Steady bipartite coherence induced by non-equilibrium environment

TL;DR

This paper investigates how two coupled two-level atoms maintain quantum coherence in a non-equilibrium environment, revealing that certain configurations and resonances can sustain significant steady-state coherence.

Contribution

It demonstrates that non-secular master equations predict persistent steady-state coherence in coupled atoms, highlighting the influence of interaction configurations and resonance conditions.

Findings

Steady-state coherence depends on system-bath interaction configurations.

Resonant atoms exhibit larger steady quantum coherence.

Additional interaction channels reduce the magnitude of coherence.

Abstract

We study the steady state of two coupled two-level atoms interacting with a non-equilibrium environment that consists of two heat baths at different temperatures. Specifically, we analyze four cases with respect to the configuration about the interactions between atoms and heat baths. Using secular approximation, the conventional master equation usually neglects steady-state coherence, even when the system is coupled with a non-equilibrium environment. When employing the master equation with no secular approximation, we find that the system coherence in our model, denoted by the off-diagonal terms in the reduced density matrix spanned by the eigenvectors of the system Hamiltonian, would survive after a long-time decoherence evolution. The absolute value of residual coherence in the system relies on different configurations of interaction channels between the system and the heat baths. We find that a large steady quantum coherence term can be achieved when the two atoms are resonant. The absolute value of quantum coherence decreases in the presence of additional atom-bath interaction channels. Our work sheds new light on the mechanism of steady-state coherence in microscopic quantum systems in non-equilibrium environments.