CN117938272A - QKD equipment quantum light source single photon nature's test system - Google Patents
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Abstract
The invention provides a system for testing single photon property of a quantum light source of QKD equipment, which comprises a QKD transmitting end, 2 QKD receiving ends, an optical switch and a control end, wherein the control end issues a command to the optical switch at an intersection point on a branch path of the transmitting end-a first receiving end and a branch path of the transmitting end-a second receiving end, a light splitting mode is started, a series of random sequences are generated and issued to the first receiving end and the second receiving end as a measuring base selection sequence, the first receiving end and the second receiving end are issued with the command, an error correction module and a security enhancement module are shielded, the QKD transmitting end starts to transmit quantum light, a key distribution process is started, after a period of key distribution, respective key sequences of the first receiving end and the second receiving end are collected, a key consistency coefficient is calculated, the lower the key consistency coefficient is, the single photon property of the quantum light source of the transmitting end is better, and the single photon property of the quantum light source of the transmitting end is judged through the actually measured key consistency coefficient. The invention can effectively utilize the existing resources of the QKD equipment to effectively detect the single photon property of the QKD system.
Description
Technical Field
The invention relates to the field of quantum communication, in particular to a quantum light source single photon property testing system of QKD equipment.
Background
Quantum key distribution (Quantum Key Distribution, QKD) is a technique that uses the indivisible, unclonable, and unmeasurable physical properties of light quanta for key distribution to secure communication security.
However, in order to achieve the safety, it is necessary to ensure that the quantum light source has good single photon property, and although some decoy schemes are used for compensating the quantum light source, the final code rate is still lower if the single photon property is too poor. The traditional mode adopts a light splitting device and a coincidence meter to calculate the second-order association degree of a light source so as to measure the single photon property of the light source, for example, the patent application with the publication number of CN111089648A provides a filtering and second-order association degree testing device of an optical fiber coupling single photon source, which comprises: helium neon laser, which is used to emit pumping light and coupled out by single mode fiber; the Y-shaped fused fiber wavelength division multiplexer is used for guiding pumping light into the optical fiber to couple with the single photon source device for excitation to generate a single quantum dot fluorescent signal; the 2x2 fusion optical fiber beam splitter is connected with the output end of the Y-shaped fusion optical fiber wavelength division multiplexer and is used for dividing the single quantum dot fluorescent signal into two paths according to the power division and outputting the two paths; the laser collimator is used for respectively converting the single quantum dot fluorescent signals with the two paths of power divided equally into two paths of space parallel fluorescent light; the filter plate group is used for filtering non-single photon signals in two paths of space parallel fluorescence respectively to obtain two paths of narrow-spectrum single photon signals; two silicon single photon counters for testing the count rate of the narrow spectrum single photon signals; and the time coincidence counting module is connected with the silicon single photon counter and is used for representing the second-order correlation degree of the single photon signal through coincidence counting.
However, two problems still exist at present, the first problem is that the coincidence meter is expensive and large in size, and no effective single photon detection method aiming at the QKD system exists at present, so that the existing resources of the QKD device cannot be effectively utilized.
Disclosure of Invention
The invention aims to solve the technical problem of how to effectively utilize the existing resources of the QKD equipment to effectively detect the single photon property of the QKD system.
The invention solves the technical problems by the following technical means: a QKD equipment quantum light source single photon nature's test system, its characterized in that: the method comprises the steps of sending a command to an optical switch at an intersection point on a branch path of a sending end-a first receiving end and a branch path of a sending end-a second receiving end by the control end, starting a light splitting mode, generating a series of random sequences, sending the random sequences to the first receiving end and the second receiving end as measurement base selection sequences, sending the command to the first receiving end and the second receiving end, shielding an error correction module and a security enhancement module, enabling the QKD sending end to start sending quantum light, starting a key distribution flow, collecting respective key sequences of the first receiving end and the second receiving end after a period of key distribution, calculating a key consistency coefficient, enabling the single photon property of a quantum light source to be better if the key consistency coefficient is lower, and judging the single photon property of the quantum light source of the sending end through the actually measured key consistency coefficient.
