Coherent heat transfer leads to genuine quantum enhancement in the performances of continuous engines

TL;DR

This paper introduces coherent quantum heat engines utilizing baths with quantum coherence, resulting in significantly higher power, reliability, and nonclassical features compared to incoherent engines, advancing quantum thermodynamics and potential applications.

Contribution

The study presents a novel design of continuous quantum heat engines that leverage coherent heat transfer, demonstrating genuine quantum enhancements over classical and incoherent counterparts.

Findings

Coherent engines deliver hundreds of times higher power output.

They operate closer to the maximum reliability set by quantum thermodynamics.

They exhibit more nonclassical features, violating classical thermodynamic relations.

Abstract

Conventional continuous quantum heat engines with incoherent heat transfer perform poorly as they exploit two-body interactions between the system and hot or cold baths, thus having limited capability to outperform their classical counterparts. We introduce distinct continuous quantum heat engines that utilize coherent heat transfer with baths, yielding genuine quantum enhancement in performance. These coherent engines consist of one qutrit system and two photonic baths and enable coherent heat transfer via two-photon transitions involving three-body interactions between the system and hot and cold baths. We demonstrate that coherent engines deliver significantly higher power output with much greater reliability, i.e., lower signal-to-noise ratio of the power, by hundreds of folds over their incoherent counterparts. Importantly, coherent engines can operate close to or at the maximal achievable reliability allowed by the quantum thermodynamic uncertainty relation. Moreover, coherent engines manifest more nonclassical features than incoherent engines because they violate the classical thermodynamic uncertainty relation by a greater amount and for a wider range of parameters. These genuine enhancements in the performance of coherent engines are directly attributed to their capacity to harness higher energetic coherence for the resonant driving case. The experimental feasibility of coherent engines and the improved understanding of how quantum properties can enhance performance may find applications in quantum-enabled technologies.