  We propose a qubit-qubit coupling scheme for superconducting flux quantum
bits (qubits), where a quantized Josephson junction resonator and microwave
irradiation are utilized. The junction is used as a tunable inductance
controlled by changing the bias current flowing through the junction, and thus
the circuit works as a tunable resonator. This enables us to make any qubits
interact with the resonator. Entanglement between two of many qubits whose
level splittings satisfy some conditions, is formed by microwave irradiation
causing a two-photon Rabi oscillation. Since the size of the resonator can be
as large as sub-millimeters and qubits interact with it via mutual inductance,
our scheme makes it possible to construct a quantum gate involving remote
qubits

Superconductivity