A quantum key distribution arbitrary passive decoy state method and generation device

Abstract

The present invention belongs to the field of quantum secure communication technology, and discloses a method and a device for generating an arbitrary passive decoy state for quantum key distribution, wherein the device includes a laser, a time-delay interferometer, a photodetector, an analog-to-digital conversion module, and a data processing module, wherein the data processing module is used to divide a digital signal into M light intensity intervals arranged in ascending order, and obtain the light intensity distribution of each light intensity interval, and the present invention also discloses a method for distributing an arbitrary passive decoy state for quantum key distribution. Compared with the prior art, the present invention uses a time-delay interferometer to convert the random phase of the spontaneous radiation of the laser into a random light intensity, and divides the light intensity distribution into an arbitrary number of light intensity intervals after real-time measurement, so as to realize the passive generation of an arbitrary number of decoy states, and reduce the influence of light intensity fluctuations on the system. And an arbitrary number of decoy states can be selected to improve the parameter estimation accuracy, thereby improving the security key rate.

Description

Technical Field

[0001] The present invention relates to the technical field of quantum secure communication, and in particular to a method and a generating device for quantum key distribution of arbitrary passive decoy states. Background Art

[0002] Quantum key distribution can provide unconditionally secure keys for both parties in long-distance communication, and can achieve unconditionally secure communication when combined with symmetric encryption methods. Since the light source in the quantum key distribution system has multi-photon components, it is different from the basic theoretical model of security and is vulnerable to photon number separation (PNS) attacks. The decoy state method can solve this problem very well. The generation of decoy states can be divided into two ways: active and passive. The former requires additional random numbers to determine the modulation of different light intensities, which increases the demand for random numbers and has modulation errors, reducing the security of the system; the latter does not require random numbers and determines the decoy state and signal state by passively measuring the light intensity. The paper Passive decoy-state quantum key distribution with practical light sources, Curty M et al., 2010 Phys. Rev. A 81(2) 022310, and the invention patent with publication number CN113225184A, use two independent lasers to interfere to obtain random light intensity, and obtain the decoy state light intensity distribution by measuring the interference light intensity. However, due to the existence of intensity fluctuations and jitter of the two lasers, the light intensity distribution changes, which leads to inaccurate estimation of the amount of eavesdropper information using the decoy state method, reducing the security of the key. In addition, since only one detector is used, only two events, "response" and "non-response", can be generated, and the corresponding number of decoy states is small, which makes the estimated value of the security key rate low, reducing the performance of the system. The invention patent with publication number CN107872316A uses a beam splitter and multiple detectors to generate 4 events, increasing the number of decoy states, but there are still problems such as intensity fluctuations, and the number of decoy states is fixed, so it is impossible to estimate the security key rate more accurately. Summary of the invention

[0003] In view of the above defects in the prior art, the present invention proposes a method and a device for generating an arbitrary passive decoy state of quantum key distribution.

[0004] The technical solution of the present invention is achieved in this way:

[0005] A quantum key distribution arbitrary passive decoy state method comprises the following steps:

[0006] S1: The laser at the transmitting end emits light pulses at a repetition frequency f;

[0007] S2: The light pulse enters the delay interferometer, causing interference between different light pulses, and the first interference result and the second interference result are emitted from two output ports of the delay interferometer respectively;

[0008] S3: Use a photoelectric detector to detect the first interference result, set M light intensity intervals in ascending order according to the light intensity distribution of the interference result, and obtain the light intensity distribution of each light intensity interval , where v is the average number of photons per pulse, and m is a positive integer in the range [1,M];

[0009] S4: The second interference result corresponding to the light intensity interval with the smallest intensity in the first interference result is taken as the signal state, and the second interference results corresponding to the remaining light intensity intervals are respectively taken as M-1 decoy states, which are transmitted to the receiving end through the quantum channel for decoding and detection after quantum state modulation;

[0010] S5: The transmitter publishes the decoy state information to the receiver, and the receiver counts the photon count rate at each light intensity. , according to M The linear equation composed of the n-photon pulse count rate is used to estimate the lower bound of the single-photon pulse count rate and the upper bound of the bit error rate. Finally, the security key rate is calculated according to the GLLP formula.

