Carnot's theorem for nonthermal stationary reservoirs

TL;DR

This paper extends Carnot's theorem to nonthermal stationary reservoirs, demonstrating their equivalence to multiple equilibrium reservoirs and exploring the potential for quantum coherence to enable unit efficiency engines.

Contribution

It generalizes Carnot's theorem to nonthermal reservoirs and shows their equivalence to multiple equilibrium reservoirs, including quantum coherence effects.

Findings

Nonthermal reservoirs can be formally equivalent to multiple thermal reservoirs.

Quantum coherence in reservoirs may enable engines with unit efficiency.

Theoretical framework for efficiency limits with nonthermal quantum reservoirs.

Abstract

Carnot's theorem poses a fundamental limit on the maximum efficiency achievable from an engine that works between two reservoirs at thermal equilibrium. We extend this result to the case of arbitrary nonthermal stationary reservoirs, even with quantum coherence. In order to do this we prove that a single nonthermal reservoir is formally equivalent to multiple equilibrium ones. Finally, we discuss the possibility of realizing an engine that works at unit efficiency by exploiting quantum coherence present in the reservoir.