开放系统中量子关联动力学研究

发布时间：2017-12-26 16:42

本文关键词：开放系统中量子关联动力学研究　出处：《安徽大学》2017年博士论文　论文类型：学位论文

【摘要】：量子关联是量子信息处理和量子通信任务的重要资源。然而,任意的开放量子系统都不可避免地与周围的噪声环境发生耦合作用而导致系统的量子关联迅速衰减甚至猝死,即量子退相干现象。因此,研究开放系统中量子退相干及关联动力学行为、探索噪声环境的特征及噪声带来的影响对推动量子信息的应用具有深远的意义。本文针对开放系统中量子关联的复活性、鲁棒性及信息流动进行了相关的研究;基于量子弱测量和翻转测量,提出了开放系统中量子失谐的增强方案和局域噪声环境中的纠缠纯化方案,并取得了以下研究成果:(1)研究了双边量子系统中的单个量子位与局域非马尔科夫(non-Markovian)环境相耦合的系统关联动力学行为及其纠缠分配的情况。结果表明:量子系统与环境的耦合可以引起纠缠阻尼衰减和复活,而系统的纠缠最终趋于一个定值。此外,通过分析复合系统中量子关联的分配和信息的流动,揭示了纠缠复活行为内在的non-Markovian机制。为了定量地描述系统中信息的流动情况,我们研究了真实的三体关联v(ρABE)、最大的双边量子互信息Imax(ρij)和局域单体信息Iloc(ρi)随时间变化的导数,并且给出了这三者之间明确的动态关系,这将给non-Markovian机制提供一个新的见解。(2)探讨了局域噪声信道中Bures distance失谐的复活现象和对抗环境的鲁棒性,并和共生纠缠进行了比较。结果表明:两粒子Bell对角态与局域噪声信道发生相互作用时,噪声强度增加到一定程度将会摧毁系统的量子关联。特别是,去极化信道中的Bures distance失谐在消失后会复活,而纠缠直接衰减到死亡。另一方面,杂化信道中下降的初始条件能使Bures distance失谐在有限时间内衰减得更平稳,但会加速纠缠的死亡。在这个意义上,Bures distance失谐在对抗噪声环境方面比纠缠更具有鲁棒性。此外,当特定初始态遭受不同的杂化信道时,环境的转换对纠缠的演化没有任何影响,却导致Bures distance失谐出现一些奇异的现象,即当比特翻转错误和比特相位翻转错误以相同的概率发生时Bures distance失谐的演化轨迹是一致的。最后,为了更好地了解这些现象,我们给出了 Bell对角态的几何解释。(3)研究了两比特分离量子态与局域噪声环境相互作用时量子失谐的生成情况,并基于量子弱测量和翻转测量提出了一系列可行的方案来提高失谐的强度。数值模拟表明,我们的增强方案可以有效地提高量子失谐的大小,这主要是由于量子操作改变了量子态中基态和激发态的比重,从而影响了量子态的相干性。此外,我们可以获得所有方案对应的量子失谐的解析表达式,并探索了成功概率和测量强度之间的权衡关系。(4)基于量子弱测量,我们提出了一系列纯化局域噪声环境中两比特纠缠的理论方案。结果表明:只要测量强度和态参数满足一定条件时,任意初始态都可以直接纯化为最大纠缠态。此外,所有方案的成功概率不仅取决于测量强度,而且与初始态存在密切的联系。
[Abstract]:Quantum correlation is an important resource for quantum information processing and quantum communication tasks. However, any open quantum system is inevitably coupled with the surrounding noise environment, resulting in the rapid decline of quantum correlation and even sudden death, namely quantum decoherence. Therefore, it is of great significance to study the quantum decoherence and associated dynamics in open system, explore the characteristics of noise environment and the impact of noise, and promote the application of quantum information. This thesis studies the resurrection of robustness, and the flow of information in the open system of quantum correlation; quantum weak measurement and flip measurement based on the proposed open system scheme and local noise environment enhance entanglement in quantum detuning purification scheme, and obtained the following results: (1) on a single qubit and quantum systems in non local bilateral Markoff (non-Markovian) correlation dynamics and entanglement distribution of the coupled environment. The results show that the coupling of the quantum system and the environment can cause the decay and resurrection of the entanglement damping, and the entanglement of the system eventually tends to a fixed value. In addition, by analyzing the distribution of quantum correlation and the flow of information in the composite system, the intrinsic non-Markovian mechanism of the entanglement resurrection is revealed. In order to quantitatively describe the flow of information in the system, we study the three correlation V true (P ABE), the largest bilateral quantum mutual information Imax (ij) and the local monomer Iloc (I) derivative changes with time, and gives a clear dynamic relationship between the three, this it will provide a new insight to the mechanism of non-Markovian. (2) the resurrection and the robustness of the Bures distance detuning in the local noise channel are discussed and compared with the symbiotic entanglement. The results show that when the two particle Bell diagonal state interacts with the local noise channel, the increase of the noise intensity to a certain extent will destroy the quantum correlation of the system. In particular, the Bures distance detuning in the depolarized channel will be resurrected after the disappearance, and the entanglement is directly attenuated to death. On the other hand, the descent of the initial condition in the hybrid channel can make the Bures distance detuning more stable in the limited time, but it will accelerate the death of the entanglement. In this sense, the Bures distance detuning is more robust than the entanglement in the noise environment. In addition, when a specific initial state from different hybrid channel, the conversion of the entanglement evolution environment has no effect, Bures distance has led to some singular detuning phenomenon, namely when the bit flip errors and bit phase flip error evolution to the same probability to occur when Bures distance detuning the trajectory is consistent. Finally, in order to get a better understanding of these phenomena, we give a geometric interpretation of the Bell diagonal state. (3) we studied the generation of quantum detuning in the interaction of two bit separated quantum states with local noise environment, and proposed a series of feasible schemes based on quantum weak measurement and overturn measurement to improve the detuning strength. Numerical simulation shows that our enhancement scheme can effectively improve the size of quantum detuning, which is mainly due to the change of the proportion of ground state and excited state in quantum state by quantum manipulation, thus affecting the coherence of quantum states. In addition, we can obtain the analytical expressions of the quantum detuning corresponding to all the schemes, and explore the tradeoff between the probability of success and the measurement intensity. (4) based on the quantum weak measurement, we propose a series of theoretical schemes for purifying two bits of entanglement in the local noise environment. The results show that any initial state can be directly purified to the maximum entangled state as long as the measured intensity and state parameters meet certain conditions. In addition, the probability of success of all schemes not only depends on the intensity of the measurement, but also is closely related to the initial state.
【学位授予单位】：安徽大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O413

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