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
Published: 2025/9/18
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.