Abstract
The inexorable miniaturisation of technologies, the relentless drive to improve efficiency and the enticing prospect of boosting performance through quantum effects are all compelling reasons to investigate microscopic machines. Thermal absorption machines are a particularly interesting class of device that operate autonomously and use only heat flows to perform a useful task. In the quantum regime, this provides a natural setting in which to quantify the thermodynamic cost of various operations such as cooling, timekeeping or entanglement generation. This article presents a pedagogical introduction to the physics of quantum absorption machines, covering refrigerators, engines and clocks in detail.
Acknowledgments
Useful discussions with John Goold during the preparation of the manuscript are gratefully acknowledged.
Disclosure statement
No potential conflict of interest was reported by the author.
ORCID
Mark T. Mitchison http://orcid.org//0000-0003-3805-3880
Notes
1 Complete positivity means that the operation is positive, where
is the identity superoperator acting on an arbitrary auxiliary system.
2 Strictly speaking, there could be multiple jump operators and rates
for each transition frequency ω, but we do not need to consider such complications here.
3 Some treatments use the alternative designation for the hottest reservoir and
for the intermediate (‘room-temperature’) reservoir.
4 Indeed, equilibrium states span the set of completely passive states, i.e. those which remain passive under composition, such that is passive for all n [Citation91–93].
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Mark T. Mitchison
Mark Mitchison is a theoretical physicist based at Trinity College Dublin. Mark wrote his PhD thesis on atomic-scale absorption refrigerators and thermometers at Imperial College London in 2016. He then worked for two years at Universität Ulm before moving to Dublin in 2018. His research focuses on open quantum systems and their applications as thermal machines and as platforms for investigating non-equilibrium physics.