CN109889274B - Novel continuous variable quantum key distribution system and phase estimation and compensation method thereof - Google Patents
Novel continuous variable quantum key distribution system and phase estimation and compensation method thereof Download PDFInfo
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Abstract
The invention discloses a novel continuous variable quantum key distribution system.A sending end adds a test frame in a high-frequency band and sends the test frame to a receiving end when sending information; the receiving end calculates the phase drift value of the system according to the received optical signal and returns the phase drift result to the control end; and the control end carries out phase compensation according to the received phase drift value. The invention also discloses a phase estimation and compensation method of the novel continuous variable quantum key distribution system. The invention can accurately perform phase compensation even under the condition of low signal-to-noise ratio, improve the accuracy of the detection result and reduce the burden of error correction negotiation; meanwhile, the invention adopts the frequency division multiplexing and local oscillation scheme based on the electro-optic phase modulator, thus improving the range and frequency spectrum efficiency of phase compensation and improving the performance of the system.
Description
Technical Field
The invention particularly relates to a novel continuous variable quantum key distribution system and a phase estimation and compensation method thereof.
Background
With the development of economic technology, the quantum field is also greatly developed.
The quantum key distribution can ensure that two parties in an untrusted quantum channel at a long distance can safely share the key, and the safety of the two parties is ensured by the inaccuracy measurement principle of quantum mechanics and the quantum unclonable theorem. Quantum key distribution is generally divided into two types, discrete variable and continuous variable. With the intensive research in recent years, continuous variable quantum key distribution fully shows its advantages, such as high detection efficiency and low experimental cost. More importantly, it can be realized by using the existing commercial optical fiber communication network, so that continuous variable quantum key distribution draws much attention and realizes many meaningful research results. However, in long-distance communication, due to the characteristics of optical fibers and optical devices, optical signals are greatly attenuated, and a random phase difference exists between received data and transmitted data, which seriously affects subsequent negotiation, and thus, the negotiation efficiency is very low. It is therefore necessary to perform phase compensation before negotiation.
Currently, there are three schemes for solving phase drift. A first solution is a constructive improvement of the interferometric system to compensate for phase drift, for example in a plug and play configuration. The second is passive compensation, which uses passive methods to reduce the effects of the external environment on the interfering system, such as temperature isolation and damping measures. The third is active compensation, which uses scanning method to obtain dynamic parameters of phase drift and compensate in real time. The phase feedback compensation algorithm belongs to active compensation, adds a sweep frequency test frame to the transmitted data, and determines the phase drift in the channel by observing the phase of the sweep test frame at the receiver, depending on the receiver's well recovery to the profile of the signal. Conventional phase feedback compensation is a convenient algorithm to overcome phase drift. However, the conventional scheme has two disadvantages. First, it can estimate the phase drift only if the signal-to-noise ratio is much larger than 1. Second, after phase drift estimation, the conventional phase compensation scheme needs to compensate the phase drift to the phase modulator of the receiver in real time, increasing the complexity of the hardware system and introducing additional noise.
In a continuous variable quantum key distribution protocol, it is necessary to realize efficient heterodyne detection. However, the presence of a local oscillator in heterodyne detection can have very adverse effects and even security holes. A strong local oscillator can significantly reduce the transmission efficiency of the signal when passing through a lossy channel, and scattered photons from the local oscillator can contaminate the signal. More importantly, an eavesdropper may have the opportunity to attack by manipulating the local oscillator, which may result in a local oscillator ripple attack, a calibration attack, and so forth. In view of these limitations, researchers have proposed a continuously variable quantum key distribution protocol for local oscillators, and their feasibility has been experimentally confirmed.
