Heralded path-entangled NOON states generation from a reconfigurable photonic chip

Maximal multi-photon entangled states,known as NOON states,play an essential role in quantum metrology.With the number of photons growing,NOON states are becoming increasingly powerful and advantageous for obtaining supersensitive and super-resolved measurements.In this paper,we propose a universal scheme for generating three-and four-photon path-entangled NOON states on a reconfigurable photonic chip via photons subtracted from pairs and detected by heralding counters.Our method is postselection free,enabling phase supersensitive measurements and sensing at the Heisenberg limit.Our NOON-state generator allows for integration of quantum light sources as well as practical and portable precision phase-related measurements.