[0011] Preferably, the time-delay interferometer is a polarization-independent unequal-arm interferometer.

[0012] Preferably, the arm length delay difference of the delay interferometer is N / f, where N is a positive integer not less than 2.

[0013] Preferably, the number of the light intensity intervals M is greater than 2.

[0014] The present invention also discloses a quantum key distribution arbitrary passive decoy state generating device, comprising a laser, a time delay interferometer, a photoelectric detector, an analog-to-digital conversion module and a data processing module.

[0015] The laser is used to generate light pulses with a repetition frequency f;

[0016] The time-delay interferometer is used to interfere different light pulses to generate a first interference result and a second interference result with random light intensity;

[0017] The photoelectric detector is used to detect the first interference result and convert the optical signal into an electrical signal;

[0018] The analog-to-digital conversion module is used to convert the electrical signal output by the photodetector into a digital signal;

[0019] The data processing module is used to divide the digital signal into M light intensity intervals arranged in ascending order and obtain the light intensity distribution of each light intensity interval. , where v is the average number of photons in the mth light intensity interval, and m is a positive integer in the range [1,M].

[0020] Preferably, the delay interferometer comprises a circulator, a beam splitter, a first delay line, a first quarter wave plate mirror and a second quarter wave plate mirror.

[0021] The first port, the second port and the third port of the circulator are respectively connected to a laser, a photodetector and an input port of a beam splitter;

[0022] The two output ports of the beam splitter are respectively connected to the first quarter wave mirror and the second quarter wave mirror; the first delay line is arranged on the optical fiber connecting the beam splitter and the first quarter wave mirror;

[0023] The other input port of the beam splitter serves as the output port of the entrapped state generating device.

[0024] Preferably, the delay interferometer comprises a circulator, a first polarization beam splitter, a second polarization beam splitter and a second delay line.

[0025] The first port, the second port and the third port of the circulator are respectively connected to the laser, the photodetector and an input port of the first polarization beam splitter;

[0026] Two output ports of the first polarization beam splitter are respectively connected to an input port and an output port of the second polarization beam splitter;

[0027] The polarization directions of the two output ports of the first polarization beam splitter and its input port connected to the circulator are respectively at an angle of 45° to the slow axis of the polarization-maintaining optical fiber;

[0028] Another input port and another output port of the second polarization beam splitter are connected via a second delay line;

[0029] The other input port of the first polarization beam splitter serves as the output port of the entrapped state generating device.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention proposes a method and device for generating an arbitrary passive decoy state for quantum key distribution, which uses a time-delay interferometer to convert the random phase of the spontaneous radiation of the laser into a random light intensity, and divides the light intensity distribution into an arbitrary number of light intensity intervals after real-time measurement, so as to realize the passive generation of an arbitrary number of decoy states, and reduce the influence of light intensity fluctuations on the system. In addition, the present invention can select an arbitrary number of decoy states, which can improve the accuracy of parameter estimation, thereby improving the security key rate. In addition, only one laser and one detector are needed, which reduces the complexity of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a flow chart of the method for distributing arbitrary passive decoy states of quantum key of the present invention;

[0033] Figure 2 This is a principle block diagram of Embodiment 1 of the device for generating arbitrary passive decoy states for quantum key distribution according to the present invention;

[0034] Figure 3 This is a principle block diagram of Embodiment 2 of the device for generating arbitrary passive decoy states for quantum key distribution according to the present invention. DETAILED DESCRIPTION

[0035] The present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0036] like Figure 1 As shown, a method for quantum key distribution of arbitrary passive decoy states comprises the following steps:

[0037] S1: The laser at the sending end of the quantum key distribution system emits light pulses at a repetition frequency f;

[0038] S2: The light pulse enters the delay interferometer, causing interference between different light pulses, and the first interference result and the second interference result are emitted from two output ports of the delay interferometer respectively;

[0039] S3: Use a photoelectric detector to detect the first interference result, set M light intensity intervals in ascending order according to the light intensity distribution of the interference result, and obtain the light intensity distribution of each light intensity interval , where v is the average number of photons per pulse, and m is a positive integer in the range [1,M];