Phase drift is a significant disturbance in continuous quantum key distribution systems: quantum state | α due to the influence of phase drift>＝|XA+iPA>Becomes | α'>＝|X'A+iP’A>Wherein X isA＝R*cos(θ)，PAR sin (θ), and
wherein R is a random variable subject to belief distribution, theta is a random variable subject to uniform distribution,
is the phase drift angle. By analysis, the phase shift can be considered as a variance of
Wherein V isxIs the signal variance of the transmitted signal. When phase shifts
When 0, the phase of the transmission signal coincides with that of the reception signal. When phase shifts
Is composed of
When the temperature of the water is higher than the set temperature,
and the mutual information quantity between the sender and the receiver is reduced to 0, which also means that the receiver is different from the sender forever in the quantum detection process. Thus, the phase drift is a continuous quantum key divisionSignificant disturbances in the system must be compensated for. However, in the current technical scheme adopting the local oscillator, the problem of phase drift is not considered, so that further phase compensation is not provided; therefore, the current technical scheme adopting the local oscillator has low reliability and low efficiency.
Disclosure of Invention
One of the purposes of the present invention is to provide a novel continuous variable quantum key distribution system which can perform phase estimation and compensation on a local oscillation continuous variable quantum key distribution system, and has high reliability and high efficiency.
The second purpose of the present invention is to provide a phase estimation and compensation method for the new continuous variable quantum key distribution system.
The invention provides a novel continuous variable quantum key distribution system which comprises a sending end controller, a sending end pulse laser, a sending end electro-optic intensity modulator, a sending end electro-optic phase modulator, a sending end adjustable attenuator, a receiving end controller, a receiving end first beam splitter, a receiving end signal frame filter, a receiving end test frame heterodyne detector, a receiving end signal frame heterodyne detector, a receiving end pulse laser, a receiving end electro-optic intensity modulator and a receiving end second beam splitter, wherein the sending end controller is connected with the sending end electro-optic phase modulator through the receiving end signal frame heterodyne detector; the transmitting end controller is connected with the transmitting end pulse laser, the transmitting end electro-optical intensity modulator, the transmitting end electro-optical phase modulator and the transmitting end adjustable attenuator; the sending end pulse laser, the sending end electro-optic intensity modulator, the sending end electro-optic phase modulator and the sending end adjustable attenuator are sequentially connected in series; the receiving end controller is connected with the receiving end pulse laser, the receiving end electro-optic intensity modulator, the receiving end test frame heterodyne detector and the receiving end signal frame heterodyne detector; the sending end controller is connected with the receiving end controller; the transmitting end controller is used for controlling the transmitting end pulse laser, the transmitting end electro-optic intensity modulator, the transmitting end electro-optic phase modulator and the transmitting end adjustable attenuator to work; the sending end pulse laser is used for generating pulse coherent signal light; the transmitting end electro-optical intensity modulator is used for controlling the intensity of the pulse coherent signal light; the transmitting end electro-optic phase modulator is used for carrying out phase modulation on the signal light output by the transmitting end electro-optic intensity modulator, and transmitting the signal light to the transmitting end adjustable attenuator after inserting a test frame in a high frequency band; the transmitting end adjustable attenuator is used for attenuating the optical signal output by the transmitting end electro-optical phase modulator and then transmitting the optical signal to the receiving end first beam splitter; the receiving end first beam splitter is used for splitting the received optical signal and respectively transmitting the optical signal to a receiving end signal frame filter and a receiving end test frame filter; the receiving end signal frame filter is used for filtering signal frames in the optical signals to obtain test frame signals and inputting the test frame signals to the receiving end test frame heterodyne detector; the receiving end test frame filter is used for filtering a test frame in the optical signal to obtain a signal frame signal and inputting the signal frame signal to the receiving end signal frame heterodyne detector; the receiving end pulse laser is used for generating pulse coherent local oscillator light; the receiving end electro-optical intensity modulator is used for modulating the amplitude of the pulse coherent local oscillator light; the receiving end second beam splitter is used for splitting the pulse coherent local oscillation light subjected to amplitude modulation into a first local oscillation light and a second local oscillation light, and respectively inputting the first local oscillation light and the second local oscillation light to a receiving end test frame heterodyne detector and a receiving end signal frame heterodyne detector; the receiving end test frame heterodyne detector is used for carrying out heterodyne detection on the first local oscillation light and the test frame to obtain a test result of the orthogonal component randomly selected by the test frame and uploading the test result to the receiving end controller; the receiving end signal frame heterodyne detector is used for carrying out heterodyne detection on the second local oscillation light and the signal light to obtain a test result of an orthogonal component randomly selected by the signal light and uploading the test result to the receiving end controller; the receiving end controller estimates a phase drift value of the system according to a test result of the orthogonal component randomly selected by the received test frame and sends the phase drift value to the sending end controller; and the sending end controller performs phase compensation on the subsequent distribution process according to the received phase drift value.
