photon source and two single-photon detectors, significantly simplifying both the quantum light source and the quantum detection components. Furthermore, using a single entangled two-photon source as the quantum light source avoids the impact of low frequency consistency between the two frequency-entangled two-photon sources on synchronization accuracy in existing simplified bidirectional quantum time synchronization schemes. Reducing the number of single-photon detectors also reduces the impact of inherent detector jitter on synchronization errors, further improving the accuracy of quantum time synchronization.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a block diagram of a simplified bidirectional quantum time synchronization system module provided by an embodiment of the present invention;

[0027] Figure 2 This is another simplified bidirectional quantum time synchronization system module block diagram provided by an embodiment of the present invention;

[0028] Figure 3 This is a flow chart of a simplified bidirectional quantum time synchronization method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0030] Example 1

[0031] See Figure 1 , Figure 1 This is a block diagram of a simplified bidirectional quantum time synchronization system module provided by an embodiment of the present invention, including a reference clock site device and a site device to be synchronized, wherein the reference clock site device includes: a frequency entangled two-photon source 1, connected to the input end of a first beam splitter 2; a first output end of the first beam splitter 2 is connected to an interface a of a first circulator 4, and a second output end is connected to a first polarization beam splitter 3; the first polarization beam splitter 3 is connected to a first input end of a polarization beam combiner 5; an interface b of the first circulator 4 is connected to a remote end device via an optical fiber link 18, and an interface c is connected to a second input end of the polarization beam combiner 5; an output end of the polarization beam combiner 5 is connected to a first single-photon detector 6, the first single-photon detector 6 is connected to a first event timer 7, and the first event timer 7 is connected to a reference clock 8;

[0032] The site equipment to be synchronized includes a second circulator 9, wherein interface a of the second circulator 9 is connected to interface b of the first circulator 4, and interface b is connected to interface a of the third circulator 10; interface b of the third circulator 10 outputs an optical signal to a fiber Faraday rotator 11, and interface c is connected to the input end of a second polarization beam splitter 12; a first output end of the second polarization beam splitter 12 is connected to a second single-photon detector 13; a second output end is connected to interface c of the second circulator 9; the second single-photon detector 13 is connected to the second event timer 14, and the second event timer 14 is connected to a clock to be synchronized 15; a data processing terminal 16 is connected to the first event timer 7 and the second event timer 14; a programming delay 17 is connected to the data processing terminal 16, and the clock to be synchronized 15 is connected to the programming delay 17.

[0033] During implementation, it is assumed that site A is the quasi-clock site equipment and site B is the site equipment to be synchronized.

[0034] 1) A frequency-entangled two-photon source 1 located at site A generates entangled photon pairs with orthogonal polarizations. These photons pass through a 10:90 first beam splitter 2, where 10% of the entangled photon pairs remain locally. The signal photons and idle photons are then separated by a first polarization beam splitter 3. The remaining 90% of the entangled photon pairs from the frequency-entangled two-photon source 1 are transmitted to site B via an optical fiber link 18 connected to the input port a of a first circulator 4 and its first output port b.

[0035] 2) At site B, optical fiber link 18 is connected to port a of second circulator 9, port b of second circulator 9 is connected to port a of third circulator 10, port b of third circulator 10 is connected to fiber Faraday rotator 11, and port c of third circulator 10 is connected to second polarization beam splitter 12. After arriving at site B, the entangled two-photon travels from port a to port b of third circulator 10, is orthogonally back-reflected by fiber Faraday rotator 11, and is output from port c of third circulator 10 to second polarization beam splitter 12.

[0036] 3) The second polarization beam splitter 12 separates the signal photons from the idle photons. The idle photons are detected by the second single-photon detector 13 at site B, and their arrival times are recorded by the second event timer 14 based on the time frequency reference of the clock to be synchronized 15. The output end of the signal photon is connected to the second input end interface c of the second circulator 9, and returns to the optical fiber link 18 through the interface a of the second circulator 9.

