Information aspects of “which-path” interference experiments with microparticles

The Schmidt expansion method is used to consider the informational aspects of the problem concerned with monitoring the process of interference of quantum particles. The far-field diffraction pattern specified by the probability density of the distribution of the particle momentum is represented as a mixture of densities of the corresponding Schmidt modes, whose number coincides with the number of slits in the screen. The optical coherence is described on the basis of the procedure of complementation of the mixture to a pure state. Information characteristics are introduced to describe the quality of the interference pattern. The relationship between the visibility of the interference pattern and the Schmidt number is found and examined. Different “which-path” experiments are analyzed. The results of numerical simulation of interference at two and three slits for Rydberg atoms, whose path passes through resonators capable of providing data on the trajectory of the atom, are described.