CN110896328B - Continuous variable quantum key distribution system based on single reference light pulse single homodyne detection - Google Patents
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Abstract
The invention provides a continuous variable quantum key distribution system based on single reference light pulse single homodyne detection, wherein a sender comprises a light source, a first unequal arm interferometer, a signal light modulation module, a synchronous light module and a wavelength division multiplexing module, and a receiver comprises a local oscillator light source, a second unequal arm interferometer, a second phase modulation unit, a homodyne detection module, a wavelength division demultiplexing module, a synchronous light detection module and a data post-processing module. Therefore, the orthogonal unbalance phenomenon of double homodyne detection is avoided by adopting a single homodyne detection mode, and only a single reference light pulse is required to be sent corresponding to each signal light pulse, so that the difficulty in preparing double homodyne reference light pulses is avoided, and the pulse use efficiency is improved. In addition, the phase estimation method adopted by the system also considers the phase shift between the reference light pulse and the signal light pulse caused by the difference of the central wavelengths of the two lasers, so that the phase of the signal light pulse subjected to Gaussian modulation relative to the local oscillator light before modulation can be estimated more accurately.
Description
Technical Field
The invention relates to the field of quantum communication, in particular to a continuous variable quantum key distribution system based on single reference light pulse single-homodyne detection.
Background
Quantum Key Distribution (QKD) has grown more and more mature as a cornerstone in the field of quantum communication, which can be divided into Discrete Variable (DV) QKD and Continuous Variable (CV) QKD according to the modulation means and detection means. The CV-QKD can be realized by using the technical means of classical coherent optical communication because a coherent detection mode such as homodyne detection is adopted. Early CV-QKD systems employed a transport local oscillator optical (TLO) scheme, i.e., both local oscillator light and signal light originated from the sender. Such a scheme is vulnerable to various attacks against local oscillator light, and thus a local oscillator light (LLO) scheme has come to receive wide attention in recent years.
For the LLO scheme, it is most important to establish a phase reference between the signal light and the local oscillator light, i.e., to perform phase estimation and phase correction. The phase estimation is to estimate the phase of the signal relative to the local oscillator light before the optical modulation, and the phase correction is to perform data correction on the modulation data of the transmitting side or the detection data of the receiving side according to the estimated phase. In the LLO scheme, because the signal light and the local oscillator light respectively use one laser, and the phases of the two lasers drift, the phase of the signal light relative to the phase of the local oscillator light changes all the time, and the relative phase needs to be measured in real time. The existing solution is to have some of the pulses sent by the laser as reference light pulses and some as signal light pulses. In general, the phase of the previous reference optical pulse relative to the local optical pulse is used as the phase of the next signal optical pulse relative to the local optical pulse when not modulated. In order to accurately obtain the relative phase of the reference light, in the existing scheme, either a double-homodyne detection mode is adopted for a single reference light pulse, that is, the X component and the P component of the reference light pulse are measured simultaneously, or a single-homodyne detection mode is adopted for double-homodyne reference light pulses, that is, the X component and the P component are measured sequentially for the two same reference light pulses. The above-described scheme of generating the reference light pulse and the signal light pulse by directly modulating the laser pulses has a relatively high demand on the two lasers. Phase drift of the laser can cause phase noise. To reduce phase noise, the repetition rate of the system may be increased, or a narrow linewidth laser may be used. In order to reduce the requirements on the laser, each pulse emitted by the laser can be divided into two pulses before and after as a reference light pulse and a signal light pulse respectively by using an unequal arm interferometer. Such a resulting reference optical pulse and signal optical pulse have the same wavefront, and the phase shift between the reference optical pulse and the signal optical pulse can be greatly reduced.
In the existing CV-QKD experiments, single homodyne detection is more common because dual homodyne detection requires not only two balanced detectors but also the addition of a 90 degree mixer. The asymmetry of the splitting ratio of the 3dB coupler inside the mixer or the mismatch of the responsivity of the photodiode may cause the mismatch of the amplitude and phase between the two signals of the X and P components, which is called the quadrature imbalance phenomenon. For this phenomenon, there is no method for compensating for CV-QKD. However, if the double-identical reference light pulse single-zero-difference detection is adopted, two identical reference light pulses need to be prepared corresponding to each signal light pulse, which not only brings difficulty to the preparation of the reference light pulses, but also only one third of the pulses can be used as the signal light pulses, thereby reducing the use efficiency of the pulses.
