Quantum Otto cycle with inner friction: finite-time and disorder effects

TL;DR

This paper models a quantum Otto cycle with inner friction caused by spin misalignment, analyzing how disorder and finite-time effects impact efficiency and power, and proposes an optical implementation for experimental validation.

Contribution

It introduces an exact physical model of inner friction in a quantum Otto cycle considering static disorder and finite-time effects, and suggests an optical realization for experiments.

Findings

Inner friction reduces efficiency and power in the quantum Otto cycle.

Disorder and finite-time effects significantly influence engine performance.

An optical implementation of the cycle is proposed for experimental testing.

Abstract

The concept of inner friction, by which a quantum heat engine is unable to follow adiabatically its strokes and thus dissipates useful energy, is illustrated in an exact physical model where the working substance consists of an ensemble of misaligned spins interacting with a magnetic field and performing the Otto cycle. The effect of this static disorder under a finite-time cycle gives a new perspective of the concept of inner friction under realistic settings. We investigate the efficiency and power of this engine and relate its performance to the amount of friction from misalignment and to the temperature difference between heat baths. Finally we propose an alternative experimental implementation of the cycle where the spin is encoded in the degree of polarization of photons.