Electron shelving of a superconducting artificial atom

Area of Science:

• Quantum technology
• Superconducting qubits
• Quantum information science

Background:

• Interfacing long-lived qubits with photons is crucial for quantum technologies.
• Cavity quantum electrodynamics (cQED) uses off-resonant cavities for qubit control and readout.
• Existing cQED architectures face limitations in resource efficiency.

Purpose of the Study:

• To demonstrate a cavityless approach for controlling superconducting qubits.
• To implement quantum non-demolition (QND) readout using the electron shelving effect.
• To establish a resource-efficient alternative to cQED.

Main Methods:

• Utilizing a three-level system in a fluxonium circuit within a microwave waveguide.
• Employing the electron shelving effect for qubit control.
• Implementing QND readout via homodyne detection of fluorescence from a cycling transition.

Main Results:

• Achieved qubit coherence times exceeding 50 μs.
• Observed a cycling transition radiative lifetime under 100 ns.
• Successfully implemented QND readout of the fluxonium qubit.
• Accounted for readout errors using an optical pumping model.

Conclusions:

• Demonstrated a viable cavityless control and readout scheme for superconducting qubits.
• The electron shelving effect provides a resource-efficient alternative to cQED.
• This method advances the development of scalable quantum technologies.