Timing error estimation method for dual-polarization quantum key distribution

Abstract

The invention discloses a timing error estimation method for dual-polarization quantum key distribution, and the method comprises the steps: multiplexing a plurality of pilots on a frequency spectrum of a first polarization sum of a communication signal, transmitting the multiplexed communication signal through an optical fiber channel, and obtaining a received signal, acquiring a plurality of pilot frequencies and phase information of the pilot frequencies according to the received signal; and determining a timing error value and a delay value according to the phase information. The signal sent by the sending end comprises the pilot frequency capable of determining the timing error value and the time delay value, the receiving end can determine the timing error value and the time delay value according to the pilot frequency contained in the received signal, the timing error value and the time delay value can be accurately determined even if the method is applied to a quantum communication system with weak signals, and the accuracy of the timing error value and the time delay value is improved. Therefore, timing error estimation is carried out. The method is widely applied to the technical field of quantum communication.

Description

Technical Field

[0001] The invention relates to the technical field of quantum communication, and in particular to a timing error estimation method for dual-polarization quantum key distribution. Background Art

[0002] Like classical optical communication, quantum communication also requires timing error estimation, which can accurately measure the amplitude and phase of optical signals. It is crucial for accurate demodulation of communication signals, high-speed transmission, and improving signal quality and system performance. In particular, when performing dual-polarization quantum key distribution, stable and reliable timing error estimation is required. However, the weak characteristics of quantum signals limit their transmission distance and bandwidth. Compared with classical optical communications, which can cover short distances from 10 kilometers to long distances from thousands of kilometers and communication rates from 40Gbps to 1Tbps, the receiver bandwidth of quantum communication is usually between 20GHz and 60GHz. Therefore, timing error estimation algorithms (clock synchronization algorithms) based on signal characteristics in classical optical communications, such as those that rely on training sequences, are difficult to achieve good results in quantum communications. Moreover, due to non-ideal factors such as chromatic dispersion (CD), polarization mode dispersion (PMD), and random polarization rotation (RSOP) in optical fiber channels, the performance of traditional timing error estimation algorithms is limited when dealing with these complex channel effects. Summary of the invention

[0003] In view of the technical problems that the timing error estimation technology currently used in classical optical communication applications is itself limited by non-ideal factors such as chromatic dispersion (CD), polarization mode dispersion (PMD) and random rotation of polarization (RSOP) in the optical fiber channel, and it is difficult to achieve good results in quantum communication, the purpose of the present invention is to provide a timing error estimation method for dual-polarization quantum key distribution.

[0004] On the one hand, an embodiment of the present invention includes a timing error estimation method for dual-polarization quantum key distribution applied to a transmitting end, and the timing error estimation method for dual-polarization quantum key distribution includes the following steps:

[0005] multiplexing the first pilot and the third pilot on the spectrum of the first polarization of the communication signal;

[0006] multiplexing a second pilot and a fourth pilot on a spectrum of a second polarization of the communication signal;

[0007] The multiplexed communication signal is transmitted through an optical fiber channel.

[0008] Furthermore, a frequency difference between the first pilot and the third pilot and a frequency difference between the second pilot and the fourth pilot are both equal to half the baud rate of the communication signal.

[0009] Furthermore, a frequency difference between the first pilot and the second pilot is equal to a frequency difference between the second pilot and the fourth pilot, and both are less than half the baud rate of the communication signal.

[0010] On the other hand, an embodiment of the present invention includes a timing error estimation method for dual-polarization quantum key distribution applied to a receiving end, and the timing error estimation method for dual-polarization quantum key distribution includes the following steps:

[0011] Acquire a received signal; the received signal is transmitted by a communication signal through an optical fiber channel, and before being sent, the communication signal is multiplexed with a first pilot and a third pilot on a spectrum of a first polarization, and a second pilot and a fourth pilot on a spectrum of a second polarization;

