High-fidelity quantum memory using nitrogen-vacancy center ensemble for   hybrid quantum computation
  We study a hybrid quantum computing system using nitrogen-vacancy center ensemble (NVE) as quantum memory, current-biased Josephson junction (CBJJ) superconducting qubit fabricated in a transmission line resonator (TLR) as quantum computing processor and the microwave photons in TLR as quantum data bus. The storage process is seriously treated by considering all kinds of decoherence mechanisms. Such a hybrid quantum device can also be used to create multi-qubit W states of NVEs through a common CBJJ. The experimental feasibility and challenge are justified using currently available technology. 
W. L. Yang, Zhang-qi Yin, Y. Hu, M. Feng, J. F. Du
quant-ph