  We theoretically investigate selective coupling of superconducting charge
qubits mediated by a superconducting stripline cavity with a tunable resonance
frequency. The frequency control is provided by a flux biased dc-SQUID attached
to the cavity. Selective entanglement of the qubit states is achieved by
sweeping the cavity frequency through the qubit-cavity resonances. The circuit
is scalable, and allows to keep the qubits at their optimal points with respect
to decoherence during the whole operation. We derive an effective quantum
Hamiltonian for the basic, two-qubit-cavity system, and analyze appropriate
circuit parameters. We present a protocol for performing Bell inequality
measurements, and discuss a composite pulse sequence generating a universal
control-phase gate.
