The Most Coherent Superconducting Qubit?

To realize a digital quantum processor based on superconducting qubits, gate error rates must be further reduced by raising coherence times and increasing anharmonicity. I report our group's progress in improving coherence and control of fluxonium superconducting qubits by optimizing the circuit's spectrum and enhancing fabrication methods. I demonstrate a device with coherence time T2 exceeding 1 millisecond and an average single-qubit gate fidelity greater than 99.99% [1].  To our knowledge, these are the highest coherence times and gate fidelities observed in a solid-state qubit to date. The coherence time is still limited by dielectric loss and can be improved by further mitigating material losses. The high gate fidelity is readily achievable due to the strong anharmonicity inherent to fluxonium's spectrum. Finally, I will present our recent work on scaling up from the single-qubit level to demonstrating two-qubit gates with capacitively coupled fluxonium circuits [2].  References: [1] A. Somoroff et al. arXiv:2103.08578 (2021) [2] Q. Ficheux et al. Phys. Rev. X 11, 021026 (2021)

Pizza and drinks served after the talk.