A quantum thermal machine surpassing the classical thermodynamic limit on precision
Abstract
Precision in nonequilibrium processes comes at a thermodynamic cost: suppressing fluctuations generally requires increased dissipation. Thermodynamic uncertainty relations (TURs) make this trade-off quantitative by linking current fluctuations to entropy production in classical stochastic dynamics. In the decade since its discovery, the canonical steady-state TUR and its finite-time generalizations have become a cornerstone of non-equilibrium thermodynamics, constraining the performance of molecular machines and allowing heat dissipation to be inferred from observable fluctuations. Whether the canonical TUR can be violated in a controlled quantum device remains an outstanding experimental question, in part because doing so requires resolving extremely small steady-state currents as well as their fluctuations. Here we experimentally show that steady-state quantum transport can surpass the precision permitted by the canonical TUR. We observe this violation in a superconducting quantum thermal machine coupled to a microwave waveguide acting as a cold bath and to a classical noise source providing an effective infinite-temperature bath. We observe a TUR ratio Q = 1.71 ± 0.17, in violation of the classical bound Q ≥ 2. Our results demonstrate a fundamental distinction between classical and quantum thermodynamics, paving the way for quantum thermal devices that achieve enhanced precision at reduced energy cost.
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BibTeX
@misc{sundelin2026quantum,
title = {{A quantum thermal machine surpassing the classical thermodynamic limit on precision}},
author = {Simon Sundelin and Ludvig Nordqvist and Khalak Mahadeviya and Vyom Kulkarni and Mohammed Ali Aamir and Mark T. Mitchison and Simone Gasparinetti},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.37149},
eprint = {2609.37149},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.37149},
}
RIS
TY - UNPB
TI - A quantum thermal machine surpassing the classical thermodynamic limit on precision
AU - Simon Sundelin
AU - Ludvig Nordqvist
AU - Khalak Mahadeviya
AU - Vyom Kulkarni
AU - Mohammed Ali Aamir
AU - Mark T. Mitchison
AU - Simone Gasparinetti
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2609.37149
UR - https://arxiv.org/abs/2609.37149
AB - Precision in nonequilibrium processes comes at a thermodynamic cost: suppressing fluctuations generally requires increased dissipation. Thermodynamic uncertainty relations (TURs) make this trade-off quantitative by linking current fluctuations to entropy production in classical stochastic dynamics. In the decade since its discovery, the canonical steady-state TUR and its finite-time generalizations have become a cornerstone of non-equilibrium thermodynamics, constraining the performance of molecular machines and allowing heat dissipation to be inferred from observable fluctuations. Whether the canonical TUR can be violated in a controlled quantum device remains an outstanding experimental question, in part because doing so requires resolving extremely small steady-state currents as well as their fluctuations. Here we experimentally show that steady-state quantum transport can surpass the precision permitted by the canonical TUR. We observe this violation in a superconducting quantum thermal machine coupled to a microwave waveguide acting as a cold bath and to a classical noise source providing an effective infinite-temperature bath. We observe a TUR ratio Q = 1.71 ± 0.17, in violation of the classical bound Q ≥ 2. Our results demonstrate a fundamental distinction between classical and quantum thermodynamics, paving the way for quantum thermal devices that achieve enhanced precision at reduced energy cost.
ER -