与振幅相干态光场相互作用的二能级原子熵的演化

与相干态光场相互作用的

2能级原子熵的纠缠与退纠缠演化

关键词：相干态光场； 2能级原子； J-C模型； 约化密度矩阵； 原子约化熵

The Evolution of Atom Entropy in the Interaction between the Coherent Field and a Two Level Atom

Abstract: Considerable interesting has been attracted to the application widely of quantum entropy theory in quantum optics and quantum information field .Quantum entropy is the foundation and powerful tool in understanding and studying such problems as quantum computation ,quantum communication ,quantum teleportation ,quantum measurement and quantum entanglement. The coherent states field is a quantum state light field which is the closest classical electromagnetic field. It is the most important theory tool for studying laser.Two energy level atom is the ideal model of the actual atom, it only has two non-degeneration energy levels, E and E . It is the important binary physical system for realizing the quantum logical gate .Also it has the important application in the quantum computation. The J-C model is a ideal model which solves a series of questions between the two energy level atoms (or member) and the single model quantization light field. This article has studied the mutual function of coherent field and two energy level atom using quantum entropy . The influence of atomic entropy is discussed from the property of the reduced atomic entropy evolution when the initial states of the light field and atom are changed. The analysis indicated that two energy level atomic entropy relies on the initial states of light field and atom intensely. When the average photon in the light field is counted small, Atomic entropy is reach the maximum in some initial parameter; we can obtain the most great entangle states of the atom and the light field. When the average photon is counted very big, entropy tends to zero in the whole of evolution. It indicated that the atom and the field draws back completely entanglement under the strong field states.

Key words: coherent field ; two level atom ; J–C model ; reduced density matrix ; atom entropy

前言：

量子纠缠是量子力学最显著和最奇妙的特性之1。量子态的非经典性和非局域性使得人们对基本的量子现象有很好的理解。1方面，在量子信息过程中，例如，量子密码，量子计算和量子远距传态中，量子纠缠是基本要素，纠缠态是重要资源。因此，量化纠缠和在好的实验条件下制备纠缠态，是量子信息处理中非常重要的问题。本文将以相干态光场作为2能级原子的环境，利用量子约化熵研究2能级原子与相干场之间的纠缠与退纠缠性质，分别讨论原子、光场的初态对原子与场之间纠缠与退纠缠的影响。考察2能级原子约化熵的演化性质来讨论与相干光场相互作用的2能级原子系统的纠缠与退纠缠现象，从而判断该系统是否是1个理想的纠缠资源。这些结论也可能在量子态传输，量子通讯，稠密编码，密钥分配，量子计算加速，量子纠错等纠缠的应用方面起1定的作用。

１ 基本理论

1.1 熵理论