Entropy-based analysis of single-qubit Otto and Carnot heat engines
Abstract
From an entropy-based formulation of the first law of thermodynamics in the quantum regime, we investigate the performance of Otto-like and Carnot-like engines for a single-qubit working medium. Within this framework, the first law includes an additional contribution -- coherence work -- that quantifies the energetic cost of deviating the quantum trajectory from its natural unitary evolution. We focus on the efficiency of the heat-to-coherence work conversion and show that the Carnot cycle achieves the classical Carnot efficiency, while the performance of the Otto cycle is upper-bounded by the Carnot efficiency corresponding to the extreme temperatures of the cycle. We identify entropy generation during the isochoric stages as the key source of irreversibility limiting the Otto cycle's efficiency.
Keywords
Cite
@article{arxiv.2505.01567,
title = {Entropy-based analysis of single-qubit Otto and Carnot heat engines},
author = {Andrés Vallejo and Catty Lissardy and Santiago Silva-Gallo and Alejandro Romanelli and Raul Donangelo},
journal= {arXiv preprint arXiv:2505.01567},
year = {2026}
}