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量子信息讲座 第四讲 量子密码通信 总被引:6,自引:0,他引:6
根据海森伯不确定性原理,任何窃听者无法窃听量子密码通信中的信息而不被发现.文章讲述了量子密钥生成与分发的基本原理,并介绍了当前实验研究的进展. 相似文献
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多数在理想条件下设计的量子密码协议没有考虑实际通信中噪音的影响,可能造成机密信息不能被准确传输,或可能存在窃听隐藏在噪音中的风险,因此分析噪音条件下量子密码协议的安全性具有重要的意义.为了分析量子BB84协议在联合旋转噪音信道上的安全性,本文采用粒子偏转模型,对量子信道中的联合噪音进行建模,定量地区分量子信道中噪音和窃听干扰;并且采用冯·诺依曼熵理论建立窃听者能窃取的信息量与量子比特误码率、噪音水平三者之间的函数关系,定量地分析噪音条件下量子信道的安全性;最后根据联合噪音模型及窃听者能窃取的信息量与量子比特误码率、噪音水平三者之间的关系,定量地分析了量子BB84协议在联合噪音条件下的安全性并计算噪音临界点.通过分析可知,在已有噪音水平条件下,窃听者最多能够从通信双方窃取25%的密钥,但是Eve的窃听行为会被检测出来,这样Alice和Bob会放弃当前协商的密钥,重新进行密钥协商,直至确认没有Eve的窃听为止.这个结果说明量子BB84协议在联合旋转噪音信道下的通信是安全的. 相似文献
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为了改善BB84协议防窃听的能力,在BB84协议的基础上提出用M(M=3,4,5…)对量子态实现量子密钥分配。为了检测其安全性,用截获-重发的方式对量子密钥分配过程进行窃听,窃听者分别采用两种检测光子状态的方法:在M组基中随机选取一种基和用Breidbart基测量,并在这两种窃听方法下分别通过计算机仿真探究M值与安全性能的关系。仿真结果表明:用多对量子态实现量子密钥分配时,发现窃听者的能力与BB84协议相同,而窃听者可以获取的正确信息要比窃听BB84协议获取的正确信息少。从而提高了量子密钥分配的安全性。 相似文献
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可控量子秘密共享协议窃听检测虚警概率分析 总被引:2,自引:2,他引:0
对孙莹等提出的利用Greenberger-Horne-Zeilinger态实现的可控量子秘密共享协议Alice-Bob信道和Alice-Charlie信道窃听检测的虚警概率进行分析,指出该协议窃听检测虚警概率不为0的原因在于窃听检测测量基选择的随机性.然后,提出一种改进的利用Greenberger-HorneZeilinger态实现的可控量子秘密共享协议,以确定性的方式选择窃听检测的测量基.理论分析表明,改进的利用Greenberger-Horne-Zeilinger态实现的可控量子秘密共享协议不仅能够以原协议2倍的概率发现任何一个内部不可信方,从而具有更高的安全性,而且窃听检测虚警概率达到0. 相似文献
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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. 相似文献
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《Physics letters. A》2020,384(16):126333
We investigate the diagonal entropy(DE) of the ground state for quantum many-body systems, including the XY model and the Ising model with next nearest neighbor interactions. We focus on the DE of a subsystem of L continuous spins. We show that the DE in many-body systems, regardless of integrability, can be represented as a volume term plus a logarithmic correction and a constant offset. Quantum phase transition points can be explicitly identified by the three coefficients thereof. Besides, by combining entanglement entropy and the relative entropy of quantum coherence, as two celebrated representatives of quantumness, we simply obtain the DE, which naturally has the potential to reveal the information of quantumness. More importantly, the DE is concerning only the diagonal form of the ground state reduced density matrix, making it feasible to measure in real experiments, and therefore it has immediate applications in demonstrating quantum supremacy on state-of-the-art quantum simulators. 相似文献
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Based on the statistical concept of the median, we propose a quantum uncertainty relation between semi-interquartile ranges of the position and momentum distributions of arbitrary quantum states. The relation is universal, unlike that based on the mean and standard deviation, as the latter may become non-existent or ineffective in certain cases. We show that the median-based one is not saturated for Gaussian distributions in position. Instead, the Cauchy-Lorentz distributions in position turn out to be the one with the minimal uncertainty, among the states inspected, implying that the minimum-uncertainty state is not unique but depends on the measure of spread used. Even the ordering of the states with respect to the distance from the minimum uncertainty state is altered by a change in the measure. We invoke the completeness of Hermite polynomials in the space of all quantum states to probe the median-based relation. The results have potential applications in a variety of studies including those on the quantum-to-classical boundary and on quantum cryptography. 相似文献
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Inspired by Ying’s work on automata theory based on quantum logic and classical automata theory, we introduce the concepts
of reversal, accessible, coaccessible and complete part of finite state automata based on quantum logic. Some properties of
them are discussed. More importantly we investigate the recognizability and accessibility properties of these types on the
framework of quantum logic by employing the approach of semantic analysis.
Foundation: supported by the National Natural Science Foundation of China (No. 10671030). 相似文献
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An efficient scheme is proposed to implement phase-covariant quantum cloning by using a superconducting transmon qubit coupled to a microwave cavity resonator in the strong dispersive limit of circuit quantum electrodynamics (QED). By solving the master equation numerically, we plot the Wigner function and Poisson distribution of the cavity mode after each operation in the cloning transformation sequence according to two logic circuits proposed. The visualizations of the quasi-probability distribution in phase-space for the cavity mode and the occupation probability distribution in the Fock basis enable us to penetrate the evolution process of cavity mode during the phase-covariant cloning (PCC) transformation. With the help of numerical simulation method, we find out that the present cloning machine is not the isotropic model because its output fidelity depends on the polar angle and the azimuthal angle of the initial input state on the Bloch sphere. The fidelity for the actual output clone of the present scheme is slightly smaller than one in the theoretical case. The simulation results are consistent with the theoretical ones. This further corroborates our scheme based on circuit QED can implement efficiently PCC transformation. 相似文献
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《Physics letters. A》2020,384(3):126078
The information loss problem in black hole evaporation is one of fundamental issues. Its resolution requires more profound understanding of information storage mechanism in quantum systems. In this Letter, we argue that when multiple unknown parameters are stored in large entangled qudits, strong chaos generated by fast scrambling in high temperature limit yields an ordered information storage structure with decoupled quantum information capsules (QICs). A rotational isometry emerges in the quantum Fisher information metric. The isometry is expected to be observed in future experiments on cold atoms in a pure entangled state. We provide a QIC speculation of black hole evaporation. 相似文献
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We present an efficient scheme for sharing an arbitrary two-qubit quantum state with n agents. In this scheme, the sender Alice first prepares an n + 2-particle GHZ state and introduces a Controlled-Not (CNOT) gate operation. Then, she utilizes the n + 2-particle entangled state as the quantum resource. After setting up the quantum channel, she performs one Bell-state measurement and another single-particle measurement, rather than two Bell-state measurements. In addition, except that the designated recover of the quantum secret just keeps two particles, almost all agents only hold one particle in their hands respectively, and thus they only need to perform a single-particle measurement on the respective particle with the basis X. Compared with other schemes based on entanglement swapping, our scheme needs less qubits as the quantum resources and exchanges less classical information, and thus obtains higher communication efficiency. 相似文献
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《Physics letters. A》2020,384(3):126082
In this paper, we derive a set of projectors on a large Hilbert space which can universally work for approximating quantum assemblages with binary inputs and outputs. The dimension of the Hilbert space depends on the accuracy of the approximation. 相似文献