A Novel Quantum Voting Scheme Based on BB84-State

BB84-state is the non-orthogonal single-photon state which has the advantage of easy implementation compared with the quantum multi-photon entanglement states. In this paper, based on BB84-state, by introducing a trusted third-party voting center, a quantum voting scheme is proposed. In this scheme, by performing corresponding unitary operation on BB84-state, all voters send their voting information to the tallyman Charlie, then Charlie counts all votes under the supervision of voting management center Bob, which ensures that the protocol can resist inside attacks. Moreover, by utilizing the decoy particles, our scheme can efficiently prevent outside attacks. Compared with other related quantum voting protocols, our protocol has higher qubit efficiency and fewer interactive times.

     

多粒子纠缠态QTDM通信方案及QMU协议

分析了未知的三个三态粒子纠缠态的隐形传送过程,结合纠缠源的特性,提出了量子信道时分复用方案.同时还提出了一种可传送多粒子纠缠态的量子时分多路通信方案和量子多用户协议.研究结果表明,该方案与采用BB84协议的量子通信系统相比,不仅能够实现量子多用户安全保密通信,而且误码率低.     

BB84协议的非一般安全性分析与模拟

给出了窃听者采用各种窃听策略,使用最先进的仪器(段-郭概率量子克隆机)的条件下BB84协议的非一般安全性分析,推导出Eve使用段-郭概率量子克隆机时,Alice和Bob间的码差错率下降为20.7%,这说明BB84协议的安全性仍然有效.最后用BB84协议对量子密钥生成与分发进行了程序模拟.     

Security of quantum key distribution using d-level systems

We consider two quantum cryptographic schemes relying on encoding the key into qudits, i.e., quantum states in a d-dimensional Hilbert space. The first cryptosystem uses two mutually unbiased bases (thereby extending the BB84 scheme), while the second exploits all d+1 available such bases (extending the six-state protocol for qubits). We derive the information gained by a potential eavesdropper applying a cloning-based individual attack, along with an upper bound on the error rate that ensures unconditional security against coherent attacks.     

B92量子密钥分配协议的变形及其无条件安全性证明

分析了Shor和Preskill证明BB84量子密钥分配协议无条件安全性的方法,指出不能用ShorPreskill方法直接证明B92量子密钥分配协议的无条件安全性。同时借鉴ShorPreskill方法,引入一种将B92协议转化为BB84协议的变换,通过证明该变换过程不会泄漏密钥信息给窃听者,以此证明B92协议的无条件安全性.也解决了Lo等人提出的关于用ShorPreskill方法证明B92协议的困难 关键词： B92协议 CSS码 量子密钥分配 量子信息     

单个N维量子系统的量子秘密共享

提出了一种单个N维量子系统的量子秘密共享方案.在该方案中，利用对Bennett和Brassard协议(BB84协议)中使用的两基四态扩展到多基多态，分发者对要共享的秘密采用多基多态编码，将被编码的单个N维量子系统发送给他的两个代理人之一，该代理人利用一个N维克隆机对接收到的粒子做幺正操作，然后把粒子发送给另一代理人.在得知最后一个代理人接收到该粒子之后，分发者告知两个代理人他所用的制备基，然后两个代理人分别对自己的系统进行测量并在合作之后获知分发者所发送的粒子的量子态.该方案的安全性基于量子不可克隆定理. 关键词： 量子秘密共享 多基多态编码 N维克隆机 量子不可克隆定理     

Security of biased BB84 quantum key distribution with finite resource

In the original BB84 quantum key distribution protocol, the states are prepared and measured randomly, which lose the unmatched detection results. To improve the sifting efficiency, biased bases selection BB84 protocol is proposed. Meanwhile, a practical quantum key distribution protocol can only transmit a finite number of signals, resulting in keys of finite length. The previous techniques for finite-key analysis focus mainly on the statistical fluctuations of the error rates and yields of the qubits. However, the prior choice probabilities of the two bases also have fluctuations by taking into account the finite-size effect. In this paper, we discuss the security of biased decoy state BB84 protocol with finite resources by considering all of the statistical fluctuations. The results can be directly used in the experimental realizations.     

