Modulation spectroscoy of neutrons refers to a measuring principle, characterized by classification of neutron histories in a probabilistic way, not the usual deterministic way. In order to accomplish this, neutron beams entering the sample are modulated by hightransmission, white beam selectors of the multislit type, such as Fourier or statistical choppers of highfrequency modulated spinflippers. In this scheme it is impossible to decide in a unique way through which particular slit any single neutron passed, but the distribution of histories for a large population of neutrons can...