Exact decoherence to pointer states in free open quantum systems is universal

Abstract

In this paper it is shown that exact decoherence to minimal uncertainty Gaussian pointer states is generic for free quantum particles coupled to a heat bath. More specifically, the paper is concerned with damped free particles linearly coupled under product initial conditions to a heat bath at arbitrary temperature, with arbitrary coupling strength and spectral densities covering the Ohmic, subohmic, and supraohmic regime. Then it is true that there exists a time t_c such that for times t>t_c the state can always be exactly represented as a mixture (convex combination) of particular minimal uncertainty Gaussian states, regardless of and independent from the initial state. This exact `localisation' is hence not a feature specific to high temperatures and weak damping limit, but is rather a generic property of damped free particles.