Effect of the driving on the entropy of a two-level atom

The effect of the driving coherent field on the entropy of a two-level atom has been studied. It is assumed that the atomic transition in the atomic system is interacting with free vacuum modes and a driving field. Here the Schrodinger equation and density matrix are used to calculate the entropy of the atomic system. It is shown that the entropy of the atomic system has an oscillatory behavior. Moreover, the duration of entanglement between the two-level atom and its spontaneous emission depends on the spontaneous decay rate of the atomic transition and it is nearly independent from the Rabi frequency of the driving field.