Fundamental limits of electron and nuclear spin qubit lifetimes in an isolated self-assembled quantum dot

Abstract

Combining external control with long spin lifetime and coherence is a key challenge for solid state spin qubits. Tunnel coupling with electron Fermi reservoir provides robust charge state control in semiconductor quantum dots, but results in undesired relaxation of electron and nuclear spins through mechanisms that lack complete understanding. Here, we unravel the contributions of tunnelling-assisted and phonon-assisted spin relaxation mechanisms by systematically adjusting the tunnelling coupling in a wide range, including the limit of an isolated quantum dot. These experiments reveal fundamental limits and trade-offs of quantum dot spin dynamics: while reduced tunnelling can be used to achieve electron spin qubit lifetimes exceeding 1 s, the optical spin initialisation fidelity is reduced below 80%, limited by Auger recombination. Comprehensive understanding of electron-nuclear spin relaxation attained here provides a roadmap for design of the optimal operating conditions in quantum dot spin qubits.

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Item Type:	Article
Authors/Creators:	Gillard, G. Griffiths, I.M. https://orcid.org/0000-0002-2744-3931 Ragunathan, G. Ulhaq, A. McEwan, C. Clarke, E. https://orcid.org/0000-0002-8287-0282 Chekhovich, E.A. https://orcid.org/0000-0003-1626-9015
Copyright, Publisher and Additional Information:	© The Author(s) 2021. Open Access: This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.
Dates:	Published: 24 February 2021 Published (online): 24 February 2021 Accepted: 26 January 2021
Institution:	The University of Sheffield
Academic Units:	The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Electronic and Electrical Engineering (Sheffield) The University of Sheffield > Faculty of Science (Sheffield) > Department of Physics and Astronomy (Sheffield)
Funding Information:	Funder Grant number ENGINEERING AND PHYSICAL SCIENCE RESEARCH COUNCIL EP/N031776/1
Depositing User:	Symplectic Sheffield
Date Deposited:	15 Mar 2021 16:18
Last Modified:	15 Mar 2021 16:18
Status:	Published
Publisher:	Springer Science and Business Media LLC
Refereed:	Yes
Identification Number:	10.1038/s41534-021-00378-2
Open Archives Initiative ID (OAI ID):	oai:eprints.whiterose.ac.uk:171792

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Fundamental limits of electron and nuclear spin qubit lifetimes in an isolated self-assembled quantum dot

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