Fast control of low-frequency fluxonium qubits*

The fluxonium qubit is a promising superconducting qubit for high fidelity quantum computing systems, due to its long coherence times. Fluxonium qubits operate at lower frequencies than typical superconducting qubits, yet have larger anharmonicities.  We adapt the methods of readout, initialization, control, and two qubit logic to this unique regime. In this talk, we present a design of two inductively coupled fluxonium qubits with a tunable coupler that can realize 0-60 MHz coupling rate in a 2D structure. We demonstrate a set of control protocols for low frequency fluxonium qubits, including state initialization based on readout feedback, fast single and two qubit gates with flux pulses, and high fidelity single shot readout. With these control options, we can take full advantage of the large anharmonicity and long coherence times of fluxonium qubits, and demonstrate its potential for realizing large scale quantum processors.