Coherence of a hole-spin flopping-mode qubit in a circuit quantum electrodynamics environment

Nature Physics (2026)Cite this article The entanglement of microwave photons and spin qubits in silicon represents an important step forwards for quantum information processing using semiconductor quantum dots. Such hybrid spin circuit quantum electrodynamics experiments have been achieved by delocalizing spins in a double quantum dot with spin–orbit interactions to produce a flopping-mode spin qubit with a substantial electric dipole moment. Unfortunately, demonstrations of these qubits have not shown the coherence properties necessary for them to be used as practical single qubits. Here we present a flopping-mode hole-spin qubit in a silicon nanowire coupled to a high-impedance niobium nitride microwave read-out resonator. We report Rabi frequencies exceeding 100 MHz with coherence times in the microsecond range, resulting in a single-gate quality factor of 380. This establishes the speed and reliability of flopping-mode spin qubits. Moreover, using the large frequency tunability of the qubit, we find that radiative decay is the main relaxation channel in our experiment and argue that photon shot noise is the main source of dephasing. These results indicate that optimized microwave engineering can unlock the potential of flopping-mode spin qubits in hybrid circuit quantum electrodynamics architectures and offer a scalable and robust platform for fast and coherent spin qubits with strong coupling to microwave photons.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 checkoutThe datasets generated and analysed during the current study are available via Zenodo at https://doi.org/10.5281/zenodo.18683389 (ref. 52).The code used to analyse the datasets are available via Zenodo at https://doi.org/10.5281/zenodo.18683389 (ref. 52).Burkard, G., Ladd, T. 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This research has been supported by the European Union’s Horizon 2020 research and innovation programme (Grant Agreement Nos. 951852 (QLSI project), 810504 (ERC project QuCube), 759388 (ERC project LONGSPIN) and. 101174557 (QLSI2)) and by the National Strategy France 2030 (Projects PEPR PRESQUILE ANR-22-PETQ-0002 and PEPR MiraclQ ANR-23-PETQ-0003). S.Z. acknowledges support from the spin–photon PEPR chair. J.C.A.-U. is supported by the Spanish Ministry of Science, innovation and Universities (Grant Nos. PID2023- 148257NA-I00 and RYC2022-037527-I).University of Grenoble Alpes, CEA, Grenoble INP, IRIG-Pheliqs, Grenoble, FranceLéo Noirot, Cécile X. Yu, Étienne Dumur, Romain Maurand & Simon ZihlmannQuTech and Kavli Institute of Nanoscience, Delft University of Technology, Delft, The NetherlandsCécile X. YuUniversity of Grenoble Alpes, CEA, IRIG-MEM-L_Sim, Grenoble, FranceJosé C. Abadillo-UrielInstituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Madrid, SpainJosé C. Abadillo-UrielUniversity of Grenoble Alpes, CEA, LETI, Minatec Campus, Grenoble, FranceHeimanu Niebojewski & Benoit BertrandSearch 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 ScholarC.X.Y. fabricated the NbN circuitry with help from S.Z. L.N. performed the measurements with the help of S.Z. L.N. analysed the data with input from R.M., É.D. and S.Z. J.C.A.-U. developed the theoretical model and helped in the interpretation of the data. L.N., R.M. and S.Z. co-wrote the Article with input from all authors. H.N. and B.B. were responsible for the front-end fabrication of the device. S.Z. supervised the work.Correspondence to Léo Noirot or Simon Zihlmann.The authors declare no competing interests.Nature Physics thanks Uri Vool 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.Supplementary information including Figs. 1–16 and Table 1.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 permissionsNoirot, L., Yu, C.X., Abadillo-Uriel, J.C. et al. Coherence of a hole-spin flopping-mode qubit in a circuit quantum electrodynamics environment. Nat. Phys. (2026). https://doi.org/10.1038/s41567-026-03262-yDownload citationReceived: 13 March 2025Accepted: 23 March 2026Published: 01 May 2026Version of record: 01 May 2026DOI: https://doi.org/10.1038/s41567-026-03262-yAnyone 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