Decoherence and the Nature of System-Environment Correlations

TL;DR

This paper explores how decoherence relates to system-environment correlations, revealing that decoherence can occur without entanglement and that classical and quantum correlations can oscillate over time.

Contribution

It provides a detailed analysis of system-environment correlations during decoherence, including conditions for entanglement and the dynamics of classical and quantum correlations.

Findings

Decoherence often occurs without entanglement in Markovian regimes.

Both separable and entangling decoherence are possible depending on conditions.

Classical and quantum correlations can periodically alternate over time.

Abstract

We investigate system-environment correlations based on the exact dynamics of a qubit and its environment in the framework of pure decoherence (phase damping). We focus on the relation of decoherence and the build-up of system-reservoir entanglement for an arbitrary (possibly mixed) initial qubit state. In the commonly employed regime where the qubit dynamics can be described by a Markov master equation of Lindblad type, we find that for almost all qubit initial states inside the Bloch sphere, decoherence is complete while the total state is still separable - no entanglement is involved. In general, both "separable" and "entangling" decoherence occurs, depending on temperature and initial qubit state. Moreover, we find situations where classical and quantum correlations periodically alternate as a function of time in the regime of low temperatures.