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

TL;DR

This paper investigates finite-time quantum Otto engines using a two-spin XY model, comparing shortcuts to adiabaticity with non-adiabatic processes, and finds conditions where non-adiabatic engines perform nearly as well as adiabatic ones.

Contribution

It analyzes the performance of finite-time quantum Otto engines with and without STA, revealing regimes where non-adiabatic operation is nearly optimal, reducing the need for external control.

Findings

Non-adiabatic engines can perform close to adiabatic ones in certain regimes.

STA provides marginal improvements over non-adiabatic protocols in some parameter ranges.

Designing the working medium Hamiltonian can reduce reliance on external control protocols.

Abstract

We propose a quantum Otto cycle in a two spin-$1/2$ anisotropic XY model in a transverse external magnetic field. We first characterize the parameter regime that the working medium operates as an engine in the adiabatic regime. 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 introducing an external control. We compare the performance of the non-adiabatic and STA engines for a fixed adiabatic efficiency but different parameters of the working medium. We observe that, for certain parameter regimes, the irreversibility, as measured by the efficiency lags, due to finite-time driving is so low that non-adiabatic engine performs quite close to the adiabatic engine, leaving the STA engine only marginally better than the non-adiabatic one. This suggests that by designing the working medium Hamiltonian one may spare the difficulty of dealing with an external control protocol.