CN110896329B - Continuous variable quantum key distribution coherent detection system based on local oscillator light scheme - Google Patents
Continuous variable quantum key distribution coherent detection system based on local oscillator light scheme Download PDFInfo
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- CN110896329B CN110896329B CN201811063468.XA CN201811063468A CN110896329B CN 110896329 B CN110896329 B CN 110896329B CN 201811063468 A CN201811063468 A CN 201811063468A CN 110896329 B CN110896329 B CN 110896329B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/70—Photonic quantum communication
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
- H04L9/0852—Quantum cryptography
Abstract
The invention relates to a continuous variable quantum key distribution coherent detection system based on a local oscillator light scheme, which can comprise a polarization controller, a first polarization-preserving optical transmission element, a second polarization-preserving optical transmission element, an unequal arm interferometer module, a phase modulator, a balance detection module and a data post-processing module. The coherent detection system sequentially measures the X and P components of the reference light pulse and the signal light pulse in the local oscillator light scheme in a time division multiplexing mode, so that the detection purpose can be realized only by using a single balanced detector, and the complexity of the system is reduced; the reference light/signal light and the local oscillator light share one unequal-arm interferometer, so that the system can realize self-stability; most importantly, the data post-processing module of the system is able to compensate for the unbalanced two orthogonal components.
Description
Technical Field
The invention relates to the field of quantum communication, in particular to a continuous variable quantum key distribution coherent detection system based on a local oscillator light scheme.
Background
The detection mode in Continuous Variable (CV) Quantum Key Distribution (QKD) differs from single-photon detection in Discrete Variable (DV) quantum key distribution, which employs coherent detection, including single-homodyne detection that measures a single orthogonal component randomly and double-homodyne detection that measures two orthogonal components simultaneously. In the existing continuous variable quantum key distribution experiments, the experiments using double homodyne detection are very rare because two balanced detectors and a 90-degree mixer are required in the existing double homodyne detection system. 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. However, the existing CV-QKD detection system has no method for processing the phenomenon. The Gram-Schmidt orthogonalization process or the method can be adopted for the orthogonal imbalance phenomenon in the classical coherent optical communication
An orthogonalization process, howeverThese two methods cannot be applied to CV-QKD because CV-QKD uses gaussian modulation, and both methods are not suitable for handling this modulation scheme.
In recent years, considering that local oscillator light in an original CV-QKD local oscillator light transmission scheme needs to go through a quantum channel and is easily attacked by a third party, so that a protocol has security holes, the CV-QKD local oscillator light transmission scheme is attracting attention. The most important of the local oscillator light scheme is to establish phase references of the signal light and the local oscillator light. A common method for achieving this is to transmit a reference optical pulse, measure two orthogonal components of the reference optical pulse, and find the phase difference between the reference optical pulse and the local oscillator optical pulse. To measure these two orthogonal components, the quadrature imbalance needs to be addressed.
Disclosure of Invention
According to the technical problems and the current situation of a coherent detection system faced by the existing continuous variable quantum key distribution system, the invention provides a continuous variable quantum key distribution coherent detection system based on a local oscillator light scheme, which sequentially measures the X and P components of a reference light pulse and a signal light pulse in the local oscillator light scheme in a time division multiplexing mode, so that the detection purpose can be realized only by using a single balanced detector, and the complexity of the system is reduced; the reference light/signal light and the local oscillator light share one unequal-arm interferometer, so that the system can realize self-stability; most importantly, the data post-processing module of the system is able to compensate for the unbalanced two orthogonal components.
The invention relates to a continuous variable quantum key distribution coherent detection system based on a local oscillator optical scheme, which is used for receiving reference optical pulses, signal optical pulses and local oscillator optical pulses and detecting interference results of the reference optical pulses, the signal optical pulses and the local oscillator optical pulses. According to the present invention, the coherent detection system for continuous variable quantum key distribution may include a polarization controller 121, a first polarization maintaining optical transmission element 122, a second polarization maintaining optical transmission element 123, an unequal arm interferometer module 124, a phase modulator 125, and a balanced detection module 126.
The polarization controller 121 is configured to control the polarization state of the reference optical pulse/the signal optical pulse to be consistent with the polarization state of the local optical pulse.
