The Most Coherent Superconducting Qubit?

Highly anharmonic artificial atoms present a promising approach to gate-based quantum computing. We report our progress in improving coherence and control of fluxonium superconducting circuits with enhancements in fabrication [1]. We demonstrate a device with coherence time T₂ exceeding 1 millisecond and an average single qubit gate fidelity greater than 99.99%. Importantly, our circuits are fabricated with robust and scalable methods compatible with existing CMOS manufacturing. This coherence time is still limited by dielectric loss and can be improved further by mitigating material losses. Finally, we discuss the implications of this result on scaling up these devices to quantum processors [2].

[1] Nguyen et al. Phys. Rev. X 9, 041041 (2019)
[2] Ficheux et al. arXiv:2011.02634 (2020)