As an optimized technical solution, the QKD transmitting end includes: the device comprises a signal light source for providing quantum light, a synchronous light source for providing synchronous light, a first negotiation light receiving and transmitting module for generating and detecting classical negotiation light, a wave combining device, a first control module, a first key extraction module, a modulation module and a first random number generator;
the wave combining device is arranged to combine the signal light generated by the signal light source with the synchronous light generated by the synchronous light source or to combine the signal light, the synchronous light and the negotiation light generated by the first negotiation light receiving and transmitting module;
The modulation module is arranged between the signal light source and the wave combining device and is used for adjusting information such as polarization/phase/light intensity of quantum light and the like, and the decoy state modulation module is included;
the first random number generator is connected to the modulation module and used for generating random numbers required in the quantum modulation process;
The first key extraction module is used for performing base pairing processing on the original data and obtaining a key;
the first control module is used for receiving control of the control end and feeding back data, and the fed back data comprise current parameter values of the sending end, synchronization information and key information acquired by the first key extraction module.
As an optimized technical scheme, the transmitting end can freely select whether the negotiation light and the signal light are subjected to common fiber transmission or not.
As an optimized technical scheme, the 2 QKD receiving ends have identical structures, and each QKD receiving end comprises: the device comprises a single photon detector for detecting quantum light, a synchronous light detector for detecting synchronous light, a second negotiation light receiving and transmitting module for generating and detecting classical negotiation light, a wave dividing device, a second control module, a second key extraction module and a demodulation module;
the wave-dividing device is arranged to divide the signal light and the synchronous light or to divide the signal light, the synchronous light and the negotiation light;
The demodulation module is connected to the signal light output end of the wave-dividing device and is used for measuring the quantum state in cooperation with the single photon detector;
the second key extraction module is used for performing base pairing processing on the original data and obtaining a key;
The second control module is used for receiving control of the control end and feeding back data, and the fed back data comprise current parameter values of the receiving end, synchronization information and key information acquired by the second key extraction module.
As an optimized technical solution, the optical switch includes: the optical switch, the light splitting module and the third control module;
the third control module is used for receiving control of the control end and feeding back data, wherein the fed back data comprise current parameter values and modes of the optical switch;
The 1*2 optical switch is arranged between an optical inlet of the optical switch and the optical splitting module and is used for determining whether to enter an optical splitting mode or realize an optical switching function, if not, the function is the same as that of the traditional optical switch, port forwarding is carried out on an optical signal, and if entering the optical splitting mode, the optical signal is split to two receiving ends in equal proportion through the optical splitting module;
the 2 x 2 optical switch is arranged between the 1*2 optical switch and an optical outlet of the optical switch and is used for realizing the forwarding function of the optical signal port;
the light splitting module is used for splitting light according to 50: 50-scale splitting to two receivers.
As an optimized technical scheme, the sending end and the receiving end can select to carry out negotiation optical communication with each other or the sending end and the receiving end both carry out negotiation optical communication with the control end.
As an optimized technical solution, the control end includes: the system comprises a man-machine interface, a third random number generator, a data processing module and a third control module;
the third random number generator is used for generating random numbers and sending the random numbers to two receiving ends to determine the selection of the measurement base;
The third control module is an interaction port between the control end and the sending end, between the control end and the optical switch and between the control end and the receiving end, and the control end sends parameter configuration instructions to the latter three through the third control module and acquires parameter information, key information and synchronous information;
the data processing module is arranged to calculate the consistency of the secret key and judge whether the single photon property of the quantum light source of the sending end is good or not after the control end obtains the secret key information and the synchronous information of the sending end, the eavesdropping end and the receiving end;
the man-machine interface is used for receiving various instructions of an operator and feeding back a single photon judgment result.
As an optimized technical scheme, the 2 receiving ends all select a measuring base to measure quantum light according to the random number issued by the control end, so that the same measuring base is adopted at each moment.
As an optimized technical scheme, the control end adopts a time division method to intermittently perform a single photon detection process in a business flow process, so that the real-time monitoring of the single photon is realized.
As an optimized technical scheme, before issuing a command to an optical switch at an intersection point on a branch path of a transmitting end-a first receiving end and a branch path of a transmitting end-a second receiving end, firstly, a QKD network service flow is operated, a control system slices time, single photon performance of a quantum light source of the transmitting end is detected at intervals of fixed time intervals, and two relatively close QKD receiving ends, the optical switch on the path and the QKD transmitting end are selected according to a routing algorithm to form a test system.
