Suppressing Spin Qubit Dephasing by Nuclear State Preparation

TL;DR

This paper demonstrates a method to prepare nuclear spins in GaAs quantum dots, significantly reducing decoherence and extending qubit coherence times, which enhances the potential for scalable quantum computing.

Contribution

It introduces a practical electrical gate technique to prepare nuclear spins, suppressing fluctuations and prolonging spin coherence in semiconductor quantum dots.

Findings

Nuclear spin fluctuations reduced by a factor of ~70

Inhomogeneous dephasing time extended beyond 1 microsecond

Nuclear state persists for over 10 seconds

Abstract

Coherent spin states in semiconductor quantum dots offer promise as electrically controllable quantum bits (qubits) with scalable fabrication. For few-electron quantum dots made from gallium arsenide (GaAs), fluctuating nuclear spins in the host lattice are the dominant source of spin decoherence. We report a method of preparing the nuclear spin environment that suppresses the relevant component of nuclear spin fluctuations below its equilibrium value by a factor of ~ 70, extending the inhomogeneous dephasing time for the two-electron spin state beyond 1 microsecond. The nuclear state can be readily prepared by electrical gate manipulation and persists for > 10 seconds.