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SiGe quantum wells with oscillating Ge concentrations for quantum dot qubits

Large-scale arrays of quantum-dot spin qubits in Si/SiGe quantum wells require large or tunable energy splittings of the valley states associated with degenerate conduction band minima. Existing proposals to deterministically enhance the valley splitting rely on sharp interfaces or modifications in...

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Autores principales: McJunkin, Thomas, Harpt, Benjamin, Feng, Yi, Losert, Merritt P., Rahman, Rajib, Dodson, J. P., Wolfe, M. A., Savage, D. E., Lagally, M. G., Coppersmith, S. N., Friesen, Mark, Joynt, Robert, Eriksson, M. A.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Nature Publishing Group UK 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9755230/
https://www.ncbi.nlm.nih.gov/pubmed/36522370
http://dx.doi.org/10.1038/s41467-022-35510-z
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author McJunkin, Thomas
Harpt, Benjamin
Feng, Yi
Losert, Merritt P.
Rahman, Rajib
Dodson, J. P.
Wolfe, M. A.
Savage, D. E.
Lagally, M. G.
Coppersmith, S. N.
Friesen, Mark
Joynt, Robert
Eriksson, M. A.
author_facet McJunkin, Thomas
Harpt, Benjamin
Feng, Yi
Losert, Merritt P.
Rahman, Rajib
Dodson, J. P.
Wolfe, M. A.
Savage, D. E.
Lagally, M. G.
Coppersmith, S. N.
Friesen, Mark
Joynt, Robert
Eriksson, M. A.
author_sort McJunkin, Thomas
collection PubMed
description Large-scale arrays of quantum-dot spin qubits in Si/SiGe quantum wells require large or tunable energy splittings of the valley states associated with degenerate conduction band minima. Existing proposals to deterministically enhance the valley splitting rely on sharp interfaces or modifications in the quantum well barriers that can be difficult to grow. Here, we propose and demonstrate a new heterostructure, the “Wiggle Well”, whose key feature is Ge concentration oscillations inside the quantum well. Experimentally, we show that placing Ge in the quantum well does not significantly impact our ability to form and manipulate single-electron quantum dots. We further observe large and widely tunable valley splittings, from 54 to 239 μeV. Tight-binding calculations, and the tunability of the valley splitting, indicate that these results can mainly be attributed to random concentration fluctuations that are amplified by the presence of Ge alloy in the heterostructure, as opposed to a deterministic enhancement due to the concentration oscillations. Quantitative predictions for several other heterostructures point to the Wiggle Well as a robust method for reliably enhancing the valley splitting in future qubit devices.
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spelling pubmed-97552302022-12-17 SiGe quantum wells with oscillating Ge concentrations for quantum dot qubits McJunkin, Thomas Harpt, Benjamin Feng, Yi Losert, Merritt P. Rahman, Rajib Dodson, J. P. Wolfe, M. A. Savage, D. E. Lagally, M. G. Coppersmith, S. N. Friesen, Mark Joynt, Robert Eriksson, M. A. Nat Commun Article Large-scale arrays of quantum-dot spin qubits in Si/SiGe quantum wells require large or tunable energy splittings of the valley states associated with degenerate conduction band minima. Existing proposals to deterministically enhance the valley splitting rely on sharp interfaces or modifications in the quantum well barriers that can be difficult to grow. Here, we propose and demonstrate a new heterostructure, the “Wiggle Well”, whose key feature is Ge concentration oscillations inside the quantum well. Experimentally, we show that placing Ge in the quantum well does not significantly impact our ability to form and manipulate single-electron quantum dots. We further observe large and widely tunable valley splittings, from 54 to 239 μeV. Tight-binding calculations, and the tunability of the valley splitting, indicate that these results can mainly be attributed to random concentration fluctuations that are amplified by the presence of Ge alloy in the heterostructure, as opposed to a deterministic enhancement due to the concentration oscillations. Quantitative predictions for several other heterostructures point to the Wiggle Well as a robust method for reliably enhancing the valley splitting in future qubit devices. Nature Publishing Group UK 2022-12-15 /pmc/articles/PMC9755230/ /pubmed/36522370 http://dx.doi.org/10.1038/s41467-022-35510-z Text en © The Author(s) 2022 https://creativecommons.org/licenses/by/4.0/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/ (https://creativecommons.org/licenses/by/4.0/) .
spellingShingle Article
McJunkin, Thomas
Harpt, Benjamin
Feng, Yi
Losert, Merritt P.
Rahman, Rajib
Dodson, J. P.
Wolfe, M. A.
Savage, D. E.
Lagally, M. G.
Coppersmith, S. N.
Friesen, Mark
Joynt, Robert
Eriksson, M. A.
SiGe quantum wells with oscillating Ge concentrations for quantum dot qubits
title SiGe quantum wells with oscillating Ge concentrations for quantum dot qubits
title_full SiGe quantum wells with oscillating Ge concentrations for quantum dot qubits
title_fullStr SiGe quantum wells with oscillating Ge concentrations for quantum dot qubits
title_full_unstemmed SiGe quantum wells with oscillating Ge concentrations for quantum dot qubits
title_short SiGe quantum wells with oscillating Ge concentrations for quantum dot qubits
title_sort sige quantum wells with oscillating ge concentrations for quantum dot qubits
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9755230/
https://www.ncbi.nlm.nih.gov/pubmed/36522370
http://dx.doi.org/10.1038/s41467-022-35510-z
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