[0012] The first pilot, the second pilot, the third pilot, the fourth pilot, the fifth pilot, the sixth pilot, the seventh pilot and the eighth pilot are acquired according to the received signal; wherein the fifth pilot is generated by a physical effect of the first pilot being transmitted through an optical fiber channel, the sixth pilot is generated by a physical effect of the second pilot being transmitted through an optical fiber channel, the seventh pilot is generated by a physical effect of the third pilot being transmitted through an optical fiber channel, and the eighth pilot is generated by a physical effect of the fourth pilot being transmitted through an optical fiber channel; the frequency of the fifth pilot is the same as that of the first pilot, the frequency of the sixth pilot is the same as that of the second pilot, the frequency of the seventh pilot is the same as that of the third pilot, and the frequency of the eighth pilot is the same as that of the fourth pilot;

[0013] Acquire phase information of the first pilot, the second pilot, the third pilot, the fourth pilot, the fifth pilot, the sixth pilot, the seventh pilot, and the eighth pilot;

[0014] According to the phase information, a timing error value and a delay value are determined.

[0015] Further, the acquiring phase information of the first pilot, the second pilot, the third pilot, the fourth pilot, the fifth pilot, the sixth pilot, the seventh pilot, and the eighth pilot includes:

[0016] Down-converting the first pilot, the second pilot, the third pilot, the fourth pilot, the fifth pilot, the sixth pilot, the seventh pilot and the eighth pilot;

[0017] The down-converted pilot signal is filtered to obtain the phase information.

[0018] Further, filtering the down-converted pilot to obtain the phase information includes:

[0019] Performing Wiener filtering on the down-converted pilot to obtain phases of the first pilot, the second pilot, the third pilot, the fourth pilot, the fifth pilot, the sixth pilot, the seventh pilot, and the eighth pilot;

[0020] Obtaining a first phase difference average value; the first phase difference average value is an average value of a phase difference between the first pilot and the third pilot and a phase difference between the sixth pilot and the eighth pilot;

[0021] Obtaining a second phase difference average value; the second phase difference average value is an average value of a phase difference between the first pilot and the seventh pilot and a phase difference between the sixth pilot and the fourth pilot;

[0022] Obtaining a third phase difference average value; the third phase difference average value is an average value of a phase difference between the fifth pilot and the third pilot and a phase difference between the second pilot and the eighth pilot;

[0023] Acquire a fourth phase difference average value; the fourth phase difference average value is an average value of a phase difference between the fifth pilot and the seventh pilot and a phase difference between the second pilot and the fourth pilot;

[0024] A timing error matrix is ​​determined using the first phase difference average value, the second phase difference average value, the third phase difference average value and the fourth phase difference average value as elements; the timing error matrix is ​​used as the phase information.

[0025] Further, the determining of a timing error matrix using the first phase difference average value, the second phase difference average value, the third phase difference average value, and the fourth phase difference average value as elements includes:

[0026] Using the first phase difference average as the first row and first column element of the timing error matrix;

[0027] Using the second phase difference average as the first row and second column element of the timing error matrix;

[0028] Using the third phase difference average as the second row and first column element of the timing error matrix;

[0029] The fourth phase difference average value is used as the second row and second column element of the timing error matrix.

[0030] Further, determining the timing error value and the delay value according to the phase information includes:

[0031] According to the formula

[0032] eτ = -Im[det(S pilot )]

[0033] Calculate; where e τ is the timing error value, S pilot is the timing error matrix, det() is the operator for taking the matrix determinant, and Im[] is the operator for taking the imaginary part of a complex number.

[0034] Further, determining the timing error value and the delay value according to the phase information includes:

[0035] According to the formula

[0036]

[0037] Calculate; where τ is the delay value, s p ilot is the timing error matrix, det() is an operator for obtaining the matrix determinant, angle[] is an operator for obtaining the complex angle, and Δf is the frequency difference between the first pilot and the third pilot.

[0038] Furthermore, the timing error estimation method for dual-polarization quantum key distribution also includes:

[0039] PID feedback control is performed according to the timing error value.

