Decoherence and thermalization dynamics of a quantum oscillator (original) (raw)

We introduce the quantitative measures characterizing the rates of decoherence and thermalization of quantum systems. We study the time evolution of these measures in the case of a quantum harmonic oscillator whose relaxation is described in the framework of the standard master equation, for various initial states (coherent, 'cat', squeezed and number). We establish the conditions under which the true decoherence measure can be approximated by the linear entropy 1 − Trρ 2. We show that at low temperatures and for highly excited initial states the decoherence process consists of three distinct stages with quite different time scales. In particular, the 'cat' states preserve 50% of the initial coherence for a long time interval which increases logarithmically with increase of the initial energy.