Coupling Circuit Resonators Among Themselves and To Nitrogen Vacancy Centers in Diamond

We propose a scheme to couple two or more NV centers in diamond through coplanar waveguide resonators, i.e., the microwave cavity-QED systems. We first split the central conductor of the resonator into several pieces which are coupled strongly with each other through simple capacitive junctions or superconducting Josephson junctions. We then put the NV centers at the junctions. The discontinuity at the junctions induces a large local magnetic field, through which the NV centers are strongly coupled to the circuit resonator. The coupling strength g between the resonator and the NV center is of order of g/2 pi = 1 similar to 10 MHz.