Quantum Coherence in Magnetic Grains

TL;DR

This paper models quantum coherence in magnetic grains, analyzing how interactions with spins, electrons, and phonons cause decoherence, and proposes experimental methods to observe coherence.

Contribution

It introduces a comprehensive model of decoherence mechanisms in magnetic grains and suggests experimental techniques to detect quantum coherence.

Findings

Decoherence arises from spins and electrons, but electron effects can be minimized in insulating substrates.

Isotopic and chemical purification are necessary for observing quantum coherence.

A 'spin echo' experiment is proposed to detect coherence in magnetic grains.

Abstract

We consider a model of the dynamics of a magnetic grain, incorporating interactions with nuclear and paramagnetic spins, conduction electrons, and phonons. Decoherence comes both from the spins and the electrons, although electron effects can be neglected if the substrate is insulating, and the grain has spin $S \le 10^5$. A successful experiment will require both isotopic and chemical purification, if coherence is to be seen; we suggest a "spin echo" arrangement to do this.