Raman quantum memory based on an ensemble of nitrogen-vacancy centers coupled to a microcavity

We propose a scheme to realize optical quantum memories in an ensemble of nitrogen-vacancy centers in diamond that are coupled to a microcavity. The scheme is based on off-resonant Raman coupling, which allows one to circumvent optical inhomogeneous broadening and store optical photons in the electronic spin coherence. This approach promises a storage time of order 1 s and a time-bandwidth product of order 107. We include all possible optical transitions in a nine-level configuration, numerically evaluate the efficiencies, and discuss the requirements for achieving high efficiency and fidelity.