Universal nuclear focusing of confined electron spins

Sergej Markmann,Gian Salis,Werner Wegscheider,Christian Reichl

doi:10.1038/s41467-019-08882-y

Sergej Markmann, Gian Salis + Show 2 more

Open Access

https://doi.org/10.1038/s41467-019-08882-y

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Journal: Nature Communications	Publication Date: Mar 7, 2019
Citations: 11	License type: open-access

Affiliation: IBM Research - Zurich, ETH Zurich

Abstract

For spin-based quantum computation in semiconductors, dephasing of electron spins by a fluctuating background of nuclear spins is a main obstacle. Here we show that this nuclear background can be precisely controlled in generic quantum dots by periodically exciting electron spins. We demonstrate this universal phenomenon in many-electron GaAs/AlGaAs quantum dot ensembles using optical pump-probe spectroscopy. A feedback mechanism between the electron spin polarization and the nuclear system focuses the electron spin precession frequency into discrete spin modes. Employing such control of nuclear spin polarization, the electron spin lifetime within individual dots can surpass the limit of nuclear background fluctuations, thus substantially enhancing the spin coherence time. This opens the door to achieve long electron spin coherence times also in lithographically defined many-electron systems that can be controlled in shape, size and position.

Highlights

For spin-based quantum computation in semiconductors, dephasing of electron spins by a fluctuating background of nuclear spins is a main obstacle
By these mechanisms, the nuclear spin polarization becomes locked within a distribution that can be much narrower than the typical low-frequency fluctuations of nuclear spins in quantum dots (QDs), enabling long spin lifetimes in systems with nuclear background noise
We have shown that the precession of localized electron spins in nano- and micrometer-sized structures can be synchronized to a periodic drive

Summary

Introduction

For spin-based quantum computation in semiconductors, dephasing of electron spins by a fluctuating background of nuclear spins is a main obstacle. From optical pump-probe measurements, we find that mode-locking is absent for depolarized nuclear spins and emerges slowly (time scale of seconds) once the laser excitation pulse train is turned on.

Results

Conclusion