Two-Level Atom at Finite Temperature
Tomasz Sowiński · Acta Physica Polonica A · 2009
Properties of a two-level atom coupled to the quantized electromagnetic field at finite temperature are determined.The analysis is based on a new method (inspired by quantum electrodynamics) of describing qubits, developed previously at zero temperature.In this paper, we make a generalization to finite temperature by introducing the Matsubara formalism and the temperature propagators.We analyze the spectral properties of different types of propagators and we derive a direct connection between the temperature propagators and the real time propagators.To show the effectiveness of this method, we calculate the temperature dependence of the polarizability of a two-level atom in the lowest order of perturbation theory and we predict an unexpected sharpening of the resonance.The whole discussion is carried out without the rotating wave approximation.