The first polarization preserving optical transmission element 122 has a first port, a second port and a third port and is arranged to receive the reference/signal optical pulses via the first port and output them from the second port towards the anisometric arm interferometer module 124.
The second polarization maintaining optical transmission element 123 has a first port, a second port and a third port and is arranged to receive the local oscillator light pulses via the first port and output them from the second port towards the interferometer module 124.
The unequal arm interferometer module 124 is configured to receive the reference optical pulse/the signal optical pulse and output a first optical pulse pair comprising a first two reference optical pulse components/signal optical pulse components toward the second port of the second polarization maintaining optical transmission element 123 based on the reference optical pulse/the signal optical pulse, and receive the local optical pulse and output a second optical pulse pair comprising a first two local optical pulse components toward the second port of the first polarization maintaining optical transmission element 122 based on the local optical pulse.
The first depolarizing optical transmission element 122 is further configured to receive the second pair of optical pulses via the second port and output them from the third port towards the balanced detection module 126.
The second polarization maintaining optical transmission element 123 is further arranged to receive the first pair of optical pulses via the second port and to output them from the third port towards the balanced detection module 126.
The phase modulator 125 is disposed between the third port of the first polarization maintaining optical transmission element 122 and the balanced detection module 126.
The balanced detection module 126 is arranged to detect the first light pulse pair and the second light pulse pair.
Preferably, the first polarization maintaining optical transmission element 122 and the second polarization maintaining optical transmission element 123 are polarization maintaining circulators.
Preferably, the unequal arm interferometer module 124 includes a first polarization maintaining beam splitter, a second polarization maintaining beam splitter, and a long arm and a short arm therebetween.
Further, the balance detection module 126 is further configured to detect an interference result of a previous reference optical pulse component/signal optical pulse component of the first optical pulse pair and a previous local oscillator optical pulse component of the second optical pulse pair to obtain an X component of the reference optical pulse/signal optical pulse, and detect an interference result of a next reference optical pulse component/signal optical pulse component of the first optical pulse pair and a next local oscillator optical pulse component of the second optical pulse pair to obtain a P component of the reference optical pulse/signal optical pulse.
Further, the coherent detection system for continuous variable quantum key distribution of the present invention may further include a data post-processing module 127, configured to perform data processing on the detection result output by the balanced detection module 126.
Further, the data post-processing module 127 is also arranged to compensate the unbalanced quadrature component for amplitude and phase.
Still further, the data post-processing module 127 is further configured to utilize a gauss-newton algorithm pair of equations
Fitting to obtain an amplitude mismatch parameter alpha and a phase mismatch parameter
Wherein A isRXAnd ARPThe pulse amplitudes for measuring the X and P components, respectively, having ARP＝αARX，
(xBR,pBR) The measurement results of the two orthogonal components X and P of the reference light pulse output by the balanced detection module 126.
According to the invention, the amplitude mismatch parameter α and the phase mismatch parameter
Is used to compensate the quadrature component of the signal light pulse.
Further, the phase modulator 125 provides phase modulation of 0 or π/2.
Drawings
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 coherent detection system 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.
In the invention, the continuous variable quantum key distribution coherent detection system is used for receiving reference light/signal light pulses and local oscillator light pulses at a receiving end of the continuous variable quantum key distribution system and carrying out coherent detection on the light pulses.
Fig. 1 shows a first embodiment of a continuous variable quantum key distribution coherent detection system according to the present invention.
As shown, the continuous variable quantum key distribution coherent detection system may include a polarization controller 121, a first polarization maintaining optical transmission element 122, a second polarization maintaining optical transmission unit 123, an unequal arm interferometer module 124, a phase modulator 125, a balanced detection module 126, and a data post-processing module 127.
The polarization controller 121 controls the polarization state of the reference light (signal light) pulse so as to coincide with the polarization state of the local oscillation light pulse.
Subsequently, the reference light (signal light) pulse enters the first port of the first optical transmission element 122 and exits the second port into the unequal arm interferometer module 124.
In the present invention, the first/second optical transmission elements 122/123 each have three ports and are arranged such that: light pulses entering from the first port exit from the second port and light pulses entering from the second port exit from the third port. As a preferred example, the optical transmission element may be a polarization maintaining circulator, but is not limited thereto.
