# Efficiency fluctuations of a quantum Otto engine

## TL;DR

This paper derives the efficiency distribution of a quantum Otto engine, analyzing stochastic efficiency, especially above unity, and explores the classical-quantum transition as temperature decreases.

## Contribution

It provides an explicit quantum efficiency distribution for a solvable two-level engine and examines efficiency fluctuations across different regimes.

## Key findings

- Efficiency can exceed unity, especially at infinity, in nonadiabatic regimes.
- Mean and variance of efficiency are computed for adiabatic driving.
- Classical-to-quantum transition effects are analyzed as temperature decreases.

## Abstract

We derive the probability distribution of the efficiency of a quantum Otto engine. We explicitly compute the quantum efficiency statistics for an analytically solvable two-level engine. We analyze the occurrence of values of the stochastic efficiency above unity, in particular at infinity, in the nonadiabatic regime and further determine mean and variance in the case of adiabatic driving. We finally investigate the classical-to-quantum transition as the temperature is lowered.