Radiation pressure as a source of decoherence

We consider the interaction of an harmonic oscillator with the quantum field via radiation pressure. We show that a “Schrödinger cat” state decoheres in a time scale that depends on the degree of “classicality” of the state components, and which may be much shorter than the relaxation time scale associated to the dynamical Casimir effect. We also show that decoherence is a consequence of the entanglement between the quantum states of the oscillator and field two-photon states. With the help of the fluctuation-dissipation theorem, we derive a relation between decoherence and damping rates valid for arbitrary values of the temperature of the field. Coherent states are selected by the interaction as pointer states.