[0040] S4: The second interference result corresponding to the light intensity interval with the smallest intensity in the first interference result is taken as the signal state, and the second interference results corresponding to the remaining light intensity intervals are respectively taken as M-1 decoy states, which are transmitted to the receiving end through the quantum channel for decoding and detection after quantum state modulation;

[0041] S5: The transmitter publishes the decoy state information to the receiver, and the receiver counts the photon count rate at each light intensity. , according to M The linear equation composed of the n-photon pulse count rate is used to estimate the lower bound of the single-photon pulse count rate and the upper bound of the bit error rate. Finally, the security key rate is calculated according to the GLLP formula.

[0042] The specific working principle is as follows:

[0043] The laser generates light pulses with random phases. After entering the delay interferometer, interference occurs between different light pulses. Since the phase generated by the spontaneous radiation of the laser is random, the phase difference between different light pulses is also random. The first interference result and the second interference result are emitted from the two output ports of the delay interferometer respectively. The two can be written as

[0044] ,

[0045] in, are the intensity of the light pulse and the phase difference between different light pulses respectively.

[0046] Use a photoelectric detector to detect the first interference result, set M light intensity intervals in ascending order according to the light intensity distribution of the interference result, and obtain the light intensity distribution of each light intensity interval , where v is the average number of photons per pulse, and m is a positive integer in the range [1,M]. The second interference result corresponding to the light intensity interval with the smallest intensity in the first interference result is taken as the signal state, and the second interference results corresponding to the remaining light intensity intervals are taken as M-1 decoy states, which are transmitted to the receiving end through the quantum channel for decoding and detection after quantum state modulation. The sending end announces the decoy state information to the receiving end, and the receiving end counts the photon count rate under each light intensity. , we can write M numbers consisting of The linear equation consisting of and n photon pulse count rate can be written in matrix form as

[0047] ,

[0048] Similarly, the bit error count rate under the mth light intensity can be written as

[0049] ,

[0050] in, The matrices are The bit error rate caused by the {m,j}th element of and the optical pulse containing j photons.

[0051] Therefore, the lower bound of the count rate and the upper bound of the bit error rate of single-photon pulses can be estimated to be

[0052] ,

[0053] ,

[0054] Finally, the security key rate is calculated according to the GLLP formula:

[0055] ,

[0056] Among them, q, , are the basis selection probability, binary Shannon entropy and error correction efficiency function, respectively. is the probability of selecting the i-th light intensity interval.

[0057] like Figure 2 As shown, embodiment 1:

[0058] A quantum key distribution arbitrary passive decoy state generating device comprises a laser LD, a time delay interferometer, a photoelectric detector PD, an analog-to-digital conversion module ADC and a data processing module DSP.

[0059] The laser LD is used to generate light pulses with a repetition frequency f;

[0060] The time-delay interferometer is used to interfere different light pulses to generate a first interference result and a second interference result with random light intensity;

[0061] The photodetector PD is used to detect the first interference result and convert the optical signal into an electrical signal;

[0062] The analog-to-digital conversion module ADC is used to convert the electrical signal output by the photodetector into a digital signal;

[0063] The data processing module DSP is used to divide the digital signal into M light intensity intervals arranged in ascending order and obtain the light intensity distribution of each light intensity interval. , where v is the average number of photons in the mth light intensity interval, and m is a positive integer in the range [1,M].

[0064] The delay interferometer comprises a circulator CIR, a beam splitter BS, a first delay line DL1, a first quarter wave plate mirror QWM1 and a second quarter wave plate mirror QWM2.

[0065] The first port, the second port and the third port of the circulator CIR are respectively connected to the laser LD, the photodetector PD and an input port of the beam splitter BS;

[0066] The two output ports of the beam splitter BS are connected to the first quarter wave mirror QWM1 and the second quarter wave mirror QWM2 respectively; the first delay line DL1 is arranged on the optical fiber connecting the beam splitter BS and the first quarter wave mirror QWM1;

[0067] The other input port of the beam splitter BS serves as the output port of the entrapped state generating device.

