The multilevel four-stroke swap engine and its environment

TL;DR

This paper introduces a solvable multilevel four-stroke quantum engine model operating far from equilibrium, analyzing its efficiency, work, and conditions for functioning as an engine or refrigerator, with implications for quantum thermodynamics.

Contribution

It presents a new solvable model of a multilevel quantum engine that works beyond thermal equilibrium and strong coupling regimes, linking thermodynamic performance to bath properties.

Findings

Derived conditions for engine and refrigerator operation.

Connected Clausius inequality to symmetrized relative entropy.

Optimized work and efficiency in the ultra-hot regime.

Abstract

A multilevel four-stroke engine where the thermalization stokes are generated by unitary collisions with bath particles is analyzed. Our model is solvable even when the engine operates far from thermal equilibrium and in the strong system-bath coupling. Necessary operation conditions for the heat machine to perform as an engine or a refrigerator are derived. We relate the work and efficiency of the device to local and non-local statistical properties of the baths (purity, mutual coincidence etc.). In particular, we relate the Clausius inequality to the symmetrized relative entropy of the baths (Jefferys divergence). Other Clausius-like inequalities are derived as well. Finally, in the ultra-hot regime we optimize the work of the multilevel engine and obtain simpler forms for the work and efficiency.