A quantum mechanical description of electromagnetic and atom Mach-Zehnder interferometers

A quantum mechanical description of a non-absorbing electromagnetic (em) be am splitter (BS) transformation is given by the use of momentum creation op erators, which also include momentum shift operators operating on the BS. T his BS transformation is used for analysing photon-statistics effects in th e em Mach-Zehnder interferometer. Also the relation between this BS transfo rmation and Welcher-Weg measurements is discussed. The analogy between em a nd atom interferometers is described with an emphasis on the use of high-or der correlation functions. The entanglement between the interfering beams i n these interferometers and the BS is taken into account in our analysis fo r treating special effects.