[0037] 4) After the signal photons returning via the original route of the optical fiber link reach location A, they are output from interface c of the first circulator 4 connected to the optical fiber link 18, and are combined with the 10% signal photons remaining at location A via the polarization combiner 5. The output signal photons are detected by the first single-photon detector 6 at location A, and their arrival time is recorded by the first event timer 7 based on the reference clock 8 as the time frequency reference.

[0038] 5) All measured photon arrival time series are transmitted via a classical data transmission link to the data processing terminal 16. A cross-correlation operation is performed based on the time correlation characteristics of the frequency entangled sources at each site.

[0039] 6) Substituting the time difference measured in the above step into the formula, the clock error t0 is obtained, which is sent to the programmable delay device 17 to adjust the output time of the clock to be synchronized B by the adjustment amount t0; at this point, the time signals of the clock to be synchronized 15 and the reference clock 8 are synchronized.

[0040] The simplified bidirectional quantum time synchronization system of this embodiment requires only one frequency-entangled two-photon source and two single-photon detectors, significantly simplifying both the quantum light source and the quantum detection components. Furthermore, using a single entangled two-photon source as the quantum light source avoids the impact of low frequency consistency between the two frequency-entangled two-photon sources on synchronization accuracy in existing simplified bidirectional quantum time synchronization schemes. Reducing the number of single-photon detectors also reduces the impact of inherent detector jitter on synchronization errors, further improving the accuracy of quantum time synchronization.

[0041] Example 2

[0042] See Figure 2 , Figure 2This is another simplified bidirectional quantum time synchronization system module block diagram provided by an embodiment of the present invention, including a reference clock site device and a site device to be synchronized, wherein the reference clock site device includes: a frequency entangled two-photon source 1, connected to the input end of a first beam splitter 2; a first output end of the first beam splitter 2 is connected to an interface a of a first circulator 4, and a second output end is connected to a first polarization beam splitter 3; the first polarization beam splitter 3 is connected to a first input end of a polarization beam combiner 5; an interface b of the first circulator 4 is connected to a remote end device via an optical fiber link 18, and an interface c is connected to a second input end of the polarization beam combiner 5; an output end of the polarization beam combiner 5 is connected to a first single-photon detector 6, the first single-photon detector 6 is connected to a first event timer 7, and the first event timer 7 is connected to a reference clock 8;

[0043] The site equipment to be synchronized includes a second circulator 9, wherein interface a of the second circulator 9 is connected to interface b of the first circulator 4, interface b is connected to the input end of the optical fiber Faraday rotator 11, and the output end of the optical fiber Faraday rotator 11 is connected to the input end of the second polarization beam splitter 12; the first output end of the second polarization beam splitter 12 is connected to the second single-photon detector 13; the second output end is connected to interface c of the second circulator 9; the second single-photon detector 13 is connected to the second event timer 14, and the second event timer 14 is connected to the clock to be synchronized 15; the data processing terminal 16 is connected to the first event timer 7 and the second event timer 14; the programming delay 17 is connected to the data processing terminal 16, and the clock to be synchronized 15 is connected to the programming delay 17.

[0044] During implementation, it is assumed that site A is the quasi-clock site equipment and site B is the site equipment to be synchronized.

[0045] 1) A frequency-entangled two-photon source 1 located at site A generates entangled photon pairs with orthogonal polarizations. These photons pass through a 10:90 first beam splitter 2, where 10% of the entangled photon pairs remain locally. The signal photons and idle photons are then separated by a first polarization beam splitter 3. The remaining 90% of the entangled photon pairs from the frequency-entangled two-photon source 1 are transmitted to site B via an optical fiber link 18 connected to the input port a of a first circulator 4 and its first output port b.

[0046] 2) At location B, optical fiber link 18 is connected to port a of second circulator 9. Port b of second circulator 9 is connected to the input of fiber Faraday rotator 11. The output of fiber Faraday rotator 11 is connected to second polarization beam splitter 12. Because fiber Faraday rotator 11 in this embodiment has two ports, the entangled two-photon pair arrives at location B, passes through the input of fiber Faraday rotator 11, and then is output from the output to second polarization beam splitter 12.

