Improved statistical fluctuation analysis for two decoy-states phase-matching quantum key distribution

Phase-matching quantum key distribution is a promising scheme for remote quantum key distribution,breaking through the traditional linear key-rate bound.In practical applications,finite data size can cause significant system performance to deteriorate when data size is below 1010.In this work,an improved statistical fluctuation analysis method is applied for the first time to two decoy-states phase-matching quantum key distribution,offering a new insight and potential solutions for improving the key generation rate and the maximum transmission distance while maintaining security.Moreover,we also compare the influence of the proposed improved statistical fluctuation analysis method on system performance with those of the Gaussian approximation and Chernoff-Hoeffding boundary methods on system performance.The simulation results show that the proposed scheme significantly improves the key generation rate and maximum transmission distance in comparison with the Chernoff-Hoeffding approach,and approach the results obtained when the Gaussian approximation is employed.At the same time,the proposed scheme retains the same security level as the Chernoff-Hoeffding method,and is even more secure than the Gaussian approximation.

Lower bound for the security of differential phase shift quantum key distribution against a one-pulse-attack

Quantum key distribution is the art of sharing secret keys between two distant parties, and has attracted a lot of attention due to its unconditional security. Compared with other quantum key distribution protocols, the differential phase shift quantum key distribution protocol has higher efficiency and simpler apparatus. Unfortunately, the uncondi- tional security of differential phase shift quantum key distribution has not been proved. Utilizing the sharp continuity of the von Neuman entropy and some basic inequalities, we estimate the upper bound for the eavesdropper Eve＇s infor- mation. We then prove the lower bound for the security of the differential phase shift quantum key distribution protocol against a one-pulse attack with Devatak-Winter＇s secret key rate formula.

Impact of Fiber Dispersion on Performance of Entanglement-Based Dispersive Optics Quantum Key Distribution

Dispersive optics quantum key distribution(DO-QKD)based on energy-time entangled photon pairs is an important QKD scheme.In DO-QKD,the arrival time of photons is used in key generation and security analysis,which would be greatly affected by fiber dispersion.In this work,we establish a theoretical model of the entanglement-based DO-QKD system,considering the protocol,physical processes(such as fiber transmission and single-photon detection),and the analysis of security tests.Based on this theoretical model,we investigate the influence of chromatic dispersion introduced by transmission fibers on the performance of DO-QKD.By analyzing the benefits and costs of dispersion compensation,the system performance under G.652 and G.655 optical fibers are shown,respectively.The results show that dispersion compensation is unnecessary for DO-QKD systems in campus networks and even metro networks.Whereas,it is still required in DO-QKD systems with longer fiber transmission distances.

New protocols for non-orthogonal quantum key distribution

Combining the passive decoy-state idea with the active decoy-state idea, a non-orthogonal （SARG04） decoy-state protocol with one vacuum and two weak decoy states is introduced based on a heralded pair coherent state photon source for quantum key distribution. Two special cases of this protocol are deduced, i.e., a one-vacuum-and-one-weak-decoy-state protocol and a one-weak-decoy-state protocol. In these protocols, the sender prepares decoy states actively, which avoids the crude estimation of parameters in the SARG04 passive decoy-state method. With the passive decoy-state idea, the detection events on Bob＇s side that are non-triggered on Alice＇s side are not discarded, but used to estimate the fractions of single-photon and two-photon pulses, which offsets the limitation of the detector＇s low efficiency and overcomes the shortcoming that the performance of the active decoy-state protocol critically depends on the efficiency of detector. The simulation results show that the combination of the active and passive decoy-state ideas increases the key generation rate. With a one-vacuum-and-two-weak-decoy-state protocol, one can achieve a key generation rate that is close to the theoretical limit of an infinite decoy-state protocol. The performance of the other two protocols is a little less than with the former, but the implementation is easier. Under the same condition of implementation, higher key rates can be obtained with our protocols than with existing methods.

