Suppression of nuclear spin fluctuations in an InGaAs quantum dot ensemble by GHz-pulsed optical excitation

TL;DR

This paper demonstrates that GHz-pulsed optical excitation can suppress nuclear spin fluctuations in InGaAs quantum dot ensembles, enabling more stable electron spin dynamics and improved control for quantum information applications.

Contribution

It introduces a method to coherently control and suppress nuclear spin fluctuations in quantum dots using GHz optical pulses, even amidst inhomogeneity.

Findings

Ensemble of quantum dots can be driven into a single Larmor precession mode.

Optical detuning induces directed dynamic nuclear polarization.

Periodic optical excitation reduces nuclear spin fluctuations effectively.

Abstract

The coherent electron spin dynamics of an ensemble of singly charged (In,Ga)As/GaAs quantum dots in a transverse magnetic field is driven by periodic optical excitation at 1 GHz repetition frequency. Despite the strong inhomogeneity of the electron $g$ factor, the spectral spread of optical transitions, and the broad distribution of nuclear spin fluctuations, we are able to push the whole ensemble of excited spins into a single Larmor precession mode that is commensurate with the laser repetition frequency. Furthermore, we demonstrate that an optical detuning of the pump pulses from the probed optical transitions induces a directed dynamic nuclear polarization and leads to a discretization of the total magnetic field acting on the electron ensemble. Finally, we show that the highly periodic optical excitation can be used as universal tool for strongly reducing the nuclear spin fluctuations and preparation of a robust nuclear environment for subsequent manipulation of the electron spins, also at varying operation frequencies.