As an optimized technical scheme, the calculation of the key consistency coefficient follows the following process:
1) Assuming that the quantum light repetition frequency is f, when the sending end and the first receiving end carry out quantum key distribution, time synchronization is carried out by utilizing synchronous light, the rising edge of a synchronous light signal is taken as a starting point, and 1/f is the interval to equally divide the time between two synchronous signals into different time stamps, so that each key bit corresponds to the time stamp one by one, and the time stamp information of each bit is attached to the output key;
2) When the sending end and the second receiving end carry out quantum key distribution, the synchronous optical signals are also utilized to add timestamp information for the output key bit, the specific mode is the same as 1), and the steps are carried out simultaneously with 1);
3) After receiving the keys of the first receiving end and the second receiving end, the control end uses the timestamp information and the correction sequence to align the two key sequences in time, and then calculates the key consistency coefficient according to the following formula:
As an optimized technical scheme, in order to eliminate the influence of synchronous optical noise, no code is formed at the position of the time stamp 0.
As an optimized technical scheme, a hierarchical synchronization mechanism is adopted, primary synchronization signals are generated at regular intervals to generate correction sequences, rising edge positions of the primary synchronization signals correspond to codes '1' of the correction sequences, the other positions correspond to codes '0', the correction sequences are utilized for calibration, large-scale signal dislocation is prevented, and keys are output while codes corresponding to the correction sequences are attached to each bit.
As an optimized technical scheme, the specific principle of judging single photon property according to the key consistency coefficient is as follows:
Providing the line attenuation between a transmitting end and an optical switch in an on splitting mode as alpha 0, wherein the line attenuation between the optical switch and single photon detectors of a first receiving end and a second receiving end is respectively alpha 1、α2;
The split ratio of the optical switch at the first receiving end and the second receiving end is fixed as follows: 50:50;
The detection efficiency of the single photon detector of the first receiving end and the second receiving end is respectively marked as eta B,ηE; the dark count rates are denoted e B,eE, and the post pulse probabilities are denoted: aP B,aPE;
Bit flip error rates from the transmitting end to the first receiving end and the second receiving end are respectively recorded as: err B,errE;
The wavelength of the quantum light is lambda, the repetition frequency is f, and the average photon number of each pulse is mu.
When the key consistency is calculated, whether bit turning errors exist or not when the sending end sends bits to the first receiving end or the second receiving end detects the keys is judged to be 2 cases actually, the other cases are equivalent to the 2 cases, and the first case is considered firstly, namely, the bit turning errors do not exist:
The pulse photon number of the quantum light emitted by the transmitting end follows poisson distribution, and the probability that the single pulse photon number is k is:
firstly, only a key sequence generated by quantum light is considered, and the probability distribution is not affected by light attenuation and light splitting of a light splitting module, so that the probability that a first receiving end generates a key bit and a transmitting end is consistent is as follows:
The inconsistency probability is:
VII＝0；
The probability of the second receiving end generating the secret key bit consistent with the sending end is as follows:
The inconsistency probability is:
X＝0；
Secondly, considering the dark counting factor, in a key sequence generated due to dark counting, the probability of the first receiving end generating the key bit consistent with the probability of the sending end is as follows:
The inconsistency probability is:
VII＝eB；
Similarly, the probability that the second receiving end generates the secret key bit to be consistent with the sending end is as follows:
The inconsistency probability is:
XI＝eE；
in the key sequence generated by the post pulse, the probability of the first receiving end generating the key bit consistent with the probability of the sending end is as follows:
The inconsistency probability is:
Similarly, the probability that the second receiving end generates the secret key bit to be consistent with the sending end is as follows:
The inconsistency probability is:
the key agreement in this case is defined according to the key agreement as:
next consider another case, the receiving end bit is not flipped, the eavesdropping end bit is flipped, then the key consistency is:
The other cases are equivalent to the two cases, and the weighted average is carried out by taking the occurrence probability of each case as the weight to obtain the final total key consistency as follows:
cons＝[errB*errE+(1-errB)(1-errE)]cons1+[(1-errB)errE+errB(1-errE)]cons2;
the relation between the key consistency ons and the average photon number mu of the single pulse is obtained.
