A method for real-time measurement of shot noise and electrical noise

Abstract

The application relates to the technical field of quantum secure communication, and discloses a device and a method for measuring shot noise and electric noise in real time, which comprises an optical coupler, a balanced detection module and a data acquisition and analysis module connected in sequence, and further comprises a first optical switch module and a second optical switch module connected with the optical coupler respectively; the first optical switch module receives quantum signal light, and the second optical switch module receives local oscillation light. The application solves the problems of the prior art, such as the incapability of monitoring shot noise and electric noise in real time, the inaccuracy of parameter estimation, the low safety code rate and the low system safety.

Description

Technical Field

[0001] This invention relates to the field of quantum secure communication technology, specifically a method for real-time measurement of shot noise and electrical noise. Background Technology

[0002] Quantum key distribution (QKD) is currently the most advanced and widely used quantum secure communication technology. Among them, continuous variable QKD (CV-QKD) technology has become the main development direction of high-speed quantum secure communication due to its compatibility with high-bandwidth and highly mature classical coherent optical communication devices.

[0003] Currently, with the continuous improvement of the maturity of CV-QKD systems, it is necessary to accurately and in real-time estimate the parameters of CV-QKD systems to improve system stability and practical safety. Accurate estimation of CV-QKD system parameters mainly involves precise and real-time measurement of shot noise and electrical noise. Shot noise, in particular, is the unit noise of the CV-QKD system; improving its measurement accuracy can enhance system stability and practical safety. Current methods for measuring shot noise and electrical noise in CV-QKD systems are mainly divided into two calibration methods (Wang H., Pi YD, Huang W., et al. High-speed Gaussian-modulated continuous-variable quantum key distribution with a local oscillator based on pilot-tone-assisted phase compensation[J]. OpticsExpress, 28(22), 32882, 2020.) and one calibration method (Zhang YC, Huang Y. D, Chen ZY, et al. One-time shot-noise unit calibration method for continuous-variable quantum key distribution[J], Physical Review Applied, 13, 024058,2019.). The two calibration method involves measuring shot noise and electrical noise twice before communication to obtain the required variances of shot noise and electrical noise in advance. However, the two-calibration method is affected by the instability of the local oscillator and detector, leading to deviations between the pre-calibrated shot noise and electrical noise values ​​and their actual values ​​during communication. This affects the accuracy of parameter estimation and the secure code generation rate of the CV-QKD system. The single-calibration method primarily uses the sum of shot noise and electrical noise as the unit noise of the CV-QKD system for parameter estimation and secure code generation rate calculation. However, it still requires a calibration measurement of the sum of shot noise and electrical noise before communication, thus remaining susceptible to the instability of the local oscillator and detector. Furthermore, the single-calibration method does not accurately calibrate electrical noise separately, failing to treat it as reliable noise, resulting in a lower secure code generation rate. Most importantly, neither the two-calibration method nor the single-calibration method can monitor shot noise and electrical noise in real time, creating certain security vulnerabilities and reducing the actual security of the system. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a real-time measurement method for shot noise and electrical noise, which solves the problems of existing technologies such as the inability to monitor shot noise and electrical noise in real time, the accuracy of parameter estimation, low secure coding rate, and low system security.

[0005] The technical solution adopted by the present invention to solve the above problems is:

[0006] A real-time measurement device for shot noise and electrical noise includes an optical coupler, a balanced detection module, and a data acquisition and analysis module connected in sequence, and further includes a first optical switch module and a second optical switch module respectively connected to the optical coupler; wherein, the first optical switch module receives quantum signal light, and the second optical switch module receives local oscillator light.

[0007] As a preferred technical solution, the first optical switch module is used to switch the quantum signal light into a periodic signal.

[0008] As a preferred technical solution, the connection time of the first optical switch module is t1, and the disconnection time is t2+t3; where t1, t2, and t3 represent different time intervals.

[0009] As a preferred technical solution, the second optical switch module is used to switch the local oscillator light into a periodic signal.

[0010] As a preferred technical solution, the connection time of the second optical switch module is t1+t2, and the disconnection time is t3.