[0047] 3) The second polarization beam splitter 12 separates the signal photons from the idle photons. The idle photons are detected by the second single-photon detector 13 at site B, and their arrival times are recorded by the second event timer 14 based on the time frequency reference of the clock to be synchronized 15. The output end of the signal photon is connected to the second input end interface c of the second circulator 9, and returns to the optical fiber link 18 through the interface a of the second circulator 9.

[0048] 4) After the signal photons returning via the original route of the optical fiber link reach location A, they are output from interface c of the first circulator 4 connected to the optical fiber link 18, and are combined with the 10% signal photons remaining at location A via the polarization combiner 5. The output signal photons are detected by the first single-photon detector 6 at location A, and their arrival time is recorded by the first event timer 7 based on the reference clock 8 as the time frequency reference.

[0049] 5) All measured photon arrival time series are transmitted via a classical data transmission link to the data processing terminal 16. A cross-correlation operation is performed based on the time correlation characteristics of the frequency entangled sources at each site.

[0050] 6) Substituting the time difference measured in the above step into the formula, the clock error t0 is obtained, which is sent to the programmable delay device 17 to adjust the output time of the clock to be synchronized B by the adjustment amount t0; at this point, the time signals of the clock to be synchronized 15 and the reference clock 8 are synchronized.

[0051] See Figure 3 This embodiment also provides a simplified bidirectional quantum time synchronization method, which is applied to the simplified bidirectional quantum time synchronization system described above. The method includes:

[0052] S1. The reference clock site equipment records the local time t of the signal photon through the first event timer. A,1 and transmit the entangled photon pair to the equipment at the site to be synchronized;

[0053] S2. The equipment at the site to be synchronized records the arrival time t of the entangled photon pair through the second event timer. B,1 And return the signal photon to the reference clock site equipment;

[0054] S3: The first event timer records the arrival time t of the device at the site to be synchronized and returns to the reference clock site. A,1 ';

[0055] S4. Calculate the clock difference t0, and adjust the output time of the device at the site to be synchronized according to the clock difference t0, so that the time signal of the device at the site to be synchronized is synchronized with the time signal of the reference clock site device, wherein the calculation formula of the clock difference t0 is:

[0056] Specifically, the implementation steps of this method are as follows:

[0057] 1) The reference clock site A and the clock to be synchronized at site B each contain a single-photon detector, an event timer, and a local time-frequency source (e.g., an atomic clock or precision crystal oscillator, with the time-frequency source outputting a 10MHz reference frequency signal and a 1PPS reference time signal). The event timer's system clock is strictly synchronized to the local time-frequency source. A frequency-entangled two-photon source is located at site A, generating entangled photon pairs with orthogonal polarizations.

[0058] 2) At site A, a frequency-entangled two-photon source is split into two beams by a 10:90 beam splitter. 10% of the entangled photon pairs remain locally, while a polarization beam splitter separates the signal photons from the idle photons. The remaining 90% of the entangled photon pairs are transmitted to site B.

[0059] 3) At site B, the transmitted entangled photon pair passes through a polarization beam splitter to separate the signal photon from the idle photon. The idle photon is detected by the detector at site B, and its arrival time is recorded by the event timer B at site B, which is expressed as {t B,1}; The signal photon returns along the original path;

[0060] 4) After the signal photons returning from the original route reach location A, they are combined with the 10% of signal photons left at location A. The output signal photons are detected by the detector at location A, and the event timer A at location A records the local time of the signal photons and the arrival time after the round trip transmission, which is expressed as {t A,1} and {t A,1 '};

[0061] 5) The recorded photon arrival time series is sent to the data processing terminal at the location of the clock to be synchronized via a classical communication channel. Based on the cross-correlation algorithm between the frequency entangled two photons, two sets of time differences can be calculated: t B,1 -t A,1 and t B,1 -t A,1 '.