The invention has the advantages that: the invention provides a system and a method for testing single photon property of a quantum light source at a quantum network QKD transmitting end, and defines a key consistency coefficient for measuring the single photon property. The method can effectively utilize the existing resources of QKD and effectively reduce the cost; on the other hand, the method can realize the real-time monitoring of the single photon property of the quantum light source of the QKD transmitting end in the QKD network, and is convenient and quick.
Drawings
The following describes the embodiments of the present invention in further detail with reference to the drawings.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 schematically illustrates a functional architecture diagram of a test system according to an embodiment of the present invention;
FIG. 2 schematically illustrates an operational schematic of a synchronization technique of an embodiment of the present invention;
FIG. 3 is a diagram showing a theoretical calculation simulation;
fig. 4 is an embodiment of a corresponding optical switch.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Specifically, the system for testing the single photon property of the quantum light source of the QKD device comprises a QKD transmitting end, 2 QKD receiving ends, an optical switch and a control end, and can be referred to in fig. 1.
In QKD networking, a control end can be enabled to configure an optical switch by itself according to requirements, and one QKD transmitting end and any two QKD receiving ends which wish to test the single photon performance form the test system.
The control terminal is arranged to perform parameter configuration and data processing on the QKD transmitting terminal, the QKD receiving terminal and the optical switch, monitor whether the single photon property of the quantum light source of the QKD transmitting terminal is normal and provide feedback to the manager; the QKD transmission side is configured to generate and output signal light and synchronization light; the QKD receiving end is configured to receive signal light, synchronization light, and decode and detect; the optical switch is configured to port-forward or split optical signals.
Further, the QKD transmitting end includes: the device comprises a signal light source for providing quantum light, a synchronous light source for providing synchronous light, a first negotiation light receiving and transmitting module for generating and detecting classical negotiation light, a wave combining device, a first control module, a first key extraction module, a modulation module and a first random number generator.
The wave combining device is arranged to combine the signal light generated by the signal light source with the synchronous light generated by the synchronous light source or to combine the signal light, the synchronous light and the negotiation light generated by the first negotiation light receiving and transmitting module.
The modulation module is arranged between the signal light source and the wave combining device and is used for adjusting information such as polarization/phase/light intensity of quantum light and the like, and the decoy state modulation module is contained.
The first random number generator is connected to the modulation module and used for generating random numbers required in the quantum modulation process.
The first key extraction module is used for performing base pairing processing on the original data and obtaining a key.
The first control module is used for receiving control of the control end and feeding back data, and the fed back data comprise current parameter values of the sending end, synchronization information and key information acquired by the first key extraction module.
Optionally, the transmitting end can freely select whether the negotiation light, the signal light and the synchronous light are subjected to co-fiber transmission.
Further, the 2 QKD receiving ends are structurally identical, each comprising: the device comprises a single photon detector for detecting quantum light, a synchronous light detector for detecting synchronous light, a second negotiation light receiving and transmitting module for generating and detecting classical negotiation light, a wave dividing device, a second control module, a second key extraction module and a demodulation module.
The demultiplexing device is configured to demultiplex the signal light and the synchronization light or demultiplex the signal light, the synchronization light and the negotiation light (corresponding to whether the transmitting end performs co-fiber transmission on the negotiation light, the signal light and the synchronization light).
The demodulation module is connected to the signal light output end of the wave-dividing device and is used for measuring the quantum state in cooperation with the single photon detector;
the second key extraction module is used for performing base pairing processing on the original data and obtaining a key.
The second control module is used for receiving control of the control end and feeding back data, and the fed back data comprise current parameter values of the receiving end, synchronization information and key information acquired by the second key extraction module.
Further, the optical switch includes: the optical switch, the beam splitting module and the third control module.
The third control module is used for receiving control of the control end and feeding back data, and the fed back data comprise current parameter values and modes of the optical switch.
The 1*2 optical switch is arranged between an optical inlet of the optical switch and the optical splitting module and is used for determining whether to enter an optical splitting mode and realizing an optical switching function, if not, the function is the same as that of the traditional optical switch, port forwarding is carried out on an optical signal, and if entering the optical splitting mode, the optical signal is split to two receiving ends in equal proportion through the optical splitting module.
The 2 x 2 optical switch is disposed between the 1*2 optical switch and the optical outlet of the optical switch, for implementing the optical signal port forwarding function.
