Fast flux qubit gates on a heavy fluxonium*

A capacitively shunted fluxonium qubit has both long life time and coherence time at the half-flux sweet spot. However, the suppressed matrix elements and low transition frequency make it challenging to perform fast fluxon gates via charge coupling. Here, we present schemes for state initialization, fast single-qubit flux gates, and plasmon assisted readout for a fluxonium qubit, demonstrating the feasibility of controlling a superconducting qubit at background temperatures much higher than the operating frequency. This scheme improves the quantum control of fluxonium qubits, making it a strong candidate for quantum information processing. We additionally present schemes for fluxonium two-qubit gates without using lossier higher levels.