BB84 Protocol and Its Security Analysis

The information of encryption depends on the security of the secret key, but not the security of the algorithm. This paper introduces the quantum cryptography and BB84 protocol, analyzes its security, and gives an example to explain the process of quantum transmission. Theory analysis shows that this kind of key distribution＇s protocolis absolutely safe.     

Security of Practical BB84 Quantum Key Distribution

Abstract. We propose a proof of the security of a practical BB84 quantum key distribution protocol against enemies with unlimited computational power. The considered protocol uses interactive key distillation, and the proof holds for implementations using imperfect optical devices.     

有噪声的BB84量子密码协议的改进

把量子力学应用到密码学中产生了一个新的学科———量子密码学。量子密码提供的密钥交换方式,能够自动检查是否有人在窃听,这是公钥体制所不具备的。该文对有噪声的BB84协议作了一些改进,以增强安全性、提高效率。这种改进方案对其它带有噪声的量子密码协议同样适用。     

一种基于BB84协议的量子密钥分配改进方案

针对BB84协议对存在窃听的有噪信道中进行量子密钥分配效率不高的问题, 提出一种改进方案。新方案在发送方与接收方都加入类似签名的过程, 能够很好地判断窃听的存在, 并且窃听者只能获取少量的密钥信息, 在保障传输过程安全的同时, 提高了量子密钥分配的效率。     

基于BB84的量子密钥分配协议的研究

以BB84协议为基础，对其中部分内容进行了改进，并将身份认证加入到协议中，使量子密钥分配协议的安全性更高。     

基于QCircuit的BB84窃听仿真与分析

该文研究量子线路模型仿真量子密钥分配协议.基于QCircuit软件运用量子线路模型设计不同攻击模型下的BB84量子密钥分配协议仿真模型,并引入rsec和I(α,E)两个指标,设计指标分析线路模型,仿真分析了不同噪声信道模型下BB84密钥分配协议在P/P、B/P和B/B三种不同截取/重发策略下的有效性及安全性.仿真结果表...     

基于BB84与椭圆曲线的数字签名方案

利用BB84协议在量子密钥分配过程中的安全性与椭圆曲线加密体制在经典加密算法中的优越性相结合,提出了一种基于BB84协议和椭圆曲线的数字签名方案,该方案利用量子密钥作为会话密钥从而使得签名过程高效、简易,此会话密钥在密钥分配过程中具备的可证明安全性与椭圆曲线加密体制的安全性相结合对该数字签名方案提供了双重安全保护,同时可以达到互相认证的效果。     

BB84协议安全判据的实用标准研究

BB84协议是针对单光子量子通信提出的经典协议。在BB84协议安全判据理论值的基础上,结合窃听者所付出成本与其所得信息价值的关系,对自由空间和光纤2种量子信道,分别提出了各自的BB84协议安全判据的实用标准。     

BB84量子密钥分配协议在专网中的应用

依据专用网络的特点,对BB84量子密钥分配协议做了改进,提出一种适用于专用网络的BB84-PN协议。该协议通过身份认证和量子物理特性,提高了安全性。同时,在通信过程中通过协商传输量子密钥规则,有效地提高了传输效率。     

基于纠缠的BB84协议仿真研究

将传统的量子密钥分发协议与纠缠光子对的纠缠特性相结合,提出了一种改进的BB84协议--基于纠缠的BB84协议.为了考察该协议的可行性,利用量子计算语言分别针对协议的正确性和安全性进行了仿真验证,并进一步考察衰落信道对协议工作的影响.仿真结果显示:理想情况下,协议安全工作时密钥生成效率为14/30,接近理论值50%;在存在第三方窃听时,其密钥生成效率仅为5/30,远远小于50%,由此通信双方可以判断出第三方窃听存在.由于信道衰落的影响,实际密钥生成效率远远低于理论值.得出结论:基于纠缠的BB84协议也是绝对安全可靠、切实可行的量子密钥分发协议;为提高密钥生成效率,应尽量减小信道衰落.最后,对协议的应用进行了展望.     

