一种新的预报单光子源诱骗态量子密钥分发方案

提出一种新的预报单光子源诱骗态量子密钥分发方案.在发端采用参量下变换产生纠缠光子对,其中之一用来进行预报探测,根据探测结果将另一路光脉冲分成两个集合,其中预报探测有响应的脉冲集合用作信号态,无响应的脉冲集合作为诱骗态.由于探测效率的问题,这两个集合都是有光子的,通过这两个集合的通过率和错误率估计出单光子的通过率和错误率.此方法不需要改变光强,简单可行.仿真结果表明：该方法可以达到完美单光子源的安全通信距离;与预报单光子源的量子密钥分发相比,密钥产生率有了很大的提高;和三强度预报单光子源诱骗态量子密钥分发的 关键词： 量子保密通信 量子密钥分发 诱骗态 预报单光子源     

Decoy State Quantum Key Distribution with Odd Coherent State

We propose a decoy state quantum key distribution scheme with odd coherent state which follows sub-Poissonian distributed photon count and has low probability of the multi-photon event and vacuum event in each pulse. The numerical calculations show that our scheme can improve efficiently the key generation rate and secure communication distance. Fhrthermore, only one decoy state is necessary to approach to the perfect asymptotic limit with infinite decoy states in our scheme, but at least two decoy states are needed in other scheme.     

Practical non-orthogonal decoy state quantum key distribution with heralded single photon source

Recently the performance of the quantum key distribution （QKD） is substantially improved by the decoy state method and the non-orthogonal encoding protocol, separately. In this paper, a practical non-orthogonal decoy state protocol with a heralded single photon source （HSPS） for QKD is presented. The protocol is based on 4 states with different intensities. i.e. one signal state and three decoy states. The signal state is for generating keys; the decoy states are for detecting the eavesdropping and estimating the fraction of single-photon and two-photon pulses. We have discussed three cases of this protocol, i.e. the general case, the optimal case and the special case. Moreover, the final key rate over transmission distance is simulated. For the low dark count of the HSPS and the utilization of the two-photon pulses, our protocol has a higher key rate and a longer transmission distance than any other decoy state protocol.     

Decoy State Quantum Key Distribution via Beam-Wandering Modeled Atmosphere Channel

We investigate the decoy state quantum key distribution via the atmosphere channels.We consider the efficient decoy state method with one-signal state and two-decoy states.Our results show that the decoy state method works even in the channels with fluctuating transmittance.Nevertheless,the key generation rate will be dramatically decreased by atmosphere turbulence,which sheds more light on the characterization of atmosphere turbulence in realistic free-space based quantum key distributions.     

Security of decoy states QKD with finite resources against collective attacks

The number of transmitted signals in practical quantum key distribution (QKD) protocol is always finite. We discuss the security of decoy states QKD protocol with finite resources by considering the statistical fluctuation for the yield and error rate of the quantum state in different sources of pulses (signal sources and decoy sources). The number of exchanged quantum signals vs positive key generation rate is given with experiment results.     

基于伪态协议的量子密钥分配系统研究

采用包含两个伪态和一个信号态的双伪态协议分析了量子密钥分配系统的性能,比较了双伪态（真空态—弱伪态）和单伪态协议条件下密钥生成率与通信距离的关系,分析了信号态的强度、量子比特误码率、单光子的增益和单光子的误码率对系统密钥生成率的影响,得出密钥生成率的最优化条件,为实现实用安全的量子密钥分配系统奠定理论基础. 关键词： 伪态协议 量子密钥生成率 量子比特误码率     

基于相干叠加态的非正交编码诱骗态量子密钥分发

非正交编码协议和诱骗态方法可以有效地抵御光子数分离攻击. 由于相干叠加态中单光子成分高达90%, 常作为单光子量子比特的替代出现, 用于量子信息过程处理和计算. 本文结合非正交编码协议和诱骗态方法提出一种新的量子密钥分发方案, 光源采用相干叠加态, 推导了单光子的密钥生成速率、计数率下限和误码率的上限, 利用Matlab 模拟了无限多诱骗态情况下和有限多诱骗态情况下密钥生成速率和传输距离的关系, 得出该方案可以提升密钥生成速率并且提高安全传输距离, 验证了该方案可以进一步提高量子密钥分发系统的性能.     

