  Superconducting flux qubits are a promising candidate for realizing quantum
information processing and quantum simulations. Such devices behave like
artificial atoms, with the advantage that one can easily tune the "atoms"
internal properties. Here, by harnessing this flexibility, we propose a
technique to minimize the inhomogeneous broadening of a large ensemble of flux
qubits by tuning only the external flux. In addition, as an example of
many-body physics in such an ensemble, we show how to observe superradiance,
and its quadratic scaling with ensemble size, using a tailored microwave
control pulse that takes advantage of the inhomogeneous broadening itself to
excite only a sub-ensemble of the qubits. Our scheme opens up an approach to
using superconducting circuits to explore the properties of quantum many-body
systems.
