Low-frequency spin qubit energy splitting noise in highly purified 28Si/SiGe

By Tom Struck, Arne Hollmann, Floyd Schauer, Olexiy Fedorets, A. Schmidbauer, K. Sawano, H. Riemann, N. Abrosimov, Ł. Cywiński, D. Bougeard and 1 more. npj Quantum Information, 2019

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We identify the dominant source for low-frequency spin qubit splitting noise in a highly isotopically-purified silicon device with an embedded nanomagnet and a spin echo decay time T2echo\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${T}_{2}^{\,\text{echo}}$$\end{document} = 128 µs. The power spectral density (PSD) of the charge noise explains both, the clear transition from a 1/f2- to a 1/f-dependence of the splitting noise PSD as well as the experimental observation of a decreasing time-ensemble spin dephasing time, from T2*≈\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${T}_{2}^{* }\approx$$\end{document} 20 µs, with increasing measurement time over several hours. Despite their strong hyperfine contact interaction, the few 73Ge nuclei overlapping with the quantum dot in the barrier do not limit T2*\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${T}_{2}^{* }$$\end{document}, likely because their dynamics is frozen on a few hours measurement scale. We conclude that charge noise and the design of the gradient magnetic field are the key to further improve the qubit fidelity in isotopically purified 28Si/SiGe.

Subfields: Atomic and Molecular Physics, and Optics, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/56cbfaa55815359cc0b32725d0fe20a020140157

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In Atomic and Molecular Physics, and Optics

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