|Rate||only classical light||no optical excitation|
|DLCZ||\( \eta (1-F) \)||✅||❌|
|BK||\( \eta^2 \)||✅||❌|
|reflection||\( \eta^2 \)||❌||✅|
You also need a color center that does not suffer from spectral diffusion or charge state instabilities.
If you end up with significant optical excitation, you also need a way to turn off the hyperfine coupling to the (nuclear) memory.