量子LDPC码在BB84协议中的应用研究

针对BB84量子密钥分配协议中量子信道存在噪声,设计一种带有量子纠错码的改进的BB84协议模型,在模型中用量子低密度奇偶校验码（量子LDPC）作为纠错码对发送量子态进行编码。通过数值仿真,从密钥传输效率的角度分析量子纠错编码对BB84协议的影响。结果表明量子LDPC码能克服噪声,提高了密钥传输效率,验证了在含噪量子信道中改进的BB84协议模型的有效性。     

基于BB84协议的空间量子通信系统

我们分析了基于BB84协议的空间量子通信系统.该系统使用大气量子信道,以因特网为经典信道.讨论了光子与大气的相互作用,利用量子计算语言对大气信道中的量子密钥分配进行了仿真.将用于量子计算仿真的语言引入量子通信的研究中,讨论了单光子脉冲系统与纠缠光子对系统的特点,分析了全球量子通信系统的可行性.     

Optimal lot-sizing problem with imperfect maintenance and imperfect production

In this paper, we develop an integrated model for the joint determination of both economic production quantity and level of preventive maintenance (PM) for an imperfect production process. This process has a general deterioration distribution with increasing hazard rate. The effect of PM activities on the deterioration pattern of the process is modelled using the imperfect maintenance concept. In this concept, it is assumed that after performing PM, the ageing of the system is reduced in proportion to the PM level. After a period of time in production, the process may shift to out-of-control states, either type I or type II. A minimal repair will remove the type I out-of-control state. If a type II out-of-control state occurs, the production process has to stop, and then restoration work is carried out. Examples of Weibull shock models are given to show that the use of PM reduces costs.     

Score operators of a qubit with applications

The score operators of a quantum system are the symmetric logarithmic derivatives of the system’s parametrically defined quantum state. Score operators are central to the calculation of the quantum Fisher information (QFI) associated with the state of the system, and the QFI determines the maximum precision with which the state parameters can be estimated. We give a simple, explicit expression for score operators of a qubit and apply this expression in a series of settings. We treat in detail the task of identifying a quantum Pauli channel from the state of its qubit output, and we show that a “balanced” probe state is highly robust for this purpose. The QFI for this task is a matrix, and we study its determinant, for which we establish a Cramér-Rao inequality.     

The capacity of transmitting atomic qubit with light

The quantum information transfer between a single photon and a two-level atom is considered as a part of a quantum channel. The channel is a degradable channel even when there are decays of the atomic excited state and the single photon state, as far as the total excitation of the combined initial state does not exceed one. The single letter formula for quantum capacity is obtained.     

Quantum dynamics of superconducting nano-circuits: phase qubit, charge qubit and rhombi chains

We have studied different quantum dynamics of superconducting nano-circuits with Josephson junctions. A dc SQUID, when it is strongly decoupled from the environment, demonstrates two-level and multilevel dynamics. We have realized a two qubits coupled circuit based on a dc SQUID in parallel with an asymmetric Cooper pair transistor (ACPT). The ACPT behaves as a charge qubit. Its asymmetry produces a strong tunable coupling with the dc SQUID which is used to realize entangled states between the two qubits and new read-out of the charge qubit based on adiabatic quantum transfer. We have measured the current–phase relations of different rhombi chains in the presence or absence of quantum fluctuations which confirm theoretical predictions.     

Chance measure for hybrid events with fuzziness and randomness

In many cases, fuzziness and randomness simultaneously appear in a system. Hybrid variable is a tool to describe this phenomena. Fuzzy random variable and random fuzzy variable are instances of hybrid variable. In order to measure hybrid event, a concept of chance measure is proposed in this paper. Furthermore, several useful properties about this measure are proved such as self-duality, subadditivity and semicontinuity. Some concepts are also presented such as chance distribution, expected value, variance, moments, critical values, entropy, distance and sequence convergences.     

Algorithmic randomness and splitting of supermartingales

Randomness in the sense of Martin-Löf can be defined in terms of lower semicomputable supermartingales. We show that such a supermartingale cannot be replaced by a pair of supermartingales that bet only on even bits (the first one) and on odd bits (the second one) knowing all the preceding bits.     

Railway freight transportation planning with mixed uncertainty of randomness and fuzziness

The railway freight transportation planning problem under the mixed uncertain environment of fuzziness and randomness is investigated in this paper, in which the optimal paths, the amount of commodities passing through each path and the frequency of services need to be determined. Based on the chance measure and critical values of the random fuzzy variable, three chance-constrained programming models are constructed for the problem with respect to different criteria. Some equivalents of objectives and constraints are also discussed in order to investigate mathematical properties of the models. To solve the models, a potential path searching algorithm, simulation algorithms and a genetic algorithm are integrated as a hybrid algorithm to solve an optimal solution. Finally, some numerical examples are performed to show the applications of the models and the algorithm.