Enhanced Electron Spin Coherence in a GaAs Quantum Emitter

TL;DR

This paper demonstrates a significant enhancement of electron spin coherence time in GaAs quantum dots through an all-optical nuclear-spin cooling scheme, advancing their use as coherent spin-photon interfaces.

Contribution

The study introduces an all-optical nuclear-spin cooling method that greatly extends electron spin coherence in GaAs quantum dots, revealing a non-collinear hyperfine interaction.

Findings

Electron spin coherence time increased 156-fold.

Presence of non-collinear hyperfine interaction in low-strain GaAs.

Potential for highly coherent, fast spin-photon interfaces.

Abstract

A spin-photon interface should operate with both coherent photons and a coherent spin to enable cluster-state generation and entanglement distribution. In high-quality devices, self-assembled GaAs quantum dots are near-perfect emitters of on-demand coherent photons. However, the spin rapidly decoheres via the magnetic noise arising from the host nuclei. Here, we address this drawback by implementing an all-optical nuclear-spin cooling scheme on a GaAs quantum dot. The electron-spin coherence time increases 156-fold from $T_2^*$ = 3.9 ns to 0.608 $\mu$s. The cooling scheme depends on a non-collinear term in the hyperfine interaction. The results show that such a term is present even though the strain is low and no external stress is applied. Our work highlights the potential of optically-active GaAs quantum dots as fast, highly coherent spin-photon interfaces.