Disclosure of Invention
The invention provides a continuous variable quantum key distribution system based on single-reference-light-pulse single-homodyne detection, which adopts a new phase estimation method, can use a single-homodyne detection mode to avoid the orthogonal imbalance phenomenon of double-homodyne detection, simultaneously only needs to send a single reference pulse corresponding to each signal light pulse, reduces the difficulty in preparing the reference light pulse, and improves the use efficiency of the light pulse. In addition, the system also considers the phase shift between the reference light pulse and the signal light pulse caused by the difference of the central wavelengths of the two lasers in post-processing, so that the phase of the signal light pulse relative to the local oscillator light when the signal light pulse is not modulated can be estimated more accurately.
The invention relates to a continuous variable quantum key distribution system based on single reference light pulse single-homodyne detection, which comprises a sender Alice and a receiver Bob.
The sender Alice may include a light source 111, a first unequal arm interferometer 112, a signal light modulation module 113, a synchronization light module 114, and a wavelength division multiplexing module 115.
The light source 111 may be used to provide laser pulses.
The first may be configured to split the laser pulse into two optical pulses, one of which is a signal optical pulse and the other of which is a reference optical pulse.
The signal light modulation module 113 may be configured to perform gaussian modulation on most of the signal light pulses passing therethrough, and not perform any modulation on the rest of the signal light pulses.
The synchronization light module 114 may be used to provide synchronization light.
The wavelength division multiplexing module 115 may be configured to perform wavelength division multiplexing on the signal optical pulse, the reference optical pulse, and the synchronization light, so that the signal optical pulse, the reference optical pulse, and the synchronization light are output along one path.
And, the receiving side Bob may include a local oscillator light source 211, a second unequal arm interferometer 212, a second phase modulation unit 213, a homodyne detection module 214, a wavelength division demultiplexing module 215, a polarization control module 216, and a synchronous optical detection module 217.
The local oscillator light source 211 may be configured to provide laser pulses.
The second unequal arm interferometer 212 may be configured to receive the laser pulse of the local oscillator light source 211 and divide the laser pulse into two optical pulses, one of the two optical pulses being a first local oscillator optical pulse and the other being a second local oscillator optical pulse.
The second phase modulation unit 213 may be configured to perform phase modulation of 0 or pi/2 on the first local optical pulse and the second local optical pulse at random, respectively.
The homodyne detection module 214 may be configured to perform homodyne detection on an interference result of the reference optical pulse and the first local oscillator optical pulse, and perform homodyne detection on an interference result of the signal optical pulse and the second local oscillator optical pulse.
The wavelength division demultiplexing module 215 may be configured to demultiplex the signal light pulse or the reference light pulse and the synchronization light.
The polarization control module 216 is configured to perform polarization control on the reference optical pulse and the signal optical pulse, so that their polarizations can be consistent with the polarizations of the first local optical pulse and the second local optical pulse.
The sync light detection module 217 may be configured to receive the sync light for use in generating a clock signal.
Preferably, the first unequal arm interferometer 112 may include a first polarization maintaining beam splitting unit 1121, a first polarization maintaining beam combining unit 1122, and a long arm and a short arm therebetween.
Preferably, the signal light modulation module 113 may include an amplitude modulation unit 1131, a first phase modulation unit 1132 and an adjustable attenuation unit 1133.
Preferably, the wavelength division multiplexing module 115 may be a dense wavelength division multiplexer.
Preferably, the second unequal-arm interferometer 212 may include a second polarization-maintaining beam splitting unit 2121, a second polarization-maintaining polarization beam combining unit 2122, and a long arm and a short arm therebetween.
Preferably, the homodyne detection module 214 may include a single balanced detection unit.
Preferably, the polarization control module 216 may be an electric polarization controller.
Preferably, the arm length difference is the same for the first unequal arm interferometer 112 and the second unequal arm interferometer 212.
