We report superconducting fluxonium qubits with coherence times largely limited by energy relaxation and reproducibly satisfying T2 > 100 microseconds (T2 > 300 microseconds in one device). Moreover, given the state of the art values of the surface loss tangent and the 1/f flux noise amplitude, coherence can be further improved beyond 1 millisecond. Our results violate a common viewpoint that the number of Josephson junctions in a superconducting circuit -- over 100 here -- must be minimized for best qubit coherence. We outline how the unique to fluxonium combination of long coherence time and large anharmonicity can benefit both gate-based and adiabatic quantum computing.
@article{arxiv.1810.11006,
title = {The high-coherence fluxonium qubit},
author = {Long B. Nguyen and Yen-Hsiang Lin and Aaron Somoroff and Raymond Mencia and Nicholas Grabon and Vladimir E. Manucharyan},
journal= {arXiv preprint arXiv:1810.11006},
year = {2019}
}