[0068] The specific working principle is as follows:

[0069] The laser LD generates an optical pulse with a random phase, which first enters the circulator CIR and reaches an input port of the beam splitter BS, where it is split into two sub-pulses with the same amplitude. They pass through the optical fiber and reach the second quarter-wave mirror QWM2 and the first quarter-wave mirror QWM1, respectively, and then return to the beam splitter BS after being reflected. One of the sub-pulses goes through the first delay line DL1 and is delayed N cycles relative to the other sub-pulse, that is, a sub-pulse of the i-th optical pulse and a sub-pulse of the i+N-th optical pulse arrive at the beam splitter BS at the same time.

[0070] Since the QWM consists of a quarter-wave plate and a reflector, and the angle between the main axis of the quarter-wave plate and the horizontal polarization direction is 45°, its Jones matrix can be written as

[0071] ,

[0072] After a light pulse of any polarization state is reflected by QWM, the polarization state becomes

[0073] ,

[0074] That is, the effect is to exchange the horizontal polarization component and the vertical polarization component of the light pulse. Therefore, after passing through the same optical fiber back and forth, the phases introduced by the fast and slow axes of the optical fiber to the two polarization components are the same, so that the polarization states of the two sub-pulses are still the same when they return to the beam splitter BS, and stable interference can be performed.

[0075] Since the phase of the spontaneous radiation generated by the laser PD is random, the phase difference between different light pulses is also random. The first interference result and the second interference result are emitted from the two input ports of the beam splitter BS respectively, and the two can be written as

[0076] ,

[0077] in, are the intensity of the light pulse and the phase difference between different light pulses respectively.

[0078] The first interference result passes through the circulator CIR and enters the photoelectric detector for detection. According to the light intensity distribution of the interference result, M light intensity intervals are set in ascending order, and the light intensity distribution of each light intensity interval is obtained. , where v is the average number of photons per pulse, and m is a positive integer in the range [1,M]. The second interference result corresponding to the light intensity interval with the smallest intensity in the first interference result is taken as the signal state, and the second interference results corresponding to the remaining light intensity intervals are taken as M-1 decoy states, which are transmitted to the receiving end through the quantum channel for decoding and detection after quantum state modulation. The sending end announces the decoy state information to the receiving end, and the receiving end counts the photon count rate under each light intensity. , we can write M numbers consisting of The linear equation consisting of and n photon pulse count rate can be written in matrix form as

[0079] ,

[0080] Similarly, the bit error count rate under the mth light intensity can be written as

[0081] ,

[0082] in, The matrices are The bit error rate caused by the {m,j}th element of and the optical pulse containing j photons.

[0083] Therefore, the lower bound of the count rate and the upper bound of the bit error rate of single-photon pulses can be estimated to be

[0084] ,

[0085] ,

[0086] Finally, the security key rate is calculated according to the GLLP formula:

[0087] ,

[0088] Among them, q, , are the basis selection probability, binary Shannon entropy and error correction efficiency function, respectively. is the probability of selecting the i-th light intensity interval.

[0089] like Figure 3 As shown, Example 2:

[0090] A quantum key distribution arbitrary passive decoy state generating device comprises a laser LD, a time delay interferometer, a photoelectric detector PD, an analog-to-digital conversion module ADC and a data processing module DSP.

[0091] The laser LD is used to generate light pulses with a repetition frequency f;

[0092] The time-delay interferometer is used to interfere different light pulses to generate a first interference result and a second interference result with random light intensity;

[0093] The photodetector PD is used to detect the first interference result and convert the optical signal into an electrical signal;

[0094] The analog-to-digital conversion module ADC is used to convert the electrical signal output by the photodetector into a digital signal;

[0095] The data processing module DSP is used to divide the digital signal into M light intensity intervals arranged in ascending order and obtain the light intensity distribution of each light intensity interval. , where v is the average number of photons in the mth light intensity interval, and m is a positive integer in the range [1,M].

[0096] The delay interferometer comprises a circulator CIR, a first polarization beam splitter PBS1, a second polarization beam splitter PBS2 and a second delay line DL2.

