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

**Authors:** Wei-Ju Lin, Hyunheung Cho, Yinqi Chen, Maxim G. Vavilov, Chen Wang, Vladimir E. Manucharyan  
**arXiv:** [2407.15783](https://arxiv.org/abs/2407.15783)  
**Date:** 2024-07-22  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/2407.15783v1/

## Key points

- Groundbreaking study by Wei-Ju Lin, Hyunheung Cho, Yinqi Chen, Maxim G. Vavilov, Chen Wang, and Vladimir E. Manucharyan on fluxonium qubits
- Fluxonium qubits offer extended coherence time and strong anharmonicity for quantum information processing
- Achieved a 60 ns direct CNOT-gate with 99.94% gate fidelity on inductively-coupled fluxonium qubits using selective darkening approach
- Gate's performance maintained above 99.9% fidelity for 24 days without recalibration
- Reduced non-decoherence-related errors during gate operations to $2 \times 10^{-4}$
- Comparison to a 60 ns identity gate with 99.96% fidelity highlights practical implementation potential of quantum computing technologies
- Addition of a simple and robust two-qubit gate to "beyond three nines" demonstrations on superconducting qubits
- Offers insights into enhancing stability and fidelity of quantum gates for advancements in quantum information processing systems

## Summary

A groundbreaking study by Wei-Ju Lin, Hyunheung Cho, Yinqi Chen, Maxim G. Vavilov, Chen Wang, and Vladimir E. Manucharyan has demonstrated the remarkable stability and high fidelity of a CNOT-gate implemented on fluxonium qubits. These qubits have extended coherence time and strong anharmonicity, making them highly promising for quantum information processing. Using a selective darkening approach, the team achieved a 60 ns direct CNOT-gate with an impressive gate fidelity of 99.94% on two inductively-coupled fluxonium qubits. What sets this research apart is the longevity of the gate's performance - maintaining a fidelity above 99.9% for an astonishing 24 days without requiring recalibration between randomized benchmarking measurements. This data sheds light on non-decoherence-related errors during gate operations and reduces them to $2 \times 10^{-4}$. By comparing their results to a 60 ns identity gate with a fidelity of 99.96%, this study highlights the potential for practical implementation of quantum computing technologies. This achievement not only adds a simple and robust two-qubit gate to the limited repertoire of "beyond three nines" demonstrations on superconducting qubits but also offers valuable insights into enhancing the stability and fidelity of quantum gates. It paves the way for advancements in quantum information processing systems.