Further, the receiver Bob may further include a data post-processing module 218, configured to perform data processing on the detection result output by the homodyne detection module 214.
Still further, the data post-processing module 218 may be further configured to estimate the phase θ of the gaussian modulated signal light pulse before modulation with respect to the local oscillator light pulse according to the detection result of the unmodulated signal light pulse and the corresponding detection result of the reference light pulse output by the homodyne detection module 214S。
The data post-processing module 218 may be further configured to perform data fitting using a gauss-newton algorithm on the following set of equations to obtain a phase shift
Wherein,
is the amplitude, x, of the reference light pulseBRFor the measurement result on the X-component of the reference light pulse,
is xBRNumber of (2), pBRFor measuring the P component of said reference light pulseAs a result of the amount of the compound,
is pBRThe number of (2);
amplitude, x, of the signal light pulse without modulationBSFor measurements on the X-component of the signal light pulse,
is xBSNumber of (2), pBSFor measurements on the P-component of the signal light pulse,
is pBSThe number of (2); the phase shift
The phase θ of the reference light pulse relative to the local oscillator light caused by the wavelength difference between the light source 111 and the local oscillator light source 211RAnd the phase theta of the signal light pulse relative to the local oscillator lightSPhase shift between them.
The data post-processing module 218 may be further configured to calculate the relative phase θ of the reference light pulse according to the following equationRWherein, for a reference light pulse measuring the X component,
wherein p isBRWhether the measured value is greater than zero is judged by whether the measured value of the reference light pulse of the adjacent measurement P component is greater than zero; for the reference light pulse for measuring the P component,
wherein x isBRWhether or not it is greater than zeroIt is judged by whether or not the measurement result of the reference light pulse of the adjacent measurement X component is larger than zero.
Preferably, the receiver Bob combines the relative phase θSFeeding back to the sender Alice so that the sender Alice can modulate the modulation data (x) used by the signal light modulation module 113A,pA) Performing phase correction, the phase-corrected modulation data being
Wherein the phase
And after the phase correction, the sender Alice reserves the same modulation data as the measurement component selected by the receiver Bob. The sender Alice and the receiver Bob then perform parameter estimation, data negotiation and privacy amplification to generate a final key.
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The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Fig. 1 shows an exemplary embodiment of a continuous variable quantum key distribution system (CV-QKD) according to the present invention.
Detailed Description
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples are provided by way of illustration in order to fully convey the spirit of the invention to those skilled in the art to which the invention pertains. Accordingly, the present invention is not limited to the embodiments disclosed herein.
Fig. 1 shows an embodiment of a continuous variable quantum key distribution system (CV-QKD) according to the present invention, which may comprise a sender Alice and a receiver Bob.
As shown, the sender Alice may include a light source 111, a first unequal arm interferometer 112, a signal light modulation module 113, a synchronization light module 114, and a wavelength division multiplexing module 115.
The light source 111 may be a laser module for providing laser pulses. As an example, the light source 111 may provide laser pulses with a wavelength of 1550 nm.
The first unequal arm interferometer 112 is used for receiving the laser pulse from the light source 111 and dividing the laser pulse into two front and back light pulse outputs. In the present invention, one of the two preceding and following light pulses originating from the same laser pulse will be used as a reference light pulse and the other will be used as a signal light pulse.
According to the present invention, the first unequal arm interferometer 112 may include a first polarization maintaining beam splitting unit 1121, a first polarization maintaining beam combining unit 1122, and a long arm and a short arm therebetween.
In the first unequal arm interferometer 112, a laser pulse output from the light source 111 is split into two optical pulses by the first polarization maintaining beam splitting unit 1121. In the present invention, the first polarization maintaining beam splitting unit 1121 is preferably a polarization maintaining Beam Splitter (BS), but is not limited thereto.
The two optical pulses split by the first polarization maintaining beam splitting unit 1121 enter the long arm and the short arm of the first unequal arm interferometer, respectively, for propagation. A signal light modulation module 113 is provided on one of the long arm and the short arm for modulating a light pulse serving as a signal light pulse, as shown in fig. 1, and the signal light modulation module 113 may be provided on the long arm as an example.