The light splitting module is used for splitting light according to 50: 50-scale splitting to two receivers.
Optionally, the sending end and the receiving end can select to negotiate optical communication with each other or the sending end and the receiving end both negotiate optical communication with the control end.
Further, the control end includes: the system comprises a man-machine interface, a third random number generator, a data processing module and a third control module.
The third random number generator is used for generating random numbers and sending the random numbers to the two receiving ends to determine the selection of the measurement base.
The third control module is an interaction port between the control end and the sending end, between the control end and the optical switch and between the control end and the receiving end, and the control end can send parameter configuration instructions to the latter three through the third control module and acquire parameter information, key information and synchronization information.
The data processing module is arranged to calculate the consistency of the key and judge whether the single photon property of the quantum light source of the sending end is good or not after the control end obtains the key information and the synchronization information of the sending end, the eavesdropping end and the receiving end.
The man-machine interface is used for receiving various instructions of an operator and feeding back a single photon judgment result.
Furthermore, both receiving ends select the measuring base to measure the quantum light according to the random number issued by the control end, so that the same measuring base is adopted at each moment.
Furthermore, the control end can adopt a time division method to intermittently perform a single photon detection process in the process of the business flow, thereby realizing the real-time monitoring of the single photon.
Further, the testing method comprises the following steps:
1) When the QKD network business flow is operated, the control system slices the time, starts to detect the single photon property of the quantum light source of the transmitting end at fixed time intervals, and selects two nearer QKD receiving ends and optical switches and QKD transmitting ends on paths to form a test system according to a routing algorithm;
2) Issuing a command to an optical switch at an intersection point on a branch path of a transmitting end, a first receiving end and a transmitting end, a second receiving end, starting a light splitting mode, generating a series of random sequences, issuing the random sequences to the first receiving end and the second receiving end as measurement base selection sequences, issuing the command to the first receiving end and the second receiving end, and shielding an error correction module and a safety enhancement module;
3) Issuing a command to enable the QKD transmitting end to start transmitting quantum light, and starting a key distribution process with the first receiving end and the second receiving end;
4) After a period of key distribution, the key sequences of the first receiving end and the second receiving end are collected, and the key consistency coefficient is calculated. The lower the key consistency coefficient is, the better the single photon property of the quantum light source is, so that the single photon property of the quantum light source at the transmitting end can be judged through the actually measured key consistency coefficient.
Further, referring to fig. 2, calculating the key agreement coefficient follows the following procedure:
1) Assuming that the quantum light repetition frequency is f, when the sending end and the first receiving end carry out quantum key distribution, time synchronization is carried out by utilizing synchronous light, the rising edge of a synchronous light signal is taken as a starting point, and 1/f is the interval to equally divide the time between two synchronous signals into different time stamps, so that each key bit corresponds to the time stamp one by one, and the time stamp information of each bit is attached to the output key;
preferably, to exclude the effects of synchronous optical noise, no code is encoded at the timestamp 0 position;
Preferably, a hierarchical synchronization mechanism is adopted, primary synchronization signals are generated at regular intervals to generate correction sequences, rising edge positions of the primary synchronization signals correspond to codes '1' of the correction sequences, other positions correspond to codes '0', the correction sequences are utilized for calibration, large-scale signal dislocation is prevented, and keys are output while codes corresponding to the correction sequences are attached to each bit;
2) When the sending end and the second receiving end carry out quantum key distribution, the synchronous optical signal is also utilized to add timestamp information for the output key bit, and the specific mode is the same as 1);
3) After receiving the keys of the first receiving end and the second receiving end, the control end uses the timestamp information and the correction sequence to align the two key sequences in time, and then calculates the key consistency coefficient according to the following formula:
Further, the specific principle of the test method is as follows:
Providing the line attenuation between a transmitting end and an optical switch in an on splitting mode as alpha 0, wherein the line attenuation between the optical switch and single photon detectors of a first receiving end and a second receiving end is respectively alpha 1、α2;
The split ratio of the optical switch at the first receiving end and the second receiving end is fixed as follows: 50:50.
The detection efficiency of the single photon detector of the first receiving end and the second receiving end is respectively marked as eta B,ηE; the dark count rates are denoted e B,eE, and the post pulse probabilities are denoted: aP B,aPE;
Bit flip error rates from the transmitting end to the first receiving end and the second receiving end are respectively recorded as: err B,errE;
The wavelength of the quantum light is lambda, the repetition frequency is f, and the average photon number of each pulse is mu.
