  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.