The signal optical modulation module 113 may include an amplitude modulation unit 1131 and a first phase modulation unit 1132 for providing amplitude and phase modulation to the signal optical pulse. In the present invention, the signal optical modulation module 113 is configured to make the amplitude modulation unit 1131 and the first phase modulation unit 1132 modulate only a part of the passing signal optical pulses, and this modulation is gaussian modulation, that is, in the signal optical pulses passing through the signal optical modulation module 113, only a part of the signal optical pulses are gaussian modulated by the amplitude modulation unit and the first phase modulation unit, and the rest of the signal optical pulses are not subjected to the modulation action of the amplitude modulation unit and the first phase modulation unit.
As a preferred example, the amplitude modulation unit 1131 may be an Amplitude Modulator (AM). The first phase modulation unit 1132 may be a Phase Modulator (PM).
According to the present invention, the signal light modulation module 113 may further preferably include an adjustable attenuation unit 1133 for attenuating the signal light pulse to a required light intensity. As a preferred example, the adjustable attenuation unit 1133 may be an adjustable attenuator (VOA).
The first polarization-preserving polarization beam combining unit 1122 is configured to combine the signal light pulse and the reference light pulse propagating along the long arm and the short arm, respectively, into two light pulse outputs. In the present invention, polarization-maintaining polarization beam combining section 1122 is provided in first unequal arm interferometer 112 for combining the signal light pulse and the reference light pulse, so that the combined signal light pulse and reference light pulse can have polarization directions perpendicular to each other, and the isolation between the signal light pulse and reference light pulse is improved.
The synchronization light module 114 is arranged to provide synchronization lights having different frequencies for clock synchronization between the sender Alice and the receiver Bob. According to the present invention, the synchronization optical module 114 may be in the form of a laser, for example, having a wavelength of 1570 nm.
The wavelength division multiplexing module 115 is configured to receive outputs of the first unequal-arm interferometer 112 and the synchronization optical module 114, and wavelength division multiplex the signal optical pulse, the reference optical pulse, and the synchronization light so as to be output from the sender Alice along the same propagation optical path. As a preferred example, the wavelength division multiplexing module 115 may be a Dense Wavelength Division Multiplexer (DWDM).
The signal light pulse, the reference light pulse and the synchronous light output by Alice propagate through the optical path towards Bob. As a preferred example, the optical path may be implemented by an optical fiber.
Referring to fig. 1 as well, the receiving party Bob may include a local oscillator light source 211, a second unequal arm interferometer 212, a second phase modulation unit 213, a homodyne detection module 214, a wavelength division demultiplexing module 215, a polarization control module 216, and a synchronous optical detection module 217.
Wavelength division demultiplexing module 215 receives the optical signal from Alice and demultiplexes it so that the signal optical pulses and the reference optical pulses are separated from the synchronization optical pulses having different frequencies.
The polarization control module 216 is used for performing polarization control on the reference optical pulse and the signal optical pulse to eliminate polarization drift that may occur during transmission, so as to recover the polarization direction thereof. As a preferred example, the polarization control module 216 may be an Electronic Polarization Controller (EPC).
The sync light detection module 217 is used to receive the sync light output by the wavelength division demultiplexing module 215 and to generate a clock signal at Bob.
At the receiver Bob, the local oscillator light source 211 may be a laser module for providing laser pulses.
The second unequal arm interferometer 212 is configured to receive the laser light pulse from the light source 211 and split it into two optical pulse outputs, a first local oscillator optical pulse and a second local oscillator optical pulse.
According to the present invention, the second unequal-arm interferometer may also include a second polarization-maintaining beam splitting unit 2121, a second polarization-maintaining polarization beam combining unit 2122, and a long arm and a short arm therebetween.
In the second unequal-arm interferometer, the laser pulse output by the light source 211 is split into two light pulses by the second polarization-maintaining beam splitting unit 2121, and the two light pulses reach the second polarization-maintaining polarization beam combining unit 2122 through the long arm and the short arm respectively; the second polarization-maintaining polarization beam combining unit 2122 is configured to combine the two optical pulses, so as to output two front and back optical pulses with polarization directions perpendicular to each other, that is, a first local oscillator optical pulse and a second local oscillator optical pulse.