The transmitting end pulse laser is a Thorlabs OPG1015 picosecond optical pulse generator.
The electro-optical phase modulator at the transmitting end is an electro-optical phase modulator with the model number of MPZ-LN-10.
The receiving end test frame heterodyne detector and the receiving end signal frame heterodyne detector are both Thorlabs PDA435A balanced amplification photoelectric detectors.
The invention also provides a phase estimation and compensation method of the novel continuous variable quantum key distribution system, which comprises the following steps:
s1, a sending end generates pulse coherent signal light and carries out intensity modulation;
s2, carrying out phase modulation on the signal light obtained in the step S1, and simultaneously inserting a test frame in a high-frequency band to form an optical signal; the test frame comprises phase compensation data agreed in advance by a sending end and a receiving end;
s3, attenuating the optical signal obtained in the step S2 and then sending the attenuated optical signal to a receiving end;
s4, the receiving end divides the received attenuated optical signals sent by the sending end into two beams and sends the two beams to a receiving end test frame filter and a receiving end signal frame filter in sequence;
s5, a receiving end test frame filter filters out a test frame in the received optical signal to obtain a signal frame signal and sends the signal frame signal to a receiving end signal frame heterodyne detector; a receiving end signal frame filter filters a signal frame in the received optical signal to obtain a test frame signal and sends the test frame signal to a receiving end test frame heterodyne detector;
s6, generating pulse coherent local oscillation light by a receiving end and carrying out intensity modulation;
s7, splitting the pulse coherent local oscillator light subjected to intensity modulation obtained in the step S6 into a first local oscillator light and a second local oscillator light, and sequentially sending the first local oscillator light and the second local oscillator light to a receiving end test frame heterodyne detector and a receiving end signal frame heterodyne detector;
s8, the receiving end test frame heterodyne detector performs heterodyne detection on the first local oscillation light and the test frame to obtain a test result of the orthogonal component randomly selected by the test frame and uploads the test result to the receiving end controller; a receiving end signal frame heterodyne detector performs heterodyne detection on the second local oscillation light and the signal light to obtain a test result of the orthogonal component randomly selected by the signal light and uploads the test result to a receiving end controller;
s9, the receiving end controller estimates a phase drift value of the system according to a test result of the orthogonal component randomly selected by the received test frame and sends the phase drift value to the sending end controller;
and S10, the sending end controller performs phase compensation on the subsequent distribution process according to the received phase drift value.
The receiving end described in step S4 divides the received attenuated optical signal sent by the sending end into two beams, specifically, the receiving end separates the received attenuated optical signal sent by the sending end into test frame signal light at 50% quantum level and signal light at 50% quantum level.
In step S7, the intensity-modulated pulse coherent local oscillator light obtained in step S6 is split into a first local oscillator light and a second local oscillator light, specifically, the intensity-modulated pulse coherent local oscillator light is split into a local oscillator light at 50% quantum level and a local oscillator light at 50% quantum level.
The receiving-end controller in step S9 estimates the phase drift value of the system according to the test result of the orthogonal component randomly selected by the received test frame, specifically by using the following steps:
A. the receiving end constructs a group of phase compensation data which is completely the same as the transmitting end and is used for phase compensation;
B. the receiving end obtains phase compensation data sent by the sending end according to a test result of orthogonal components randomly selected by a received test frame;
C. calculating a cross-correlation value between the phase compensation data obtained by the construction in the step A and the received phase compensation data obtained in the step B;
D. and C, calculating a phase drift value according to the cross correlation value obtained in the step C.
The calculating step C calculates a cross-correlation value between the phase compensation data obtained in the step a and the received phase compensation data obtained in the step B, specifically, the cross-correlation value is calculated by using the following formula: suppose the transmitted test data is xtThe received data is ytThe mathematical expectation can be calculated as
Wherein R is a random variable subject to belief distribution, and theta is a random variable subject to uniform distribution，
For the phase drift angle, ε is noise and satisfies ε -N (0, σ)2) Since the variables are independent variables, mathematical expectations can be calculated separately, and the above formula can be rewritten as
Wherein VAIs the variance of the transmitted signal, representing the degree of correlation of the received phase test frame with its original data, is known.
