Electron shelving of a superconducting artificial atom

Interfacing long-lived qubits with propagating photons is crucial in quantum technology. This paper demonstrates electron shelving in a fluxonium circuit atom coupled to a microwave waveguide, eliminating the need for a cavity resonator. The qubit coherence time exceeds 50 µs, while the cycling transition's radiative lifetime is under 100 ns. A quantum non-demolition (QND) readout is implemented via homodyne fluorescence detection, with readout errors modeled using an optical pumping model. This cavityless approach provides a resource-efficient alternative to conventional circuit quantum electrodynamics (cQED).

Nathanaël Cottet, Haonan Xiong, Long B. Nguyen, Yen-Hsiang Lin, Vladimir E. Manucharyan