The laws of thermodynamics regulate the operational principles of macroscopic heat machines. Their statistical nature means that if we were able to realize microscopic ones, composed of just a few quantum systems, deviations from these laws may be possible. This regime is within experimental reach, as proven by Gleb Maslennikov and co-workers, who have now reported the creation of the quantum version of an absorption refrigerator — a machine first invented in 1850 (pictured) — with three trapped ytterbium ions.
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In the language of thermodynamics, the hot and cold bodies and the work medium of this machine are modes of motion of the three-ion chain. The authors observed near-equilibrium and far-from-equilibrium cooling of the cold mode. In the latter scenario, non-thermal occupation of the modes was reported, a sign that quantum coherence is transiently created during the fridge’s evolution. Squeezing the initial state of the work medium showed that the presence of quantum resources impacted the fridge’s operation, but didn’t lead to overall improved performances.
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Levi, F. Chilling motion. Nature Phys 15, 110 (2019). https://doi.org/10.1038/s41567-019-0431-x
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DOI: https://doi.org/10.1038/s41567-019-0431-x
