Dynamics of a two-level system coupled to a quantum oscillator: transformed rotating-wave approximation

C. J. Gan; H. Zheng

doi:10.1140/epjd/e2010-00182-8

EPJ

Dynamics of a two-level system coupled to a quantum oscillator: transformed rotating-wave approximation

C. J. Gan and H. Zheng^a

Department of Physics, Shanghai Jiao Tong University, Shanghai, 200240, P.R. China

Received: 12 January 2010
Revised: 20 May 2010
Published online: 6 July 2010

Abstract

For studying the dynamics of a two-level system coupled to a quantum oscillator we have presented an analytical approach, the transformed rotating-wave approximation, which takes into account the effect of the counter-rotating terms but still keeps the simple mathematical structure of the ordinary rotating-wave approximation. We have calculated the energy levels of ground and lower-lying excited states, as well as the time-dependent quantum dynamics. It is obvious that the approach is quite simple and can be easily extended to more complicated situation. Besides, the results are compared with the numerically exact ones to show that for weak to intermediate coupling and moderate detuning our analytic calculations are quantitatively in good agreement with the exact ones.