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  • Open Access

Thermodynamic uncertainty relations for relativistic quantum thermal machines

Dimitris Moustos* and Obinna Abah†

  • School of Mathematics, Statistics, and Physics, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom

  • *Contact author: dimitris.moustos@newcastle.ac.uk
  • †Contact author: obinna.abah@newcastle.ac.uk
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Phys. Rev. D 113, 065005 – Published 9 March, 2026

DOI: https://doi.org/10.1103/25jj-1h67

Abstract

We investigate a two-qubit SWAP thermal machine—a streamlined analog of the four-stroke Otto cycle—whose working medium comprises inertially moving Unruh-DeWitt qubit detectors, each coupled to a thermal quantum field bath prepared at a different temperature. In the presence of relative motion between the working medium and the thermal baths, we derive thermodynamic uncertainty relations (TURs) that quantify the trade-off between performance, entropy production, and power fluctuations. Our analysis identifies regimes where relativistic motion leads to stronger violation of classical TURs, previously observed in static quantum setups. In addition, we establish generalized performance bounds for the thermal machine operating as either a heat engine or a refrigerator, and discuss how relativistic motion can enhance their performances beyond the standard Carnot limits defined by rest-frame temperatures.

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Phys. Rev. D 113, 065005– Published 9 March, 2026
  • Received 25 November 2025
  • Accepted 13 February 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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