[0097] The first port, the second port and the third port of the circulator CIR are respectively connected to the laser LD, the photodetector PD and an input port of the first polarization beam splitter PBS1;

[0098] Two output ports of the first polarization beam splitter PBS1 are respectively connected to an input port and an output port of the second polarization beam splitter PBS2;

[0099] The polarization directions of the two output ports of the first polarization beam splitter PBS1 and its input port connected to the circulator CIR are respectively at an angle of 45° with the slow axis of the polarization-maintaining optical fiber;

[0100] Another input port and another output port of the second polarization beam splitter PBS2 are connected via a second delay line DL2;

[0101] The other input port of the first polarization beam splitter PBS1 serves as the output port of the entrapped state generating device.

[0102] The specific working principle is as follows:

[0103] The laser LD generates an optical pulse with a random phase, which first enters the circulator CIR and reaches an input port of the first polarization beam splitter PBS1. The polarization is first rotated 45°, and the horizontal polarization component and the vertical polarization component are respectively emitted from the two output ports of the first polarization beam splitter PBS1, and the polarization states of the two are rotated 45°, becoming the first component and the second component respectively, and arrive at an input port and an output port of the second polarization beam splitter PBS2 from opposite directions at the same time.

[0104] The first component is polarized and split into two sub-pulses with the same amplitude by the second polarization beam splitter PBS2. One of the sub-pulses enters the second delay line DL2, propagates once and returns to the second polarization beam splitter PBS2 again. It is delayed by N cycles relative to the other sub-pulse directly emitted from the second polarization beam splitter PBS2, that is, a sub-pulse of the i-th light pulse and a sub-pulse of the i+N-th light pulse arrive at the second polarization beam splitter PBS2 at the same time, and the polarizations of the two are perpendicular to each other, and polarization beam combination is performed. Since the phase generated by the spontaneous radiation of the laser is random, the phase difference between different light pulses is also random, and the polarization state formed after the two are polarized and combined is also random, which can be written as

[0105] ,

[0106] The amplitudes of H and V are equal. Therefore, the combined light pulse is polarized by 45° before returning to the first polarization beam splitter PBS1, becoming

[0107] ,

[0108] That is, the horizontal polarization component and the vertical polarization component interfere with each other and are finally polarized and split by the first polarization beam splitter PBS1. The first interference result and the second interference result are emitted from the two input ports of the first polarization beam splitter PBS1 respectively. The two can be written as

[0109] ,

[0110] in, are the intensity of the light pulse and the phase difference between different light pulses respectively.

[0111] The first interference result passes through the circulator CIR and enters the photoelectric detector for detection. According to the light intensity distribution of the interference result, M light intensity intervals are set in ascending order, and the light intensity distribution of each light intensity interval is obtained. , where v is the average number of photons per pulse, and m is a positive integer in the range [1,M]. The second interference result corresponding to the light intensity interval with the smallest intensity in the first interference result is taken as the signal state, and the second interference results corresponding to the remaining light intensity intervals are taken as M-1 decoy states, which are transmitted to the receiving end through the quantum channel for decoding and detection after quantum state modulation. The sending end announces the decoy state information to the receiving end, and the receiving end counts the photon count rate under each light intensity. , we can write M numbers consisting of The linear equation consisting of and n photon pulse count rate can be written in matrix form as

[0112] ,

[0113] Similarly, the bit error count rate under the mth light intensity can be written as

[0114] ,

[0115] in, The matrices are The bit error rate caused by the {m,j}th element of and the optical pulse containing j photons.

[0116] Therefore, the lower bound of the count rate and the upper bound of the bit error rate of single-photon pulses can be estimated to be

[0117] ,

[0118] ,

[0119] Finally, the security key rate is calculated according to the GLLP formula:

[0120] ,

[0121] Among them, q, , are the basis selection probability, binary Shannon entropy and error correction efficiency function, respectively. is the probability of selecting the i-th light intensity interval.

[0122] It can be seen from the various embodiments of the present invention that the present invention proposes a method and a device for generating an arbitrary passive decoy state for quantum key distribution, which uses a time-delay interferometer to convert the random phase of the spontaneous radiation of the laser into a random light intensity, and divides the light intensity distribution into an arbitrary number of light intensity intervals after real-time measurement, so as to realize the passive generation of an arbitrary number of decoy states, and reduce the influence of light intensity fluctuations on the system. In addition, the present invention can select an arbitrary number of decoy states, which can improve the accuracy of parameter estimation, thereby improving the security key rate. In addition, only one laser and one detector are needed, which reduces the complexity of the system.

