  We propose a Quantum Field Theory description of beams on a Mach-Zehnder
Interferometer and apply the method to describe Interaction Free Measurements
(IFMs), concluding that there is a change of momentum of the fields in IFMs.
Analysing the factors involved in the probability of emission of low-energy
photons, we argue that they do not yield meaningful contributions to the
probabilities of the IFMs.
