Optimal operation of hole spin qubits

Nature Physics (2025)Cite this article Hole spins in silicon or germanium quantum dots have emerged as a capable platform for scalable solid-state quantum processors. In addition to benefiting from well-established manufacturing technologies, the large spin–orbit coupling of hole spin qubits enables fast control mediated by an electric field. Unfortunately, this coupling typically makes hole spin qubits susceptible to charge noise, which usually limits qubit coherence. Here we experimentally establish the existence of so-called sweet lines in the parameter space of field orientation where the qubit becomes insensitive to charge noise. We do this by varying the direction of a magnetic field applied to a silicon metal–oxide–semiconductor hole qubit. We also find that the observed sweet lines contain the points of maximal driving efficiency, in agreement with recent theoretical predictions. Furthermore, we show that moderate adjustments in gate voltages can substantially shift the sweet lines. This tunability allows several qubits to be simultaneously made insensitive to electrical noise, making it possible to design scalable qubit architectures that feature all-electrical spin control of many qubits.This is a preview of subscription content, access via your institution Access Nature and 54 other Nature Portfolio journals Get Nature+, our best-value online-access subscription $32.99 / 30 days cancel any timeSubscribe to this journal Receive 12 print issues and online access $259.00 per yearonly $21.58 per issueBuy this articleUSD 39.95Prices may be subject to local taxes which are calculated during checkoutAll data underlying this study are available via Zenodo at https://doi.org/10.5281/zenodo.17378720 (ref. 40).Maurand, R. et al. A CMOS silicon spin qubit. Nat. Commun. 7, 13575 (2016).Watzinger, H. et al. A germanium hole spin qubit. Nat. 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Zenodo https://doi.org/10.5281/zenodo.17378720 (2025).Download referencesThis work is supported by the French National Research Agency under the programme France 2030 (PEPR PRESQUILE - ANR-22-PETQ-0002), by the European Union’s Horizon 2020 research innovation programme through projects QLSI1 and QLSI2 (Grant Agreement Nos. 951852 and 101135712, respectively) and the European Research Council project QuCube (Grant Agreement No. 810504). J.C.A.-U. is supported by Grant Nos. RYC2022-037527-I and PID2023-148257NA-I00 funded by MCIU/AEI/10.13039/501100011033 and by the ESF+. V.C. acknowledges support from the Program QuantForm-UGA ANR-21-CMAQ-0003 France 2030 and by the LabEx LANEF ANR-10-LABX-51-01.Université Grenoble Alpes, CEA, Grenoble INP, IRIG, Pheliqs, Grenoble, FranceM. Bassi, B. Brun, S. Zihlmann, T. Nguyen, V. Champain, R. Maurand, X. Jehl, S. De Franceschi & V. SchmittUniversity Grenoble Alpes, CEA, IRIG-MEM-L_Sim, Grenoble, FranceE. A. Rodríguez-Mena, J. C. Abadillo-Uriel & Y.-M. NiquetInstituto de Ciencia de Materiales de Madrid, CSIC, Madrid, SpainJ. C. Abadillo-UrielUniversité Grenoble Alpes, CEA, LETI, Minatec Campus, Grenoble, FranceB. Bertrand & H. NiebojewskiSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarM.B., B. Brun, T.N., V.C. and V.S. performed the experiments with support from S.Z., R.M. and X.J. and advice from all co-authors. M.B, E.A.R.-M., J.C.A.-U., Y.-M.N. and V.S. performed the simulations and the data analysis. B. Bertrand and H.N. designed and supervised the fabrication of the device. M.B., E.A.R.-M., Y.-M.N., S.D.F. and V.S. co-wrote the paper with input from all co-authors. V.S. led the experiments. S.D.F. initiated the project.Correspondence to S. De Franceschi or V. Schmitt.The authors declare no competing interests.Nature Physics thanks Hendrik Bluhm and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.Blue (red) points are g-factors measured by EDSR of Q3 (Q4). Solid lines are the fitted g-factors using the g-matrix formalism presented in Methods and Supplementary Section 2. The g-factor configuration presented for the qubit Q3 correspond to the left panel of Fig. 2. The tilt of the principal axes of the lobes with respect to the device axes is most likely due to inhomogeneous strains14,24,25.a Ramsey coherence time (green points) plotted as a function of magnetic field angle θ in the sample plane. In red are depicted the absolute values of β∥(T3) and the corresponding fit presented in the main text. Dashed lines evidence the sweet-spot positions where the coherence time is expected to increase. b Inverse of Hahn-Echo coherence time plotted as a function of magnetic field direction in the sample plane (NP). The red solid line is the fit to ∣β∥(T3)∣ presented in the main text. c Rabi frequency variations according to magnetic field direction in the sample plane (NP). Red line and points (fit) represent ∣β∥(T3)∣. At the sweet-spot orientations two distinct cases are observed: one sweet spot with a fast electrical control (θ = − 20°) and the second one (θ = 35°) with a much slower Rabi frequency.Supplementary Sections I–V and Figs. 1–5.Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.Reprints and permissionsBassi, M., Rodríguez-Mena, E.A., Brun, B. et al. Optimal operation of hole spin qubits. Nat. Phys. (2025). https://doi.org/10.1038/s41567-025-03106-1Download citationReceived: 11 February 2025Accepted: 21 October 2025Published: 12 December 2025Version of record: 12 December 2025DOI: https://doi.org/10.1038/s41567-025-03106-1Anyone you share the following link with will be able to read this content:Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative