Broadband, noise-free optical quantum memory with neutral   nitrogen-vacancy centers in diamond
  It is proposed that the ground-state manifold of the neutral nitrogen-vacancy center in diamond could be used as a quantum two-level system in a solid-state-based implementation of a broadband, noise-free quantum optical memory. The proposal is based on the same-spin $\Lambda$-type three-level system created between the two E orbital ground states and the A$_1$ orbital excited state of the center, and the cross-linear polarization selection rules obtained with the application of transverse electric field or uniaxial stress. Possible decay and decoherence mechanisms of this system are discussed, and it is shown that high-efficiency, noise-free storage of photons as short as a few tens of picoseconds for at least a few nanoseconds could be possible at low temperature. 
E. Poem, C. Weinzetl, J. Klatzow, K. T. Kaczmarek, J. H. D. Munns, T.   F. M. Champion, D. J. Saunders, J. Nunn, and I. A. W...
quant-ph cond-mat.mes-hall