  We report on the realization of a superinductor, a dissipationless element
whose microwave impedance greatly exceeds the resistance quantum. The design of
the superinductor, implemented as a ladder of nanoscale Josephson junctions,
enables tuning of the inductance and its nonlinearity by a weak magnetic field.
The Rabi decay time of the superinductor-based qubit exceeds 1 microsecond. The
high kinetic inductance and strong nonlinearity offer new types of
functionality, including the development of qubits protected from both flux and
charge noises, fault tolerant quantum computing, and high-impedance isolation
for electrical current standards based on Bloch oscillations.