When the key consistency is calculated, whether bit overturn exists or not actually exists only in 2 cases when the sending end sends bits and is detected by the first receiving end or the second receiving end, the other cases are equivalent to the 2 cases, and the first case is considered firstly, namely, bit overturn does not exist either:
The pulse photon number of the quantum light emitted by the transmitting end follows poisson distribution, and the probability that the single pulse photon number is k is:
firstly, only a key sequence generated by quantum light is considered, and the probability distribution is not affected by light attenuation and light splitting of a light splitting module, so that the probability that a first receiving end generates a key bit and a transmitting end is consistent is as follows:
The inconsistency probability is:
VII＝0；
The probability of the second receiving end generating the secret key bit consistent with the sending end is as follows:
The inconsistency probability is:
X＝0。
secondly, considering the dark counting factor, even if neither the first receiving end nor the second receiving end detects photons, the single photon detector still has a certain probability response so as to generate a secret key. In the key sequence generated due to dark counting, the probability that the first receiving end generates the key bit to be consistent with the sending end is as follows:
The inconsistency probability is:
VII＝eB；
Similarly, the probability that the second receiving end generates the secret key bit to be consistent with the sending end is as follows:
The inconsistency probability is:
XI＝eE；
in the key sequence generated by the post pulse, the probability of the first receiving end generating the key bit consistent with the probability of the sending end is as follows:
The inconsistency probability is:
Similarly, the probability that the second receiving end generates the secret key bit to be consistent with the sending end is as follows:
The inconsistency probability is:
the key agreement in this case is defined according to the key agreement as:
next consider another case, the receiving end bit is not flipped, the eavesdropping end bit is flipped, then the key consistency is:
The other cases are equivalent to the two cases, and the weighted average is carried out by taking the occurrence probability of each case as the weight to know the consistency of the final total key as follows:
cons＝[errB*errE+(1-errB)(1-errE)]cons1+[(1-errB)errE+errB(1-errE)]cons2;
The relationship between the key agreement ons and the average photon number μ of the single pulse can be obtained assuming that
α0＝0.25,α1＝0.1,ηB＝ηE=0.2,eB＝eE＝5*10-6,aPB＝aPE＝0.035,errB＝errE＝0.04,λ＝1350nm,f＝126MHz, A computational simulation can be given as shown in fig. 3, with the abscissa being the mean photon number of a single pulse and the ordinate being the key agreement:
The calculation result shows that the better the single photon property is, the lower the key consistency coefficient is, so that the single photon property of the quantum light source of the transmitting end can be judged through the actually measured key consistency coefficient.
Fig. 4 is an example of an implementation of the optical switch of the present invention, only an example of an optical switch of 2 x 2 is shown here as an example. Ports 1 and 2 are input ports of the optical switch of 2 x 2, and 3 and 4 are output ports of the optical switch of 2 x 2; the two 1*2 optical switches are used for selecting whether to start a light splitting mode, and if not, optical signals are respectively emitted from the ports 5 and 6; 42 x 2 optical switches form an optical switch of the crossbar type, and any input light of the ports 5 and 6 can be output from the ports 3 and 4 by adjusting the 2 x 2 optical switches.
If the on splitting mode is selected, the optical signals incident from ports 1 and 2 are emitted from ports 7 and 8 and pass through 50:50 are split into two beams of light, which are emitted from ports 3,4, respectively.
The specific implementation manner of the transmitting end and the receiving end is not greatly different from that of the common QKD equipment, and is not repeated here.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A QKD equipment quantum light source single photon nature's test system, its characterized in that: the method comprises the steps of sending a command to an optical switch at an intersection point on a branch path of a sending end-a first receiving end and a branch path of a sending end-a second receiving end by the control end, starting a light splitting mode, generating a series of random sequences, sending the random sequences to the first receiving end and the second receiving end as measurement base selection sequences, sending the command to the first receiving end and the second receiving end, shielding an error correction module and a security enhancement module, enabling the QKD sending end to start sending quantum light, starting a key distribution flow, collecting respective key sequences of the first receiving end and the second receiving end after a period of key distribution, calculating a key consistency coefficient, enabling the single photon property of a quantum light source to be better if the key consistency coefficient is lower, and judging the single photon property of the quantum light source of the sending end through the actually measured key consistency coefficient.
