Entanglement of mechanical oscillators coupled to a non-equilibrium environment

TL;DR

This paper investigates how non-equilibrium environments influence entanglement in coupled mechanical oscillators, revealing an optimal dissipation level for maximum entanglement using a comprehensive quantum Langevin framework.

Contribution

It introduces a general exact quantum Langevin equation approach applicable to arbitrary bath spectra, demonstrating the limitations of the Lindblad method in non-equilibrium settings.

Findings

Maximum entanglement occurs at an optimal dissipation strength.

Lindblad approach fails to accurately predict entanglement in non-equilibrium environments.

The framework applies to arbitrary bath spectra, both in and out of equilibrium.

Abstract

Recent experiments aim at cooling nanomechanical resonators to the ground state by coupling them to non-equilibrium environments in order to observe quantum effects such as entanglement. This raises the general question of how such environments affect entanglement. Here we show that there is an optimal dissipation strength for which the entanglement between two coupled oscillators is maximized. Our results are established with the help of a general framework of exact quantum Langevin equations valid for arbitrary bath spectra, in and out of equilibrium. We point out why the commonly employed Lindblad approach fails to give even a qualitatively correct picture.