New estimates of single photon parameters for satellite-based QKD

A new decoy state method has been presented to tighten the lower bound of the key generation rate for BB84 using one decoy state and one signal state. It can give us different lower and upper bounds of the fraction of single-photon counts and single-photon QBER, respectively, for one decoy state protocol. We have also analyzed the feasibility of performing quantum key distribution (QKD), with different exiting protocols, in earth-satellite and intersatellite links. Our simulation shows the choice of intensity of signal state and the effect of choosing the number of decoy states on key generation rate. The final key rate over transmission distance has been simulated, which shows that security proofs give a zero key generation rate at long distances (larger than 16,000 km). It has been shown that the practical QKD can be established with low earth orbit and medium earth orbit satellites.     

基于弱相干态光源的非正交编码被动诱骗态量子密钥分配

基于改造的弱相干态光源,提出了一种非正交编码被动诱骗态量子密钥分配方案.该方案不主动制备诱骗态,而是根据发送端探测器是否响应,将接收端的探测结果分为响应集合和未响应集合,以此分别作为信号态和诱骗态,并利用这两个集合来估计参量和生成密钥.数值仿真表明,非正交编码被动诱骗态方案的密钥生成效率和安全传输距离都优于现有的被动诱骗态方案,且性能非常接近主动无穷诱骗态方案的理论极限值;未响应集合对密钥生成的参与使方案性能免受发送端探测效率的影响,弥补了实际探测器探测效率低下的缺陷;由于不需要主动制备诱骗态,该方案实现非常简单,适用于高速量子密钥分配的场合. 关键词： 量子光学 量子密钥分配 被动诱骗态 密钥生成效率     

Decoy state quantum key distribution with finite resources

We apply the finite key analysis to the decoy state quantum key distribution scheme and obtain a practical key rate. By simulating an practical experiment setups and the Vacuum + Weak decoy state method, we show that both the key rate and maximal secure distance are reduced when the finite key analysis is considered.     

Round-Robin Differential Phase Shift with Heralded Single-Photon Source

Round-robin differential phase shift(RRDPS) is a novel quantum key distribution protocol which can bound information leakage without monitoring signal disturbance. In this work, to decrease the effect of the vacuum component in a weak coherent pulses source, we employ a practical decoy-state scheme with heralded singlephoton source for the RRDPS protocol and analyze the performance of this method. In this scheme, only two decoy states are needed and the yields of single-photon state and multi-photon states, as well as the bit error rates of each photon states, can be estimated. The final key rate of this scheme is bounded and simulated over transmission distance. The results show that the two-decoy-state method with heralded single-photon source performs better than the two-decoy-state method with weak coherent pulses.     

Decoy states and two way quantum key distribution schemes

We study the possible application of the decoy state method on a basic two way quantum key distribution (QKD) scheme to extend its distance. Noting the obvious advantage of such a QKD scheme in allowing for single as well as double photon contributions, we derive relevant lower bounds on the corresponding gains in a practical decoy state implementation using two intensities for decoy states. We work with two different approaches in this vein and compare these with an ideal infinite decoy state case as well as the simulation of the original.     

基于条件参量下转换光子对的非正交编码诱惑态量子密钥分发

诱惑态方法和非正交编码协议可以有效的抵制光子数分束攻击,所以近来得到了广泛的关注.这里结合了这两种方法提出了一种新方案,光源采用呈泊松分布的参量下转换光子对,发送方随机的改变抽运光的强度获得不同强度的信号光,信号态用来产生密钥,诱惑态用来监测窃听,并估算单光子和两光子的计数率和量子误码率,模拟了密钥产生率与传输距离的关系曲线,分析了该方案可以进一步提高安全量子密钥分发的性能.     