2. The QKD device quantum light source single-photon property testing system of claim 1, wherein: the QKD transmitting end includes: the device comprises a signal light source for providing quantum light, a synchronous light source for providing synchronous light, a first negotiation light receiving and transmitting module for generating and detecting classical negotiation light, a wave combining device, a first control module, a first key extraction module, a modulation module and a first random number generator;
the wave combining device is arranged to combine the signal light generated by the signal light source with the synchronous light generated by the synchronous light source or to combine the signal light, the synchronous light and the negotiation light generated by the first negotiation light receiving and transmitting module;
The modulation module is arranged between the signal light source and the wave combining device and is used for adjusting information such as polarization/phase/light intensity of quantum light and the like, and the decoy state modulation module is included;
the first random number generator is connected to the modulation module and used for generating random numbers required in the quantum modulation process;
The first key extraction module is used for performing base pairing processing on the original data and obtaining a key;
the first control module is used for receiving control of the control end and feeding back data, and the fed back data comprise current parameter values of the sending end, synchronization information and key information acquired by the first key extraction module.
3. The QKD device quantum light source single-photon property testing system of claim 1, wherein: the 2 QKD receiving ends are identical in structure and all comprise: the device comprises a single photon detector for detecting quantum light, a synchronous light detector for detecting synchronous light, a second negotiation light receiving and transmitting module for generating and detecting classical negotiation light, a wave dividing device, a second control module, a second key extraction module and a demodulation module;
the wave-dividing device is arranged to divide the signal light and the synchronous light or to divide the signal light, the synchronous light and the negotiation light;
The demodulation module is connected to the signal light output end of the wave-dividing device and is used for measuring the quantum state in cooperation with the single photon detector;
the second key extraction module is used for performing base pairing processing on the original data and obtaining a key;
The second control module is used for receiving control of the control end and feeding back data, and the fed back data comprise current parameter values of the receiving end, synchronization information and key information acquired by the second key extraction module.
4. The QKD device quantum light source single-photon property testing system of claim 1, wherein: the optical switch includes: the optical switch, the light splitting module and the third control module;
the third control module is used for receiving control of the control end and feeding back data, wherein the fed back data comprise current parameter values and modes of the optical switch;
The 1*2 optical switch is arranged between an optical inlet of the optical switch and the optical splitting module and is used for determining whether to enter an optical splitting mode and realizing an optical switching function, if not, the function is the same as that of the traditional optical switch, port forwarding is carried out on an optical signal, and if entering the optical splitting mode, the optical signal is split to two receiving ends in equal proportion through the optical splitting module;
the 2 x 2 optical switch is arranged between the 1*2 optical switch and an optical outlet of the optical switch and is used for realizing the forwarding function of the optical signal port;
the light splitting module is used for splitting light according to 50: 50-scale splitting to two receivers.
5. The QKD device quantum light source single-photon property testing system of claim 1, wherein: the control end comprises: the system comprises a man-machine interface, a third random number generator, a data processing module and a third control module;
the third random number generator is used for generating random numbers and sending the random numbers to two receiving ends to determine the selection of the measurement base;
The third control module is an interaction port between the control end and the sending end, between the control end and the optical switch and between the control end and the receiving end, and the control end sends parameter configuration instructions to the latter three through the third control module and acquires parameter information, key information and synchronous information;
the data processing module is arranged to calculate the consistency of the secret key and judge whether the single photon property of the quantum light source of the sending end is good or not after the control end obtains the secret key information and the synchronous information of the sending end, the eavesdropping end and the receiving end;
the man-machine interface is used for receiving various instructions of an operator and feeding back a single photon judgment result.
6. The QKD device quantum light source single-photon property testing system of claim 1, wherein: before issuing a command to an optical switch at the intersection point of the branch paths of the transmitting end, the first receiving end and the transmitting end, the second receiving end, the control system firstly operates the QKD network service flow, the control system slices the time, the single photon property of the quantum optical light source of the transmitting end is detected at fixed time intervals, and two nearer QKD receiving ends, the optical switch on the paths and the QKD transmitting end are selected according to a routing algorithm to form a test system.
