量子相变对三量子比特耦合XY自旋链的退纠缠影响马海福C-arXiv.PDFVIP

      量子相变对三量子比特耦合 XY 自旋链的退纠缠影响 　　 马海福      C ○2010 摘要 近年来，随着量子信息这一新兴领域的蓬勃发展，量子纠缠逐渐成为人们的热门话 题。量子纠缠是量子力学不同于经典物理的，存在于多子系量子系统中的一种最奇妙、 最不可思议的现象。而在实际的量子信息处理过程中，系统不可避免地与环境发生相互 作用，从而造成系统的量子相干性破坏或量子态的塌缩，这种现象在量子力学中被称为 量子退相干。 本文研究了外场的量子相变对中心粒子退纠缠的影响。本文讨论三量子比特与 XY 自旋链耦合的模型，并研究了其退纠缠的动力学过程。首先对体系的哈密顿量进行求解， 找到相干性因子的精确表达式。然后通过对相干性因子及系统参数的讨论，证实量子临 界现象对中心自旋粒子退纠缠有极大的影响。并通过分析得到了一个比例规则。 关键词：量子比特；XY自旋链；相干性因子；退纠缠；量子相变 I Abstract Recently, along with the development of quantum information, quantum entanglemant became a hot topic of people. Quantum entanglemant is one of the most amazing phenomenon in quantum mechanics that is totally different from classical physics. However, system would interact with environment in the practical quantum information process. The entanglement would be broken. In this paper, we study the disentanglement evolution of three spin qubits in an XY spin-chain environment. The dynamical process of the disentanglement is investigated. We found the exact expression of the coherence factor. We discuss the coherence factor and the parameters, and then we illustrate that the disentanglement of central spins is best enhanced by the quantum critical behavior of the environmental spin chain. Furthermore, a scaling rule is obtained. Key Words: qub