[0011] A method for real-time measurement of shot noise and electrical noise, using the aforementioned real-time measurement device for shot noise and electrical noise, includes the following steps:

[0012] S1, the quantum signal light is switched into a periodic signal after passing through the first optical switch module. The connection time of the first optical switch module is t1, and the disconnection time is t2+t3.

[0013] S2, the local oscillator light is switched into a periodic signal by the second optical switch module. The connection time of the second optical switch module is t1+t2, and the disconnection time is t3.

[0014] S3, the switched quantum signal light and local oscillator light are coupled into the balanced detection module through the optical coupler for detection. The output electrical signal after detection is analyzed by the data acquisition and analysis module to obtain the signal variance V1 in time t1, the signal variance V2 in time t2, and the signal variance V3 in time t3.

[0015] S4. By measuring V1, V2, and V3, the quantum signal variance V1-V2-V3, shot noise variance V2-V3, and electrical noise variance V3 of the CV-QKD system are obtained, thus realizing the parameter estimation of the CV-QKD system.

[0016] As a preferred technical solution, the signal variance within time t1 is:

[0017] V1=V q +V sn1 +V ele1 ;

[0018] Among them, V q V represents the variance of the quantum signal during time t1. sn1 V represents the variance of shot noise within time t1. ele1 This represents the variance of electrical noise over time t1.

[0019] As a preferred technical solution, the signal variance within time t2 is:

[0020] V2=V sn2 +V ele2 ;

[0021] Among them, V sn2 V represents the variance of shot noise over time t2. ele2 This represents the variance of electrical noise over time t2.

[0022] As a preferred technical solution, the signal variance within time t3 is:

[0023] V3=V ele3 .

[0024] As a preferred technical solution, the magnitude of t1+t2+t3 is on the order of milliseconds.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) By optimizing the switching time of the two optical switch modules, the present invention can realize real-time measurement of shot noise and electrical noise in a short time without the need to pre-calibrate shot noise and electrical noise before CV-QKD communication, thus overcoming the influence of the instability of local oscillator light and detector and ensuring the stable and secure coding performance of CV-QKD system.

[0027] (2) The present invention can realize real-time security monitoring of quantum signals, shot noise and electrical noise, eliminate quantum hacking attacks by eavesdroppers targeting the security vulnerabilities of local oscillator and detector, and improve the actual security of CV-QKD system. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a real-time measurement device for shot noise and electrical noise according to the present invention.

[0029] The labels and their corresponding names in the attached diagram are as follows: 1. First optical switch module, 2. Second optical switch module, 3. Optical coupler, 4. Balanced detection module, 5. Data acquisition and analysis module. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0031] Example 1

[0032] like Figure 1 To address the technical problem that shot noise and electrical noise in current CV-QKD systems cannot be measured and monitored in real time, resulting in insufficient stability and actual safety of CV-QKD systems, this invention provides a real-time measurement device and method for shot noise and electrical noise in CV-QKD systems.

[0033] A real-time measurement device for shot noise and electrical noise includes a first optical switch module 1, a second optical switch module 2, an optical coupler 3, a balanced detection module 4, and a data acquisition and analysis module 5. The quantum signal light arriving at the receiving end is input to the first optical switch module 1, and the local oscillator light is input to the second optical switch module 2. The outputs of the first and second optical switch modules are respectively optically connected to the two inputs of the optical coupler 3. Finally, the output of the optical coupler 3 is optically connected to the balanced detection module 4, and the balanced detection module 4 is electrically connected to the data acquisition and analysis module 5.

[0034] A method for real-time measurement of shot noise and electrical noise includes the following steps:

[0035] Step 1: The quantum signal light arriving at the receiving end is switched into a periodic signal through the first optical switch module 1. The connection time of the first optical switch module 1 is t1, and the disconnection time is t2+t3. Here, t1, t2, and t3 represent different time intervals, which are set in advance according to the actual working conditions.

[0036] Step 2: The local oscillator light is switched into a periodic signal by the second optical switch module 2. The connection time of the second optical switch module 2 is t1+t2, and the disconnection time is t3.

