Based on a unitary transformation and a generalized rotating-wave approximation, the effect of the counter-rotating wave terms on the trace distance of quantum states for the qubit in the Rabi model is investigated. The analytical expressions of the eigenenergies and eigenstates of the qubit–field coupling system are obtained approximately. Starting from the two initial Bell states for the qubit and field, in which the qubit is in the same states, we find that the time evolution of the trace distance for the qubit states is only related to the...
