On the operation of machines powered by quantum non-thermal baths

TL;DR

This paper explores how quantum non-thermal baths can power machines that surpass traditional efficiency limits, revealing mechanisms where such baths impart both heat and work, leading to hybrid engine-refrigerator behavior.

Contribution

It demonstrates that quantum non-thermal baths can provide both heat and work, challenging the applicability of the Carnot bound and revealing dual-action machine capabilities.

Findings

Quantum baths can impart work and heat simultaneously.

Machines can operate as both engines and refrigerators with high efficiency.

Traditional thermodynamic principles still apply despite unconventional performance.

Abstract

Diverse models of engines energised by quantum-coherent, hence non-thermal, baths allow the engine efficiency to transgress the standard thermodynamic Carnot bound. These transgressions call for an elucidation of the underlying mechanisms. Here we show that non-thermal baths may impart not only heat, but also mechanical work to a machine. The Carnot bound is inapplicable to such a hybrid machine. Intriguingly, it may exhibit dual action, concurrently as engine and refrigerator, with up to 100% efficiency. We conclude that even though a machine powered by a quantum bath may exhibit an unconventional performance, it still abides by the traditional principles of thermodynamics.