Collective effects on the performance and stability of quantum heat engines

Abstract

Recent predictions for quantum-mechanical enhancements in the operation of small heat engines have raised renewed interest in their study both from a fundamental perspective and in view of applications. One essential question is whether collective effects may help to carry enhancements over larger scales, when increasing the number of systems composing the working substance of the engine. Such enhancements may consider not only power and efficiency, that is, its performance, but, additionally, its constancy, that is, the stability of the engine with respect to unavoidable environmental fluctuations. We explore this issue by introducing a many-body quantum heat engine model composed by spin pairs working in continuous operation. We study how power, efficiency, and constancy scale with the number of spins composing the engine and introduce a well-defined macroscopic limit where analytical expressions are obtained. Our results predict power enhancements, in both finite-size and macroscopic cases, for a broad range of system parameters and temperatures, without compromising the engine efficiency, accompanied by coherence-enhanced constancy for finite sizes. We discuss these quantities in connection to thermodynamic uncertainty relations.

Enhancing the performance of coupled quantum Otto thermal machines without entanglement and quantum correlations

“…Our results go in the same way as in [88][89][90][91][92], which show the effect of the coupling on the performance of QHEs. We hope to investigate further our study concerning the global and the local thermodynamics more thoroughly, or in general, when both the unitary and the thermalization strokes are in finite time.…”

A photonic engine fueled by entangled two atoms

“…Such quantum thermal devices can provide a paradigm to combine quantum mechanics and thermodynamics, apart from their promising advantages for the use of industrial applications. One of the interesting initial steps was a single atom heat engine realized experimentally [16] and extended into other platforms involving quantum correlations [17,18], quantum coherences [19][20][21] and collective phenomena [22,23].…”

Quantum-enhanced performance in superconducting Andreev-reflection engines

“…Moreover, the TUR has been used to asses the universal trade-off between efficiency, power and their fluctuations in steadystate heat engines, predicting an inevitable drop of stability in any classical engine as their power and efficiency simultaneously increase [53]. As a consequence, violations of the TUR have been proposed as a witness of quantum-thermodynamic signatures in the operation of quantum devices in general [54][55][56], and quantum heat engines in particular [57][58][59][60][61][62]. However, the relevance of the regimes where the TUR has been found to break down in previous works is still unclear, given also the small magnitude of the observed violations in many cases.…”