Cooling classical many-spin systems using feedback control

TL;DR

This paper introduces a feedback control method to polarize and cool classical many-spin systems by converting fluctuations into a conserved degree of freedom, demonstrated through simulations achieving high polarization.

Contribution

The paper presents a novel feedback control technique for cooling classical many-body systems, validated with simulations achieving significant polarization from unpolarized states.

Findings

Achieved 90% polarization in a 1000-spin lattice.

Validated the method with numerical simulations resembling NMR experiments.

Demonstrated conversion of fluctuations into conserved quantity growth.

Abstract

We propose a technique for polarizing and cooling finite many-body classical systems using feedback control. The technique requires the system to have one collective degree of freedom conserved by the internal dynamics. The fluctuations of other degrees of freedom are then converted into the growth of the conserved one. The proposal is validated using numerical simulations of classical spin systems in a setting representative of Nuclear Magnetic Resonance experiments. In particular, we were able to achieve 90 percent polarization for a lattice of 1000 classical spins starting from an unpolarized infinite temperature state.