[0037] Step 3: The switched quantum signal light and local oscillator light are coupled into the balanced detection module 4 via optical coupler 3 for detection. The detected electrical signal is analyzed by the data acquisition and analysis module 5, and the sum of the variances of the quantum signal, shot noise, and electrical noise within time t1 is obtained as V1 = Vq +V sn1 +V ele1 The sum of the variances of shot noise and electrical noise within time t2 is obtained as V2 = V sn2 +V ele2 The variance of the electrical noise during time t3 is obtained as V3 = V ele2 ;

[0038] Step 4: By measuring the signal variances at times t1, t2, and t3 respectively, the variances of the quantum signal V1-V2-V3, shot noise V2-V3, and electrical noise V3 can be obtained, thereby realizing parameter estimation of the CV-QKD system.

[0039] Furthermore, to ensure that the variance of shot noise in the CV-QKD system is approximately equal during time periods t1 and t2, and that the variance of electrical noise is approximately equal during time periods t1, t2, and t3, the time period t1+t2+t3 of the first optical switch module 1 and the second optical switch module 2 should be set as small as possible.

[0040] Furthermore, to reduce the communication data overhead of the CV-QKD system, the time lengths of t1, t2, and t3 need to be optimized, and t1 should be as long as possible.

[0041] The present invention has the following advantages:

[0042] (1) By optimizing the switching time of the two optical switch modules, the present invention can realize real-time measurement of shot noise and electrical noise in a short time without the need to pre-calibrate shot noise and electrical noise before CV-QKD communication, thus overcoming the influence of the instability of local oscillator light and detector and ensuring the stable and secure coding performance of CV-QKD system.

[0043] (2) The present invention can realize real-time security monitoring of quantum signals, shot noise and electrical noise, eliminate quantum hacking attacks by eavesdroppers targeting the security vulnerabilities of local oscillator and detector, and improve the actual security of CV-QKD system.

[0044] Example 2

[0045] like Figure 1 As a further optimization of Embodiment 1, this embodiment also includes the following technical features based on Embodiment 1:

[0046] like Figure 1As shown, the present invention provides a real-time measurement device for shot noise and electrical noise, including a first optical switch module 1, a second optical switch module 2, an optical coupler 3, a balanced detector, and a data acquisition and analysis module 5. The quantum signal light arriving at the receiving end is connected to the input end of the first optical switch module 1, and the local oscillator light is connected to the input end of the second optical switch module 2. The output ends of the first optical switch module 1 and the second optical switch module 2 are optically connected to the two input ends of the optical coupler 3. The output end of the optical coupler 3 is optically connected to the balanced detector, and the balanced detector is electrically connected to the data acquisition and analysis module 5.

[0047] The present invention provides a real-time measurement method for shot noise and electrical noise as follows:

[0048] The quantum signal light arriving at the receiving end is switched by the first optical switch module 1 into a periodic signal with a connection time of t1 and a disconnection time of t2+t3. The local oscillator light is switched by the second optical switch module 2 into a periodic signal with a connection time of t1+t2 and a disconnection time of t3. The switched quantum signal light and local oscillator light are coupled into the balanced detection module 4 via the optical coupler 3 for detection. Then, the data acquisition and analysis module 5 analyzes the detected electrical signal to obtain the signal variance within time t1:

[0049] V1=V q +V sn1 +V ele1 (1)

[0050] Among them, V q V is the variance of the quantum signal during time t1. sn1 Let V be the variance of shot noise within time t1, and V ele1 Let be the variance of electrical noise during time t1.

[0051] The signal variance within time t2 obtained by data acquisition and analysis module 5 is:

[0052] V2=V sn2 +V ele2 (2)

[0053] Among them, V sn2 The variance of shot noise and V during time t2 ele2 Let be the variance of electrical noise over time t2.

[0054] The signal variance within time t3 obtained by data acquisition and analysis module 5 is:

[0055] V3=V ele3 (3)

[0056] Among them, V ele3 Let be the variance of electrical noise over time t3.

