Multilevel quantum thermodynamic swap engines

TL;DR

This paper investigates multilevel quantum swap engines, analyzing their thermodynamic behavior, fluctuations, and efficiency limits, bridging two-qubit and bosonic models, and revealing how increasing system dimension affects performance and uncertainty relations.

Contribution

It introduces a comprehensive analysis of multilevel quantum thermodynamic engines, extending previous two-qubit models to higher dimensions and exploring their thermodynamic properties and limitations.

Findings

Identifies three operational regimes: heat engine, refrigerator, and thermal accelerator.

Derives the full joint probability distribution of work and heat fluctuations.

Shows how increasing system dimension affects efficiency and uncertainty relations.

Abstract

We study energetic exchanges and fluctuations in two-stroke quantum thermodynamic engines where the working fluid is represented by two multilevel quantum systems, i.e. qudits, the heat flow is allowed by relaxation with two thermal reservoirs at different temperatures, and the work exchange is operated by a partial-swap unitary interaction. We identify three regimes of operation (heat engine, refrigerator, and thermal accelerator), present the thermodynamic uncertainty relations between the entropy production and the signal-to-noise ratio of work and heat, and derive the full joint probability of the stochastic work and heat. Our results bridge the gap between two-qubit and two-mode bosonic swap engines, and show which properties are maintained (e.g., a non fluctuating Otto efficiency) and which are lost for increasing dimension (e.g., small violations of the standard thermodynamic uncertainty relations or the possibility of beating the Curzon-Ahlborn efficiency).