CN103199994B - The Active phase compensate method of Combisweep and device - Google Patents
The Active phase compensate method of Combisweep and device Download PDFInfo
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Abstract
Description
技术领域technical field
本发明涉及量子密钥分发领域，更具体地，涉及一种联合扫描的主动相位补偿方法及装置。The present invention relates to the field of quantum key distribution, and more specifically, to an active phase compensation method and device for joint scanning.
背景技术Background technique
相位漂移是相位编码的量子密钥分发(QKD)系统固有的问题，是影响QKD系统实用性能的重要因素之一。单相位扫描主动相位的补偿方案：假设Alice端的相位调制器加载的电压和所调制的相位是线性的，从而只扫描Bob端的干涉曲线。在实际器件中相位调制器加载的电压和所调制的相位并不是线性的，因此提出了四相位扫描法的主动相位补偿方案。但是四相位扫描法需要扫描Bob端的干涉曲线4次，增加了相位扫描的时间和复杂度，且需要Bob将扫描结果通过公共信道传输给Alice，这样Eve便能够获取相位扫描的信息，为实施相位重映射攻击或边信道攻击提供可能，引起相关的安全性问题。Phase drift is an inherent problem in phase-encoded quantum key distribution (QKD) systems, and is one of the important factors affecting the practical performance of QKD systems. Compensation scheme for single-phase scanning active phase: Assume that the voltage applied to the phase modulator at Alice's end and the modulated phase are linear, so that only the interference curve at Bob's end is scanned. In actual devices, the voltage loaded by the phase modulator and the modulated phase are not linear, so an active phase compensation scheme of four-phase scanning method is proposed. However, the four-phase scanning method needs to scan the interference curve at Bob's end four times, which increases the time and complexity of phase scanning, and requires Bob to transmit the scanning results to Alice through a public channel, so that Eve can obtain the information of phase scanning. Remapping attacks or side-channel attacks provide the possibility, causing related security issues.
发明内容Contents of the invention
为了克服现有技术的不足，本发明首先提出一种联合扫描的主动相位补偿方法，在提高系统安全性的同时，缩短了扫描时间。In order to overcome the deficiencies of the prior art, the present invention first proposes an active phase compensation method of joint scanning, which shortens the scanning time while improving system security.
为了实现上述目的，其技术方案为：In order to achieve the above object, its technical scheme is:
一种联合扫描的主动相位补偿方法，在Alice端加入一个中间环，所述中间环为MZ干涉环或FM干涉环，中间环分别与Alice和Bob端的环进行干涉，扫描分别得到Alice端和Bob端的干涉曲线，从而获得相位调制器的相位漂移参数，再对Alice和Bob端分别进行主动相位补偿。An active phase compensation method for joint scanning, adding an intermediate ring at the Alice end, the intermediate ring is an MZ interference ring or an FM interference ring, and the intermediate ring interferes with the rings at the Alice and Bob ends respectively, and scans to obtain Alice and Bob respectively. The interference curve of the terminal is used to obtain the phase drift parameters of the phase modulator, and then active phase compensation is performed on Alice and Bob respectively.
其中，在一定的时间范围内，中间环的相位差是恒定的，分别换取Alice和Bob端相对中间环的相位漂移，将Alice和Bob端的相位漂移与中间环作比较，得到Alice和Bob端的相位漂移参数。此时Alice端的相位扫描完全是在本地完成，不经过长程光纤，Eve不能获取任何关于Alice端相位扫描的信息或改变Alice端发送的量子态，在这个条件下，Alice端发出的量子态是两两正交的量子态，已知的相位重映射攻击则不能实施。Among them, within a certain time range, the phase difference of the middle ring is constant, and the phase drift of Alice and Bob relative to the middle ring is exchanged respectively, and the phase drift of Alice and Bob is compared with the middle ring to obtain the phase of Alice and Bob Drift parameter. At this time, the phase scanning of Alice is completely completed locally, without going through the long-distance optical fiber, Eve cannot obtain any information about the phase scanning of Alice or change the quantum state sent by Alice. Under this condition, the quantum state sent by Alice is two For two orthogonal quantum states, known phase remapping attacks cannot be implemented.
