Abstract

NOON states are a class of path-entangled or polarization-entangled states consisting of N photons that achieves better performance in phase estimation compared to coherent states as input. These NOON states have proven to achieve super-resolution and to break the shot-noise limit. Ideally they achieve the Heisenberg limit for any value of the phase. This is an advantage over squeezed states, which show improved sensitivity only for certain phases. While squeezed light has been shown to increase the sensitivity in atomic spectroscopy and atomic magnetometry [1], photonic NOON states were so far not suitable for interaction with atoms, because of their production method: Spontaneous parametric down-conversion (SPDC). SPDC produces photons with a bandwidth many orders of magnitude larger than the linewidth of atomic transitions. Spectral filtering to the atomic linewidth of both SPDC photons of a pair reduces the count rate dramatically.

© 2011 IEEE