A little question I'm not quite sure of. When you try to do a Quantum Non-Demolition measurement, you have an atom which first goes into a Ramsey zone, and then into a cavity which shoots some photons at it. After that it comes out into another Ramsey zone again. And for the atom in a Ramsey zone the atoms state gets transformed by something like |+> -> (1/sqrt(2))(|-> + |+>) if I remember correctly. But does it also gets transformed when it goes into the cavity and gets time dependent, or does it only get the time dependent factor multiplied ?