优选地，所述Alice端的扫描过程为：Preferably, the scanning process at the Alice end is:
S11.将Alice端相位调制器PMA的调相电压从Vmin以步长△V扫描到Vmax，Vmin为最小调相电压，Vmax为最大调相电压；S11. Sweep the phase modulation voltage of the Alice terminal phase modulator PMA from Vmin to Vmax with a step size of △V, where Vmin is the minimum phase modulation voltage, and Vmax is the maximum phase modulation voltage;
S12.在各个电压值Vi处等待N个同步脉冲，并对单光子探测器的计数进行累加，得到计数Ci，得到一组数据{Vi，Ci}，数据组{Vi，Ci}构成的曲线为Alice端的单光子干涉曲线；S12. Wait for N synchronous pulses at each voltage value Vi, and accumulate the counts of the single photon detector to obtain the count Ci, and obtain a set of data {Vi, Ci}, and the curve formed by the data set {Vi, Ci} is The single-photon interference curve at the Alice end;
S13.根据Alice端的单光子干涉曲线得到Alice端相位调制器的半波电压Vπ,a以及加载0，π/2，π，3π/2相位时的电压Va,0,Va,π, S13. Obtain the half-wave voltage V π,a of the phase modulator at the Alice end according to the single-photon interference curve at the Alice end and the voltage V a,0 when loading 0, π/2, π, 3π/2 phases, V a,π ,
所述Bob端的扫描过程为：The scanning process at the Bob end is:
S21.将Bob端相位调制器PMB的调相电压从V’min以步长△V扫描到V’max，V’min为最小调相电压，V’max为最大调相电压；S21. The phase modulation voltage of the phase modulator PMB at the Bob end is scanned from V'min to V'max with a step size △V, V'min is the minimum phase modulation voltage, and V'max is the maximum phase modulation voltage;
S22.在各个电压值V’i处等待M个同步脉冲，并对单光子探测器的计数进行累加，得到计数C’i，得到一组数据{V’i，C’i}，数据组{V’i，C’i}构成的曲线为Bob端的单光子干涉曲线；S22. Wait for M synchronization pulses at each voltage value V'i, and accumulate the counts of the single photon detectors to obtain the count C'i, and obtain a set of data {V'i, C'i}, the data set { The curve formed by V'i, C'i} is the single-photon interference curve at Bob's end;
S23.根据Bob端的单光子干涉曲线得到Bob端相位调制器的半波电压Vπ,b以及加载0，π/2，π，3π/2相位时的电压Vb,0,Vb,π, S23. Obtain the half-wave voltage V π,b of the phase modulator at the Bob end and the voltage V b,0 when loading 0, π/2, π, 3π/2 phases according to the single-photon interference curve at the Bob end, V b,π ,
优选地，所述步骤S11中Vmin到Vmax至少覆盖2π的相位范围；所述步骤S21中V’min到V’max至少覆盖2π的相位范围。Preferably, in the step S11, Vmin to Vmax cover at least a phase range of 2π; in the step S21, V'min to V'max cover at least a phase range of 2π.
优选地，所述Alice端主动相位补偿方式为：Preferably, the active phase compensation method at the Alice end is:
Alice端的单光子干涉曲线中，选取相位差为π的点电压为参考电压Vref,a，则： In the single-photon interference curve at the Alice end, the point voltage with a phase difference of π is selected as the reference voltage V ref,a , then:
其中，为中间环由长度差引起的固有相位差，为Alice端干涉环的固有相位差，则为随机的相位漂移；in, is the inherent phase difference caused by the length difference of the middle ring, is the inherent phase difference of the interference ring at the Alice end, Then it is a random phase drift;
Alice端的相位调制的调制电压工作点即为：The modulation voltage operating point of the phase modulation at the Alice end is:
则Alice端相位调制器加载的电压为Va,i时，相位差为：Then when the voltage loaded by the phase modulator at the Alice terminal is V a,i , the phase difference is:
所述Bob端主动相位补偿方式为：The active phase compensation mode of the Bob end is:
Bob端的单光子干涉曲线中，选取相位差为π的点电压为参考电压Vref,b，则 In the single-photon interference curve at the Bob end, the point voltage with a phase difference of π is selected as the reference voltage V ref,b , then
其中，为中间环由长度差引起的固有相位差，为Bob端干涉环的固有相位差，则为随机的相位漂移；in, is the inherent phase difference caused by the length difference of the middle ring, is the inherent phase difference of the interference ring at the Bob end, Then it is a random phase drift;
Bob端的相位调制的调制电压工作点即为：The modulation voltage operating point of the phase modulation at the Bob end is:
则Bob端相位调制器加载的电压为Vb,j时，相位差为：Then when the voltage loaded by the phase modulator at the Bob end is V b,j , the phase difference is:
本发明还提出一种用于实现上述方法的补偿装置，用于实现自动补偿，降低相位扫描的时间和复杂度并用于实现Alice和Bob端的独立扫描避免相位重映射攻击或边信道攻击。The present invention also proposes a compensation device for implementing the above method, which is used to realize automatic compensation, reduce the time and complexity of phase scanning, and realize independent scanning of Alice and Bob to avoid phase remapping attack or side channel attack.
其具体实现方案如下：Its specific implementation plan is as follows:
一种应用于联合扫描的主动相位补偿方法的装置，包括Alice端和与Alice端连接的Bob端，在所述Alice端加入一个中间环，所述中间环为MZ干涉环或FM干涉环，所述中间环用于分别与Alice端和Bob端进行干涉，分别扫描得到Alice端和Bob端的干涉曲线，从而获得相位调制器的相位漂移参数，再对Alice和Bob端分别进行主动相位补偿。A device applied to the active phase compensation method of joint scanning, comprising an Alice end and a Bob end connected to the Alice end, adding an intermediate ring at the Alice end, the intermediate ring being an MZ interference ring or an FM interference ring, the The intermediate ring is used to interfere with the Alice end and the Bob end respectively, and the interference curves of the Alice end and the Bob end are obtained by scanning respectively, so as to obtain the phase drift parameters of the phase modulator, and then active phase compensation is performed on the Alice end and the Bob end respectively.
