System-bath entanglement in nanothermodynamics

TL;DR

This paper investigates quantum entanglement between a harmonic oscillator and its environment, finding a temperature threshold above which entanglement disappears, and clarifying its role in thermodynamic violations.

Contribution

It provides an exact measure of system-bath entanglement and identifies a critical temperature, clarifying its relation to thermodynamic anomalies.

Findings

Entanglement vanishes above a critical temperature.

System-bath entanglement is not responsible for Clausius inequality violations.

Exact negativity measure used to quantify entanglement.

Abstract

We consider a quantum harmonic oscillator linearly coupled to a bath of harmonic oscillators and evaluate the degree of entanglement between system and bath using the negativity as an exact entanglement measure. We establish the existence of a critical temperature above which the system-bath negativity vanishes. Our results imply that system-bath entanglement is not responsible for the violation of the Clausius inequality observed in the low temperature/strong coupling regime [Phys. Rev. Lett. 85, 1799 (2000)], as the latter still occurs well above the critical temperature.