In the present invention, the second polarization maintaining beam splitter unit 2121 is preferably a polarization maintaining beam splitter; the second polarization-maintaining polarization beam combiner unit 2122 is preferably a polarization-maintaining polarization beam combiner. As a preferred example, the arm length difference of the first unequal arm interferometer and the second unequal arm interferometer may be the same.
The second phase modulation unit 213 is configured to perform phase modulation of 0 or pi/2 on the first local oscillation light pulse and the second local oscillation light pulse at random, respectively.
According to the present invention, Bob is configured to make the reference optical pulse and the signal optical pulse respectively reach the homodyne detection module 214 simultaneously with the first local oscillator optical pulse and the second local oscillator optical pulse.
The homodyne detection module 214 is configured to perform homodyne detection on an interference result of the received reference optical pulse/signal optical pulse and the first/second local oscillator optical pulses. Accordingly, in this embodiment, the homodyne detection module 214 may include a single balanced detection unit, which performs homodyne detection on the interference results of the reference optical pulse and the first local oscillator optical pulse, and the signal optical pulse and the second local oscillator optical pulse sequentially.
According to the present invention, Bob may further include a data post-processing module 218, which is configured to perform data processing on the detection result output by the homodyne detection module 214.
As a preferred example, the data post-processing module 218 may include a first analog-to-digital converter (ADC)2181 and a Digital Signal Processor (DSP)2183 for converting the analog signal output by the homodyne detection module 214 into a digital signal. Further, the data post-processing module 218 may also be configured to generate a clock signal, which may include a second analog-to-digital converter 2182 for receiving the analog signal output by the synchronous light detection module 217 and converting it into a digital signal.
In the invention, the signal light modulation module is set to perform Gaussian modulation on only part of signal light pulses and not modulate the rest signal light pulses at the Alice end, so that the detection result of the unmodulated signal light pulses and the detection result of the corresponding reference light pulses can be obtained at the Bob end.
In the Bob-side data post-processing module 218, the amplitude A of the reference pulse can be determined from these detection resultsR. If the measurement result of measuring the X component of the reference light pulse is XBRAnd is provided with
As a result, if the measurement result of the component of the reference light pulse P is measured as PBRAnd is provided with
As a result of this, the amplitude of the reference pulse is then
From this it can be derived the relative phase of the reference light pulse measuring the X component
For reference light pulses measuring the X component, pBRIs unknown, but pBRWhether or not it is larger than zero may be judged by whether or not the measurement result of the reference light pulse of the adjacent measurement P component is larger than zero.
And the relative phase of the reference light pulse for measuring the P component is
Also, for the reference light pulse for measuring the P component, xBRIs unknown, but xBRWhether or not it is larger than zero may be judged by whether or not the measurement result of the reference light pulse of the adjacent measurement X component is larger than zero.
Pulse amplitude A for unmodulated signal light pulsesSIf the measurement result of the X component of the unmodulated signal light pulse is XBSAnd is provided with
As a result of this, if the measurement result of the unmodulated signal light pulse P component is measured as PBSAnd is provided with
As a result of this, the amplitude of the unmodulated signal light pulse is then
To obtain the relative phase theta of the signal light pulse before modulationSTwo lasers also need to be consideredThe phase shift between the phase of the reference light pulse relative to the local oscillator light and the phase of the signal light pulse relative to the local oscillator light caused by the difference in wavelength (e.g., light source 111 and local oscillator light source 211)
Four types of detection results (x) from reference light pulses and unmodulated signal light pulsesBR,xBS)，(xBR,pBS)，(pBR,pBS) And (p)BR,xBS) The following system of equations may be established
For unknowns in the equation
The data fitting can be carried out by adopting a Gaussian-Newton algorithm in a least square method.