优选地，所述联合扫描的主动相位补偿装置是基于双MZ系统，所述中间环为MZ干涉环，Preferably, the joint scanning active phase compensation device is based on a double MZ system, the middle ring is an MZ interference ring,
所述Alice端包括第一、二激光器、相位调制器PMA、延迟环DL1、隔离器ISO1、隔离器ISO2、耦合器C1—C2、单光子探测器SPD3和中间环；中间环包括耦合器C3、C4、延迟环DL3；The Alice end includes first and second lasers, a phase modulator PMA, a delay ring DL1, an isolator ISO1, an isolator ISO2, a coupler C1-C2, a single photon detector SPD3 and an intermediate ring; the intermediate ring includes a coupler C3, C4, delay loop DL3;
所述第一激光器通过耦合器C1分别接相位调制器PMA及延迟环DL1，相位调制器PMA及延迟环DL1并联连接，相位调制器PMA及延迟环DL1分别接接耦合器C2的两个输入端，耦合器C2的一输出端接耦合器C3的一输入端，耦合器C2的另一输出端接隔离器ISO1的输入端，隔离器ISO1的输出端接耦合器C3的一输出端，耦合器C3通过MZ干涉环接至耦合器C4，耦合器C4的一输出端接单光子探测器SPD3，耦合器C4的一输入端接隔离器ISO2的输出端，第二激光器接ISO2的输入端；The first laser is respectively connected to the phase modulator PMA and the delay loop DL1 through the coupler C1, the phase modulator PMA and the delay loop DL1 are connected in parallel, and the phase modulator PMA and the delay loop DL1 are respectively connected to the two input ends of the coupler C2 , one output terminal of the coupler C2 is connected to one input terminal of the coupler C3, the other output terminal of the coupler C2 is connected to the input terminal of the isolator ISO1, the output terminal of the isolator ISO1 is connected to an output terminal of the coupler C3, and the coupler C3 is connected to the coupler C4 through the MZ interference ring, an output end of the coupler C4 is connected to the single photon detector SPD3, an input end of the coupler C4 is connected to the output end of the isolator ISO2, and the second laser is connected to the input end of the ISO2;
所述Bob端包括相位调制器PMB、延迟环DL2、耦合器C5、C6和单光子探测器SPD1、SPD2，耦合器C5的一输出端通过相位调制器PMB接耦合器C6的一输入端，耦合器C6的一输出端接单光子探测器SPD1；耦合器C5的另一输出端通过延迟环DL2接耦合器C6的另一输入端，耦合器C6的另一输出端接单光子探测器SPD2；Described Bob end comprises phase modulator PMB, delay loop DL2, coupler C5, C6 and single photon detector SPD1, SPD2, an output end of coupler C5 is connected to an input end of coupler C6 by phase modulator PMB, coupling One output end of the coupler C6 is connected to the single photon detector SPD1; the other output end of the coupler C5 is connected to the other input end of the coupler C6 through the delay loop DL2, and the other output end of the coupler C6 is connected to the single photon detector SPD2;
所述Alice端通过长程光纤与Bob端连接；长程光纤接隔离器ISO1的输出端。The Alice end is connected to the Bob end through a long-distance optical fiber; the long-distance optical fiber is connected to the output end of the isolator ISO1.
Alice端的扫描过程：第一激光器发出的光脉冲通过耦合器C1，分成两个脉冲，一个走短路经过相位调制器PMA进入耦合器C2，一个走长路经过延迟环DL1进入C2，再一前一后进入C3，经过C3之后分为4个脉冲，分别通过中间环的长臂光纤和短臂光纤。4个脉冲中先走长臂光纤、后走短臂光纤的脉冲和先走短臂光纤、后走长臂光纤的脉冲在C4处干涉，由光子探测器SPD3探测单光子干涉曲线。The scanning process at the Alice end: the light pulse emitted by the first laser passes through the coupler C1 and is divided into two pulses. One goes through the phase modulator PMA and enters the coupler C2 through a short circuit, and the other goes through a delay loop DL1 and enters C2 through a long path. After entering C3, after passing through C3, it is divided into 4 pulses, which pass through the long-arm optical fiber and short-arm optical fiber of the middle ring respectively. Among the four pulses, the pulses of the long-arm fiber first and then the short-arm fiber and the pulses of the short-arm fiber first and then the long-arm fiber interfere at C4, and the single-photon interference curve is detected by the photon detector SPD3.
Bob端的扫描过程：第二激光器发出的光脉冲通过耦合器C4分成两个脉冲，通过中间环之后进入C3，一前一后进入长程光纤，到达Bob端经过耦合器C5分成4个，分别经过相位调制器PMB和延迟环DL2之后在耦合器C6处干涉，光子探测器由SPD1和SPD2进行密钥的探测。The scanning process at the Bob end: the light pulse emitted by the second laser is divided into two pulses through the coupler C4, and then enters the C3 after passing through the middle ring, and enters the long-distance optical fiber one after the other, and reaches the Bob end and is divided into 4 pulses through the coupler C5, respectively. The modulator PMB and the delay loop DL2 then interfere at the coupler C6, and the photon detectors are detected by SPD1 and SPD2 for the key.
