标题： 两能级系统在外部时间依赖场中的特性 显示英文标题

标题： Aspects of Two-Level Systems under External Time Dependent Fields

摘要： 考虑时间依赖背景中两能级系统的动力学。 我们提出了一些在随时间衰减的特殊背景中的新精确解。 另一方面，根据费曼、弗里德曼和赫尔瓦思的想法，我们详细讨论了将量子动力学简化为经典哈密顿系统的可能性。 这尤其开辟了直接应用经典力学的强大方法（例如KAM方法）来研究量子系统。 按照这种思路，当外部背景在时间上是周期性或准周期性时，我们得出了与“量子混沌”相关的结论。 显示英文摘要

摘要： The dynamics of two-level systems in time-dependent backgrounds is under consideration. We present some new exact solutions in special backgrounds decaying in time. On the other hand, following ideas of Feynman, Vernon and Hellwarth, we discuss in detail the possibility to reduce the quantum dynamics to a classical Hamiltonian system. This, in particular, opens the possibility to directly apply powerful methods of classical mechanics (e.g. KAM methods) to study the quantum system. Following such an approach, we draw conclusions of relevance for ``quantum chaos'' when the external background is periodic or quasi-periodic in time.