Energy-conversion Device Using a Quantum Engine with the Work Medium of Two-Atom Entanglement

Although entanglement is considered as an essential resource for quantuminformation processing, whether entanglement helps for energy conversion oroutput in the quantum regime is still lack of experimental witness. Here wereport on an energy-conversion device operating as a quantum engine with theworking medium acted by two entangled ions confined in a harmonic potential.The two ions are entangled by virtually coupling to one of the vibrationalmodes shared by the two ions, and the quantum engine couples to a quantum load,which is another shared vibrational mode. We explore the energy conversionefficiency of the quantum engine and investigate the useful energy (i.e., themaximum extractable work) stored in the quantum load by tuning the two ions indifferent degrees of entanglement as well as detecting the change of thephonons in the load. Our observation provides, for the first time, quantitativeevidence that entanglement fuels the useful energy produced by the quantumengine, but not helpful for the energy conversion efficiency. We consider thatour results may be useful to the study of quantum batteries for which one ofthe most indexes is the maximum extractable energy.