Integer Fluxonium Qubit

We describe a superconducting qubit derived from operating a properly designed fluxonium circuit in a zero magnetic field. The qubit has a frequency of about 4 GHz and an energy relaxation quality factor Q approximate to 0.7 x 10(7), even though the dielectric loss quality factor of the circuit components is in the low-105 range. The Ramsey coherence time exceeds 100 mu s, and the average fidelity of Clifford gates is benchmarked to F > 0.999. These figures are expected to improve with optimized fabrication and measurement procedures. Our work establishes a ready-to-use "partially protected" superconducting qubit functioning in the frequency range of conventional transmons.