Strong coupling of a microwave photon to an electron on helium

Nature Physics (2026) Cite this article Electrons bound to the surface of superfluid helium have been proposed as a scalable platform for charge- and spin-based quantum computing. Cavity quantum electrodynamics provides a promising method to implement quantum measurement and control of superfluid helium-bound electrons. In this approach, a cavity amplifies the strength of the interaction between the electron and a single photon for coherent exchange of quantum information and qubit readout. This strong coupling regime has been used for quantum measurement in different platforms such as superconducting qubits, atoms and semiconductor quantum dots. Here we demonstrate strong coupling between a microwave photon and the quantized motional state of a single electron on helium using a device comprising a quantum dot and superconducting resonator. Access to this regime provides a basis for developing single-electron spin qubit readout protocols using spin–orbit hybridization techniques that have already been demonstrated in semiconductor quantum dots.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.20086616 (ref. 32). Source data are provided with this paper.The codes used to analyse the datasets are available via Zenodo at https://doi.org/10.5281/zenodo.20086616 (ref. 32).Platzman, P. M. & Dykman, M. I. Quantum computing with electrons floating on liquid helium. Science 284, 1967–1969 (1999).Article Google Scholar Dykman, M. I., Platzman, P. M. & Seddighrad, P. Qubits with electrons on liquid helium. Phys. Rev. B 67, 155402 (2003).Article ADS Google Scholar Schuster, D. I., Fragner, A., Dykman, M. I., Lyon, S. A. & Schoelkopf, R. J. Proposal for manipulating and detecting spin and orbital states of trapped electrons on helium using cavity quantum electrodynamics. Phys. Rev. Lett. 105, 040503 (2010).Article ADS Google Scholar Lyon, S. A. Spin-based quantum computing using electrons on liquid helium. Phys. Rev. A 74, 052338 (2006).Article ADS Google Scholar Kawakami, E., Chen, J., Benito, M. & Konstantinov, D. Blueprint for quantum computing using electrons on helium. Phys. Rev. Appl. 20, 054022 (2023).Article ADS Google Scholar Bradbury, F. R. et al. Efficient clocked electron transfer on superfluid helium. Phys. Rev. Lett. 107, 266803 (2011).Article ADS Google Scholar Castoria, K. E. et al. Sensing and control of single trapped electrons above 1 K. Phys. Rev. X 15, 041002 (2025).

Google Scholar Koolstra, G., Yang, G. & Schuster, D. I. Coupling a single electron on superfluid helium to a superconducting resonator. Nat. Commun. 10, 5323 (2019).Article ADS Google Scholar Wallraff, A. et al. Strong coupling of a single photon to a superconducting qubit using circuit quantum electrodynamics. Nature 431, 162–167 (2004).Article ADS Google Scholar Chiorescu, I. et al. Coherent dynamics of a flux qubit coupled to a harmonic oscillator. Nature 431, 159–162 (2004).Article ADS Google Scholar Boca, A. et al. Observation of the vacuum rabi spectrum for one trapped atom. Phys. Rev. Lett. 93, 233603 (2004).Article ADS Google Scholar Maunz, P. et al. Normal-mode spectroscopy of a single-bound-atom–cavity system. Phys. Rev. Lett. 94, 033002 (2005).Article ADS Google Scholar Samkharadze, N. et al. Strong spin–photon coupling in silicon. Science 359, 1123–1127 (2018).Article ADS Google Scholar Mi, X. et al. A coherent spin–photon interface in silicon. Nature 555, 599–603 (2018).Article ADS Google Scholar Glasson, P. et al. Observation of dynamical ordering in a confined wigner crystal. Phys. Rev. Lett. 87, 176802 (2001).Article ADS Google Scholar Koolstra, G. et al. High-impedance resonators for strong coupling to an electron on helium. Phys. Rev. Appl. 23, 024001 (2025).Article ADS Google Scholar Zhou, X. et al. Single electrons on solid neon as a solid-state qubit platform. Nature 605, 46–50 (2022).Article ADS Google Scholar Beysengulov, N. ZeroHelilumKit. Zenodo https://doi.org/10.5281/zenodo.19985198 (2026).Rieger, D. et al. Fano interference in microwave resonator measurements. Phys. Rev. Appl. 20, 014059 (2023).Article ADS Google Scholar Sanchez-Mondragon, J. J., Narozhny, N. B. & Eberly, J. H. Theory of spontaneous-emission line shape in an ideal cavity. Phys. Rev. Lett. 51, 550–553 (1983).Article ADS Google Scholar Mi, X., Cady, J. V., Zajac, D. M., Deelman, P. W. & Petta, J. R. Strong coupling of a single electron in silicon to a microwave photon. Science 355, 156–158 (2017).Article ADS Google Scholar Burkard, G., Gullans, M. J., Mi, X. & Petta, J. R. Superconductor–semiconductor hybrid-circuit quantum electrodynamics. Nat. Rev. Phys. 2, 129–140 (2020).Article Google Scholar Schuster, D. I. et al. ac Stark shift and dephasing of a superconducting qubit strongly coupled to a cavity field. Phys. Rev. Lett. 94, 123602 (2005).Article ADS Google Scholar Dykman, M. I., Asban, O., Chen, Q., Jin, D. & Lyon, S. A. Spin dynamics in quantum dots on liquid helium. Phys. Rev. B 107, 035437 (2023).Article ADS Google Scholar Rojas-Arias, J. S. et al. Spatial noise correlations beyond nearest neighbors in 28Si/Si-Ge spin qubits. Phys. Rev. Appl. 20, 054024 (2023).Article ADS Google Scholar Li, X. et al. Solid neon as a noise-resilient host for electron qubits above 100 mK. Nat. Electron. https://doi.org/10.1038/s41928-026-01613-4 (2026).Krantz, P. et al. A quantum engineer’s guide to superconducting qubits. Appl. Phys. Rev. 6, 021318 (2019).Article ADS Google Scholar Li, J. Room temperature reactive sputtering deposition of titanium nitride with high sheet kinetic inductance. Preprint at https://arxiv.org/abs/2509.14133 (2025).Frisk Kockum, A., Miranowicz, A., De Liberato, S., Savasta, S. & Nori, F. Ultrastrong coupling between light and matter. Nat. Rev. Phys. 1, 19–40 (2019).Article Google Scholar Yang, G. et al. Coupling an ensemble of electrons on superfluid helium to a superconducting circuit. Phys. Rev. X 6, 011031 (2016).

