泡利和退极化噪声下纠缠动力学及量子隐形传输理论研究

发布时间：2018-05-12 22:37

本文选题：量子纠缠 + 纠缠突然死亡　；参考：《哈尔滨工业大学》2014年博士论文

【摘要】：量子纠缠是量子信息领域中的一种重要资源，但是它又是极其脆弱的。现实量子系统不可能孤立于周围环境单独存在，必须考虑量子噪声对量子系统纠缠的影响。量子噪声会导致量子纠缠衰减甚至突然死亡，影响量子信息处理过程，有必要对不同量子噪声环境下的系统纠缠演化进行研究。控制量子系统的纠缠演化，了解量子噪声对量子系统纠缠演化的影响将为量子信息处理过程中维持量子纠缠的最大存在提供有力理论支撑，是量子信息技术得以应用的重要环节。与此同时，由于量子噪声等因素而产生的纠缠混态在实际量子信息处理过程中呈主导作用，因此研究纠缠混态在量子噪声环境下的纠缠演化特性对量子信息技术的应用具有重大现实意义。本文针对量子信息中纠缠突然死亡现象，给出了一类可控二原子量子系统纠缠演化模型，重点研究了量子信息中常见的两类特殊二粒子纠缠混态在局域独立（或局域共同）Pauli和退极化量子噪声环境下的纠缠演化特性，特别是当量子信道受上述量子噪声环境影响时的单量子比特量子隐形传输理论。本论文的主要研究内容如下：研究了囚禁于腔场中的二原子纠缠动力学。讨论了分别以两类不可以通过局域操作和经典通信相互转化的三原子W态为原子初始态以及不同粒子数态为腔场初始态时二原子纠缠并发度和负值度的演化。分析了系统纠缠演化过程中出现纠缠突然死亡的原因。结果发现原子初始态和腔场粒子数态对原子纠缠突然死亡现象的出现有重要影响。研究了两类特殊二粒子纠缠态在局域独立（或局域共同）Pauli和退极化量子噪声环境下的纠缠动力学。一类为Bell态与|00（或|11）混合情况下的二粒子纠缠态，另一类为扩展的类Werner态。针对每一类量子系统，均利用量子主方程的方法给出了其密度矩阵在不同噪声环境下演化的解析表达式，并就每种量子噪声环境，依次给出了局域独立和局域共同环境下系统并发度随各参量的变化规律，同时对这两种情况下的并发度进行了比较分析，评估了混合比例和纯度对各自量子系统纠缠演化的影响，，分析了系统在纠缠演化过程中出现纠缠突然死亡和纠缠得以保持的原因。结果发现无论哪种量子系统，在某些局域共同Pauli量子噪声环境下，均存在一个特定区域使量子系统纠缠度始终保持与初始状态一致。研究了量子信道在不同Pauli和退极化量子噪声环境下的单量子比特量子隐形传输理论。结合量子隐形传输量子线路模型给出了当量子信道（分别以四个不同Bell态为量子信道）经历局域独立（或局域共同）Pauli和退极化量子噪声环境时量子隐形传输的保真度和平均保真度，针对每种噪声环境，比较分析了局域独立和局域共同环境下的平均保真度。发现当量子信道受到不同Pauli和退极化噪声环境影响时，四个Bell态中只有一个最适合作为量子信道。本论文的研究工作对加深纠缠突然死亡出现原因的理解以及实际量子信息传输过程中如何保持纠缠提供了一定的理论参考，为获得高平均保真度量子隐形传输提供了理论依据。
[Abstract]:Quantum entanglement is an important resource in the field of quantum information, but it is extremely fragile. The real quantum system can not isolate in the surrounding environment alone. We must consider the effect of quantum noise on the entanglement of quantum systems. Quantum noise can cause quantum entanglement attenuation or even sudden death, affecting the process of quantum information processing. It is necessary to study the entanglement evolution of systems under different quantum noise environments.
To control the entanglement evolution of quantum systems and to understand the influence of quantum noise on the entanglement evolution of quantum systems will provide a powerful theoretical support for the maximum existence of quantum entanglement in the process of quantum information processing. It is an important link in the application of quantum information technology. At the same time, the entanglement state produced by quantum noise and other factors is real. It is of great practical significance to study the entanglement and the evolution characteristics of entanglement and mixed state in quantum noise environment for the application of quantum information technology.
In this paper, the entanglement evolution model of a class of controllable two atom quantum systems is given in quantum information. The entanglement evolution characteristics of two special two particle entangled states in quantum information in the local independent (or local common) Pauli and depolarized quantum noise environment are studied emphatically, especially when the quantum signal is used as a quantum letter. The single qubit quantum teleportation theory is affected by the above quantum noise environment. The main contents of this paper are as follows:
The two atom entanglement dynamics in a cavity field are studied. The concurrency of the entanglement and the negative value of the two atom in the initial state of the three atom W state which can not be transformed by the local operation and the classical communication can not be transformed by the local operation and the classical communication are discussed respectively. The evolution process of the entanglement in the system is analyzed. The cause of entanglement sudden death is found. It is found that the initial state of atoms and the number of states in the cavity have important effects on the sudden death of entanglement.
The entanglement dynamics of two special two particle entangled states in local independent (or local common) Pauli and depolarized quantum noise environment are studied. A class of entangled states of two particles in the mixture of Bell States and |00 (or |11), and another class of extended Werner states. The analytic expression of its density matrix evolves under different noise environment, and each quantum noise environment is given in order to give the variation of the system concurrency with each parameter in local independent and local common environment. At the same time, the concurrency of the two cases is compared and analyzed, and the mixture ratio and purity are evaluated for each quantum system. The influence of entanglement evolution is analyzed. The cause of the entanglement sudden death and entanglement in the process of entanglement evolution is analyzed. It is found that no matter which quantum system, in some local common Pauli quantum noise environment, there is a particular region that keeps the entanglement of quantum system consistent with the initial state.
The quantum teleportation theory of quantum channel in different Pauli and depolarized quantum noise environment is studied. Combining quantum teleportation quantum circuit model, a quantum channel (four different Bell states as a quantum channel) is given to experience local independent (or local common) Pauli and depolarized quantum noise environment The fidelity and average fidelity of the subsurface transmission are analyzed for each noise environment, and the average fidelity in local independent and local common environment is compared and analyzed. It is found that only one of the best cooperative quantum channels in the four Bell states when the quantum channel is affected by different Pauli and depolarizing noise environment.
The research work in this paper provides a theoretical reference for deepening the understanding of the cause of the sudden death of entanglement and how to maintain entanglement in the actual quantum information transmission process, and provides a theoretical basis for obtaining high average fidelity quantum teleportation.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：O413;TN918

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