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量子态演化过程中的保真度问题
【作者】 陈雨；
【导师】 隆正文；
【作者基本信息】 贵州大学 ， 理论物理， 2008， 硕士
【摘要】 近年来量子信息光学引起人们的极大兴趣,保真度是量子光学和量子信息科学两个领域中一个重要的概念,它是表示信息在传输过程中保持原来状态的程度,并广泛应用于量子通信和量子计算理论研究中。本文运用纯量子理论,研究了一些典型有意义的量子光学模型保真度演化规律对光场与原子相互作用的保真度演化特性作了较深入的研究,并引入描述量子信息传输性能好坏的另一个物理量保真度振幅,保真度越高,保真度振幅越小,系统的保真性能越好。文中具体研究了单模光场与原子相互作用系统、双模光场与原子相互系统、多光子过程与原子相互作用系统的保真度的演化特性,在文中我运用了全量子理论,并且考虑了原子间的偶极相互作用。通过计算Tavis-Cummings模型下压缩真空态的保真度,阐明了在双模压缩真空态与环境(原子)通过双光子发生相互作用过程中量子信息的保真程度随时间的演化关系。通过计算机模拟出两原子处于各种初态下时原子、光场和系统的保真度随时间的演化图象,分析出三者在压缩指数r、偶极相互作用常数g_α和相位φ等改变时的变化情况,结果表明r和k值的改变对于提高保真度具有重要意义。当两原子处于基态时减小r和当两原子处于一Bell基时增大r都可以显著的提高体系的保真度。
【Abstract】 Quantum information is an advanced research topic in modern science and technology. The fresh subject devotes to exploit the fundamental principle of quantum mechanics and the wonderful characteristic of quantum state,such as quantum entanglement, squeezing,superposition etc,to perform the processing,study the fidelity of computation and transmission of information is unabsent.In this paper,cavity QED as an investigation subject,based on the research foundation of Jaynes—Cummings(JC)Model,the fidelity are studied via completely quantum theory. Firstly,we introduce the background and progress of quantum information.Secondly,we summarize the definition of entangled state fdelity.Thirdly,we discuss state evolution of Jaynes—Cummings models and introduce several Jaynes-Cummings models widely spread out.Lastly,the fidelities quantum states system in two-mode squeezing vacuum state Tavis-Cummings model has being considered.I have studied the system useing the full quantum theory.The dipole-dipole interaction of the two atoms have been considered.By considering the interaction between the two-mode squeezing vacuum state field and the environment(atoms),we investigate the quantum information fidelities of the atoms the field and the system in two-mode squeezing vacuum state Tavis-Cummings model.With the help of the computer’s simulation,we get the system the atoms and the field’s figures of proceeding evolution by time.finally.Analyze the changes of the above three when change the squeezing index r the dipole-dipole interaction constant g_a and the phaseφ.The result of our discussion indicates that r and k are important to the fidelity of the quantum information of the above three.When the two atoms are initially in the groud state,decrease r can increase the three fidelities.On the contrary,when the two atoms are initially in one of the Bell states,increase r can increase the three fidelites.