[0040] The beneficial effects of the present invention are as follows: in the timing error estimation method for dual-polarization quantum key distribution in the embodiment, the signal sent by the transmitting end includes a pilot that can determine the timing error value and the delay value, and the receiving end can determine the timing error value and the delay value based on the pilot contained in the received signal. Even if it is applied to a quantum communication system with a relatively weak signal, the timing error value and the delay value can be accurately determined, thereby performing timing error estimation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a schematic diagram of a quantum communication system to which the timing error estimation method for dual-polarization quantum key distribution in an embodiment can be applied;

[0042] Figure 2 Schematic diagram of the steps of the timing error estimation method for dual-polarization quantum key distribution performed by the transmitting end in the embodiment;

[0043] Figure 3 Schematic diagram of the spectrum of the communication signal after the polarization multiplexing pilot signal is sent by the transmitting end in the embodiment;

[0044] Figure 4 Schematic diagram of the steps of the timing error estimation method for dual-polarization quantum key distribution performed by the receiving end in the embodiment;

[0045] Figure 5 FIG. 4 is a schematic diagram of a frequency spectrum of a received signal received by a receiving end in an embodiment. DETAILED DESCRIPTION

[0046] The timing error estimation method for dual-polarization quantum key distribution in this embodiment can be applied to Figure 1 In the quantum communication system shown in Figure 1, Figure 1 The quantum communication system includes a transmitting end, a receiving end and an optical fiber channel, wherein the transmitting end needs to send information to the receiving end through the optical fiber channel. The information to be sent is mainly presented in the form of a quantum communication signal. The content of the information to be sent can be a dual-polarization quantum key, thereby realizing dual-polarization quantum key distribution (also called continuous variable quantum key distribution, Continuous Variable Quantum Key Distribution, CVQKD) from the transmitting end to the receiving end.

[0047] In this embodiment, the complete timing error estimation method for dual-polarization quantum key distribution includes steps S1A-S3A executed by the transmitting end and steps S1B-S4B executed by the receiving end.

[0048] Reference Figure 1 The transmitting end includes a laser light source and a signal modulation module. The laser light source generates a laser beam with a single frequency. The laser beam is input into the signal modulation module. On the one hand, the signal modulation module modulates the communication signal into the laser. On the other hand, the signal modulation module executes steps S1A-S3A.

[0049] In this embodiment, since the signal is carried by laser, unless otherwise specified, it is not necessary to distinguish between the "communication signal" itself and the laser beam carrying the communication signal. Similarly, it is also possible not to distinguish between the "receiving signal" itself and the laser beam carrying the receiving signal.

[0050] Reference Figure 2 , the timing error estimation method for dual-polarization quantum key distribution performed by the transmitting end comprises the following steps:

[0051] S1A multiplexing the first pilot and the third pilot on the spectrum of the first polarization of the communication signal;

[0052] S2A multiplexing the second pilot and the fourth pilot on the second polarization spectrum of the communication signal;

[0053] S3A. Transmit the multiplexed communication signal through an optical fiber channel.

[0054] In steps S1A-S2A, the first polarization and the second polarization are polarizations in two mutually orthogonal directions. For example, in this embodiment, the first polarization is X polarization, and the second polarization is Y polarization.

[0055] In this embodiment, the spectrum of the communication signal after the polarization multiplexing pilot is performed in steps S1A-S2A is as follows: Figure 3 As shown, Figure 3 The portion labeled "communication signal" corresponds to the spectrum of the communication signal before the polarization multiplexing pilot.

[0056] Reference Figure 3 The communication signal before multiplexing the polarization pilot has two components, an X polarization component and a Y polarization component. In step S1A, two pilots, a first pilot (pilot 1) and a third pilot (pilot 3), are multiplexed on a spectrum of a first polarization, i.e., X polarization. In step S2A, two pilots, a second pilot (pilot 2) and a fourth pilot (pilot 4), are multiplexed on a spectrum of a second polarization, i.e., Y polarization.

