Nonequilibrium fluctuations in quantum heat engines: Theory, example, and possible solid state experiments

TL;DR

This paper explores the stochastic thermodynamics of quantum heat engines, demonstrating fluctuation relations, analyzing an optimal two-qubit engine, and discussing potential solid state experimental implementations.

Contribution

It introduces a detailed stochastic thermodynamics framework for quantum heat engines and proposes feasible solid state experiments to observe these phenomena.

Findings

Fluctuation relations enforce the Carnot efficiency limit.

An optimal two-qubit heat engine model illustrates stochastic heat and work statistics.

Potential for on-chip calorimetric measurements of quantum stochastic events.

Abstract

We study the stochastic energetic exchanges in quantum heat engines. Due to microreversibility, these obey a fluctuation relation, called the heat engine fluctuation relation, which implies the Carnot bound: no machine can have an efficiency larger than Carnot's efficiency. The stochastic thermodynamics of a quantum heat engine (including the joint statistics of heat and work and the statistics of efficiency) is illustrated by means of an optimal two-qubit heat engine, where each qubit is coupled to a thermal bath and a two-qubit gate determines energy exchanges between the two qubits. We discuss possible solid state implementations with Cooper pair boxes and flux qubits, quantum gate operations, and fast calorimetric on-chip measurements of single stochastic events.