The unequal arm interferometer module 124 is used to change an incoming one pulse of reference light (signal light) into a pair of light pulses including two light pulses one after the other. As a preferred example, as shown in FIG. 1, the unequal-arm interferometer module 124 may include a first polarization-maintaining beam splitter, a second polarization-maintaining beam splitter, and a long arm and a short arm therebetween. In the preferred example, a reference light (signal light) pulse is first split into two pulses by a polarization-maintaining beam splitter, wherein a certain delay is generated for one pulse relative to the other pulse (even if one of the light pulses propagates along the long arm and the other light pulse propagates along the short arm), and then the two light pulses are combined into two pulses in front and back by the polarization-maintaining beam splitter, thereby forming a light pulse pair.
A pair of optical pulses comprising two optical pulses enters the second port of the second optical transmission element 123 and exits the third port thereof. And the local oscillator light pulse enters from the first port of the second optical transmission element 123 and exits from the second port to enter the unequal arm interferometer module 124.
Similarly, the unequal arm interferometer module 124 also splits and combines the local oscillator light into a light pulse pair comprising two front and back local oscillator light pulses.
Subsequently, the optical pulse pair including the two local oscillation optical pulses enters the second port of the first optical transmission element 122 and exits the third port thereof.
Then, the two local oscillator light pulses are sequentially phase-modulated by the phase modulator 125 by 0 and pi/2, and finally, the two local oscillator light pulses and the two reference light (signal light) pulses interfere at the balanced detection module 126 and are detected by the balanced detector to obtain two orthogonal components X and P of the reference light (signal light) pulses.
The detected electrical signals are sent to the post-processing module 127, where an analog-to-digital converter (ADC) converts the electrical signals into digital signals, and then a Digital Signal Processor (DSP) processes the digital signals.
In the data post-processing module 127, the measurement results (x) of the light pulses are referred toBR,pBR) Satisfy the equation
Wherein theta isRFor measuring the phase of a reference light pulse, ARXAnd ARPThe pulse amplitudes for measuring the X and P components, respectively, having ARP＝αARX，
Where a and
amplitude mismatch and phase mismatch due to quadrature imbalance.
To compensate for the unbalanced quadrature component, first the sum of α needs to be obtained
In this case, equation set (1) can be reduced to
Equation (2) can be fitted by using the Gauss-Newton algorithm in the least square method to obtain parameter ARX，ARPAnd
then, the sum of alpha can be obtained
Then, the two orthogonal components of the reference light pulse are compensated
Measurement of the same signal light pulse (x)BS,pBS) Also satisfies the equation
Wherein theta isSFor measuring the phase of the signal light pulse, ASXAnd ASPThe pulse amplitudes for measuring the X-component and P-component, respectively, of the signal light are also ASP＝αASX. Alpha sum calculated by measuring with reference light pulse
The orthogonal component compensation can be carried out on the signal light pulse to obtain
In this embodiment, the reference light (signal light) pulse and the local oscillator light pulse are divided into two pulses by the unequal-arm interferometer module, and then the X component and the P component of the reference light (signal light) pulse are measured in sequence, so that the detection can be realized by using only a single balanced detector. Because the unequal arm interferometer module is shared, the self-stabilization of the system can be realized. Most importantly, the data post-processing module can process the orthogonal imbalance phenomenon during measurement.
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 coherent detection system based on a local oscillator optical scheme, configured to receive a reference optical pulse, a signal optical pulse, and a local oscillator optical pulse, and perform coherent detection on the reference optical pulse, the signal optical pulse, and the local oscillator optical pulse, where:
the continuous variable quantum key distribution coherent detection system comprises a polarization controller (121), a first polarization maintaining optical transmission element (122), a second polarization maintaining optical transmission element (123), an unequal arm interferometer module (124), a phase modulator (125) and a balanced detection module (126), wherein,
the polarization controller (121) is configured to control the polarization state of the reference optical pulses/the signal optical pulses to be consistent with the polarization state of the local oscillator optical pulses;
the first polarization preserving optical transmission element (122) has a first port, a second port and a third port and is arranged to receive the reference/signal optical pulses via the first port and output them from the second port towards the unequal arm interferometer module (124);
the second polarization maintaining optical transmission element (123) has a first port, a second port and a third port and is arranged to receive the local oscillator light pulses via the first port and output them from the second port towards the unequal arm interferometer module (124);
the interferometer module (124) is configured to receive the reference/signal light pulses and to output a first optical pulse pair comprising two preceding and two following reference/signal light pulse components towards the second port of the second polarization maintaining optical transmission element (123) based on the reference/signal light pulses and to receive the local optical pulse and to output a second optical pulse pair comprising two preceding and two local optical pulse components towards the second port of the first polarization maintaining optical transmission element (122) based on the local optical pulse;
the first polarization preserving optical transmission element (122) is further arranged to receive the second pair of optical pulses via the second port and to output them from the third port towards the balanced detection module (126);
said second polarization maintaining optical transmission element (123) being further arranged to receive said first pair of optical pulses via said second port and to output them from said third port towards said balanced detection module (126);
the phase modulator (125) is disposed between the third port of the first polarization maintaining optical transmission element (122) and the balanced detection module (126);
the balanced detection module (126) is arranged to detect an interference result of the first and second light pulse pairs.