[0057] In this embodiment, refer to Figure 3 , the frequency difference between the first pilot (pilot 1) and the third pilot (pilot 3), and the frequency difference between the second pilot (pilot 2) and the fourth pilot (pilot 4) are equal, both are Δf. In this embodiment, the value of Δf is equal to half the baud rate of the communication signal (baudrat e )equal.

[0058] In this embodiment, refer to Figure 3 , there is a small frequency difference between the first pilot (pilot 1) and the second pilot (pilot 2), and between the third pilot (pilot 3) and the fourth pilot (pilot 4). Specifically, the frequency difference between the first pilot (pilot 1) and the second pilot (pilot 2), and the frequency difference between the third pilot (pilot 3) and the fourth pilot (pilot 4) are equal, both are df. In this embodiment, df can be a value much smaller than Δf, specifically 2-3 orders of magnitude smaller than Δf, for example, the value of df can be 10MHz.

[0059] In step S3A, the transmitting end sends the multiplexed communication signal, that is, the spectrum as Figure 3 The signal shown is transmitted through an optical fiber channel to a receiving end.

[0060] because Figure 3 The dual-polarized laser shown in the figure is transmitted in the optical fiber channel and is affected by physical effects such as polarization state (SOP) rotation and polarization mode dispersion (PDM). Therefore, the form of the signal received by the receiving end from the optical fiber channel is different from the communication signal sent by the transmitting end in terms of spectrum and other aspects. Therefore, in this embodiment, the signal received by the receiving end from the optical fiber channel is called a received signal to distinguish it from the communication signal sent by the transmitting end.

[0061] Reference Figure 1 ,The receiving end includes a signal receiving module, a timing error estimation module and a PID feedback control module.

[0062] In this embodiment, refer to Figure 4 , the timing error estimation method for dual-polarization quantum key distribution performed by the receiving end comprises the following steps:

[0063] S1B. Get the received signal;

[0064] S2B obtains the first pilot, the second pilot, the third pilot, the fourth pilot, the fifth pilot, the sixth pilot, the seventh pilot and the eighth pilot according to the received signal;

[0065] S3B obtains the phase information of the first pilot, the second pilot, the third pilot, the fourth pilot, the fifth pilot, the sixth pilot, the seventh pilot and the eighth pilot;

[0066] S4B. Determine the timing error value and delay value based on the phase information.

[0067] In step S1B, a received signal may be acquired by a signal receiving module.

[0068] In step S2B, due to the physical effects occurring in the optical channel, the received signal received by the receiving end has Figure 5 The spectral structure shown. Figure 5 The “communication signal” contained in the received signal is equivalent to the spectrum component of the communication signal before the polarization multiplexing pilot, where the pilot P X1 The spectrum component is the same as the first pilot (pilot 1) in the communication signal after the polarization multiplexing pilot, so the received signal is still called the first pilot and is recorded as the first pilot P. X1 Similarly, pilot frequency P X3 The spectrum component of the third pilot (pilot 3) in the communication signal after the polarization multiplexing pilot is the same, that is, the received signal contains the third pilot P X3 ; Pilot P y2 The spectrum component of the second pilot (pilot 2) in the communication signal after the polarization multiplexing pilot is the same, that is, the received signal contains the second pilot P y2 ; Pilot P y4 The spectrum component of the fourth pilot (pilot 4) in the communication signal after the polarization multiplexing pilot is the same, that is, the received signal contains the fourth pilot P y4 .

[0069] Reference Figure 5 The received signal received by the receiving end also includes the first pilot signal P X1 The fifth pilot signal P generated by the physical effect of optical fiber channel transmissiony1 , by the second pilot P y2 The sixth pilot signal P generated by the physical effect of the optical fiber channel transmission X2 , by the third pilot signal P X3 The seventh pilot frequency P generated by the physical effect of optical fiber channel transmission y3 , and the fourth pilot P y4 The eighth pilot frequency P generated by the physical effect of optical fiber channel transmission X4 .

[0070] Reference Figure 5 , the sixth pilot frequency P X2 With the eighth pilot frequency P X4 The frequency difference between the fifth pilot signal P y1 With the seventh pilot P y3 The frequency difference between them is also Δf.