[0057] When the time interval t1+t2+t3 is short, such as on the order of milliseconds, the variance of shot noise within time intervals t1 and t2 can be approximated as equal (V0). sn1 ≈V sn2 The variances of electrical noise during time intervals t1, t2, and t3 can be approximated as equal (V). ele1 ≈V ele2 ≈V ele3 Thus, the electrical noise variance measurement of the CV-QKD system during real-time communication is V3, the shot noise variance measurement is V2-V3, and the quantum signal variance measurement is V1-V2-V3. Real-time parameter estimation and monitoring of the CV-QKD system can be achieved in a single communication, ensuring the stability and practical security of the CV-QKD system's secure coding.

[0058] As described above, the present invention can be implemented well.

[0059] All features disclosed in all embodiments of this specification, or steps in all methods or processes implied in the disclosure, may be combined and / or extended or replaced in any way, except for mutually exclusive features and / or steps.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Based on the technical essence of the present invention, any simple modifications, equivalent substitutions, and improvements made to the above embodiments within the spirit and principles of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method of real-time measurement of shot and electrical noise, characterized in that, A kind of real-time measurement device of shot noise and electric noise is adopted, and the measurement device includes: The light coupler (3) connected in turn, balanced detection module (4), data acquisition and analysis module (5), also include first optical switch module (1) being connected with the light coupler (3), second optical switch module (2);Wherein, first optical switch module (1) receives quantum signal light, and second optical switch module (2) receives local oscillator light; The measurement method includes the following steps: S1, quantum signal light is switched to periodic signal by first optical switch module (1), and the communication time of first optical switch module (1) is t1, and the off time is t2+t3; S2, local oscillator light is switched to periodic signal by second optical switch module (2), and the communication time of second optical switch module (2) is t1+t2, and the off time is t3; S3, after switching, quantum signal light and local oscillator light are coupled into balanced detection module (4) by light coupler (3) and are detected, and the electrical signal output after detection is analyzed by data acquisition and analysis module (5), and the signal variance V1 in t1 time, the signal variance V2 in t2 time, the signal variance V3 in t3 time are obtained; S4, the quantum signal variance V1-V2-V3 of CV-QKD system, the shot noise variance V2-V3 of CV-QKD system, the electric noise variance V3 of CV-QKD system are obtained by V1, V2, V3 obtained by measurement, and the parameter estimation of CV-QKD system is realized; To ensure CV The variance of the shot noise in the QKD system t1 and t2 is approximately equal, the variance of the electric noise in t1, t2 and t3 is approximately equal, and the time period t1+t2+t3 of the first optical switch module and the second optical switch module is set as small as possible. When t1+t2+t3 is of the order of ms, the shot noise variance in t1 and t2 is approximated as equal to V sn1 ≈V sn2 The electrical noise variance in t1, t2 and t3 is approximated as equal to V ele1 ≈V ele2 ≈V ele3 , V sn1 denotes the shot noise variance in t1, V sn2 denotes the shot noise variance in t2, V ele1 denotes the electrical noise variance in t1, V ele2 denotes the electrical noise variance in t2, V ele3 denotes the electrical noise variance in t3.

2. The method of claim 1, wherein, The signal variance in t1 time is: V1=V q +V sn1 +V ele1 ; where V q represents the variance of the quantum signal over time t1.

3. The method of claim 2, wherein, The signal variance in t2 time is: V2 = V sn2 +V ele2 .

4. The method of claim 2, wherein, The signal variance in t3 time is: V3 = V ele3 .

5. The method of claim 1, wherein, First optical switch module (1) is used to switch quantum signal light into periodic signal.

6. The method of real-time measurement of shot noise and electrical noise according to claim 5, wherein, The communication time of first optical switch module (1) is t1, and the off time is t2+t3;Wherein, t1, t2, t3 represent different time intervals respectively.

7. The method of real-time measurement of shot noise and electrical noise according to claim 6, wherein, Second optical switch module (2) is used to switch local oscillator light into periodic signal.

8. The method of real-time measurement of shot noise and electrical noise according to claim 7, wherein, The communication time of second optical switch module (2) is t1+t2, and the off time is t3.

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