Decay of Gaussian correlations in local thermal reservoirs

TL;DR

This paper analyzes how quantum correlations, specifically entanglement and discord, decay over time in a two-mode squeezed thermal state interacting with local thermal reservoirs, providing analytic expressions and observing discord enhancement.

Contribution

It derives analytic expressions for entanglement-death time in specific reservoir configurations and investigates the evolution and potential increase of Gaussian quantum discord.

Findings

Entanglement decays at a rate determined by reservoir properties.

All pure Gaussian states lose entanglement simultaneously under certain conditions.

Quantum discord can increase over time in specific scenarios, especially with zero-temperature reservoirs.

Abstract

In this paper we examine the decay of quantum correlations for the radiation field in a two-mode squeezed thermal state in contact with local thermal reservoirs. Two measures of the evolving quantum correlations are compared: the entanglement of formation and the quantum discord. We derive analytic expressions of the entanglement-death time in two special cases: when the reservoirs for each mode are identical, as well as when a single reservoir acts on the first mode only. In the latter configuration, we show that all the pure Gaussian states lose their entanglement at the same time determined solely by the field-reservoir coupling. Also investigated is the evolution of the Gaussian quantum discord for the same choices of thermal baths. We notice that the discord can increase in time above its initial value in a special situation, namely, when it is defined by local measurements on the attenuated mode and the input state is mixed. This enhancement of discord is stronger for zero-temperature reservoirs and increases with the input degree of mixing.