Energy-conversion device using a quantum engine with the work medium of two-atom entanglement

TL;DR

This paper demonstrates a quantum engine using two entangled ions as the work medium, providing experimental evidence that entanglement enhances the useful energy output but does not improve energy conversion efficiency.

Contribution

First experimental demonstration of entanglement-enhanced energy extraction in a quantum engine with two entangled ions as the work medium.

Findings

Entanglement increases the maximum extractable work from the quantum engine.

Entanglement does not improve the overall energy conversion efficiency.

Quantitative evidence linking entanglement to useful energy in quantum systems.

Abstract

Although entanglement is considered as an essential resource for quantum information processing, whether entanglement helps for energy conversion or output in the quantum regime is still lack of experimental witness. Here we report on an energy-conversion device operating as a quantum engine with the working medium acted by two entangled ions confined in a harmonic potential. The two ions are entangled by virtually coupling to one of the vibrational modes shared by the two ions, and the quantum engine couples to a quantum load, which is another shared vibrational mode. We explore the energy conversion efficiency of the quantum engine and investigate the useful energy (i.e., the maximum extractable work) stored in the quantum load by tuning the two ions in different degrees of entanglement as well as detecting the change of the phonons in the load. Our observation provides, for the first time, quantitative evidence that entanglement fuels the useful energy produced by the quantum engine, but not helpful for the energy conversion efficiency. We consider that our results may be useful to the study of quantum batteries for which one of the most indexes is the maximum extractable energy.