Practical Security of the Continuous-Variable Quantum Key Distribution with Locally-Generated Local Oscillators

Continuous-variable quantum key distribution (CVQKD) with the local local oscillator (LLO) is confronted with new security problems due to the reference pulses transmitted together with quantum signals over the insecure quantum channel. In this paper, we propose a method of phase attack on reference pulses of the LLO-CVQKD with time-multiplexing. Under this phase attack, the phase drifts of reference pulses are manipulated by eavesdroppers, and then the phase compensation error is increased. Consequently, the secret key rate is reduced due to the imperfect phase compensation for quantum signals. Based on the noise model of imperfect phase compensation, the practical security of LLO-CVQKD under phase attack is analyzed. The simulation results show that the practical security is reduced due to the phase attack, yet it is still tight when system parameters are estimated by training signals.

Active phase compensation of quantum key distribution system

Quantum key distribution (QKD) system must be robust enough in practical communication. Besides birefringence of fiber, system performance is notably affected by phase drift. The Faraday-Michelson QKD system can auto-compensate the birefringence of fiber, but phase shift is still a serious problem in its practical operation. In this paper, the major reason of phase drift and its effect on Faraday- Michel- son QKD system is analyzed and an effective active phase compensation scheme is proposed. By this means, we demonstrate a quantum key distribution system which can stably run over 37-km fiber in practical working condition with the long-time averaged quantum bit error rate of 1.59% and the stan- dard derivation of 0.46%. This result shows that the active phase compensation scheme is suitable to be used in practical QKD systems based on double asymmetric interferometers without additional de- vices and thermal controller.

Real-time compensation of phase drift for phase-encoded quantum key distribution systems

Phase drift is an inherent problem in phase-encoded quantum key distribution(QKD) systems.The current active phase trackingand compensation solutions cannot satisfy the requirements of a system with nonlinearity in phase modulation.This paper presents a four-phase scanning method,which is based on the quantitative analysis of the quantum bit error rate(QBER) from phasedrift and the performance requirements of phase compensation.By obtaining the four interference fringes and adjusting the codingmatrix of the system,this method automatically calculates the accurate driving voltages for the phase modulator.The implementation and experimental tests show that the proposed method can compensate phase drift caused by environmental changes and thesystem's nonlinearity,and is applicable to large-scale QKD networks.

Silicon-based decoder for polarization-encoding quantum key distribution

Silicon-based polarization-encoding quantum key distribution(QKD)has been extensively studied due to its advantageous characteris-tics of its low cost and robustness.However,given the difficulty of fabricating polarized independent components on the chip,previ-ous studies have only adopted off-chip devices to demodulate the quantum states or perform polarization compensation.In the cur-rent work,a fully chip-based decoder for polarization-encoding QKD was proposed.The chip realized a polarization state analyzer and compensated for the BB84 protocol without the requirement of additional hardware,which was based on a polarization-to-path conversion method utilizing a polarization splitter-rotator.The chip was fabricated adopting a standard silicon photonics foundry,which was of a compact design and suitable for mass production.In the experimental stability test,an average quantum bit error rate of 0.59%was achieved through continuous operation for 10 h with-out any polarization feedback.Furthermore,the chip enabled the automatic compensation of the fiber polarization drift when utiliz-ing the developed feedback algorithm,which was emulated by a ran-dom fiber polarization scrambler.Moreover,a finite-key secret rate of 240 bps over a fiber spool of 100 km was achieved in the case of the QKD demonstration.This study marks an important step to-ward the integrated,practical,and large-scale deployment of QKD systems.

Simultaneous measurement-device-independent continuous variable quantum key distribution with realistic detector compensation

We propose a novel scheme for measurement-device-independent(MDI)continuous-variable quantum key distribution(CVQKD)by simultaneously conducting classical communication and QKD,which is called“simultaneous MDI-CVQKD”protocol.In such protocol,each sender(Alice,Bob)can superimpose random numbers for QKD on classical information by taking advantage of the same weak coherent pulse and an untrusted third party(Charlie)decodes it by using the same coherent detectors,which could be appealing in practice due to that multiple purposes can be realized by employing only single communication system.What is more,the proposed protocol is MDI,which is immune to all possible side-channel attacks on practical detectors.Security results illustrate that the simultaneous MDI-CVQKD protocol can secure against arbitrary collective attacks.In addition,we employ phase-sensitive optical amplifiers to compensate the imperfection existing in practical detectors.With this technology,even common practical detectors can be used for detection through choosing a suitable optical amplifier gain.Furthermore,we also take the finite-size effect into consideration and show that the whole raw keys can be taken advantage of to generate the final secret key instead of sacrificing part of them for parameter estimation.Therefore,an enhanced performance of the simultaneous MDI-CVQKD protocol can be obtained in finite-size regime.

