  The promise of single Cooper pair quantum circuits based on tunnel junctions
for metrology and quantum information applications is severely limited by the
influence of "offset" charges - random, slowly drifting microscopic charges
inherent to many solid-state systems. By shunting a small junction with the
Josephson kinetic inductance of a series array of large capacitance tunnel
junctions, thereby ensuring that all superconducting islands are connected to
the circuit by at least one large junction, we have realized a new
superconducting artificial atom which is totally insensitive to offset charges.
Yet, its energy levels manifest the anharmonic structure associated with single
Cooper pair effects, a useful component for solid state quantum computation.

Mesoscale and Nanoscale Physics;Superconductivity