Quantum Equivalence and Quantum Signatures in Heat Engines

TL;DR

This paper demonstrates that all quantum heat engines are thermodynamically equivalent in the small action regime and introduces quantum signatures detectable through thermodynamic measurements, highlighting quantum coherence's role in power output.

Contribution

It establishes thermodynamical equivalence among all quantum heat engine types in the small action limit and identifies quantum signatures via thermodynamic measurements.

Findings

All engine types have identical power, heat, and efficiency in the quantum small action regime.

Quantum coherence can be detected through thermodynamic measurements as a quantum signature.

Coherent engines can produce power far exceeding stochastic engines.

Abstract

Quantum heat engines (QHE) are thermal machines where the working substance is quantum. In the extreme case the working medium can be a single particle or a few level quantum system. The study of QHE has shown a remarkable similarity with the standard thermodynamical models, thus raising the issue what is quantum in quantum thermodynamics. Our main result is thermodynamical equivalence of all engine type in the quantum regime of small action. They have the same power, the same heat, the same efficiency, and they even have the same relaxation rates and relaxation modes. Furthermore, it is shown that QHE have quantum-thermodynamic signature, i.e thermodynamic measurements can confirm the presence of quantum coherence in the device. The coherent work extraction mechanism enables power outputs that greatly exceed the power of stochastic (dephased) engines.