[0062] Let t A,0 , t B,0 represents the proper time of the time frequency source at locations A and B respectively. The clock difference t0 between the two locations can be expressed as t0 = t B,0 -t A,0 Let τ AB , τ BA Represent the forward and reverse transmission delays respectively. The above two sets of time differences can be expressed as:

[0063] t B,1 -t A,0 =t B,0 -t A,0 +τ AB (1)

[0064] t B,1 -t A,0 =t B,0 -t A,0 -τ BA (2)

[0065] From formulas (1) and (2), we can see that when τ AB =τ BA , the clock difference t0 between the two places can be expressed as:

[0066]

[0067] 6) The clock error t0 measured in the above step is sent to the programmable delay device to adjust the output time of the end to be synchronized, and the adjustment amount is t0; at this point, the time signal of the end to be synchronized is synchronized with the time signal of the source time frequency source.

[0068] This embodiment also provides a simplified bidirectional quantum time synchronization reference clock station device, which is characterized by including:

[0069] A frequency-entangled two-photon source, configured to generate a frequency-entangled entangled photon pair, wherein the entangled photon pair comprises a signal photon and an idler photon;

[0070] a first beam splitter, configured to split the entangled photon pair into a first photon pair and a second photon pair, and send the second photon pair to the to-be-synchronized site device so that the to-be-synchronized site device records the arrival time of the idle photon in the second photon pair, and obtains the signal photon returned by the to-be-synchronized site device;

[0071] The first single-photon detector is used to detect the signal photons returned by the device at the site to be synchronized, so that the first event timer records the local time of the signal photons in the first photon pair and the arrival time of the signal photons returned by the device at the site to be synchronized, so that the device at the site to be synchronized calculates the clock difference according to the arrival time of the idle photons in the second photon pair, the local time of the signal photons in the first photon pair and the arrival time of the signal photons returned by the device at the site to be synchronized, so as to adjust the time signal of the site to be synchronized according to the clock difference, so that the time signal of the site to be synchronized is synchronized with the time signal of the reference clock site.

[0072] In a specific embodiment, the clock error calculation formula is: Among them, t B,1 is the arrival time of the idle photon in the second photon pair, t A,1 is the local time of the signal photon in the first photon pair, t A,1 ' is the arrival time of the signal photon returned by the equipment at the site to be synchronized.

[0073] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0074] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0075] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art can understand and implement other changes to the disclosed embodiments by reviewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple situations. A single data processing terminal or other unit can implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0076] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A simplified bidirectional quantum time synchronization system, comprising a reference clock station device and a station device to be synchronized, characterized in that: The reference clock site equipment includes: a frequency entangled two-photon source, connected to the input end of a first beam splitter; the first output end of the first beam splitter is connected to the first circulator interface a, and the second output end is connected to the first polarization beam splitter; the first polarization beam splitter is connected to the first input end of a polarization beam combiner; the first circulator interface b is connected to a remote end device through an optical fiber link, and the interface c is connected to the second input end of the polarization beam combiner; the output end of the polarization beam combiner is connected to a first single-photon detector, the first single-photon detector is connected to a first event timer, and the first event timer is connected to a reference clock; The site equipment to be synchronized includes a second circulator, wherein the second circulator interface a is connected to the first circulator interface b, and the interface b is connected to the third circulator interface a; the third circulator interface b outputs an optical signal to the fiber Faraday rotator, and the interface c is connected to the input end of the second polarization beam splitter; the first output end of the second polarization beam splitter is connected to the second single-photon detector; the second output end is connected to the second circulator interface c; the second single-photon detector is connected to a second event timer, and the second event timer is connected to the clock to be synchronized; the data processing terminal is connected to the first event timer and the second event timer via a communication link; a programming delay is connected to the data processing terminal, and the clock to be synchronized is connected to the programming delay.

2. The simplified bidirectional quantum time synchronization system according to claim 1, characterized in that: The splitting ratio of the first beam splitter is 10:90, and 90% of the light beam is output to the first circulator.

