24 days-stable CNOT-gate on fluxonium qubits with over 99.9% fidelity

TL;DR

This paper demonstrates a highly stable and high-fidelity 60 ns CNOT gate on fluxonium qubits, maintaining over 99.9% fidelity for 24 days without recalibration, advancing quantum gate reliability.

Contribution

First implementation of a 60 ns CNOT gate on fluxonium qubits with over 99.9% fidelity sustained for 24 days without recalibration.

Findings

Fidelity of 99.94% achieved for the CNOT gate.

Fidelity remains above 99.9% for 24 days without recalibration.

Non-decoherence errors during gate operations are extremely low.

Abstract

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 $2 \times 10^{-4}$. 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.