优选地，所述联合扫描的主动相位补偿装置是基于双FM系统，所述中间环为FM干涉环，Preferably, the joint scanning active phase compensation device is based on a dual FM system, and the middle ring is an FM interference ring,
所述Alice端包括法拉第镜FM1—FM2、第一、二激光器、相位调制器PMA、耦合器BS1、环形器CIR1—CIR2、延迟环DL1、单光子探测器SPD和中间环，所述中间环包括延迟环DL2、耦合器BS2和法拉第镜FM3—FM4；The Alice end includes Faraday mirrors FM1-FM2, first and second lasers, a phase modulator PMA, a coupler BS1, a circulator CIR1-CIR2, a delay ring DL1, a single photon detector SPD and an intermediate ring, and the intermediate ring includes Delay loop DL2, coupler BS2 and Faraday mirror FM3-FM4;
第一激光器发出的激光进入耦合器BS1分为两个脉冲，分别走长臂和短臂，由法拉第镜FM1和法拉第镜FM2反射回耦合器BS1的另外一端进入环形器CIR1的第一端口，由环形器CIR1的第二端口进入中间环，经过耦合器BS2后分为4个脉冲分别由法拉第镜FM3和法拉第镜FM4反射回耦合器BS2；先走长臂后走短臂和先走短臂后走长臂的两个脉冲在耦合器BS2处干涉，由单光子探测器SPD探测到单光子干涉曲线；，从而获得Alice端的相位漂移参数The laser light emitted by the first laser enters the coupler BS1 and is divided into two pulses, which go through the long arm and the short arm respectively, and are reflected back by the Faraday mirror FM1 and Faraday mirror FM2. The other end of the coupler BS1 enters the first port of the circulator CIR1. The second port of the circulator CIR1 enters the middle ring, and after passing through the coupler BS2, it is divided into 4 pulses which are respectively reflected by the Faraday mirror FM3 and Faraday mirror FM4 and returned to the coupler BS2; The two pulses of the long arm interfere at the coupler BS2, and the single-photon interference curve is detected by the single-photon detector SPD; thereby obtaining the phase shift parameter at the Alice end
所述Bob端包括法拉第镜FM5—FM6、相位调制器PMB、耦合器BS3、延迟环DL3、光子探测器SPD1和环形器CIR3，第二激光器发出的激光经过环形器CIR2进入耦合器BS2，分为两个脉冲分别走耦合器BS2的长臂和短臂，再由法拉第镜FM3和法拉第镜FM4反射回耦合器BS2一前一后进入环形器CIR1的第二端口，经过末端口进入长程光纤；由长程光纤进入Bob端环形器CIR3的第一端口，经过第二端口进入耦合器BS3分为4个脉冲，分别有法拉第镜FM5和法拉第镜FM6反射回耦合器BS3；同样，先走长臂后走短臂和先走短臂后走长臂的两个脉冲在耦合器BS3处干涉，由SPD1得到单光子干涉曲线，获取Bob端的相位漂移参数。Described Bob end comprises Faraday mirror FM5-FM6, phase modulator PMB, coupler BS3, delay ring DL3, photon detector SPD1 and circulator CIR3, the laser light that the second laser sends enters coupler BS2 through circulator CIR2, is divided into The two pulses go through the long arm and the short arm of the coupler BS2 respectively, and then are reflected by the Faraday mirror FM3 and the Faraday mirror FM4 back to the coupler BS2 one after the other and enter the second port of the circulator CIR1, and enter the long-distance optical fiber through the end port; The long-distance optical fiber enters the first port of the circulator CIR3 at Bob's end, and enters the coupler BS3 through the second port, and is divided into 4 pulses, which are respectively reflected by the Faraday mirror FM5 and Faraday mirror FM6 and reflected back to the coupler BS3; similarly, first go through the long arm and then go The two pulses of the short arm and the short arm first and then the long arm interfere at the coupler BS3, and the single-photon interference curve is obtained by SPD1, and the phase shift parameters at the Bob end are obtained.
优选地，所述环形器为三端口开环环形器，即光路由第一端口输入则第二端口输出，第二端口输入则第三端口输出；所述末端口为第三端口。Preferably, the circulator is a three-port open-loop circulator, that is, the optical route is input to the first port and then the second port is output, and the second port is input and the third port is output; the last port is the third port.
与现有技术相比，本发明的有益效果为：本发明通过在Alice端增加一个干涉中间环来进行主动相位补偿。此方案较现有的主动补偿方案有以下提高：Compared with the prior art, the beneficial effect of the present invention is that: the present invention performs active phase compensation by adding an interference intermediate ring at the Alice end. Compared with the existing active compensation scheme, this scheme has the following improvements:
1、Alice端和Bob端分别与中间环进行干涉，获得各自密钥分发的工作电压点，且Alice端的相位扫描过程完全在本地完成，避免了在公共信道中传输相位扫描结果，使得Eve不能获取相位扫描的信息，提高了系统的安全性。1. Alice and Bob interfere with the intermediate ring respectively to obtain the operating voltage point of their respective key distribution, and the phase scanning process of Alice is completely completed locally, avoiding the transmission of the phase scanning results in the public channel, so that Eve cannot obtain Phase scanning information improves system security.
