Observation of coherent flux-charge interaction in a gate-tunable fluxonium

Demonstrates a drive-induced flux-charge interaction in a gate-tunable semiconductor-junction fluxonium, using parity selection rules to separate the interaction from ordinary capacitive driving.

Key Results

• Gate modulation coherently drove the even-parity $|0⟩\to |2⟩$ transition at half flux, where purely capacitive excitation is forbidden.
• The charge-insensitive-with-variable-$E_J$ (ChIVE) point retained finite flux-charge coupling while making the transition frequency first-order insensitive to gate-voltage noise.
• At the ChIVE point, the $|0⟩\to |2⟩$ transition was 3.61 GHz; the supplementary measurements reported $T_1=6.62\mu \mathrm{s}$ and Ramsey $T_2=144$ ns for that transition.

Links

• arXiv: 2607.07798

Zoo Links

• gatemonium
• fluxonium