And D, calculating a phase drift value according to the cross-correlation value obtained in the step C, specifically calculating the phase drift value by adopting the following formula: the final expression in step C also takes into account the influence of the channel transmission coefficient T, so that the expression is modified to
To calculate the transmission coefficient T and the phase drift
Only another set x needs to be constructedtThe phase shift value to which Δ θ' is added constitutes xt', that is to say that
Two mathematic expectation equations are combined, and the phase drift value can be calculated
The novel continuous variable quantum key distribution system and the phase estimation and compensation method thereof provided by the invention apply a local oscillator phase compensation method of frequency division multiplexing to the continuous variable quantum key distribution, and carry out phase compensation by inserting a small number of test frames into a transmission signal, detecting and calculating a phase drift value by analyzing the phase drift condition of a corresponding part of a received signal; therefore, the system and the method can accurately perform phase compensation even under the condition of low signal-to-noise ratio, improve the accuracy of the detection result and reduce the burden of error correction negotiation; meanwhile, the invention adopts the frequency division multiplexing and local oscillation scheme based on the electro-optic phase modulator, thus improving the range and frequency spectrum efficiency of phase compensation and improving the performance of the system.
Drawings
FIG. 1 is a functional block diagram of the system of the present invention.
FIG. 2 is a schematic flow chart of the method of the present invention.
Detailed Description
FIG. 1 shows a functional block diagram of the system of the present invention: the invention provides a novel continuous variable quantum key distribution system which comprises a sending end controller, a sending end pulse laser, a sending end electro-optic intensity modulator, a sending end electro-optic phase modulator, a sending end adjustable attenuator, a receiving end controller, a receiving end first beam splitter, a receiving end signal frame filter, a receiving end test frame heterodyne detector, a receiving end signal frame heterodyne detector, a receiving end pulse laser, a receiving end electro-optic intensity modulator and a receiving end second beam splitter, wherein the sending end controller is connected with the sending end electro-optic phase modulator through the receiving end signal frame heterodyne detector; the transmitting end controller is connected with the transmitting end pulse laser, the transmitting end electro-optical intensity modulator, the transmitting end electro-optical phase modulator and the transmitting end adjustable attenuator; the sending end pulse laser, the sending end electro-optic intensity modulator, the sending end electro-optic phase modulator and the sending end adjustable attenuator are sequentially connected in series; the receiving end controller is connected with the receiving end pulse laser, the receiving end electro-optic intensity modulator, the receiving end test frame heterodyne detector and the receiving end signal frame heterodyne detector; the sending end controller is connected with the receiving end controller; the transmitting end controller is used for controlling the transmitting end pulse laser, the transmitting end electro-optic intensity modulator, the transmitting end electro-optic phase modulator and the transmitting end adjustable attenuator to work; the sending end pulse laser is used for generating pulse coherent signal light; the transmitting end electro-optical intensity modulator is used for controlling the intensity of the pulse coherent signal light; the transmitting end electro-optic phase modulator is used for carrying out phase modulation on the signal light output by the transmitting end electro-optic intensity modulator, and transmitting the signal light to the transmitting end adjustable attenuator after inserting a test frame in a high frequency band; the transmitting end adjustable attenuator is used for attenuating the optical signal output by the transmitting end electro-optical phase modulator and then transmitting the optical signal to the receiving end first beam splitter; the receiving end first beam splitter is used for splitting the received optical signal and respectively transmitting the optical signal to a receiving end signal frame filter and a receiving end test frame filter; the receiving end signal frame filter is used for filtering signal frames in the optical signals to obtain test frame signals and inputting the test frame signals to the receiving end test frame heterodyne detector; the receiving end test frame filter is used for filtering a test frame in the optical signal to obtain a signal frame signal and inputting the signal frame signal to the receiving end signal frame heterodyne detector; the receiving end pulse laser is used for generating pulse coherent local oscillator light; the receiving end electro-optical intensity modulator is used for modulating the amplitude of the pulse coherent local oscillator light; the receiving end second beam splitter is used for splitting the pulse coherent local oscillation light subjected to amplitude modulation into a first local oscillation light and a second local oscillation light, and respectively inputting the first local oscillation light and the second local oscillation light to a receiving end test frame heterodyne detector and a receiving end signal frame heterodyne detector; the receiving end test frame heterodyne detector is used for carrying out heterodyne detection on the first local oscillation light and the test frame to obtain a test result of the orthogonal component randomly selected by the test frame and uploading the test result to the receiving end controller; the receiving end signal frame heterodyne detector is used for carrying out heterodyne detection on the second local oscillation light and the signal light to obtain a test result of an orthogonal component randomly selected by the signal light and uploading the test result to the receiving end controller; the receiving end controller estimates a phase drift value of the system according to a test result of the orthogonal component randomly selected by the received test frame and sends the phase drift value to the sending end controller; and the sending end controller performs phase compensation on the subsequent distribution process according to the received phase drift value.