2、Alice端的相位扫描过程完全在本地完成，扫描过程中光子不经过长程光纤，避免了Eve在相位扫描过程中改变Alice发送的量子态，防御相位重映射攻击及其可能的变形。2. The phase scanning process on the Alice side is completely completed locally. During the scanning process, the photons do not pass through the long-distance optical fiber, which prevents Eve from changing the quantum state sent by Alice during the phase scanning process, and defends against phase remapping attacks and possible deformations.
3、Alice和Bob只需分别扫描一次，得到各自的干涉曲线即可得出各自的电压工作点，降低了扫描的复杂度，缩短了扫描的时间，这便意味着提高了信息的占空比。3. Alice and Bob only need to scan once to obtain their respective interference curves to obtain their respective voltage operating points, which reduces the complexity of scanning and shortens the scanning time, which means that the duty cycle of information is improved .
4、只扫描一次的前提是假设相位调制器的调制曲线是线性的，在实际器件中，调制曲线并不是线性的。对于相位调制器调制曲线非线性的问题，可以分为两个方面来考虑。一方面是关于相位调制器调制曲线非线性的问题，虽然实际器件中调制曲线不可能做到完全线性，但目前常用的铌酸锂相位调制器的线性度已经能够满足QKD的要求，对于密钥分发的影响较小。另一方面是关于相位调制器半波电压随时间变化的问题。通过实验观察发现，相位调制器的半波电压在长时间使用之后会产生变化，影响加载相位的准确性。此方案中，Alice和Bob端相位调制器的半波电压都是通过扫描结果得到，实时地反映了相位调制器的半波电压，因此很好的解决了半波电压发生变化的问题。4. The premise of scanning only once is that the modulation curve of the phase modulator is assumed to be linear, but in actual devices, the modulation curve is not linear. As for the non-linear problem of the modulation curve of the phase modulator, it can be considered in two aspects. On the one hand, it is about the non-linearity of the modulation curve of the phase modulator. Although the modulation curve in the actual device cannot be completely linear, the linearity of the commonly used lithium niobate phase modulator can already meet the requirements of QKD. For the key Distribution has less impact. Another aspect concerns the time variation of the half-wave voltage of the phase modulator. Through experimental observation, it is found that the half-wave voltage of the phase modulator will change after a long time of use, which will affect the accuracy of the loading phase. In this solution, the half-wave voltages of the phase modulators at Alice and Bob are obtained through scanning results, which reflect the half-wave voltages of the phase modulators in real time, thus solving the problem of half-wave voltage changes.
附图说明Description of drawings
图1为本发明应用于双MZ系统中Alice端的扫描示意图。FIG. 1 is a schematic diagram of the present invention applied to scanning at the Alice end in a dual MZ system.
图2为本发明应用于双MZ系统中Bob端结构示意图。Fig. 2 is a schematic diagram of the structure of the Bob terminal in the application of the present invention in the dual MZ system.
图3为本发明应用于FM系统的Alice端结构示意图。Fig. 3 is a schematic diagram of the structure of the Alice terminal where the present invention is applied to the FM system.
图4为FM系统的Bob端的结构示意图。FIG. 4 is a schematic structural diagram of the Bob end of the FM system.
具体实施方式detailed description
下面结合附图对本发明做进一步的描述，但本发明的实施方式并不限于此。The present invention will be further described below in conjunction with the accompanying drawings, but the embodiments of the present invention are not limited thereto.
