Engineering selection rules of transitions in a multi-level fluxonium superconducting artificial atom

Snacks and Drinks at 4 pm.

A Fluxonium artificial atom is a multi-level system with tunable transition dipole, which allows us to engineer selections rules of transitions. In this talk will demonstrate measurements of the energy decay time T1 in a specially designed fluxonium circuit as a function of its flux-tunable transition dipole. Remarkably, T1 grew by two orders of magnitude proportionally to the inverse transition dipole squared and reached values above 2 ms without signs of saturation. This is the first time demonstrated a hardware-level protection of a superconducting qubit against bit-flip errors. I will also demonstrate a fluorescence "shelving" readout scheme of atomic physics applied to a fluxonium artificial atom. In this scheme, the short-lived readout transition is tuned in the passband of a 3D waveguide while the long-lived qubit transition is below the waveguide’s cutoff frequency. The state of qubit can be measured by measuring reflection coefficient at frequency of readout transition. Such device can also serve as a tool to characterize and optimize thermalization of the measurement lines in superconducting qubit experiments.