Coherence of a dynamically decoupled quantum-dot hole spin

TL;DR

This paper investigates the coherence properties of a heavy hole spin in an InGaAs quantum dot, demonstrating how dynamical decoupling extends the spin's coherence time to 4.4 microseconds by understanding and mitigating decoherence mechanisms.

Contribution

It identifies regimes for high coherence in hole spins and shows how dynamical decoupling significantly prolongs coherence time in these quantum dot systems.

Findings

Crossover from hyperfine to electrical-noise dominated decoherence with magnetic field

Longest observed ground-state coherence time of 4.4 microseconds

Quantitative support from analysis of local electrical environment

Abstract

A heavy hole confined to an InGaAs quantum dot promises the union of a stable spin and optical coherence to form a near perfect, high-bandwidth spin-photon interface. Despite theoretical predictions and encouraging preliminary measurements, the dynamic processes determining the coherence of the hole spin are yet to be understood. Here, we establish the regimes that allow for a highly coherent hole spin in these systems, recovering a crossover from hyperfine to electrical-noise dominated decoherence with a few-Tesla external magnetic field. Dynamical decoupling allows us to reach the longest ground-state coherence time, T2, of 4.4 $\mu$s, observed in this system. The improvement of coherence we measure is quantitatively supported by an independent analysis of the local electrical environment.