# Revealing the strokes of autonomous quantum heat engines with work and heat fluctuations

## TL;DR

This paper investigates the detailed energy transfer processes in an autonomous quantum heat engine composed of superconducting qubits, using fluctuation analysis to reveal the engine's underlying cyclical dynamics.

## Contribution

It introduces a method to analyze work and heat fluctuations in a quantum heat engine, uncovering the hidden cyclical energy transfer strokes through correlation functions.

## Key findings

- Correlation functions reveal the engine's energy transfer cycles
- Work and heat fluctuations can be derived from steady state observables
- The analysis uncovers the engine's underlying dynamical strokes

## Abstract

We analyze an autonomous thermoelectric engine composed of two superconducting qubits coupled to separate heat baths and connected by a Josephson junction. Work and heat are process quantities and not observables of the engine quantum system, but their rates can be derived from the steady state expectation value of appropriate system observables and their fluctuations are given by correlation functions determined with the GKLS master equation and quantum regression theorem. The correlation functions also reveal a cyclical, dynamical transfer of energy - the strokes of the engine - hiding underneath the steady state.