Optimization of Asymmetric Quantum Otto Engine Cycles

Understand

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 $r_u$.