Maximally effcient quantum thermal machines fuelled by nonequilibrium steady states

TL;DR

This paper investigates the efficiency and power of two-stage quantum heat engines fueled by non-equilibrium steady states, optimizing their performance using quantum systems like qutrits and coupled qubits.

Contribution

It introduces a detailed analysis and optimization of quantum heat engines operating with non-equilibrium steady states, highlighting the role of quantum dynamics in their efficiency.

Findings

Optimized quantum heat engine efficiency using non-equilibrium steady states.

Demonstrated work extraction from quantum systems like qutrits and coupled qubits.

Provided insights into the role of quantum dynamics in engine performance.

Abstract

The concept of thermal machines has evolved from the canonical steam engine to the recently proposed nanoscopic quantum systems as working fluids. The latter obey quantum open system dynamics and frequently operate in non-equilibrium conditions. However, the role of this dynamics in the overall performance of quantum heat engines remains an open problem. Here, we analyse and optimize the efficiency and power output of two-stage quantum heat engines fuelled by non-equilibrium steady states. In a charging first stage, the quantum working fluid consisting of a qutrit or two coupled qubits is connected to two reservoirs at different temperatures, which establish a heat current that stores ergotropy in the system; the second stage comprises a coherent driving force that extracts work from the machine in finite a amount of time; finally, the external drive is switched off and the machine enters a new cycle.