量子态制备与浓缩研究

发布时间：2019-01-14 15:26

【摘要】：随着科学的不断发展,结合了量子力学和信息科学的量子信息学迅速崛起,并取得了突飞猛进的发展。量子信息学包含两个部分,其一为量子通信,其二为量子计算机。量子通信,由于其理论上已被证明是绝对安全的,因而受到诸多研究机构,甚至国家层面的关注。量子计算机,其独有的多量子态并行计算能力远远快于经典计算机,对现行的经典加密体系提出了严峻的挑战。量子纠缠态作为量子信息中必不可少的资源,在量子通信和量子计算机中扮演着至关重要的角色。因而,人们首先面对的问题就是制备纠缠态。其次,在量子通信的过程中,环境噪声不可避免地会对纠缠态产生影响,可能导致最大纠缠态退化为部分纠缠态,这会严重影响量子通信的质量,甚至会对量子通信的安全造成威胁。对于制备纠缠态的问题,本文针对于目前热门的纠缠相干态和concatenated Greenberger-Horne-Zeilinger(C-GHZ)型纠缠态,综合分析其优缺点后,结合量子通信的实际需求,提出了C-GHZ型相干态,并给出了此纠缠态的制备方案。该方案是基于线性光学的,可以构造任意粒子数的C-GHZ型相干态,且能够在现今的实验条件下实现。对于纠缠态的退相干问题,本文针对于目前热门的复合纠缠态(Hybrid entangled state),分别提出了Bell-type,W-type,Cluster-type复合纠缠态的三个纠缠浓缩方案。这三个方案是完全基于线性光学元器件实现的,可以将退相干的部分纠缠态恢复至最大纠缠态,在现有技术条件下更容易实现,对长距离量子通信具有很大的现实意义。此外,本文还针对现有量子通信技术进行相关研究。对于Bennett提出的纠缠成分的概念做了一些工作:两步测量超纠缠态的concurrence。该方案利用了非线性Kerr介质去构建量子非破坏性测量技术,并不需要复杂的CNOT门,在未来的实验技术下是可行的。
[Abstract]:With the development of science, quantum informatics, which combines quantum mechanics and information science, has developed rapidly. Quantum informatics consists of two parts, one is quantum communication, the other is quantum computer. Quantum communication, which has been proved to be absolutely safe in theory, has attracted much attention from many research institutions, even at the national level. Quantum computer, whose unique parallel computing power of multi-quantum states is much faster than the classical computer, poses a severe challenge to the current classical encryption system. As an indispensable resource in quantum information, quantum entangled states play a crucial role in quantum communication and quantum computers. Therefore, the first problem people face is the preparation of entangled states. Secondly, in the process of quantum communication, environmental noise will inevitably affect the entangled state, which may lead to the degradation of the maximal entangled state to partially entangled state, which will seriously affect the quality of quantum communication. It could even pose a threat to the security of quantum communications. For the problem of preparing entangled states, this paper aims at the popular entangled coherent states and concatenated Greenberger-Horne-Zeilinger (C-GHZ) entangled states. After analyzing their advantages and disadvantages, a C-GHZ coherent state is proposed according to the actual requirements of quantum communication. The preparation scheme of the entangled state is also given. The scheme is based on linear optics and can construct C-GHZ coherent states with arbitrary number of particles and can be implemented under the present experimental conditions. For the decoherence of entangled states, this paper proposes three entanglement concentration schemes for Bell-type,W-type,Cluster-type complex entangled states, aiming at the popular complex entangled states (Hybrid entangled state),. These three schemes are completely based on linear optical components and can restore the decoherence partially entangled state to the maximum entangled state, which is easier to implement under the existing technical conditions, and has great practical significance for long-distance quantum communication. In addition, this paper also studies the existing quantum communication technology. Some work has been done on the concept of entangled components proposed by Bennett: Two-step measurement of concurrence. of hyperentangled states This scheme uses nonlinear Kerr medium to construct quantum nondestructive measurement technology. It does not need complex CNOT gates and is feasible in the future experimental technology.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN918;O413

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