Refocusing dipolar interactions between electronic spins of donors in silicon

TL;DR

This paper identifies specific magnetic field values where dipolar interactions between electron spins in silicon can be refocused, enabling better control of entanglement despite always-on interactions.

Contribution

It introduces the concept of dipolar refocusing points (DRPs) that allow refocusing of dipolar interactions in silicon spin systems at arbitrary coupling strengths and times.

Findings

DRPs exist at specific magnetic fields for silicon electron spins.

Refocusing occurs for arbitrary coupling strengths and times.

Potential signatures of DRPs are analyzed in coherence decay studies.

Abstract

We note the existence of a set of magnetic field values where a simple Hahn echo sequence refocuses the dynamics of the full dipolar interaction, for spin systems of electron donors in silicon. As the refocussing occurs for both arbitrary coupling strengths and arbitrary times, these dipolar refocusing points (DRPs) offer new possibilities for regulating entanglement due to the always-on spin dipolar interaction. While the experimental effects of DRPs will be strongly diluted in the measured coherences of thermal (unpolarized) spin ensembles, we investigate possible signatures in coherence decays arising from a study of the combined effects of decoherence arising from instantaneous diffusion and direct flip-flops