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Quantum Detectors as Autonomous Machines: Assessing the Nonequilibrium Thermodynamics of Information Acquisition

Emanuel Schwarzhans1,2,*, Tony J. G. Apollaro1,†, Ilia Khomchenko1,‡, Maximilian P. E. Lock2,3,§, Mark T. Mitchison4,5,∥, and Marcus Huber2,3,¶

  • 1Department of Physics, University of Malta, Msida MSD 2080, Malta
  • 2Atominstitut, TU Wien, 1020 Vienna, Austria
  • 3Institute for Quantum Optics and Quantum Information (IQOQI), Austrian Academy of Sciences, 1090 Vienna, Austria
  • 4School of Physics, Trinity College Dublin, College Green, Dublin 2, D02 K8N4, Ireland
  • 5Department of Physics, King’s College London, Strand, London, WC2R 2LS, United Kingdom

  • *Contact author: emanuel.schwarzhans@um.edu.mt
  • †Contact author: tony.apollaro@um.edu.mt
  • ‡Contact author: ilia.khomchenko@um.edu.mt
  • §Contact author: maximilian.paul.lock@tuwien.ac.at
  • ∥Contact author: mark.mitchison@kcl.ac.uk
  • Contact author: marcus.huber@tuwien.ac.at
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PRX Quantum 7, 033001 – Published 1 July, 2026

DOI: https://doi.org/10.1103/wm5p-tjtg

Abstract

We formulate a minimal model of a quantum particle detector as an autonomous quantum thermal machine. Our goal is to establish how entropy production, which is needed to maintain the detector out of equilibrium, is linked to the quality of the measurement process. Using our model, we perform a detailed investigation of the detector’s key performance characteristics: namely, detection efficiency, gain, jitter, dead time, and dark counts. We find that entropy production constrains both the efficiency and temporal precision of the detection process, in the sense that improved performance generally requires more dissipation. We also find that reducing either the detection jitter or dead time unavoidably increases the rate of dark counts. Our work establishes a quantitative connection between entropy production and the quality of the irreversible detection process, highlights fundamental tradeoffs in the performance of particle detectors, and provides a framework for further investigations of the non-equilibrium thermodynamics of quantum measurement and amplification.

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Popular Summary

The fact that measurements of quantum systems require the expenditure of work, while never being perfect, is well known among both theoretical and experimental quantum physicists. The actual energy costs and limitations, however, are not discernable from the axiomatic postulates of quantum mechanics itself. To get an insight into these questions one thus needs a physical model for the measurement process, which presents a daunting challenge, as there are infinitely many possible ways a measurement could be realized. In this work we thus constrain the set of possible dynamical models of measurement by reasonable criteria they should fulfil, and then present a minimal autonomous model that satisfies all reasonable criteria. This model can then reveal not only the energy expenditure (or entropy dissipation) associated with a measurement: it can also connect those to the most desirable properties of quantum detectors, such as dark count rate, single photon efficiency and timing jitter. The model reveals interesting trade-off relations that follow intrinsically from the thermodynamic nature of quantum detectors and that are also seen in modern quantum technologies.

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PRX Quantum 7, 033001– Published 1 July, 2026
  • Received 5 September 2025
  • Accepted 14 May 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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