Converting coherence into work with a fully quantum engine

TL;DR

This paper reports the experimental realization of a fully quantum heat engine that converts quantum coherence into work, demonstrating quantum-enhanced performance with nearly double the work output of classical engines.

Contribution

It introduces a novel quantum engine that uses a solid-state spin and a coherent bath to convert coherence into work, with established criteria for success.

Findings

Almost 200% more work produced compared to classical engine

Quantum coherence is harnessed throughout the engine cycle

Demonstrates a nanomachine with all parts exhibiting quantum coherence

Abstract

Heat engines convert thermal energy into mechanical work. We here report the experimental realization of a fully quantum engine that converts quantum coherence into work. A single solid-state spin in diamond is fueled by a coherent bath and cyclically stores energy in a spin quantum battery. We establish quantum-enhanced performance by showing that almost 200$\%$ more work is produced after a few cycle compared to the corresponding classical engine. We obtain concrete criteria for successful coherence-to-work conversion, and highlight the importance of a coherent motor-battery interaction. This device harnesses nonclassical features during all stages of its cycle, and demonstrates the functionality of a nanomachine whose parts are all quantum coherent.