实施例一Embodiment one
如图1、2所示，为本发明在双MZ系统中应用时Alice端的扫描示意图；在Alice端加入一个中间环，由它分别和Alice和Bob端的环干涉，得出Alice和Bob端相位调制器的相位漂移参数，然后分别进行补偿。所述Alice端包括第一、二激光器、相位调制器PMA、延迟环DL1、隔离器ISO1、隔离器ISO2、耦合器C1—C2、单光子探测器SPD3和中间环；中间环包括耦合器C3、C4、延迟环DL3；As shown in Figures 1 and 2, it is the scanning schematic diagram of the Alice end when the present invention is applied in the dual MZ system; an intermediate ring is added at the Alice end, and it interferes with the rings of the Alice and Bob ends respectively to obtain the phase modulation of the Alice and Bob ends The phase drift parameters of the detector are then compensated separately. The Alice end includes first and second lasers, a phase modulator PMA, a delay ring DL1, an isolator ISO1, an isolator ISO2, a coupler C1-C2, a single photon detector SPD3 and an intermediate ring; the intermediate ring includes a coupler C3, C4, delay loop DL3;
所述第一激光器通过耦合器C1分别接相位调制器PMA及延迟环DL1，相位调制器PMA及延迟环DL1并联连接，相位调制器PMA及延迟环DL1分别接接耦合器C2的两个输入端，耦合器C2的一输出端接耦合器C3的一输入端，耦合器C2的另一输出端接隔离器ISO1的输入端，隔离器ISO1的输出端接耦合器C3的一输出端，耦合器C3通过MZ干涉环接至耦合器C4，耦合器C4的一输出端接单光子探测器SPD3，耦合器C4的一输入端接隔离器ISO2的输出端，第二激光器接ISO2的输入端；The first laser is respectively connected to the phase modulator PMA and the delay loop DL1 through the coupler C1, the phase modulator PMA and the delay loop DL1 are connected in parallel, and the phase modulator PMA and the delay loop DL1 are respectively connected to the two input ends of the coupler C2 , one output terminal of the coupler C2 is connected to one input terminal of the coupler C3, the other output terminal of the coupler C2 is connected to the input terminal of the isolator ISO1, the output terminal of the isolator ISO1 is connected to an output terminal of the coupler C3, and the coupler C3 is connected to the coupler C4 through the MZ interference ring, an output end of the coupler C4 is connected to the single photon detector SPD3, an input end of the coupler C4 is connected to the output end of the isolator ISO2, and the second laser is connected to the input end of the ISO2;
所述Bob端包括相位调制器PMB、延迟环DL2、耦合器C5、C6和单光子探测器SPD1、SPD2，耦合器C5的一输出端通过相位调制器PMB接耦合器C6的一输入端，耦合器C6的一输出端接单光子探测器SPD1；耦合器C5的另一输出端通过延迟环DL2接耦合器C6的另一输入端，耦合器C6的另一输出端接单光子探测器SPD2；Described Bob end comprises phase modulator PMB, delay loop DL2, coupler C5, C6 and single photon detector SPD1, SPD2, an output end of coupler C5 is connected to an input end of coupler C6 by phase modulator PMB, coupling One output end of the coupler C6 is connected to the single photon detector SPD1; the other output end of the coupler C5 is connected to the other input end of the coupler C6 through the delay loop DL2, and the other output end of the coupler C6 is connected to the single photon detector SPD2;
所述Alice端通过长程光纤与Bob端连接；长程光纤接隔离器ISO1的输出端。The Alice end is connected to the Bob end through a long-distance optical fiber; the long-distance optical fiber is connected to the output end of the isolator ISO1.
假设在一定的时间范围内，中间环的相位差是恒定的那么Alice和Bob只需要分别与中间环做相位扫描。各自确定相位漂移的参数，那么干涉时的相位差，则由Alice和Bob端相位调制器加载的相位差决定。这样Alice端的相位扫描过程则完全在本地完成，不经过长程光纤，Eve不能获取任何关于Alice端相位扫描的信息或改变Alice端发送的量子态，在这个条件下，Alice端发出的量子态是两两正交的量子态，已知的相位重映射攻击则不能实施。Assuming that within a certain time range, the phase difference of the middle ring is constant, then Alice and Bob only need to perform phase scans with the middle ring respectively. Each determines the parameters of the phase drift, then the phase difference during interference is determined by the phase difference loaded by the phase modulator at Alice and Bob. In this way, the phase scanning process at the Alice end is completely completed locally. Without going through the long-distance optical fiber, Eve cannot obtain any information about the phase scanning at the Alice end or change the quantum state sent by the Alice end. Under this condition, the quantum state sent by the Alice end is two For two orthogonal quantum states, known phase remapping attacks cannot be implemented.
在本实施例的方案中Alice和Bob的扫描过程在间隔很近的时间内进行，并且此方案得到的结果不是每两个环的相位漂移，而是密钥分发的工作点，那么扫描得到的结果与第三个环的相位漂移是无关的。In the scheme of this embodiment, the scanning process of Alice and Bob is carried out in a very close time interval, and the result obtained by this scheme is not the phase drift of every two rings, but the working point of the key distribution, then the scanning obtained The results are independent of the phase shift of the third ring.
下面以MZ系统为例，具体描述其扫描与补偿的过程。The following takes the MZ system as an example to describe its scanning and compensation process in detail.
一、扫描的过程1. Scanning process
Alice端的扫描过程如下：Alice's scanning process is as follows:
1、将Alice端相位调制器PMA的调相电压从Vmin以步长△V扫描到Vmax，Vmin到Vmax至少要覆盖2π的相位范围。1. Sweep the phase modulation voltage of the phase modulator PMA at the Alice end from Vmin to Vmax with a step size of ΔV, and the phase range from Vmin to Vmax must cover at least 2π.
2、在每一个电压值Vi处等待N个同步脉冲，并对单光子探测器的计数进行累加，得到计数Ci，得到一组数据{Vi，Ci}，这条曲线即为单光子干涉曲线。2. Wait for N synchronous pulses at each voltage value Vi, and accumulate the counts of the single-photon detector to obtain the count Ci, and obtain a set of data {Vi, Ci}. This curve is the single-photon interference curve.
