Optimization of Asymmetric Quantum Otto Engine Cycles

TL;DR

This paper investigates how asymmetry in the durations of work strokes affects the optimization of work output and reliability in finite-time quantum Otto heat engines with harmonic or two-level systems.

Contribution

It introduces a detailed analysis of cycle asymmetry, revealing discontinuities and optimal points for maximizing work and reliability in quantum Otto engines.

Findings

Optimal asymmetry parameter shows discontinuities with cycle time.

Cycles of specific durations maximize both work and reliability.

Asymmetry influences work output and fluctuations significantly.

Abstract

We consider the optimization of the work output and fluctuations of a finite-time quantum Otto heat engine cycle consisting of compression and expansion work strokes of unequal duration. The asymmetry of the cycle is characterized by a parameter $r_u$ giving the ratio of the times for the compression and expansion work strokes. For such an asymmetric quantum Otto engine cycle, with working substance chosen as a harmonic oscillator or a two-level system, we find that the optimal values of $r_u$ maximising the work output and the reliability (defined as the ratio of average work output to its standard deviation) shows discontinuities as a function of the total time taken for the cycle. Moreover we identify cycles of some specific duration where both the work output and the reliability take their largest values for the same value of the asymmetry parameter $r_u$.