Decoherence through Coupling to the Radiation Field

We consider a quantum particle in a coherent superposition of two well localized wave packets. Through an external harmonic potential the two wave packets are accelerated towards each other, start to overlap, and an interference pattern emerges. When the particle is coupled to the radiation eld, assumed to be in a thermal state, the interference pattern is partially suppressed, which deenes the decoherence amplitude. For our model we compute both the decoherence and the friction rate. They are given in terms of fundamental constants and a certain scaling function of the temperature. With the exception of unphysical regimes our results are in agreement with the prediction of the master equation for this system.