Controlling the charge dispersion of a nearly-open superconducting island*

We investigate the charge dispersion of a nanowire transmon hosting an accidental resonant level in the junction. We observe rapid suppression of the charge dispersion consistent with the scaling law resulting from diabatic transitions between Andreev bound states. We also observe improved qubit coherence times at the point of highest charge dispersion suppression. Our observations further our fundamental understanding of charging effects in superconductors and suggests novel approaches for building charge-insensitive qubits. Finally, we will discuss prospects for exploring the competition between superconductivity and Coulomb blockade by embedding a gate-defined quantum dot in the junction of the nanowire transmon.