Revealing Nonclassical Light with Zero-Photon Subtraction

Zero-photon subtraction (ZPS) is a conditional measurement process that can noiselessly attenuate quantum optical states despite removing no photons from the system. Here we show that in addition to reducing mean photon number, ZPS can also transform certain super-Poissonian states into sub-Poissonian states, and vice versa. Using well-known properties of conditional measurements, we note this is only possible for nonclassical input states and develop a new set of non-classicality criteria that could be directly measured in a ZPS experiment. We identify several classes of states which are guaranteed to violate these criteria and have their sub/super-Poissonian character changed by the ZPS process. Further analysis reveals that observable quantities in ZPS are directly related to the moment and cumulant generating functions of the photon number distribution. This can be used to extract higher-order statistics for the input and output states, allowing for a more complete description of the ZPS transformation.