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arXiv · 2509.14506

Strong coupling of a microwave photon to an electron on helium

G. Koolstra·E. O. Glen·N. R. Beysengulov·H. Byeon·K. E. Castoria·M. Sammon·S. A. Lyon·D. G. Rees·J. Pollanen
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Abstract

Electrons bound to the surface of superfluid helium have been proposed for scalable charge and spin-based quantum computing. However single electron quantum measurement in this system has remained elusive. Here we use a hybrid circuit quantum electrodynamic (cQED) device that comprises a quantum dot and a high-impedance superconducting resonator to demonstrate, for the first time, strong coupling between the resonator microwave field and the motional quantum state of the electron. We find a coupling strength between the electron motion and a resonator photon of $g/2\pi=118$ MHz, exceeding both the electron motional state decoherence and the resonator loss. These experiments open new avenues for investigating light-matter interaction at the single electron level, and are a key step towards measurement and control of electrons on helium-based spin qubits.

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G. Koolstra, E. O. Glen, N. R. Beysengulov, H. Byeon, K. E. Castoria, M. Sammon, S. A. Lyon, D. G. Rees, J. Pollanen. 2025-09-18. Strong coupling of a microwave photon to an electron on helium. https://doi.org/10.1038/s41567-026-03342-z

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