The relative phase of the signal light pulse after Gaussian modulation before modulation is the relative phase
After obtaining the relative phase thetaSThen, the receiver Bob converts the phase difference θSTells the sender Alice. Alice modulates data (x) to itA,pA) Performing phase correction to obtain corrected modulation data of
Thus, a phase reference is established between the modulation data of the sender Alice and the probe data of the receiver Bob. And after the phase correction, the sender Alice reserves the same modulation data as the measurement component selected by the receiver Bob. The sender Alice and the receiver Bob then perform parameter estimation, data negotiation and privacy amplification to generate a final key.
Therefore, the CV-QKD system adopts a new phase estimation method, the method can utilize a single homodyne detection mode of a single reference light pulse to carry out phase estimation, the orthogonal imbalance phenomenon of double homodyne detection is avoided, only a single reference pulse is needed to be sent corresponding to each signal light pulse, the difficulty in preparing double homodyne reference pulses is avoided, and the pulse use efficiency is improved. More importantly, the system considers the phase shift between the reference light pulse and the signal light pulse caused by the difference of the central wavelengths of the two lasers in post-processing, and can estimate the relative phase of the signal light pulse subjected to Gaussian modulation before modulation more accurately.
In addition, in the embodiment, the Bob end only uses a single balanced detector to perform homodyne detection on the reference light pulse and the signal light pulse, so that the detection system is greatly simplified.
The above description is not intended to limit the present invention, and the present invention is not limited to the above examples. Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
Claims (10)
1. A continuous variable quantum key distribution system based on single-homodyne detection of a single reference light pulse, comprising a sender Alice and a receiver Bob, characterized in that:
the sender Alice comprises a light source (111), a first unequal arm interferometer (112), a signal light modulation module (113), a synchronous light module (114) and a wavelength division multiplexing module (115),
the light source (111) is used for providing laser pulses;
the first unequal arm interferometer (112) is used for dividing the laser pulse into two front and back light pulses, wherein one of the two light pulses is a signal light pulse, and the other light pulse is a reference light pulse;
the signal light modulation module (113) is arranged to perform Gaussian modulation on the passing most of the signal light pulses, and the rest of the signal light pulses do not perform any modulation;
the synchronization light module (114) is used for providing synchronization light; and is
The wavelength division multiplexing module (115) is used for performing wavelength division multiplexing on the signal light pulse, the reference light pulse and the synchronous light to enable the signal light pulse, the reference light pulse and the synchronous light to be output along one path;
the receiver Bob comprises a local oscillator light source (211), a second unequal arm interferometer (212), a second phase modulation unit (213), a homodyne detection module (214), a wavelength division demultiplexing module (215), a polarization control module (216) and a synchronous optical detection module (217), wherein,
the local oscillator light source (211) is used for providing laser pulses;
the second unequal arm interferometer (212) is used for receiving the laser pulse of the local oscillation light source (211) and dividing the laser pulse into a front optical pulse and a rear optical pulse, wherein one of the two optical pulses is a first local oscillation optical pulse, and the other one of the two optical pulses is a second local oscillation optical pulse;
the second phase modulation unit (213) is configured to perform phase modulation of 0 or pi/2 on the first local oscillator light pulse and the second local oscillator light pulse at random, respectively;
the homodyne detection module (214) is configured to perform homodyne detection on an interference result of the reference optical pulse and the first local oscillator optical pulse, and perform homodyne detection on an interference result of the signal optical pulse and the second local oscillator optical pulse;
the wavelength division demultiplexing module (215) is used for demultiplexing the signal light pulse, the reference light pulse and the synchronous light;
the polarization control module (216) is configured to perform polarization control on the reference optical pulse and the signal optical pulse such that their polarizations coincide with those of the first local optical pulse and the second local optical pulse;
the synchronization light detection module (217) is configured to receive the synchronization light for use in generating a clock.
2. The continuous variable quantum key distribution system of claim 1, wherein the first unequal arm interferometer (112) comprises a first polarization maintaining beam splitting unit (1121), a first polarization maintaining beam combining unit (1122), and a long arm and a short arm therebetween; and/or the second unequal-arm interferometer (212) comprises a second polarization-maintaining beam splitting unit (2121), a second polarization-maintaining polarization beam combining unit (2122) and a long arm and a short arm located therebetween.