配电网储能型DSTATCOM电能质量综合补偿策略

为解决新能源发电、单相负荷等规模化接入给配电网所带来的多重电能质量问题,提出采用储能型配电网静止同步补偿器实现对配电网电压波动、电压越限、三相不平衡的综合补偿。首先,建立由正序控制环与负序控制环组成的统一控制器,其中,正序控制环可对光伏电源出力进行平滑控制,同时在出现大量有功反送时对公共点电压进行限幅安全控制;负序控制环引入虚拟复导纳对公共点电压三相不平衡进行补偿,同时通过推导出最优导纳角对储能型DSTATCOM输出的负序补偿电流进行优化。另外,采用自抗扰技术对正、负序电流环的动态性能进行提升。最后,在MATLAB/Simulink中搭建系统仿真模型。仿真结果表明,基于所提电能质量综合补偿策略的储能型DSTATCOM能够有效治理配电网电能质量问题。

基于对地参数测量的配电网故障选相与有源消弧方法研究

由于在单相接地故障前后配电网对地参数发生变化,传统有源消弧法以配电网正常运行状态下的对地参数为依据得到的补偿电流参考值与实际值存在偏差。针对故障点残流无法实现完全补偿导致熄弧困难的问题,通过中性点接入的有源消弧装置向配电网注入特征频率电流信号,消除系统频率对配电网对地等效参数测量精度的影响,构建特征信号流通回路,实现配电网在接地故障后的对地等效参数测量。然后根据实时测量的对地参数和零序电压,动态计算补偿电流,控制有源消弧装置向中性点注入电流实现故障消弧,并提出通过注入零序电流的方法得到故障相电压的幅值及相位,实现故障相辨识。最后,在PSCAD/EMTDC仿真软件中验证了所提方法能够实时反映配电网对地参数变化,实现了故障支路电流全补偿,达到配电网接地故障快速熄弧的目的。

主动配电网三相解耦潮流算法

随着主动配电网技术迅速发展,分布式电源(DG)规模化接入,传统配电网潮流算法难以满足主动配电网潮流计算的要求。针对这一情况,提出一种能高效处理多类型DG规模化接入和环网的主动配电网三相解耦潮流算法。该算法基于序分量法和不对称线路三序解耦-补偿模型,结合主动配电网的特点和道路-回路分析法,详细推导PQ、PQ(V)、PV和PI节点类型DG规模化并网和无功补偿设备接入的潮流模型,采用三相解耦及并行计算,极大地提高算法计算速度和效率,节省内存空间,实现高效的主动配电网三相解耦潮流计算。通过IEEE 37、69和123母线测试系统验证了该算法的有效性、良好的收敛性以及较强的处理多类型DG规模化接入和环网的能力,且算法性能远优于传统算法。

单相光伏大量接入的三相不平衡配电网无功优化

随着光伏发电等大量非全相运行的分布式电源(DG)接入,配电网固有的三相不平衡特征更加突出,传统无功优化方法因忽略了三相不平衡导致效果较差。文中提出一种三相不平衡主动配电网的无功优化模型,以系统负序电压最小和网络损耗最小为目标,考虑有载调压变压器、分组投切电容器、静止无功补偿装置等离散和连续控制变量,形成一个带有二次约束的混合整数二次规划问题。利用分支定界法处理该混合整数规划问题,将原问题松弛为多个不含离散变量的子问题,分别求得各子问题中设备的控制量,进而求得原问题的最优解。采用扩展的IEEE 33节点三相测试系统仿真计算,验证了所述模型和方法的有效性。

