Coherences and the thermodynamic uncertainty relation: Insights from quantum absorption refrigerators

TL;DR

This paper investigates how quantum coherences influence heat current fluctuations in quantum absorption refrigerators and confirms the thermodynamic uncertainty relation's validity in the quantum regime.

Contribution

It provides a detailed analysis of the role of quantum coherences on fluctuations and the thermodynamic uncertainty relation in quantum thermal machines.

Findings

Quantum coherence can suppress or enhance cooling power.

Presence of coherence increases relative noise in cooling power.

Thermodynamic uncertainty relation holds in quantum absorption refrigerators.

Abstract

The thermodynamic uncertainty relation, originally derived for classical Markov-jump processes, provides a trade-off relation between precision and dissipation, deepening our understanding of the performance of quantum thermal machines. Here, we examine the interplay of quantum system coherences and heat current fluctuations on the validity of the thermodynamics uncertainty relation in the quantum regime. To achieve the current statistics, we perform a full counting statistics simulation of the Redfield quantum master equation. We focus on steady-state quantum absorption refrigerators where nonzero coherence between eigenstates can either suppress or enhance the cooling power, compared with the incoherent limit. In either scenario, we find enhanced relative noise of the cooling power (standard deviation of the power over the mean) in the presence of system coherence, thereby corroborating the thermodynamic uncertainty relation. Our results indicate that fluctuations necessitate consideration when assessing the performance of quantum coherent thermal machines.