Non-local nuclear spin quieting in quantum dot molecules: Optically-induced extended two-electron spin coherence time

TL;DR

This paper demonstrates that optical control of one quantum dot in a molecule can non-locally suppress nuclear spin fluctuations, significantly extending two-electron spin coherence times in quantum dot molecules.

Contribution

It introduces a method to extend electron spin coherence by non-locally quieting nuclear spins through optical addressing of a single quantum dot in a molecule.

Findings

Extended two-electron spin coherence times observed.

Nuclear spin fluctuations suppressed non-locally.

First measurement of Overhauser field distribution quieting.

Abstract

We demonstrate the extension of coherence between all four two-electron spin ground states of an InAs quantum dot molecule (QDM) via non-local suppression of nuclear spin fluctuations in both constituent quantum dots (QDs), while optically addressing only the upper QD transitions. Long coherence times are revealed through dark-state spectroscopy as resulting from nuclear spin locking mediated by the exchange interaction between the QDs. Lineshape analysis provides the first measurement of the quieting of the Overhauser field distribution correlating with reduced nuclear spin fluctuations.