Entropy and variance squeezing for time-dependent two-coupled atoms in an external magnetic field

Abstract

A model of a two-coupled two-level atom under the action of an external magnetic field is introduced. The system is assumed to be isotropic and the coupling between the atoms is taken to be explicitly time dependent. Direct solution for the equations of motion in the Heisenberg picture is used to obtain the explicit expression for the dynamical operators when we assumed the coupling parameter is constant. In the meantime we have employed the rotating wave approximation for the case in which the coupling parameter is time dependent. The variance and entropy squeezing for both cases are discussed. It has been shown that the variance squeezing and entropy squeezing are sensitive to any change in the atomic states, so that there is no variance squeezing reported for the case in which one or both the atoms are in the pure states (e.g., lower or excited states). Further, the phenomenon of squeezing is also affected by the value of the coupling parameter, where we have noted that for a strong coupling parameter the squeezing is pronounced for a long period of time. © 2008 IOP Publishing Ltd.