Quantum structure of neutron beams and possibilities for establishing it experimentally

The possibility of experimentally distinguishing between pure and mixed sta tes of beams that was previously discussed in the literature has been analy zed in terms of a density matrix. A specific theory of relevant phenomena h as been developed. In general, beams have a modulated density, and waves th at are similar to sound waves and which have a discrete spectrum propagate kinematically along them. The wavelength has a lower bound that is of a pur ely quantum origin and which is determined by the coherence length greatly exceeding the de Broglie wavelength, provided that the energy spread of the beam is insignificant. A theoretical possibility of transforming a cold-ne utron beam in such a way as to increase the length and to decrease the freq uency of the modulation wave propagating along the beam is found, and a pra ctical way to implement this possibility is proposed. Prospects for relevan t experiments in the near future are discussed.