2. The continuous variable quantum key distribution coherent detection system according to claim 1, wherein the first/second polarization maintaining optical transmission element (122/123) is a polarization maintaining circulator.
3. The continuous variable quantum key distribution coherent detection system of claim 1 wherein the unequal arm interferometer module (124) comprises a first polarization maintaining beam splitter, a second polarization maintaining beam splitter, and a long arm and a short arm therebetween.
4. The continuous variable quantum key distribution coherent detection system of claim 1, wherein the balanced detection module (126) comprises a third polarization maintaining beam splitter and a balanced detector.
5. The continuous variable quantum key distribution coherent detection system according to claim 1, wherein the balanced detection module (126) is further configured to detect an interference result of a previous reference optical pulse component/signal optical pulse component of the first optical pulse pair and a previous local oscillator optical pulse component of the second optical pulse pair at a third polarization maintaining beam splitter with a balanced detector to obtain an X-component of the reference optical pulse/signal optical pulse, and detect an interference result of a next reference optical pulse component/signal optical pulse component of the first optical pulse pair and a next local oscillator optical pulse component of the second optical pulse pair at a third polarization maintaining beam splitter to obtain a P-component of the reference optical pulse/signal optical pulse.
6. The continuous variable quantum key distribution coherent detection system according to claim 1, further comprising a data post-processing module (127) for data processing of the detection results output by the balanced detection module (126).
7. The continuous variable quantum key distribution coherent detection system of claim 6, wherein the data post-processing module (127) is arranged to compensate for amplitude and phase of unbalanced quadrature components.
8. The continuous variable quantum key distribution coherent detection system of claim 7, wherein the data post-processing module (127) is further configured to apply a gauss-newton algorithm to an equation
Fitting to obtain an amplitude mismatch parameter alpha and a phase mismatch parameter
Wherein A isRXAnd ARPThe pulse amplitudes for measuring the X and P components, respectively, having ARP＝αARX，
(xBR,pBR) A measurement of two orthogonal components X and P of the reference light pulse output by the balanced detection module (126).
9. The continuous variable quantum key distribution coherent detection system of claim 8,characterized in that said amplitude mismatch parameter α and said phase mismatch parameter α
Is used to compensate the quadrature component of the signal light pulse.
10. The continuous variable quantum key distribution coherent detection system of claim 1, wherein the phase modulator (125) provides a phase modulation of 0 or pi/2.
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| CN111786730B (en) * | 2020-06-08 | 2021-06-04 | 中国电子科技集团公司第三十研究所 | Pilot frequency assisted local oscillator continuous variable quantum key distribution system and method |
| 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 |
| CN114268433B (en) * | 2021-12-27 | 2024-04-16 | 中南大学 | Nonlinear compensation method of high-speed continuous variable quantum key distribution 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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| FR2879381B1 (en) * | 2004-12-15 | 2008-12-26 | Thales Sa | QUANTUM QUANTUM DISTRIBUTION SYSTEM OF CONTINUOUSLY VARIABLE ENCRYPTION KEY |
| KR100890389B1 (en) * | 2006-12-05 | 2009-03-26 | 한국전자통신연구원 | Polarization-insensitive one way quantum key receiver, transmitter/receiver system |
| JP6010955B2 (en) * | 2012-03-22 | 2016-10-19 | 日本電気株式会社 | Coherent optical receiver and optical receiving method |
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