Fluxonium qubit is a promising building block for quantum information processing due to its long coherence time and strong anharmonicity. In this paper, we realize a 60 ns direct CNOT-gate on two inductively-coupled fluxonium qubits using selective darkening approach, resulting in a gate fidelity as high as 99.94%. The fidelity remains above 99.9% for 24 days without any recalibration between randomized benchmarking measurements. Compared with the 99.96% fidelity of a 60 ns identity gate, our data brings the investigation of the non-decoherence-related errors during gate operations down to 2×10−4. The present result adds a simple and robust two-qubit gate into the still relatively small family of "the beyond three nines" demonstrations on superconducting qubits.
@article{arxiv.2407.15783,
title = {24 days-stable CNOT-gate on fluxonium qubits with over 99.9% fidelity},
author = {Wei-Ju Lin and Hyunheung Cho and Yinqi Chen and Maxim G. Vavilov and Chen Wang and Vladimir E. Manucharyan},
journal= {arXiv preprint arXiv:2407.15783},
year = {2024}
}