Coherence enhanced quantum metrology in a nonequilibrium optical molecule

TL;DR

This paper demonstrates that steady-state coherence in a nonequilibrium optical molecular system can enhance quantum metrology, with the coherence sustained by temperature differences and linked to the coherence heat current, offering new avenues for quantum technology.

Contribution

It reveals how nonequilibrium conditions sustain coherence that improves quantum metrology, and clarifies the role of coherence heat current in this enhancement.

Findings

Steady-state coherence is enhanced by temperature differences.

Coherence heat current is linked to steady-state coherence.

Coherence can flow from low to high temperature reservoirs.

Abstract

We explore the quantum metrology in an optical molecular system coupled to two environments with different temperatures, using a quantum master equation beyond secular approximation. We discover that the steady-state coherence originating from and sustained by the nonequilibrium condition can enhance quantum metrology. We also study the quantitative measures of the nonequilibrium condition in terms of the curl flux, heat current and entropy production at the steady state. They are found to grow with temperature difference. However, an apparent paradox arises considering the contrary behaviors of the steady-state coherence and the nonequilibrium measures in relation to the inter-cavity coupling strength. This paradox is resolved by decomposing the heat current into a population part and a coherence part. Only the latter, coherence heat current, is tightly connected to the steady-state coherence and behaves similarly with respect to the inter-cavity coupling strength. Interestingly, the coherence heat current flows from the low-temperature reservoir to the high-temperature reservoir, opposite to the direction of the population heat current. Our work offers a viable way to enhance quantum metrology for open quantum systems through steady-state coherence sustained by the nonequilibrium condition, which can be controlled and manipulated to maximize its utility. The potential applications go beyond quantum metrology and extend to areas such as device designing, quantum computation and quantum technology in general.