原子分子光子系统的耗散相互作用和退相干

原子分子系统与量子化的电磁场或光子模式耦合的系统是非相对论量子力学理论研究和实验研究的主要对象和模型. 现实系统必然与外界环境耦合，且即便原子隔绝较好、光学腔壁品质因子足够高，原子系统也不等价于少数几个能级构成的简单模型：它仍然有不为零的几率跃迁到不可控的能级空间、与原子相互作用的自由空间真空场的量子效应也必须考虑. 本文将结合开放量子系统理论的基本要素与原子光子的基本模型，对原子分子系统在电磁场中发生的耗散以及量子退相干过程做简单综述，并重点介绍描述量子系统退相干过程的主流理论工具——主方程.

Relaxation and decoherence process of the atom-photon system

Atomic and molecular systems coupled to the quantized electro-magnetic field or photons constitute the most part of the interested systems or models in the field of non-relativistic quantum mechanics. Even for the well-isolated atomic system as well as the high Q-factor cavity, the quantum mechanical system cannot be considered as a simple model consisted of several levels. In practice, it is affected by the surrounding environment. For instances, the quantum system has nonzero probability to jump out of the subspace under control and it is subject to the quantum effect raised by the interaction with the vacuum state of the free space. In the framework of open-quantum-system dynamics combining with the fundamental models of atomic optics, we will briefly review the relevant basic concepts of the dissipation and decoherence processes of the atomic systems coupled to external fields. The focus of the paper is to introduce the quantum master equation as the mainstream tool for the investigation of quantum decoherence.