In specific implementation, the transmitting end pulse laser is a Thorlabs OPG1015 picosecond optical pulse generator which can generate laser pulses with the frequency of 10GHz and less than or equal to 3 ps; the electro-optical phase modulator at the transmitting end is an electro-optical phase modulator with the model number of MPZ-LN-10, has the characteristics of high extinction ratio (>20dB), low loss (2.5dB) and high bandwidth (10GHz), can meet the requirement of a quantum key communication system with higher speed, and reduces extra loss brought by optical devices as much as possible; the receiving end test frame heterodyne detector and the receiving end signal frame heterodyne detector are both a Thorlabs PDA435A balanced amplification photoelectric detector, the common mode rejection ratio is more than 20dB, and the bandwidth can reach 350 MHz; meanwhile, in the data transmission and optical signal transmission processes, the quantum channel is a single-mode fiber or a transmission medium formed by a free space, the single-mode fiber has a stable attenuation coefficient which is about 0.2dB/km, the anti-interference capability is strong, and the cost is low; a classical channel is a transmission medium formed by classical wireless, wire line, or optical fiber.
FIG. 2 is a schematic flow chart of the method of the present invention: the phase estimation and compensation method of the novel continuous variable quantum key distribution system provided by the invention comprises the following steps:
s1, a sending end generates pulse coherent signal light and carries out intensity modulation;
s2, carrying out phase modulation on the signal light obtained in the step S1, and simultaneously inserting a test frame in a high-frequency band to form an optical signal; the test frame comprises phase compensation data agreed in advance by a sending end and a receiving end;
s3, attenuating the optical signal obtained in the step S2 and then sending the attenuated optical signal to a receiving end;
s4, the receiving end divides the received attenuated optical signals sent by the sending end into two beams and sends the two beams to a receiving end test frame filter and a receiving end signal frame filter in sequence;
in specific implementation, a receiving end separates a received attenuated optical signal sent by a sending end into test frame signal light with a quantum level of 50% and signal light with a quantum level of 50%;
s5, a receiving end test frame filter filters out a test frame in the received optical signal to obtain a signal frame signal and sends the signal frame signal to a receiving end signal frame heterodyne detector; a receiving end signal frame filter filters a signal frame in the received optical signal to obtain a test frame signal and sends the test frame signal to a receiving end test frame heterodyne detector;
s6, generating pulse coherent local oscillation light by a receiving end and carrying out intensity modulation;
s7, splitting the pulse coherent local oscillator light subjected to intensity modulation obtained in the step S6 into a first local oscillator light and a second local oscillator light, and sequentially sending the first local oscillator light and the second local oscillator light to a receiving end test frame heterodyne detector and a receiving end signal frame heterodyne detector;
in specific implementation, the pulse coherent local oscillation light subjected to intensity modulation is separated into local oscillation light at a 50% quantum level and local oscillation light at a 50% quantum level;
s8, the receiving end test frame heterodyne detector performs heterodyne detection on the first local oscillation light and the test frame to obtain a test result of the orthogonal component randomly selected by the test frame and uploads the test result to the receiving end controller; a receiving end signal frame heterodyne detector performs heterodyne detection on the second local oscillation light and the signal light to obtain a test result of the orthogonal component randomly selected by the signal light and uploads the test result to a receiving end controller;
s9, the receiving end controller estimates a phase drift value of the system according to a test result of the orthogonal component randomly selected by the received test frame and sends the phase drift value to the sending end controller; specifically, the method comprises the following steps:
A. the receiving end constructs a group of phase compensation data which is completely the same as the transmitting end and is used for phase compensation;
B. the receiving end obtains phase compensation data sent by the sending end according to a test result of orthogonal components randomly selected by a received test frame;
C. calculating a cross-correlation value between the phase compensation data obtained by the construction in the step A and the received phase compensation data obtained in the step B; suppose the transmitted test data is xtThe received data is ytThe mathematical expectation can be calculated as
Wherein R is a random variable subject to belief distribution, theta is a random variable subject to uniform distribution,
for the phase drift angle, ε is noise and satisfies ε -N (0, σ)2) Since the variables are independent variables, mathematical expectations can be calculated separately, and the above formula can be rewritten as
Wherein VAIs the variance of the transmitted signal, representing the degree of correlation of the received phase test frame with its original data, and is known;
D. and C, calculating a phase drift value according to the cross-correlation value obtained in the step C, specifically calculating the phase drift value by adopting the following formula: the final expression in step C also takes into account the influence of the channel transmission coefficient T, so that the expression is modified to
To calculate the transmission coefficient T and the phase drift
Only another set x needs to be constructedtThe phase shift value to which Δ θ' is added constitutes xt', that is to say that
Two mathematic expectation equations are combined, and the phase drift value can be calculated
And S10, the sending end controller performs phase compensation on the subsequent distribution process according to the received phase drift value.
The technical scheme provided by the invention is used when the sending end and the receiving end carry out communication for the first time. When the sending end sends information, adding a test frame in a high frequency band and sending the test frame to the receiving end; the receiving end calculates the phase drift value of the system according to the received optical signal and returns the phase drift result to the control end; and the control end carries out phase compensation according to the received phase drift value.
Specifically, a sending end and a receiving end must agree a phase compensation data in advance, and both sides of the phase compensation data know; meanwhile, when the sending end and the receiving end perform the first-stage signal optical communication, the sending end generally only sends some data information required by physical layer communication, such as frame synchronization, bit synchronization section and the like; meanwhile, a sender additionally adds a test frame (including phase compensation data agreed in advance) in a high frequency band besides the sent information; then the data added with the test frame is sent to a receiving end, and the receiving end calculates a phase drift value according to the technical scheme provided by the invention and then sends the phase drift value to the sending end; after receiving the phase drift value, the sending end performs phase compensation according to the received phase drift value each time when performing each subsequent segment of signal optical communication.
