Quantum computing and condensed matter physics with microwave photons

Nanowire Superinductance Fluxonium Qubit

T. M. Hazard, A. Gyenis, A. Di Paolo, A. T. Asfaw, S. A. Lyon, A. Blais, and A.A. Houck

Disordered superconducting materials provide a new capability to implement novel circuit designs due to their high kinetic inductance. Here, we realize a fluxonium qubit in which a long NbTiN nanowire shunts a single Josephson junction. We explain the measured fluxonium energy spectrum with a nonperturbative theory accounting for the multimode structure of the device in a large frequency range. Making use of multiphoton Raman spectroscopy, we address forbidden fluxonium transitions and observe multilevel Autler-Townes splitting. Finally, we measure lifetimes of several excited states ranging from T1 = 620 ns to T1 = 20 µs, by applying consecutive π-pulses between multiple fluxonium levels. Our measurements demonstrate that NbTiN is a suitable material for novel superconducting qubit designs.