[0071] Reference Figure 5 In this embodiment, the first pilot signal P X1 , the second pilot signal P y2 , the third pilot signal P X3 , the fourth pilot frequency P y4 , the fifth pilot frequency P y1 , the sixth pilot frequency P X2 , the seventh pilot frequency P y3 With the eighth pilot frequency P X4 The frequencies of the fifth pilot signal P are all greater than the frequencies of the communication signals before the polarization multiplexing pilot signal. y1 The frequency of the first pilot signal P X1 The frequency of the sixth pilot signal P X2 The frequency of the second pilot signal P y2 The seventh pilot frequency P y3 The frequency of the third pilot signal P X3 The frequency of the eighth pilot frequency P X4 The frequency of the fourth pilot signal P y4 The frequency is the same.

[0072] In step S3B, the timing error estimation module may obtain the first pilot signal P X1 , the second pilot signal P y2 , the third pilot signal P X3 , the fourth pilot frequency P y4 , the fifth pilot frequency P y1 , the sixth pilot frequency P X2 , the seventh pilot frequency P y3 and the eighth pilot frequency P X4 Specifically, the phase information includes the phases of these pilots and the phase difference between two pilots.

[0073] When executing step S3B, the timing error estimation module may estimate the first pilot signal P X1 , the second pilot signal P y2 , the third pilot signal P X3 , the fourth pilot frequency P y4 , the fifth pilot frequency P y1 , the sixth pilot frequency P X2 , the seventh pilot frequency P y3 and the eighth pilot frequency P X4 Down-conversion is performed, that is, these pilots are moved to the baseband respectively. Then, the timing error estimation module filters the down-converted pilots respectively to obtain the phase information of each of these pilots. Specifically, the timing error estimation module can perform Wiener filtering on the down-converted pilots.

[0074] The timing error estimation module obtains the first pilot frequency P by filtering. X1 The phase θ px1 , the second pilot signal P y2 The phase θ py2 , the third pilot signal P X3 The phase θ px3 , the fourth pilot frequency P y4 The phase θ py4 , the fifth pilot frequency P y1 The phase θ py1 , the sixth pilot frequency P X2 The phase θ px2 , the seventh pilot frequency P y3 The phase θ px3 and the eighth pilot frequency P X4 The phase θ px4 .

[0075] When executing step S3B, the timing error estimation module calculates the first pilot frequency P X1 With the third pilot P X3 The phase difference θ px1 -θ px3 , and the sixth pilot frequency P X2 With the eighth pilot frequency P X4 The phase difference θ px2 -θ px4 , and calculate the average of these two phase differences to obtain the first phase difference average value

[0076] When executing step S3B, the timing error estimation module calculates the first pilot frequency P X1 With the seventh pilot P y3 The phase difference θ px1 -θ py3 , and the sixth pilot frequency P X2 With the fourth pilot P y4 The phase difference θ px2 -θpy4 , and calculate the average of these two phase differences to obtain the second phase difference average value

[0077] When executing step S3B, the timing error estimation module calculates the fifth pilot frequency P y1 With the third pilot P X3 The phase difference θ py1 -θ px3 , and the second pilot P y2 With the eighth pilot frequency P X4 The phase difference θ py2 -θ px4 , and calculate the average of these two phase differences to obtain the third phase difference average

[0078] When executing step S3B, the timing error estimation module calculates the fifth pilot frequency P y1 With the seventh pilot P y3 The phase difference θ py1 -θ py3 , and the second pilot P y2 With the fourth pilot P y4 The phase difference θ py2 -θ py4 , and calculate the average of these two phase differences to obtain the fourth phase difference average

[0079] When executing step S3B, the timing error estimation module uses the first phase difference average value As the first row and first column element, that is, the (1, 1) item, the second phase difference average As the first row and second column element, that is, the (1, 2) item, the third phase difference average As the second row and first column element, that is, the (2, 1) item, the fourth phase difference average As the second row and second column element, that is, the (2,2) item, the timing error matrix S is formed. pilot That is, in this embodiment, the timing error matrix S pilo t can be expressed as

[0080]

[0081] Timing error matrix S pilot The phase difference information between each pilot signal is included, and can be used as the phase information to be obtained by the timing error estimation module to execute step S3B.