Claims (10)
1. A novel continuous variable quantum key distribution system is characterized by comprising a sending end controller, a sending end pulse laser, a sending end electro-optic intensity modulator, a sending end electro-optic phase modulator, a sending end adjustable attenuator, a receiving end controller, a receiving end first beam splitter, a receiving end signal frame filter, a receiving end test frame heterodyne detector, a receiving end signal frame heterodyne detector, a receiving end pulse laser, a receiving end electro-optic intensity modulator and a receiving end second beam splitter; the transmitting end controller is connected with the transmitting end pulse laser, the transmitting end electro-optical intensity modulator, the transmitting end electro-optical phase modulator and the transmitting end adjustable attenuator; the sending end pulse laser, the sending end electro-optic intensity modulator, the sending end electro-optic phase modulator and the sending end adjustable attenuator are sequentially connected in series; the receiving end controller is connected with the receiving end pulse laser, the receiving end electro-optic intensity modulator, the receiving end test frame heterodyne detector and the receiving end signal frame heterodyne detector; the sending end controller is connected with the receiving end controller; the transmitting end controller is used for controlling the transmitting end pulse laser, the transmitting end electro-optic intensity modulator, the transmitting end electro-optic phase modulator and the transmitting end adjustable attenuator to work; the sending end pulse laser is used for generating pulse coherent signal light; the transmitting end electro-optical intensity modulator is used for controlling the intensity of the pulse coherent signal light; the transmitting end electro-optic phase modulator is used for carrying out phase modulation on the signal light output by the transmitting end electro-optic intensity modulator, and transmitting the signal light to the transmitting end adjustable attenuator after inserting a test frame in a high frequency band; the transmitting end adjustable attenuator is used for attenuating the optical signal output by the transmitting end electro-optical phase modulator and then transmitting the optical signal to the receiving end first beam splitter; the receiving end first beam splitter is used for splitting the received optical signal and respectively transmitting the optical signal to a receiving end signal frame filter and a receiving end test frame filter; the receiving end signal frame filter is used for filtering signal frames in the optical signals to obtain test frame signals and inputting the test frame signals to the receiving end test frame heterodyne detector; the receiving end test frame filter is used for filtering a test frame in the optical signal to obtain a signal frame signal and inputting the signal frame signal to the receiving end signal frame heterodyne detector; the receiving end pulse laser is used for generating pulse coherent local oscillator light; the receiving end electro-optical intensity modulator is used for modulating the amplitude of the pulse coherent local oscillator light; the receiving end second beam splitter is used for splitting the pulse coherent local oscillation light subjected to amplitude modulation into a first local oscillation light and a second local oscillation light, and respectively inputting the first local oscillation light and the second local oscillation light to a receiving end test frame heterodyne detector and a receiving end signal frame heterodyne detector; the receiving end test frame heterodyne detector is used for carrying out heterodyne detection on the first local oscillation light and the test frame to obtain a test result of the orthogonal component randomly selected by the test frame and uploading the test result to the receiving