Generation of maximally entangled charge-qubit arrays via a cavity mode
  We describe an assembly of N Cooper-pair boxes (CPB) contained in a single mode cavity. In the dispersive regime, the correlation between the cavity field and each Cooper-pair box results in an effective interaction between CPBs that can be used to dynamically generate maximally entangled states. With only collective manipulations, we show how to create maximally entangled quantum states and how to use these states to reach the Heisenberg limit in the determination of a spectroscopy frequency. This scheme can be applied to other types of superconducting qubits. 
Alexandre Guillaume (1) and Jonathan P. Dowling (2 and 3) ((1) Jet   Propulsion Laboratory, California Institute of Technolo...