[0082] In step S4B, the timing error estimation module can use the formula

[0083] eτ = -Im[det(S pilot )]

[0084] Calculate and obtain the timing error value e τ . Among them, det() is an operator for obtaining the matrix determinant, and Im[] is an operator for obtaining the imaginary part of a complex number.

[0085] In step S4B, the timing error estimation module can use the formula

[0086]

[0087] Calculate to obtain the delay value τ. Wherein, det() is the operator for taking the matrix determinant, angle[] is the operator for finding the complex angle, Δf is the first pilot frequency P X1 and the third pilot frequency P X3 The frequency difference between the two is also the second pilot frequency P y2 With the fourth pilot P y4 The frequency difference between the sixth pilot signal P X2 With the eighth pilot frequency P X4 The frequency difference between the fifth pilot signal P y1 With the seventh pilot P y3 The frequency difference between them.

[0088] By executing steps S1A-S3A, the signal sent by the transmitting end includes the timing error value e τ The receiving end can determine the timing error value e according to the pilot signal contained in the received signal by executing steps S1B-S4B. τ and delay value τ; even if applied to quantum communication systems with relatively weak signals, the timing error value and delay value can be accurately determined, thereby performing timing error estimation. The performance of timing error estimation is better when the pilot frequency is higher.

[0089] In this embodiment, the receiving end may perform the following steps based on the execution of steps S1B-S4B:

[0090] S5B. Perform PID feedback control according to the timing error value.

[0091] Reference Figure 1 After executing steps S1B-S4B, the timing error estimation module obtains the timing error value e τ Afterwards, the timing error value e can be τ The PID feedback control module sends the error value to the PID feedback control module. τ A feedback signal is generated, and the signal receiving module is adjusted according to the feedback signal, thereby achieving the effect of reducing or even eliminating the timing error.

[0092] A computer program for executing the timing error estimation method for dual-polarization quantum key distribution in this embodiment can be written and written into a computer device or a storage medium. When the computer program is read out and run, the timing error estimation method for dual-polarization quantum key distribution in this embodiment is executed, thereby achieving the same technical effect as the timing error estimation method for dual-polarization quantum key distribution in the embodiment.

[0093] It should be noted that, unless otherwise specified, when a feature is referred to as "fixed" or "connected" to another feature, it may be directly fixed or connected to the other feature, or it may be indirectly fixed or connected to the other feature. In addition, the descriptions of up, down, left, right, etc. used in the present disclosure are only relative to the relative positional relationship of the components of the present disclosure in the accompanying drawings. The singular forms of "a" and "the" used in the present disclosure are also intended to include the plural forms, unless the context clearly indicates other meanings. In addition, unless otherwise defined, all technical and scientific terms used in this embodiment have the same meaning as those generally understood by technicians in this technical field. The terms used in the specification of this embodiment are only for describing specific embodiments, not for limiting the present invention. The term "and / or" used in this embodiment includes any combination of one or more related listed items.

[0094] It should be understood that, although the term first, second, third etc. may be adopted to describe various elements in the present disclosure, these elements should not be limited to these terms. These terms are only used to distinguish the same type of elements from each other. For example, without departing from the scope of the present disclosure, the first element may also be referred to as the second element, and similarly, the second element may also be referred to as the first element. The use of any and all examples or exemplary language ("for example", "such as" etc.) provided by the present embodiment is only intended to better illustrate embodiments of the present invention, and unless otherwise required, the scope of the present invention will not be limited.

