Two-Level System in a Periodic External Field

B. A. Zon, Boris G. Katsnelson

Yu. S. Oseledchik, G. A. Miroshnik

J. C. A. Barata, D.A. Cortez

Lei Wang, Jiushu Shao

The quantum dynamics of the two-level system under a periodic external potential is mapped to the classical one of a charged particle moving in the harmonic-oscillator potential plus a magnetic field in a plane. The behavior of tunneling and localization is fully described by the radial trajectory of the particle. It is shown that localization may happen only if the radial trajectory is periodic. The possible period is an integral multiple of that of the external force. Three models are studied.

Xian-Geng Zhao

We study the dynamics of two-level systems under the influence of time-dependent external fields. An oscillation period describing the transition between two states is obtained analytically by the use of perturbation theory, from which the results for any special case can be derived. We illustrate two examples to show the advantage of our theory, in which the phenomenon of localization/delocalization can be addressed uniformly by oscillation period.