预报单光子源诱骗态量子密钥产生率及数值计算

独立推导预报单光子源诱骗态量子密钥分发的密钥产生率计算公式,讨论密钥产生率和发送端探测效率的关系;进行弱相干光和预报单光子源诱骗态量子密钥分发的最优强度估计和密钥产生率数值计算.结果表明,预报单光子源诱骗态量子密钥分发的密钥产生率随着发送端探测效率的增加而增加,其安全通信距离与完美单光子源的通信距离一致;诱骗态量子密钥分发可提高安全通信距离和密钥产生率;预报单光子源由于减少了暗计数的影响,进一步提高了安全通信距离.     

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.     

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.     

Practical SARG04 quantum key distribution

We have presented a method to estimate parameters of the decoy state method based on one decoy state protocol for SARG04. This method has given lower bound of the fraction of single-photon counts (y ₁), the fraction of two-photon counts (y ₂), the upper bound QBER of single-photon pulses (e ₁), the upper bound QBER of two-photon pulses (e ₂), and the lower bound of key generation rate for both BB84 and SARG04. The numerical simulation has shown that the fiber based QKD and free space QKD systems using the proposed method for BB84 are able to achieve both a higher secret key rate and greater secure distance than that of SARG04. Also, it is shown that bidirectional ground to satellite and inter-satellite communications are possible with our protocol.     

Security of the Decoy State Two-Way Quantum Key Distribution with Finite Resources

The quantum key distribution(QKD) allows two parties to share a secret key by typically making use of a one-way quantum channel However,the two-way QKD has its own unique advantages,which means the two-way QKD has become a focus recently.To improve the practical performance of the two-way QKD,we present a security analysis of a two-way QKD protocol based on the decoy method with heralded single-photon sources(HSPSs).We make use of two approaches to calculate the yield and the quantum bit error rate of single-photon and two-photon pulses.Then we present the secret key generation rate based on the GLLP formula.The numerical simulation shows that the protocol with HSPSs has an advantage in the secure distance compared with weak coherent state sources.In addition,we present the final secret key generation rate of the LM05 protocol with finite resources by considering the statistical fluctuation of the yield and the error rate.     

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.     

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     

The Decoy-State Measurement-Device-Independent Quantum Key Distribution with Heralded Single-Photon Source

Based on heralded single-photon source (HSPS), a decoy-state measurement-device-independent quantum key distribution (MDI-QKD) protocol is proposed in this paper. The MDI-QKD protocol mainly uses orbital angular momentum (OAM) states and pulse position modulation (PPM) technology to realize the coding of the signal states in heralded single-photon source. The three-intensity decoy states are used to avoid the attacks against the light source. Moreover, the formula of key generation rate is given by computing the lower bound of the yield of single-photon pairs and the upper bound of the error rate of single-photon pairs. Numerical simulation shows that the new MDI-QKD protocol has high key generation rate and low error rate. Moreover, the secure communication distance can be up to 450 km.

     

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.     

基于两种光源的诱发态量子密钥分配性能分析

单光子的衰减特性及其易受干扰的缺点限制了纯单光子量子系统的传输码率及距离.弱相干光脉冲(WCP)光源和准单光子源(HSPS)则具有更高的实用价值.本文将这两种光源和诱发态方案相结合并采用Lütkenhaus和Gottesman-Lo- Lütkenhaus-Preskill (GLLP)两种数据后处理方法进行性能分析.仿真结果表明:HSPS在传输距离上要优于WCP,对应相同传输距离时系统量子误码率(QBER)要小些,但相对密钥生成率低. 关键词： 量子密钥分配 诱发态 WCP光源 HSPS光源     

Practical decoy state quantum key distribution with finite resource

In this paper, we consider the controllably secure quantum key distribution (QKD) with coherent source, i.e., the practical decoy state QKD with finite resource is studied within the scope of some controllable security parameters. Our simulation shows the controllably secure QKD is more resource-consuming compared with the practical decoy QKD with relatively statistical fluctuation. However, further numerically solutions show that both protocols agree well with each other in the asymptotic limit, where the resource is large enough but not infinite. Our work shows the dark counts will contribute apparently to the transmission distance when communication distance approaches to the asymptotic limit. It also shows that both the secure transmission distance and the rate of the secure final key can be increased apparently when the security estimation parameters are not fixed but numerically optimized.     

Finite-key analysis of practical time-bin high-dimensional quantum key distribution with afterpulse effect

High-dimensional quantum resources provide the ability to encode several bits of information on a single photon, which can particularly increase the secret key rate rate of quantum key distribution (QKD) systems. Recently, a practical four-dimensional QKD scheme based on time-bin quantum photonic state, only with two single-photon avalanche detectors as measurement setup, has been proven to have a superior performance than the qubit-based one. In this paper, we extend the results to our proposed eight-dimensional scheme. Then, we consider two main practical factors to improve its secret key bound. Concretely, we take the afterpulse effect into account and apply a finite-key analysis with the intensity fluctuations. Our secret bounds give consideration to both the intensity fluctuations and the afterpulse effect for the high-dimensional QKD systems. Numerical simulations show the bound of eight-dimensional QKD scheme is more robust to the intensity fluctuations but more sensitive to the afterpulse effect than the four-dimensional one.     

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     

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.     

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     

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.     

基于厄米-高斯光束的单光子捕获理论研究

从光波电磁场方程的TEM10和TEM01模厄米-高斯光束出发,推导了自由空间量子密钥分配的单光子捕获概率表达式.针对低轨卫星-地面站间激光链路,进行了单光子捕获分析.理论研究表明,对于低轨卫星-地面站间量子密钥分配,采用TEM10和TEM01模厄米-高斯型高度衰减激光脉冲作为单光子源是可行的.     

Expandable quantum key distribution networks based on secret bits comparison

A scheme of quantum network based on multiuser differential phase shift quantum key distribution system (DPS-QKD) is proposed. In this quantum network, arbitrary two users can achieve secret bits sharing by point-to-multipoint quantum key distribution and secret bits comparison. A protocol of secret bits sharing between arbitrary two users is presented. This network can implement secret bits distribution over 200 km with higher key generation rate by today's technologies. In theory, the capacity of user numbers in this network is unlimited. Hence, our proposed quantum network can serve for a metropolitan QKD network. A wide area QKD network can be constructed with this metropolitan QKD network.     

联合调制量子密钥分配系统

本文提出了一种对每一个单光子信号进行相位和偏振两种 编码调制的联合调制量子密钥分配(QKD)系统. 结合复合QKD系统的双速协议, 本文给出了在理想情形下可以通过一个信号光子生成两比特密钥的QKD协议, 明显提高了QKD协议的内禀光子利用率. 在稳定性方面, 本文发展了联合调制的Michelson型QKD系统, 从而在原理上解决了联合调制QKD系统的稳定性问题. 关键词： 量子密钥分配 双速协议 联合调制 量子密钥分配系统的稳定性