7. The QKD device quantum light source single-photon property testing system of claim 1, wherein: calculating the key agreement coefficient follows the following procedure:
1) Assuming that the quantum light repetition frequency is f, when the sending end and the first receiving end carry out quantum key distribution, time synchronization is carried out by utilizing synchronous light, the rising edge of a synchronous light signal is taken as a starting point, and 1/f is the interval to equally divide the time between two synchronous signals into different time stamps, so that each key bit corresponds to the time stamp one by one, and the time stamp information of each bit is attached to the output key;
2) When the sending end and the second receiving end carry out quantum key distribution, the synchronous optical signal is also utilized to add timestamp information for the output key bit, and the specific mode is the same as 1);
3) After receiving the keys of the first receiving end and the second receiving end, the control end uses the timestamp information and the correction sequence to align the two key sequences in time, and then calculates the key consistency coefficient according to the following formula:
8. The QKD device quantum light source single-photon property testing system of claim 7, wherein: to exclude the effect of synchronous optical noise, no code is encoded at the time stamp 0 position.
9. The QKD device quantum light source single-photon property testing system of claim 7, wherein: and a hierarchical synchronization mechanism is adopted, primary synchronization signals are generated at regular intervals to generate correction sequences, the rising edge positions of the primary synchronization signals correspond to the codes '1' of the correction sequences, the other positions correspond to the codes '0', the correction sequences are utilized for calibration, large-scale signal dislocation is prevented, and the keys are output while each bit corresponds to the correction sequence codes.
10. The QKD device quantum light source single-photon property testing system of claim 7, wherein: the specific principle of judging the single photon performance by using the key consistency coefficient is as follows:
Providing the line attenuation between a transmitting end and an optical switch in an on splitting mode as alpha 0, wherein the line attenuation between the optical switch and single photon detectors of a first receiving end and a second receiving end is respectively alpha 1、α2;
the split ratio of the optical switch at the first receiving end and the second receiving end is fixed as follows: 50:50;
The detection efficiency of the single photon detector of the first receiving end and the second receiving end is respectively marked as eta B,ηE; the dark count rates are denoted e B,eE, and the post pulse probabilities are denoted: aP B,aPE;
Bit flip error rates from the transmitting end to the first receiving end and the second receiving end are respectively recorded as: err B,errE;
The wavelength of the quantum light is lambda, the repetition frequency is f, and the average photon number of each pulse is mu.
When the key consistency is calculated, whether bit overturn exists or not actually exists only in 2 cases when the sending end sends bits and is detected by the first receiving end or the second receiving end, the other cases are equivalent to the 2 cases, and the first case is considered firstly, namely, bit overturn does not exist either:
The pulse photon number of the quantum light emitted by the transmitting end follows poisson distribution, and the probability that the single pulse photon number is k is:
firstly, only a key sequence generated by quantum light is considered, and the probability distribution is not affected by light attenuation and light splitting of a light splitting module, so that the probability that a first receiving end generates a key bit and a transmitting end is consistent is as follows:
The inconsistency probability is:
VII＝0；
The probability of the second receiving end generating the secret key bit consistent with the sending end is as follows:
The inconsistency probability is:
X＝0；
Secondly, considering the dark counting factor, in a key sequence generated due to dark counting, the probability of the first receiving end generating the key bit consistent with the probability of the sending end is as follows:
The inconsistency probability is:
VII＝eB；
Similarly, the probability that the second receiving end generates the secret key bit to be consistent with the sending end is as follows:
The inconsistency probability is:
XI＝eE；
in the key sequence generated by the post pulse, the probability of the first receiving end generating the key bit consistent with the probability of the sending end is as follows:
The inconsistency probability is:
Similarly, the probability that the second receiving end generates the secret key bit to be consistent with the sending end is as follows:
The inconsistency probability is:
the key agreement in this case is defined according to the key agreement as:
next consider another case, the receiving end bit is not flipped, the eavesdropping end bit is flipped, then the key consistency is:
The other cases are equivalent to the two cases, and the weighted average is carried out by taking the occurrence probability of each case as the weight to obtain the final total key consistency as follows:
cons＝[errB*errE+(1-errB)(1-errE)]cons1+[(1-errB)errE+errB(1-errE)]cons2;
the relation between the key consistency ons and the average photon number mu of the single pulse is obtained.
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