  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.