[0095] It should be appreciated that embodiments of the present invention may be implemented or enforced by computer hardware, a combination of hardware and software, or by computer instructions stored in a non-transitory computer-readable memory. The method may be implemented in a computer program using standard programming techniques - including a non-transitory computer-readable storage medium configured with a computer program, wherein the storage medium so configured causes the computer to operate in a specific and predefined manner - according to the methods and drawings described in the specific embodiments. Each program may be implemented in a high-level procedural or object-oriented programming language to communicate with a computer system. However, if desired, the program may be implemented in assembly or machine language. In any case, the language may be a compiled or interpreted language. In addition, the program may be run on a programmed dedicated integrated circuit for this purpose.

[0096] In addition, the operations of the process described in this embodiment may be performed in any suitable order, unless otherwise indicated in this embodiment or otherwise clearly contradicted by the context. The process described in this embodiment (or variations and / or combinations thereof) may be performed under the control of one or more computer systems configured with executable instructions, and may be implemented as a code (e.g., executable instructions, one or more computer programs, or one or more applications) executed on one or more processors in common, by hardware or a combination thereof. A computer program includes a plurality of instructions that may be executed by one or more processors.

[0097] Further, the method can be implemented in any type of computing platform that is operably connected to a suitable computer, including but not limited to a personal computer, a minicomputer, a mainframe, a workstation, a network or distributed computing environment, a separate or integrated computer platform, or in communication with a charged particle tool or other imaging device, etc. Various aspects of the present invention can be implemented in machine-readable code stored on a non-transitory storage medium or device, whether removable or integrated into a computing platform, such as a hard disk, an optical read and / or write storage medium, a RAM, a ROM, etc., so that it can be read by a programmable computer, and when the storage medium or device is read by the computer, it can be used to configure and operate the computer to perform the process described herein. In addition, the machine-readable code, or part thereof, can be transmitted via a wired or wireless network. When such media includes instructions or programs that implement the above steps in conjunction with a microprocessor or other data processor, the invention of this embodiment includes these and other different types of non-transitory computer-readable storage media. When programmed according to the methods and techniques of the present invention, the present invention also includes the computer itself.

[0098] The computer program can be applied to input data to perform the functions of the present embodiment, thereby converting the input data to generate output data stored in a non-volatile memory. The output information can also be applied to one or more output devices such as a display. In a preferred embodiment of the present invention, the converted data represents a physical and tangible object, including a specific visual depiction of the physical and tangible object produced on the display.

[0099] The above are only preferred embodiments of the present invention. The present invention is not limited to the above embodiments. As long as the technical effects of the present invention are achieved by the same means, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention. Within the scope of protection of the present invention, its technical solutions and / or implementation methods may have various modifications and changes.

Claims

1. A timing error estimation method for dual-polarization quantum key distribution, applied to a transmitting end, characterized in that: The timing error estimation method for dual-polarization quantum key distribution includes: multiplexing the first pilot and the third pilot on the spectrum of the first polarization of the communication signal; multiplexing a second pilot and a fourth pilot on a spectrum of a second polarization of the communication signal; The multiplexed communication signal is transmitted through an optical fiber channel.

2. The timing error estimation method for dual-polarization quantum key distribution according to claim 1, characterized in that: A frequency difference between the first pilot and the third pilot, and a frequency difference between the second pilot and the fourth pilot, are both equal to half the baud rate of the communication signal.

3. The timing error estimation method for dual-polarization quantum key distribution according to claim 2, characterized in that: A frequency difference between the first pilot and the second pilot is equal to a frequency difference between the second pilot and the fourth pilot, and both are less than half the baud rate of the communication signal.

