Realizing high-fidelity and low-leakage gates in a fluxonium processor

High-fidelity quantum operations are critical for performing quantum error correction. Although impressive advancements have been made for the transmon qubit, further improvements in its fidelity are impeded by its decoherence. In addition, large leakage error caused by its weak nonlinearity can induce correlated errors that threaten quantum error correction. In contrast, with its low decoherence and large anharmonicity, fluxonium is an attractive qubit for fault-tolerance. Here, we perform on a fluxonium processor single-qubit gates with up to 99.98% fidelity and a two-qubit entangling gate with up to 99.72% fidelity. Our analysis shows that the leakage errors of these operations are substantially lower than those commonly observed in a transmon system. This result paves a clear path toward fault-tolerant quantum computing through fluxonium processors.