Multidimensional minimum-work control of a 2D Ising model

TL;DR

This paper develops multidimensional control protocols for a 2D Ising model that minimize excess work by exploiting flexible control paths, leading to faster, more efficient state transitions closer to equilibrium.

Contribution

It introduces a numerical method to design multidimensional control protocols that reduce work and improve efficiency in driving the 2D Ising model between states.

Findings

Multidimensional protocols outperform one-dimensional ones in reducing work.

Designed protocols avoid high-resistance regions and utilize system relaxation.

Protocols significantly decrease work and speed up spin-inversion reactions.

Abstract

A system's configurational state can be manipulated using dynamic variation of control parameters, such as temperature, pressure, or magnetic field; for finite-duration driving, excess work is required above the equilibrium free-energy change. Minimum-work protocols in multidimensional control-parameter space have potential to significantly reduce work relative to one-dimensional control. By numerically minimizing a linear-response approximation to the excess work, we design protocols in control-parameter spaces of a 2D Ising model that efficiently drive the system from the all-down to all-up configuration. We find that such designed multidimensional protocols take advantage of more flexible control to avoid control-parameter regions of high system resistance, heterogeneously input and extract work to make use of system relaxation, and flatten the energy landscape, making accessible many configurations that would otherwise have prohibitively high energy and thus decreasing spin correlations. Relative to one-dimensional protocols, this speeds up the rate-limiting spin-inversion reaction, thereby keeping the system significantly closer to equilibrium for a wide range of protocol durations, and significantly reducing resistance and hence work.