Google Scholar Mikolas, C. A. et al. Plasmon mode engineering with electrons on helium. Nat. Commun. 16, 4959 (2025).Article ADS Google Scholar Koolstra, G. et al. Strong coupling of a microwave photon to an electron on helium. Zenodo https://doi.org/10.5281/zenodo.20086616 (2026).Download referencesWe thank J. Theis for technical support. We also acknowledge C. Wang, B. Dizdar, D. Schuster, J. Lane and M. Dykman for helpful discussions. This work made use of the Pritzker Nanofabrication Facility, part of the Pritzker School of Molecular Engineering at the University of Chicago, which receives support from Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633), a node of the National Science Foundation’s National Nanotechnology Coordinated Infrastructure (RRID: SCR_022955).These authors contributed equally: Gerwin Koolstra, Elena O. Glen, Niyaz R. Beysengulov.EeroQ Corporation, Chicago, IL, USAGerwin Koolstra, Elena O. Glen, Niyaz R. Beysengulov, Heejun Byeon, Kyle E. Castoria, Michael Sammon, Stephen A. Lyon, David G. Rees & Johannes PollanenSearch 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 ScholarG.K. and E.O.G. performed the experiments with assistance from N.R.B., D.G.R. and K.E.C. The data were analysed by G.K. and E.G. N.R.B. conceived of the device design. N.R.B. and M.S. designed and simulated the device, which was fabricated by H.B. Theoretical calculations to support the experimental work were primarily performed by G.K. and M.S. E.O.G., G.K., N.R.B and J.P. prepared the paper with input from all authors. J.P., S.A.L. and D.G.R. supervised and assisted in the project and provided guidance.Correspondence to Johannes Pollanen.The authors declare no competing interests.Nature Physics thanks Kimitoshi Kono, Alexander Korsch and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.Supplementary Figs. 1–16 and Tables 1–3.Contains .txt and .jpeg data for Fig. 1.Contains .txt data for Fig. 2.Contains .txt data for Fig. 3.Contains .txt data for Fig. 4.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 permissionsKoolstra, G., Glen, E.O., Beysengulov, N.R. et al. Strong coupling of a microwave photon to an electron on helium. Nat. Phys. (2026). https://doi.org/10.1038/s41567-026-03342-zDownload citationReceived: 14 November 2025Accepted: 21 May 2026Published: 15 June 2026Version of record: 15 June 2026DOI: https://doi.org/10.1038/s41567-026-03342-zAnyone 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