Quantum key distribution using three basis states

This note presents a method of public key distribution using quantum communication of n photons that simultaneously provides a high probability that the bits have not been tampered. It is a variant of the quantum method of Bennett and Brassard (BB84) where the transmission states have been decreased from 4 to 3 and the detector states have been increased from 2 to 3. Under certain assumptions regarding method of attack, it provides superior performance (in terms of the number of usable key bits) for n<18m, where m is the number of key bits used to verify the integrity of the process in the BB84-protocol.     

Integration of quantum cryptography into fiber-optic telecommunication systems

The prototype of a new quantum cryptosystem is described. Such a cryptosystem is naturally called time-shift quantum cryptography. It realizes all basic quantum-cryptography protocols [BB84, B92, BB84(4+2)] in a common fiber-optic system. This scheme does not involve Mach-Zehnder interferometers, which enables one to naturally realize the multiplex mode of secure key distribution and to naturally integrate this quantum-cryptography scheme into traditional fiber-optic telecommunication systems. The proposed time coding method in quantum cryptography makes it possible to significantly simplify experimental schemes and to exclude the finest fiber-optic part, the interferometer. In essence, the fundamental difference of the time coding method from the phase coding method is that the part using phase relations in superposition between “parts” of a quantum state is eliminated from the phase-coding method, and only the part using the time division principle is retained. The time division principle is common for both methods and is minimally necessary, in contrast to the phasecoding method, which can be excluded altogether. The proposed scheme is briefly compared with the two most developed phase-coding schemes (without self-compensation and with passive self-compensation).     

Quantum key distribution in a single-photon regime with nonorthogonal basis states

A quantum key distribution protocol with nonorthogonal basis states is a generalization of the known BB84 key distribution protocol. The critical error and length of a secure key have been determined for the protocol with nonorthogonal basis states for an arbitrary angle between information states. An explicit optimal attack on the distributed key has been constructed; this attack maximizes eavesdropper information at a given error on the receiver side.     

QKD扩展BB84协议的Breidbart基窃听问题

给出了六态扩展BB84协议的Breidbart基窃听方案,分析并计算了各种截取重发策略下的AliceEve平均交互信息量和施行QKD标准纠错手续后的有效平均交互信息量,结果显示Breidbart基窃听Breidbart基重发策略(BB策略)最为有效.考虑到Alice和Bob可以在公开讨论阶段利用废弃数据检验是否存在BB窃听以降低秘密性增强算法的强度,减少量子密钥的损失,提出了修改BB84协议的建议.给出了可能较QKD标准纠错手续更为安全的量子密钥二次生成纠错方法 关键词： 量子密码 BB84协议 Breidbart基窃听     

Quantum scheme for an optimal attack on quantum key distribution protocol BB84

A quantum scheme for an optimal attack on protocol BB84, the most studied protocol of quantum cryptography, is constructed. The physical implementation of this scheme on the basis of linear fiber-optical elements and the two-particle “controlled NOT” quantum transformation is proposed.     

Participant Attack and Improvement to Multiparty Quantum Secret Sharing Based on GHZ States

A multiparty quantum secret sharing protocol based on GHZ states was proposed by Hwang et al. (Phys. Scr. 83:045004, 2011). Its major advantage is high efficiency, but soon another paper (Liu and Pan in Phys. Scr. 84:045015, 2011) shown that the protocol is insecure for one dishonest agent and give a improvement of protocol. Here, we analyze the security of both protocols, and point out that both protocols would lead to all the secret information leakage under a special attack, which is different from the attack strategy proposed by the paper (Liu and Pan in Phys. Scr. 84:045015, 2011). Furthermore, we discuss the deep reason of this insecurity, and propose a novel and efficient secure protocol, which keep the important weakness of original protocol free, i.e., correlation-extractability. The security of our scheme is equivalent to that of BB84 protocol.     