3、根据曲线可以得到Alice端相位调制器的半波电压Vπ,a以及加载0，π/2，π，3π/2相位时的电压Va,0,Va,π, 3. According to the curve, the half-wave voltage V π,a of the phase modulator at the Alice end and the voltage V a,0 when loading phases of 0, π/2, π, 3π/2 V a,π ,
Bob端的扫描过程与Alice端类似，不同的是Bob扫描时，是从Alice端的laser2激光器发出的光，经过中间环之后进入长程光纤，然后再到Bob端进行干涉。经过上述1、2、3个步骤之后同样得到Bob端的干涉曲线，并得到Bob端相位调制器的半波电压Vπ,b以及加载0，π/2，π，3π/2相位时的电压Vb,0,Vb,π, The scanning process at the Bob end is similar to that at the Alice end. The difference is that when Bob scans, the light emitted from the laser2 laser at the Alice end passes through the middle ring and then enters the long-distance optical fiber, and then goes to the Bob end for interference. After the above 1, 2, and 3 steps, the interference curve at the Bob end is also obtained, and the half-wave voltage V π,b of the phase modulator at the Bob end and the voltage V when the phase is loaded with 0, π/2, π, 3π/2 b,0 , V b,π ,
二、相位漂移补偿2. Phase drift compensation
1、Alice端的主动相位补偿1. Active phase compensation at the Alice end
两次扫描过程都会得到单光子的干涉曲线，以Alice端的扫描为例。单光子干涉曲线中，计数最大点对应的电压，与计数最小点的电压之差为补偿后Alice端相位调制器的半波电压Vπ,a，选取相位差为π的点电压为参考电压Vref,a，则有下式成立：The single-photon interference curve will be obtained in the two scanning processes, taking the scanning at the Alice end as an example. In the single-photon interference curve, the difference between the voltage corresponding to the maximum count point and the voltage at the minimum count point is the half-wave voltage V π,a of the phase modulator at the Alice end after compensation, and the voltage at the point with a phase difference of π is selected as the reference voltage V ref,a , then the following formula holds:
其中，为中间环由长度差引起的固有相位差，为Alice端干涉环的固有相位差，则为随机的相位漂移。in, is the inherent phase difference caused by the length difference of the middle ring, is the inherent phase difference of the interference ring at the Alice end, is a random phase shift.
Alice端的相位调制的调制电压工作点即为：The modulation voltage operating point of the phase modulation at the Alice end is:
则Alice端相位调制器加载的电压为Va,i时，相位差为：Then when the voltage loaded by the phase modulator at the Alice terminal is V a,i , the phase difference is:
2、Bob端的主动相位补偿2. Active phase compensation at the Bob end
同样选取相位差为π的点电压为参考电压Vref,b，则Also select the point voltage with a phase difference of π as the reference voltage V ref,b , then
同理我们可以推导出Bob端的相位调制器的调制电压工作点：In the same way, we can deduce the modulation voltage operating point of the phase modulator at Bob's end:
则Bob端相位调制器加载的电压为Vb,j时，相位差为：Then when the voltage loaded by the phase modulator at the Bob end is V b,j , the phase difference is:
当假设在一定的时间范围内，中间环的固有相位差保持不变，且Alice和Bob端干涉环固有的相位差相等时，相位漂移得到补偿。The phase drift is compensated when it is assumed that the intrinsic phase difference of the intermediate ring remains constant and the intrinsic phase difference of the interfering rings at Alice and Bob ends is equal over a certain time range.
实施例二Embodiment two
如图3、4，Alice端包括法拉第镜FM1—FM2、第一、二激光器、相位调制器PMA、耦合器BS1—BS2、环形器CIR1—CIR2、延迟环DL1、单光子探测器SPD和中间环，所述中间环包括延迟环DL2和法拉第镜FM3—FM4；第一激光器发出的激光进入耦合器BS1分为两个脉冲，分别走长臂和短臂，由法拉第镜FM1和法拉第镜FM2反射回耦合器BS1的另外一端进入环形器CIR1的第一端口，由环形器CIR1的第二端口进入中间环，经过耦合器BS2后分为4个脉冲分别由法拉第镜FM3和法拉第镜FM4反射回耦合器BS2；先走长臂后走短臂和先走短臂后走长臂的两个脉冲在耦合器BS2处干涉，由单光子探测器SPD探测到单光子干涉曲线；，从而获得Alice端的相位漂移参数As shown in Figure 3 and 4, the Alice end includes Faraday mirrors FM1-FM2, first and second lasers, phase modulator PMA, coupler BS1-BS2, circulator CIR1-CIR2, delay ring DL1, single photon detector SPD and intermediate ring , the intermediate ring includes a delay ring DL2 and Faraday mirrors FM3-FM4; the laser light emitted by the first laser enters the coupler BS1 and is divided into two pulses, which go through the long arm and the short arm respectively, and are reflected back by Faraday mirror FM1 and Faraday mirror FM2 The other end of the coupler BS1 enters the first port of the circulator CIR1, and the second port of the circulator CIR1 enters the intermediate ring, and after passing through the coupler BS2, it is divided into 4 pulses, which are respectively reflected back to the coupler by the Faraday mirror FM3 and the Faraday mirror FM4 BS2; the two pulses of walking the long arm first and then the short arm and the short arm and then the long arm interfere at the coupler BS2, and the single photon interference curve is detected by the single photon detector SPD; thus obtaining the phase shift at the Alice end parameter
