Finite-time two-spin quantum Otto engines:Shortcuts to adiabaticity vs. irreversibility

Abstract

We propose a quantum Otto cycle in a two spin-1/2anisotropic XY model in a transverse external magneticfield. We first characterize the parameter regime that the working medium operates as an engine in the adiabaticregime. Then, we consider finite-time behavior of the engine with and without utilizing a shortcut to adiabaticity (STA)technique. STA schemes guarantee that the dynamics of a system follows the adiabatic path, at the expense of introducingan external control. We compare the performance of the nonadiabatic and STA engines for a fixed adiabatic efficiencybut different parameters of the working medium. We observe that, for certain parameter regimes, the irreversibility, asmeasured by the efficiency lags, due to finite-time driving is so low that nonadiabatic engine performs quite close tothe adiabatic engine, leaving the STA engine only marginally better than the nonadiabatic one. This suggests that bydesigning the working medium Hamiltonian one may spare the difficulty of dealing with an external control protocol.