end controller; the receiving end signal frame heterodyne detector is used for carrying out heterodyne detection on the second local oscillation light and the signal light to obtain a test result of an orthogonal component randomly selected by the signal light and uploading the test result to the receiving end controller; the receiving end controller estimates a phase drift value of the system according to a test result of the orthogonal component randomly selected by the received test frame and sends the phase drift value to the sending end controller; and the sending end controller performs phase compensation on the subsequent distribution process according to the received phase drift value.
2. The system according to claim 1, wherein said transmitting end pulse laser is a Thorlabs OPG1015 picosecond optical pulse generator.
3. The system according to claim 1, wherein the transmitter electro-optic phase modulator is an electro-optic phase modulator model MPZ-LN-10.
4. The system of claim 1, wherein the receiver-side test frame heterodyne detector and the receiver-side signal frame heterodyne detector are both Thorlabs PDA435A balanced amplified photodetectors.
5. A phase estimation and compensation method of a novel continuous variable quantum key distribution system as claimed in any one of claims 1 to 4, comprising the steps of:
s1, a sending end generates pulse coherent signal light and carries out intensity modulation;
s2, carrying out phase modulation on the signal light obtained in the step S1, and simultaneously inserting a test frame in a high-frequency band to form an optical signal; the test frame comprises phase compensation data agreed in advance by a sending end and a receiving end;
s3, attenuating the optical signal obtained in the step S2 and then sending the attenuated optical signal to a receiving end;
s4, the receiving end divides the received attenuated optical signals sent by the sending end into two beams and sends the two beams to a receiving end test frame filter and a receiving end signal frame filter in sequence;
s5, a receiving end test frame filter filters out a test frame in the received optical signal to obtain a signal frame signal and sends the signal frame signal to a receiving end signal frame heterodyne detector; a receiving end signal frame filter filters a signal frame in the received optical signal to obtain a test frame signal and sends the test frame signal to a receiving end test frame heterodyne detector;
s6, generating pulse coherent local oscillation light by a receiving end and carrying out intensity modulation;
s7, splitting the pulse coherent local oscillator light subjected to intensity modulation obtained in the step S6 into a first local oscillator light and a second local oscillator light, and sequentially sending the first local oscillator light and the second local oscillator light to a receiving end test frame heterodyne detector and a receiving end signal frame heterodyne detector;
s8, the receiving end test frame heterodyne detector performs heterodyne detection on the first local oscillation light and the test frame to obtain a test result of the orthogonal component randomly selected by the test frame and uploads the test result to the receiving end controller; a receiving end signal frame heterodyne detector performs heterodyne detection on the second local oscillation light and the signal light to obtain a test result of the orthogonal component randomly selected by the signal light and uploads the test result to a receiving end controller;
s9, the receiving end controller estimates a phase drift value of the system according to a test result of the orthogonal component randomly selected by the received test frame and sends the phase drift value to the sending end controller;
and S10, the sending end controller performs phase compensation on the subsequent distribution process according to the received phase drift value.
