Understanding drive-induced state transitions in fluxonium: part 1/2

Fluxonium is a promising qubit platform with long coherence times. Systematically achieving fast, high-fidelity readout in fluxonium qubits is crucial to their scaling up. Stronger coupling and a stronger drive through the readout resonator dispersively coupled to the qubit typically improve the signal-to-noise ratio of the readout. However, recent work has shown that drives can induce undesired measurement-induced transitions, degrading the quantum non-demolition (QND) character of the readout.

In this presentation, we experimentally study dispersive readout of fluxonium qubits. We use Floquet calculations and multilevel branch analysis to model and understand the observed features. In part 1 of this two-part talk, we will discuss the loss of QND-ness when driving near the resonator frequency, as a function of resonator drive power and qubit flux.