用于BB84相位编码量子密钥分发系统的不间断式主动相位补偿方案

提出一种新的不间断的主动相位补偿方案,在进行量子密钥分发的同时统计不匹配基量子比特在干涉仪不同输出端口上的随机计数分布,给出了由不匹配基量子比特统计数值计算相位漂移参数的计算公式,并由统计数值计算得到相位漂移参数。结果表明:该方案允许系统并行处理量子密钥分发与相位补偿,也充分利用了在原BB84协议中会被丢弃的不匹配基量子比特信息。

电力生产业务的量子广域网加密技术研究

针对电力生产业务的通信特点以及安全需求,提出了基于量子通信卫星的电力天地一体量子保密通信方案,并且针对地面链路中电力架空环境下长距离量子通信的问题,提出采用线路偏振无关的FaradayMichelson型量子密钥分配系统的方案,并通过试验证明了方案在电力应用环境中的可行性,最后对电力架空环境下的相位补偿技术做出了分析。

基于补偿系数的有源配电网自适应电流差动保护

分布式电源的大规模接入使传统辐射型配电网的拓扑结构和故障特性发生了实质性的改变,给有源配电网的继电保护带来了严峻的挑战。为此研究了不同类型分布式电源的故障电流特征,深入分析了常规电流差动保护在幅相平面上的动作特性,归纳出几种常见的故障情形,并以此为基础提出了一种新型电流差动保护。该方案采用改造后的sigmoid函数构建补偿系数,可以根据两侧电流的幅值比决定补偿的程度,从而自适应的调整测量电流的幅值和相位。与常规差动保护相比,该方案能够适应有源配电网不同场景下的保护需求且具有更高的灵敏度。PSCAD/EMTDC平台的仿真实验验证了该保护方案的有效性和可靠性。

谐振接地系统单相接地故障有源电流注入全补偿消弧研究

针对中/低压谐振接地配电网的故障消弧难题,提出一种消弧线圈结合单相级联H桥变流器的新型的主从式有源消弧方案。通过实时采集并跟踪故障残流,设计了H桥逆变器和PI控制系统,通过向中性点注入与故障残流等幅反相的可控电流实现接地故障电流全补偿,进而达到故障有效灭弧目的。仿真结果显示,所提方案能够较好满足接地故障电流全补偿的要求,可以快速、有效地补偿配网单相接地故障电流的有功、无功以及谐波分量,实现可靠熄弧,提高配电网的供电可靠性。

CVQKD中块平均参考相位估计算法的性能优化

块平均参考相位估计算法能够有效降低连续变量量子密钥分发的相位补偿噪声方差。为了使块平均参考相位估计算法的性能达到最优,根据相位漂移变化的数学模型,从理论上分析了该算法的均方误差特性,并得到最优的块长度取值。仿真结果表明:最优相位估计可使系统的相位补偿噪声方差降低72%,从而最大化提升安全密钥的成码距离。

低压配电网三相不平衡治理措施

在低压三相四线制的城市居民和农网供配电系统中,由于单相负荷分布的不均衡和投入使用的随机性,使得三相电流不平衡客观存在并且无规律性可循,对电能质量带来很大影响,成为低压配电网运行维护中一个突出的问题;阐述三相不平衡对配电变压器和线路损耗的影响,介绍有源不平衡补偿装置的原理和对三相不平衡的治理效果。

基于有源逆变技术的综合消弧方法

我国配电网中性点大多为不接地或经消弧线圈接地,针对消弧线圈无法完全补偿故障电流,消弧效果不佳的问题,提出了一种消弧线圈与有源逆变装置相结合的综合消弧方法。在配电网中发生单相接地故障时,首先投入消弧线圈进行无源消弧,出现电流残流而无法自熄的情形,然后投入有源逆变装置分相注入补偿电流进行有源消弧,以完成对故障输入电流的全补偿。仿真结果表明,该方法将消弧线圈和有源逆变装置灵活结合,高效补偿了配电网单相接地故障电流,不仅实现了可靠熄弧,而且适应于不同接地电阻的故障情况。