Claims

1. A method for quantum key distribution of arbitrary passive decoy states, characterized in that: The steps include: S1: The laser at the transmitting end emits light pulses at a repetition frequency f; S2: The light pulse enters the delay interferometer, causing interference between different light pulses, and the first interference result and the second interference result are emitted from two output ports of the delay interferometer respectively; S3: Use a photoelectric detector to detect the first interference result, set M light intensity intervals in ascending order according to the light intensity distribution of the interference result, and obtain the light intensity distribution of each light intensity interval , where v is the average number of photons per pulse, and m is a positive integer in the range [1,M]; S4: The second interference result corresponding to the light intensity interval with the smallest intensity in the first interference result is taken as the signal state, and the second interference results corresponding to the remaining light intensity intervals are respectively taken as M-1 decoy states, which are transmitted to the receiving end through the quantum channel for decoding and detection after quantum state modulation; S5: The transmitter publishes the decoy state information to the receiver, and the receiver counts the photon count rate at each light intensity. , according to M The linear equation composed of the n-photon pulse count rate is used to estimate the lower bound of the single-photon pulse count rate and the upper bound of the bit error rate. Finally, the security key rate is calculated according to the GLLP formula.

2. The arbitrary passive decoy state method for quantum key distribution according to claim 1, characterized in that: The time-delay interferometer is a polarization-independent unequal-arm interferometer.

3. The arbitrary passive decoy state method for quantum key distribution according to claim 2, characterized in that: The arm length delay difference of the delay interferometer is N / f, where N is a positive integer not less than 2.

4. The arbitrary passive decoy state method for quantum key distribution according to claim 1, characterized in that: The number of the light intensity intervals M is greater than 2.

5. A device for generating an arbitrary passive decoy state for quantum key distribution, used to implement any one of the methods for quantum key distribution arbitrary passive decoy states in claims 1 to 4, characterized in that: Including laser, time-delay interferometer, photoelectric detector, analog-to-digital conversion module and data processing module, The laser is used to generate light pulses with a repetition frequency f; The time-delay interferometer is used to interfere different light pulses to generate a first interference result and a second interference result with random light intensity; The photoelectric detector is used to detect the first interference result and convert the optical signal into an electrical signal; The analog-to-digital conversion module is used to convert the electrical signal output by the photodetector into a digital signal; The data processing module is used to divide the digital signal into M light intensity intervals arranged in ascending order and obtain the light intensity distribution of each light intensity interval. , where v is the average number of photons in the mth light intensity interval, and m is a positive integer in the range [1,M].

6. The device for generating arbitrary passive decoy states for quantum key distribution according to claim 5, characterized in that: The delay interferometer comprises a circulator, a beam splitter, a first delay line, a first quarter wave plate mirror and a second quarter wave plate mirror. The first port, the second port and the third port of the circulator are respectively connected to a laser, a photodetector and an input port of a beam splitter; Two output ports of the beam splitter are connected to a first quarter wave mirror and a second quarter wave mirror respectively; a first delay line is arranged on an optical fiber connecting the beam splitter and the first quarter wave mirror; The other input port of the beam splitter serves as the output port of the entrapped state generating device.

7. The device for generating arbitrary passive decoy states for quantum key distribution according to claim 5, characterized in that: The delay interferometer comprises a circulator, a first polarization beam splitter, a second polarization beam splitter and a second delay line. The first port, the second port and the third port of the circulator are respectively connected to the laser, the photodetector and an input port of the first polarization beam splitter; Two output ports of the first polarization beam splitter are respectively connected to an input port and an output port of the second polarization beam splitter; The polarization directions of the two output ports of the first polarization beam splitter and its input port connected to the circulator are respectively at an angle of 45° to the slow axis of the polarization-maintaining optical fiber; Another input port and another output port of the second polarization beam splitter are connected via a second delay line; The other input port of the first polarization beam splitter serves as the output port of the entrapped state generating device.

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