所述Bob端包括法拉第镜FM5—FM6、相位调制器PMB、耦合器BS3、延迟环DL3、光子探测器SPD1、SPD2和环形器CIR3，第二激光器发出的激光经过环形器CIR2进入耦合器BS2，分为两个脉冲分别走耦合器BS2的长臂和短臂，再由法拉第镜FM3和法拉第镜FM4反射回耦合器BS2一前一后进入环形器CIR1的第二端口，经过末端口进入长程光纤；由长程光纤进入Bob端环形器CIR3的第一端口，经过第二端口进入耦合器BS3分为4个脉冲，分别有法拉第镜FM5和法拉第镜FM6反射回耦合器BS3；同样，先走长臂后走短臂和先走短臂后走长臂的两个脉冲在耦合器BS3处干涉，由SPD1或SPD2得到单光子干涉曲线，获取Bob端的相位漂移参数。Described Bob end comprises Faraday mirror FM5-FM6, phase modulator PMB, coupler BS3, delay ring DL3, photon detector SPD1, SPD2 and circulator CIR3, the laser that the second laser sends enters coupler BS2 through circulator CIR2, It is divided into two pulses and goes to the long arm and short arm of the coupler BS2, and then reflected by the Faraday mirror FM3 and Faraday mirror FM4 back to the coupler BS2 one after the other and enters the second port of the circulator CIR1, and enters the long-distance optical fiber through the end port ; Enter the first port of the circulator CIR3 at Bob's end from the long-distance optical fiber, enter the coupler BS3 through the second port and divide into 4 pulses, which are reflected back to the coupler BS3 by Faraday mirror FM5 and Faraday mirror FM6 respectively; similarly, go to the long arm first The two pulses of walking the short arm later and walking the short arm first and then the long arm interfere at the coupler BS3, and the single-photon interference curve is obtained by SPD1 or SPD2, and the phase shift parameters at the Bob end are obtained.
在本实施例中，环形器为三端口开环环形器，即光路由第一端口输入则第二端口输出，第二端口输入则第三端口输出；所述末端口为第三端口。In this embodiment, the circulator is a three-port open-loop circulator, that is, the optical route is input to the first port, then the second port is output, and the second port is input, then the third port is output; the last port is the third port.
本发明在FM系统中的扫描与补偿的过程与MZ系统一致。The process of scanning and compensation in the FM system of the present invention is consistent with that of the MZ system.
本发明所采用的联合扫描主动相位补偿方案有以下优势：The combined scanning active phase compensation scheme adopted in the present invention has the following advantages:
1、Alice和Bob只需要分别进行一次扫描，即可以得到相位漂移参数，缩短扫描时间，降低扫描的复杂度，提高了系统的信息占空比。1. Alice and Bob only need to perform one scan respectively to obtain the phase drift parameters, shorten the scan time, reduce the complexity of the scan, and improve the information duty cycle of the system.
2、在单相位和四相位扫描法中，Bob均需要将相位扫描的结果通过经典信道告知Alice，这样便给Eve从中获取相位信息的可能，导致其有机会影响或改变相位补偿的结果。在此方案中Alice和Bob的扫描结果完全由各自分别得到，他们之间的经典信息传输不会涉及相位扫描的结果，Eve则无法从公共信道中获取相位扫描的相关信息，从而提高了系统的安全性。2. In both the single-phase and four-phase scanning methods, Bob needs to inform Alice of the phase scanning results through the classical channel, so that it is possible for Eve to obtain phase information from it, resulting in the opportunity to influence or change the phase compensation results. In this scheme, the scanning results of Alice and Bob are completely obtained separately, and the classical information transmission between them will not involve the results of the phase scanning, and Eve cannot obtain the relevant information of the phase scanning from the public channel, thus improving the system efficiency. safety.
3、Alice端的扫描完全在本地完成，窃听者不能获取任何关于Alice端相位扫描的信息或改变Alice发送的量子态。这样Alice端发出的4个量子态相互之间一定是两两正交，完全符合BB84协议的标准，已知的相位重映射攻击及其可能的变形便失去了其物理依据，所以便不能实施，因此，提高了系统的安全性。3. The scanning of Alice is completely completed locally, and the eavesdropper cannot obtain any information about the phase scanning of Alice or change the quantum state sent by Alice. In this way, the four quantum states sent by Alice must be orthogonal to each other, fully complying with the standard of the BB84 protocol. The known phase remapping attack and its possible deformation will lose their physical basis, so they cannot be implemented. Therefore, the security of the system is improved.
以上所述的本发明的实施方式，并不构成对本发明保护范围的限定。任何在本发明的精神原则之内所作出的修改、等同替换和改进等，均应包含在本发明的权利要求保护范围之内。The embodiments of the present invention described above are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.
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