A method was proposed for achieving coherent coupling between nitrogen-vacancy centers in diamond and superconducting flux qubits. The resulting coupling could be used to create a coherent interaction between the spin states of distant nitrogen-vacancy centers mediated by the flux qubit. Furthermore, the magnetic coupling could be used to achieve a coherent transfer of quantum information between the flux qubit and an ensemble of nitrogen-vacancy centers. This enables a long-term memory for a superconducting quantum processor and possibly an interface between superconducting qubits and light.

Coupling Nitrogen-Vacancy Centers in Diamond to Superconducting Flux Qubits. D.Marcos, M.Wubs, J.M.Taylor, R.Aguado, M.D.Lukin, A.S.Sørensen: Physical Review Letters, 2010, 105[21], 210501