运行双协议相位调制的量子密钥分发系统

基于差分编码方式提出一种改进方案.在Alice端用光纤马赫-曾德干涉仪产生双脉冲差分信号；在Bob端，用双法拉第反射式麦克尔逊干涉仪代替光纤马赫-曾德干涉仪，这种干涉仪能自动补偿环境引起的偏振抖动和光纤双折射引起的相位漂移，从而提高系统稳定性.双协议(即双脉冲差分协议联合BB84协议)的使用，增强了系统的安全性.该系统具有高效、安全、简洁、稳定等优点，在实验上实现了长期稳定的密钥分发和量子保密通信，误码率<5%，传输距离达80km.     

On the information-splitting essence of two types of quantum key distribution protocols

With the help of a simple quantum key distribution (QKD) scheme, we discuss the relation between BB84-type protocols and two-step-type ones. It is shown that they have the same essence, that is, information splitting. The choice of an orthogonal carrier or a nonorthogonal carrier, which looks like the main difference between these two types of protocols, is not an important, even not a very explicit matter. This result is instructive for related scheme designing and security analyzing.     

Differential phase shift quantum key distribution

A novel quantum cryptography scheme is proposed, in which a single photon is prepared in a linear superposition state of three basis kets. A photon split to three pulses is sent from Alice to Bob, where the phase difference between sequential two pulses carries bit information. Bob measures the phase difference by passive differential phase detection. This scheme is suitable for fiber transmission systems and offers a key creation efficiency higher than conventional fiber-based BB84.     

QKD系统在Breidbart基窃听下BB84协议的信息量研究

给出了BB84协议的Breidbart基窃听的方案,分析并计算了各种截取/重发策略下施行QKD标准纠错手续后Alice/Eve的有效平均交互信息量和对Bob引起的错误率.结果显示了Breidbart基窃听/Breidbart基重发策略(B/B策略)最为有效,并提出了各种窃听方案下Alice和 Bob采取相应的反攻击策略.     

A fundamental threat to quantum cryptography: gravitational attacks

An attack on the “Bennett-Brassard 84” (BB84) quantum key-exchange protocol in which Eve exploits the action of gravitation to infer information about the quantum-mechanical state of the qubit exchanged between Alice and Bob, is described. It is demonstrated that the known laws of physics do not allow to describe the attack. Without making assumptions that are not based on broad consensus, the laws of quantum gravity, unknown up to now, would be needed even for an approximate treatment. Therefore, it is currently not possible to predict with any confidence if information gained in this attack will allow to break BB84. Contrary to previous belief, a proof of the perfect security of BB84 cannot be based on the assumption that the known laws of physics are strictly correct, yet. A speculative parameterization that characterizes the time-evolution operator of quantum gravity for the gravitational attack is presented. It allows to evaluate the results of gravitational attacks on BB84 quantitatively. It is proposed to perform state-of-the-art gravitational attacks, both for a complete security assurance of BB84 and as an unconventional search for experimental effects of quantum gravity.     

A full quantum network scheme

In this paper, we study the thermodynamic features of a two-dimensional charged black hole. Weinhold curvature and Ruppeiner curvature are explored as information geometry, respectively. Moreover, based on the Legendre invariant proposed by Hernando Quevedo, the geometro-thermodynamics behavior of this black hole is investigated.     

Quantum secure dialogue by using single photons

By combining the idea of quantum secure direct communication (QSDC) and BB84 quantum key distribution (QKD), we propose a secure quantum dialogue protocol via single photons. Comparing with the previous bidirectional quantum secure communication scheme [24] in which the EPR pairs are used, our protocol is not only feasible in practice but also can overcome the drawback “information leakage” or “classical correlation”. Our scheme possesses the characters of security and high efficiency.