Entanglement and discord in two-mode Gaussian open quantum systems

TL;DR

This paper analyzes how quantum entanglement and discord evolve over time in two-mode Gaussian systems interacting with a thermal environment, highlighting phenomena like entanglement sudden death and the decay of quantum correlations.

Contribution

It provides a detailed description of the dynamics of entanglement and discord in open Gaussian systems using covariance matrices, including conditions for entanglement preservation and decay.

Findings

Separable initial states remain separable at all times.

Entangled states experience entanglement sudden death at non-zero temperatures.

Quantum discord decays asymptotically over time.

Abstract

In the framework of the theory of open systems, we give a description of quantum entanglement and quantum discord for two non-interacting modes embedded in a thermal environment. We describe the evolution of entanglement in terms of the covariance matrix for Gaussian input states. For all values of the temperature of the thermal reservoir, an initial separable squeezed thermal state remains separable for all times. In the case of an entangled initial squeezed thermal state, entanglement suppression (entanglement sudden death) takes place, for non-zero temperatures of the environment. The Gaussian quantum discord, which is a measure of all quantum correlations in the state, including entanglement, decays asymptotically in time.