Fast microwave-driven two-qubit gates between fluxonium qubits with a transmon coupler

Superconducting qubits have enabled recent progress in experiments with large quantum computing circuits. In these, transmon has been the broadly used qubit of choice. To further

improve the performance of such circuits, the introduction of the fluxonium qubit can bring added benefits of longer coherence times and larger anharmonicity.

However, the most optimum architecture for implementing two qubit gates with fluxoniums is yet to be established. In this work we connect two fluxoniums capacitively with a flux-tunable

transmon in the middle. We drive the transmon selectively, which yields a conditional phase gate between the two fluxonium qubits. In our experiment we observe low leakage, fast two

qubit gates (< 50ns) and high two-qubit gate fidelities (>99%). We demonstrate experimentally that different pulse schemes can speed up the duration of the gate without the need for

additional experimental calibration.