Thermodynamics is one of the oldest and well-established branches of physicsthat sets boundaries to what can possibly be achieved in macroscopic systems.While it started as a purely classical theory, it was realized in the earlydays of quantum mechanics that large quantum devices, such as masers or lasers,can be treated with the thermodynamic formalism. Remarkable progress has beenmade recently in the miniaturization of heat engines all the way to the singleBrownian particle as well as to a single atom. However, despite severaltheoretical proposals, the implementation of heat machines in the fully quantumregime remains a challenge. Here, we report an experimental realization of aquantum absorption refrigerator in a system of three trapped ions, with threeof its normal modes of motion coupled by a trilinear Hamiltonian such that heattransfer between two modes refrigerates the third. We investigate the dynamicsand steady-state properties of the refrigerator and compare its coolingcapability when only thermal states are involved to the case when squeezing isemployed as a quantum resource. We also study the performance of such arefrigerator in the single shot regime, and demonstrate cooling below both thesteady-state energy and the benchmark predicted by the classical thermodynamicstreatment.
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