Correlative and phase locking methods for atom interferometry

Philippe Bouyer
LP2N, Institut d'Optique d'Aquitaine

The sensitivity of an atomic interferometer increases when the phase evolution of its quantum superposition state is measured over a longer interrogation interval. In practice, a limit is set by the measurement process, which returns not the phase, but its projection in terms of population difference on two energetic levels. The phase interval over which the relation can be inverted is thus limited and going beyond it introduces an ambiguity in the read out, hence a sensitivity loss. This often limits the usability of atom interferometer based sensors to a quiet environment and hinders its performance when used, for instance, in a mobile vehicle. I will present various approaches when a classical and a quantum sensors are correlated, or even phase locked to remove the ambiguity.