Fast initialization of the spin state of an electron in a quantum dot in the Voigt configuration

TL;DR

This paper demonstrates a rapid and high-fidelity method for initializing an electron spin in a quantum dot using optical pumping in a Voigt magnetic field configuration, significantly outperforming traditional parallel field setups.

Contribution

It introduces a fast, high-fidelity spin initialization technique in quantum dots by applying a perpendicular magnetic field, surpassing previous methods reliant on slower hole spin-flip processes.

Findings

Near-unity fidelity achievable within a few trion relaxation times

The Voigt configuration is several orders faster than the parallel field setup

Error rates are very small for InAs quantum dots

Abstract

We consider the initialization of the spin-state of a single electron trapped in a self-assembled quantum dot via optical pumping of a trion level. We show that with a magnetic field applied perpendicular to the growth direction of the dot, a near-unity fidelity can be obtained in a time equal to a few times the inverse of the spin-conserving trion relaxation rate. This method is several orders-of-magnitude faster than with the field aligned parallel, since this configuration must rely on a slow hole spin-flip mechanism. This increase in speed does result in a limit on the maximum obtainable fidelity, but we show that for InAs dots, the error is very small.