4. A timing error estimation method for dual-polarization quantum key distribution, applied to a receiving end, characterized in that: The timing error estimation method for dual-polarization quantum key distribution includes: Acquire a received signal; the received signal is transmitted by a communication signal through an optical fiber channel, and before being sent, the communication signal is multiplexed with a first pilot and a third pilot on a spectrum of a first polarization, and a second pilot and a fourth pilot on a spectrum of a second polarization; The first pilot, the second pilot, the third pilot, the fourth pilot, the fifth pilot, the sixth pilot, the seventh pilot and the eighth pilot are acquired according to the received signal; wherein the fifth pilot is generated by a physical effect of the first pilot being transmitted through an optical fiber channel, the sixth pilot is generated by a physical effect of the second pilot being transmitted through an optical fiber channel, the seventh pilot is generated by a physical effect of the third pilot being transmitted through an optical fiber channel, and the eighth pilot is generated by a physical effect of the fourth pilot being transmitted through an optical fiber channel; the frequency of the fifth pilot is the same as that of the first pilot, the frequency of the sixth pilot is the same as that of the second pilot, the frequency of the seventh pilot is the same as that of the third pilot, and the frequency of the eighth pilot is the same as that of the fourth pilot; Acquire phase information of the first pilot, the second pilot, the third pilot, the fourth pilot, the fifth pilot, the sixth pilot, the seventh pilot, and the eighth pilot; According to the phase information, a timing error value and a delay value are determined.

5. The timing error estimation method for dual-polarization quantum key distribution according to claim 4, characterized in that: The acquiring phase information of the first pilot, the second pilot, the third pilot, the fourth pilot, the fifth pilot, the sixth pilot, the seventh pilot, and the eighth pilot includes: Down-converting the first pilot, the second pilot, the third pilot, the fourth pilot, the fifth pilot, the sixth pilot, the seventh pilot and the eighth pilot; The down-converted pilot signal is filtered to obtain the phase information.

6. The timing error estimation method for dual-polarization quantum key distribution according to claim 5, characterized in that: The filtering of the down-converted pilot signal to obtain the phase information includes: Performing Wiener filtering on the down-converted pilot to obtain phases of the first pilot, the second pilot, the third pilot, the fourth pilot, the fifth pilot, the sixth pilot, the seventh pilot, and the eighth pilot; Obtaining a first phase difference average value; the first phase difference average value is an average value of a phase difference between the first pilot and the third pilot and a phase difference between the sixth pilot and the eighth pilot; Obtaining a second phase difference average value; the second phase difference average value is an average value of a phase difference between the first pilot and the seventh pilot and a phase difference between the sixth pilot and the fourth pilot; Obtaining a third phase difference average value; the third phase difference average value is an average value of a phase difference between the fifth pilot and the third pilot and a phase difference between the second pilot and the eighth pilot; Acquire a fourth phase difference average value; the fourth phase difference average value is an average value of a phase difference between the fifth pilot and the seventh pilot and a phase difference between the second pilot and the fourth pilot; A timing error matrix is ​​determined using the first phase difference average value, the second phase difference average value, the third phase difference average value and the fourth phase difference average value as elements; the timing error matrix is ​​used as the phase information.

7. The timing error estimation method for dual-polarization quantum key distribution according to claim 6, characterized in that: The determining of a timing error matrix using the first phase difference average value, the second phase difference average value, the third phase difference average value, and the fourth phase difference average value as elements includes: Using the first phase difference average as the first row and first column element of the timing error matrix; Using the second phase difference average as the first row and second column element of the timing error matrix; Using the third phase difference average as the second row and first column element of the timing error matrix; The fourth phase difference average value is used as the second row and second column element of the timing error matrix.

8. The timing error estimation method for dual-polarization quantum key distribution according to claim 6 or 7, characterized in that: Determining a timing error value and a delay value according to the phase information includes: According to the formula e τ =-Im[det(S pilot )] Calculate; where e τ is the timing error value, S pilot is the timing error matrix, det() is the operator for taking the matrix determinant, and Im[] is the operator for taking the imaginary part of a complex number.

9. The timing error estimation method for dual-polarization quantum key distribution according to claim 6 or 7, characterized in that: Determining a timing error value and a delay value according to the phase information includes: According to the formula Calculate; where τ is the delay value, S pilot is the timing error matrix, det() is a matrix determinant operator, angle[] is an operator for obtaining a complex angle, and Δf is a frequency difference between the first pilot and the third pilot.

10. The timing error estimation method for dual-polarization quantum key distribution according to any one of claims 4 to 7, characterized in that: The timing error estimation method for dual-polarization quantum key distribution also includes: PID feedback control is performed according to the timing error value.

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