Deterministic preparation of spin qubits in droplet etched GaAs quantum dots using quasi-resonant excitation

TL;DR

This paper demonstrates a method for deterministic spin state preparation in GaAs quantum dots using quasi-resonant excitation, achieving high fidelity and providing insights into decay times and environmental effects.

Contribution

It introduces a novel excitation scheme for spin preparation in GaAs quantum dots with high fidelity and analyzes the impact on quantum dot properties and coherence.

Findings

Achieved 85% maximum spin preparation fidelity.

Observed non-radiative decay times as low as 29 ps.

Showed excitation scheme influences quantum dot charge and coherence.

Abstract

We present a first comprehensive study on deterministic spin preparation employing excited state resonances of droplet etched GaAs quantum dots. This achievement facilitates future investigations of spin qubit based quantum memories using the GaAs quantum dot material platform. By observation of excitation spectra for a range of fundamental excitonic transitions the properties of different quantum dot energy levels, i.e. shells, are revealed. The innovative use of polarization resolved excitation and detection in quasi-resonant excitation spectroscopy facilitates determination of $85$ $\%$ maximum spin preparation fidelity - irrespective of the relative orientations of lab and quantum dot polarization eigenbases. Additionally, the characteristic non-radiative decay time is investigated as a function of ground state, excitation resonance and excitation power level, yielding decay times as low as $29$ ps for s-p-shell exited state transitions. Finally, by time resolved correlation spectroscopy it is demonstrated that the employed excitation scheme has a significant impact on the electronic environment of quantum dot transitions thereby influencing its charge and coherence.