Entangling gates using Josephson circuits coupled through non-classical microwaves

A system consisting of two Josephson qubits coupled through a quantum monochromatic electromagnetic field mode of a resonant tank circuit is studied. It is shown that for certain values of the parameters, it can be used as an entangling gate, which entangles the two qubits whilst the electromagnetic field remains disentangled. The gate operates with decent fidelity to a rootSWAP gate and could form the basis for initial experimental investigations of coupled superconducting qubits. (C) 2003 Elsevier B.V. All rights reserved.