title: Quantum dephasing of a two-state system by a nonequilibrium harmonic oscillator.
abstract: In this paper, we investigate coherent quantum dynamics in a nonequilibrium environment. We focus on a two-state quantum system strongly coupled to a single classical environmental oscillator, and explore the effect of nonstationary statistical properties of the oscillator on the quantum evolution. A simple nonequilibrium model, consisting of an oscillator with a well-defined initial phase which undergoes subsequent diffusion, is introduced and studied. Approximate but accurate analytic expressions for the evolution of the off-diagonal density matrix element of the quantum system are derived in the second-order cumulant approximation. The effect of the initial phase choice on the subsequent quantum evolution is quantified. It is observed that the initial phase can have a significant effect on the preservation of coherence on short time scales, suggesting this variable as a control parameter for optimizing coherence in many-body quantum systems.
authors.affiliation: Department of Chemistry, University of California, Irvine, California 92697-2025, USA. cmartens@uci.edu
authors.forename: Craig C
authors.initials: CC
authors.lastname: Martens
mesh_terms: D003198:Computer Simulation; D004058:Diffusion; D008956:Models, Chemical; D009991:Oscillometry; D011789:Quantum Theory