Experimental quantum key distribution with decoy states

To increase dramatically the distance and the secure key generation rate of quantum key distribution (QKD), the idea of quantum decoys--signals of different intensities--has recently been proposed. Here, we present the first experimental implementation of decoy state QKD. By making simple modifications to a commercial quantum key distribution system, we show that a secure key generation rate of 165 bit/s, which is 1/4 of the theoretical limit, can be obtained over 15 km of a telecommunication fiber. We also show that with the same experimental parameters, not even a single bit of secure key can be extracted with a non-decoy-state protocol. Compared to building single photon sources, decoy state QKD is a much simpler method for increasing the distance and key generation rate of unconditionally secure QKD.     

利用诱骗信号方案进行实用的量子密钥分发

真实量子密钥分发系统中不完善的单光子源和信道损耗的存在,使得现有基于弱相干态的量子密码实验在分束攻击下并不安全,诱骗信号方案能实现基于现有技术绝对安全的量子密钥分发,并能有效提高密钥分发率和安全传输距离,因此成为近年来量子通信研究的热点问题.结合现实量子密码系统的一般模型,介绍目前几种典型的诱骗信号方案以及实验进展,综述了诱骗信号方案的发展情况和最新成果,并对未来的研究方向进行了展望.     

Cryptanalysis of Multiparty Quantum Secret Sharing of Quantum State Using Entangled States

Security of a quantum secret sharing of quantum state protocol proposed by Guo et al. [Chin. Phys. Lett. 25 （2008） 16] is reexamined. It is shown that an eavesdropper can obtain some of the transmitted secret information by monitoring the classical channel or the entire secret by intercepting the quantum states, and moreover, the eavesdropper can even maliciously replace the secret message with an arbitrary message without being detected. Finally, the deep reasons why an eavesdropper can attack this protocol are discussed and the modified protocol is presented to amend the security loopholes.     

Beating the photon-number-splitting attack in practical quantum cryptography

We propose an efficient method to verify the upper bound of the fraction of counts caused by multiphoton pulses in practical quantum key distribution using weak coherent light, given whatever type of Eve's action. The protocol simply uses two coherent states for the signal pulses and vacuum for the decoy pulse. Our verified upper bound is sufficiently tight for quantum key distribution with a very lossy channel, in both the asymptotic and nonasymptotic case. So far our protocol is the only decoy-state protocol that works efficiently for currently existing setups.     

Experimental Decoy State Quantum Key Distribution Over 120km Fibre

Decoy state quantum key distribution （QKD）, being capable of beating PNS attack and being unconditionally secure has become attractive recently. However, in many QKD systems, disturbances of transmission channel make the quantum bit error rate （QBER） increase, which limits both security distance and key bit rate of real-world decoy state QKD systems. We demonstrate the two-intensity decoy QKD with a one-way Faraday- Michelson phase modulation system, which is free of channel disturbance and keeps an interference fringe visibility （99%） long period, over a 120 km single mode optical fibre in telecom （1550nm） wavelength. This is the longest distance fibre decoy state QKD system based on the two-intensity protocol.     

诱惑态在“双探测器”准单光子光源量子密钥分发系统中的应用

现在诱惑态已被证明是一种可以大大提高量子密钥分发安全性能的现实可行的方法.由于考虑到现实应用中激光器在调制过程中的消光比不能做到100%,以及激光器固有的自发辐射因而使得制备真空态并不是一件容易的事情. 因此本文将对理想情况下准单光子光源量子密钥分发系统应用中的诱惑态结论作了补充和扩展,提出了两个弱光强态的诱惑态方案和一个弱光强诱惑态方案.最后,将“双探测器”的理论应用在准单光子源(HSPS)光源系统中,使系统的安全传输距离可达到2215km,比使用普通探测器的系统增加了约50km. 关键词： 量子密钥分发 诱惑态 HSPS光源 双探测器     

Quantum key distribution with high loss: toward global secure communication

We propose a decoy-pulse method to overcome the photon-number-splitting attack for Bennett-Brassard 1984 quantum key distribution protocol in the presence of high loss: A legitimate user intentionally and randomly replaces signal pulses by multiphoton pulses (decoy pulses). Then they check the loss of the decoy pulses. If the loss of the decoy pulses is abnormally less than that of signal pulses, the whole protocol is aborted. Otherwise, to continue the protocol, they estimate the loss of signal multiphoton pulses based on that of decoy pulses. This estimation can be done with an assumption that the two losses have similar values. We justify that assumption.