Spin Squeezing and Non-linear Atom Interferometry with Bose-Einstein Condensates - Christian Gross - Bog

Interferometry, the most precise measurement technique known today, exploits the wave-like nature of the atoms or photons in the interferometer. As expected from the laws of quantum mechanics, the granular, particle-like features of the individually independent atoms or photons are responsible for the precision limit, the shot noise limit.