3. The simplified bidirectional quantum time synchronization system according to claim 1, characterized in that: The data processing terminal calculates the clock error formula as follows: Among them, t B,1 is the arrival time of the idler photon in the second photon pair measured by the second single-photon detector, t A,1 is the local time of the signal photon in the first photon pair measured by the first single-photon detector, t A,1 ' is the arrival time of the signal photon returned by the device at the site to be synchronized, measured by the first single-photon detector.

4. A simplified bidirectional quantum time synchronization system, comprising a reference clock station device and a station device to be synchronized, characterized in that: The reference clock site equipment includes: a frequency entangled two-photon source, connected to the input end of a first beam splitter; the first output end of the first beam splitter is connected to the first circulator interface a, and the second output end is connected to the first polarization beam splitter; the first polarization beam splitter is connected to the first input end of a polarization beam combiner; the first circulator interface b is connected to a remote end device through an optical fiber link, and the interface c is connected to the second input end of the polarization beam combiner; the output end of the polarization beam combiner is connected to a first single-photon detector, the first single-photon detector is connected to a first event timer, and the first event timer is connected to a reference clock; The site equipment to be synchronized includes a second circulator, wherein the second circulator interface a is connected to the first circulator interface b, the interface b is connected to the input end of the optical fiber Faraday rotator mirror, and the output end of the optical fiber Faraday rotator mirror is connected to the input end of the second polarization beam splitter; the first output end of the second polarization beam splitter is connected to the second single-photon detector, and the second output end is connected to the second circulator interface c; the second single-photon detector is connected to a second event timer, and the second event timer is connected to the clock to be synchronized; the data processing terminal is connected to the first event timer and the second event timer via a communication link; a programming delay is connected to the data processing terminal, and the clock to be synchronized is connected to the programming delay.

5. The simplified bidirectional quantum time synchronization system according to claim 1, characterized in that: The optical fiber Faraday rotator mirror is a dual-port Faraday rotator mirror.

6. A simplified bidirectional quantum time synchronization method, characterized in that: Applied to the simplified bidirectional quantum time synchronization system according to any one of claims 1 to 4, the method comprises: S1. The reference clock site equipment records the local time t of the signal photon through the first event timer. A,1 and transmit the entangled photon pair to the equipment at the site to be synchronized; S2. The equipment at the site to be synchronized records the arrival time t of the entangled photon pair through the second event timer. B,1 And return the signal photon to the reference clock site equipment; S3: The first event timer records the arrival time t of the device at the site to be synchronized and returns to the reference clock site. A,1 '; S4. Calculate the clock difference t0, and adjust the output time of the device at the site to be synchronized according to the clock difference t0, so that the time signal of the device at the site to be synchronized is synchronized with the time signal of the reference clock site device, wherein the calculation formula of the clock difference t0 is:

7. A simplified bidirectional quantum time synchronization reference clock station device, characterized in that: include: A frequency-entangled two-photon source, configured to generate a frequency-entangled entangled photon pair, wherein the entangled photon pair comprises a signal photon and an idler photon; a first beam splitter, configured to split the entangled photon pair into a first photon pair and a second photon pair, and send the second photon pair to the to-be-synchronized site device so that the to-be-synchronized site device records the arrival time of the idle photon in the second photon pair, and obtains the signal photon returned by the to-be-synchronized site device; The first single-photon detector is used to detect the signal photons returned by the device at the site to be synchronized, so that the first event timer records the local time of the signal photons in the first photon pair and the arrival time of the signal photons returned by the device at the site to be synchronized, so that the device at the site to be synchronized calculates the clock difference according to the arrival time of the idle photons in the second photon pair, the local time of the signal photons in the first photon pair and the arrival time of the signal photons returned by the device at the site to be synchronized, so as to adjust the time signal of the site to be synchronized according to the clock difference, so that the time signal of the site to be synchronized is synchronized with the time signal of the reference clock site.

8. The simplified bidirectional quantum time synchronization reference clock station device according to claim 7, characterized in that: The clock error calculation formula is: Among them, t B,1 is the arrival time of the idle photon in the second photon pair, t A,1 is the local time of the signal photon in the first photon pair, t A,1 ' is the arrival time of the signal photon returned by the equipment at the site to be synchronized.

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