3. The continuous variable quantum key distribution system of claim 1, wherein the signal light modulation module (113) comprises an amplitude modulation unit (1131) and a first phase modulation unit (1132) and an adjustable attenuation unit (1133); and/or the wavelength division multiplexing module (115) is a dense wavelength division multiplexer.
4. The continuous variable quantum key distribution system of claim 1, wherein the homodyne detection module (214) comprises a single balanced detection unit.
5. The continuous variable quantum key distribution system of claim 1, wherein the arm length difference of the first unequal arm interferometer and the second unequal arm interferometer is the same; and/or the polarization control module (216) is an electric polarization controller.
6. The continuous variable quantum key distribution system of claim 1, wherein the receiver (Bob) further comprises a data post-processing module (218) arranged to calculate a phase θ of the gaussian modulated signal light pulse relative to the local oscillator light pulse before modulation from the detection results output by the homodyne detection module (214) on the unmodulated signal light pulse and the corresponding detection results of the reference light pulseS。
7. The continuous variable quantum key distribution system of claim 6, wherein the data post-processing module (218) is further configured to data fit the following system of equations using a gauss-newton algorithm to derive the phase shift
Wherein,
is the amplitude, x, of the reference light pulseBRFor the measurement result on the X-component of the reference light pulse,
is xBRNumber of (2), pBRFor the measurement result on the reference light pulse P component,
is pBRThe number of (2);
amplitude, x, of the signal light pulse without modulationBSFor measurements on the X-component of the signal light pulse,
is xBSNumber of (2), pBSFor measurements on the P-component of the signal light pulse,
is pBSThe number of (2); the phase shift
Is the light source (111) and the local oscillatorA phase θ of the reference light pulse relative to the local oscillator light due to a wavelength difference between light sources (211)RAnd the phase theta of the signal light pulse relative to the local oscillator lightSPhase shift between them.
8. The continuous variable quantum key distribution system of claim 7, the data post-processing module (218) further arranged to calculate the relative phase θ of the reference light pulse according to the following formulaRFor the reference light pulse measuring the X component,
wherein p isBRWhether the measured value is greater than zero is judged by whether the measured value of the reference light pulse of the adjacent measurement P component is greater than zero; for the reference light pulse measuring the P-component,
wherein x isBRWhether or not it is larger than zero is judged by whether or not the measurement result of the reference light pulse of the adjacent measurement X component is larger than zero.
9. The continuous variable quantum key distribution system of claim 8, the receiver Bob to phase θSFeeding back to the sender Alice so that the sender Alice can conveniently modulate the modulation data (x) used by the signal light modulation module (113)A,pA) Performing phase correction, the phase-corrected modulation data being
Wherein the phase
10. The continuous variable quantum key distribution system of claim 9, wherein after the phase correction, the sender Alice retains the same modulated data as the measured component selected by the receiver Bob, and then the sender Alice and the receiver Bob perform parameter estimation, data negotiation, and privacy amplification to produce a final key.
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| CN112393809B (en) * | 2020-11-19 | 2021-10-19 | 中国科学技术大学 | Self-interference-based method for measuring optical frequency difference between two independent lasers |
| CN112929170B (en) * | 2021-02-08 | 2022-07-05 | 北京中创为南京量子通信技术有限公司 | Signal detection method and device of continuous variable quantum key distribution system |
| CN112887033B (en) * | 2021-05-06 | 2021-08-24 | 北京中创为南京量子通信技术有限公司 | CV-QKD system and quantum key distribution method |
| CN113114356B (en) * | 2021-06-15 | 2021-08-13 | 国开启科量子技术(北京)有限公司 | Method and apparatus for detecting quantum communication system |
| CN116192366B (en) * | 2021-11-29 | 2024-10-01 | 科大国盾量子技术股份有限公司 | TF-QKD system and method |
| CN115225246B (en) * | 2022-07-11 | 2023-12-01 | 北京邮电大学 | Phase modulation bidirectional time synchronization device, method and system |
| CN117278131B (en) * | 2023-11-21 | 2024-01-30 | 北京中科国光量子科技有限公司 | Time division multiplexing conjugate homodyne detection device |
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