6. The phase estimation and compensation method according to claim 5, wherein the receiving end divides the received attenuated optical signal sent by the sending end into two beams, specifically, the receiving end separates the received attenuated optical signal sent by the sending end into the test frame signal light of 50% quantum level and the signal light of 50% quantum level.
7. The phase estimation and compensation method according to claim 5, wherein in step S7, the intensity-modulated pulse coherent local oscillator light obtained in step S6 is split into a first local oscillator light and a second local oscillator light, and specifically, the intensity-modulated pulse coherent local oscillator light is split into a local oscillator light at 50% quantum level and a local oscillator light at 50% quantum level.
8. The phase estimation and compensation method according to claim 5, wherein the receiving-end controller of step S9 estimates the phase drift value of the system according to the test result of the orthogonal component randomly selected by the received test frame, specifically by using the following steps:
A. the receiving end constructs a group of phase compensation data which is completely the same as the transmitting end and is used for phase compensation;
B. the receiving end obtains phase compensation data sent by the sending end according to a test result of orthogonal components randomly selected by a received test frame;
C. calculating a cross-correlation value between the phase compensation data obtained by the construction in the step A and the received phase compensation data obtained in the step B;
D. and C, calculating a phase drift value according to the cross correlation value obtained in the step C.
9. The phase estimation and compensation method according to claim 8, wherein the step C calculates the cross-correlation value between the phase compensation data obtained in step a and the received phase compensation data obtained in step B, specifically, the cross-correlation value is calculated by using the following formula:
wherein xtTo test data, ytFor the received data, R is a random variable subject to an endian distribution, theta is a random variable subject to a uniform distribution,
for angle of phase drift, VAIs the variance of the transmitted signal and represents the degree of correlation of the received phase test frame with the original data.
10. The phase estimation and compensation method according to claim 9, wherein the phase drift value is calculated according to the cross-correlation value obtained in step D, specifically, the phase drift value is calculated by using the following method: combined stand
And
solving out the phase drift value
Wherein x istTo test data, ytFor the received data, R is a random variable subject to an endian distribution, theta is a random variable subject to a uniform distribution,
for angle of phase drift, VAIs the variance of the transmitted signal and is representedThe correlation degree between the received phase test frame and the original data, T is the transmission coefficient, xt' is in test data xtThe phase shift value of delta theta' is added.
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| CN112398545A (en) * | 2020-10-14 | 2021-02-23 | 中国电子科技集团公司第三十研究所 | Quantum signal modulation variance control and calibration method and system for CVQKD system |
| CN112688740B (en) * | 2021-03-10 | 2021-08-31 | 南京大学 | Floodlight quantum key distribution method and system without phase feedback |
| JP2023014764A (en) * | 2021-07-19 | 2023-01-31 | 国立研究開発法人情報通信研究機構 | Phase modulator calibration method, balance type optical detector calibration method and phase modulator calibration system |
| CN114221758A (en) * | 2021-11-29 | 2022-03-22 | 湖南大学 | Round-trip double-phase modulation quantum key sharing system and method |
| CN116707808B (en) * | 2023-08-10 | 2023-10-03 | 北京中科国光量子科技有限公司 | Frame synchronization method for passive continuous variable quantum key distribution system |
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| CN108540284A (en) * | 2018-06-01 | 2018-09-14 | 北京大学 | A kind of continuous variable quantum key distribution post-processing heterodyne detection phase compensating method |
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