Decoherence mechanisms in a fluxonium qubit

We report measurements of energy relaxation (T1) and dephasing (T2) of various transitions of a flux-tunable 3D fluxonium circuit. Relaxation measurements span an order of magnitude frequency variation of qubit transitions (1 - 10 GHz) and the observed lifetimes vary from microseconds to milliseconds. We utilize flux knob to enhance/reduce the sensitivity of the qubit to Purcell effect, dielectric loss, and quasiparticle tunneling. T2 measurement is performed both at the spots maximally-sensitive to flux noise - where it never drops below a microsecond - and at the flux sweet spots.