Quantum Mechanics of ‘Two Path’ Experiments: Comparison of Neutrino Oscillations and the Young Double Slit

Abstract

Feynman path integral analyses of a two-neutrino-flavour electron appearence experiment and the Young double slit are compared. The comparison reveals a conceptual flaw in previous work of the present author that led to a false claim of the incorrectness of standard formulas for the oscillation phase. In both calculations, path amplitudes add coherently, but no putative 'neutrino flavour eigenstates' are invoked in the former case. It is shown that the coherent production of these eigenstates is incompatible with the measured values of Γ (π → eν)/Γ (π → µν) and the PMNS matrix elements. Applications of the path integral approach to other two-path quantum interference experiments are compared with neutrino oscillations, and other treatments of the latter in the literature are critically discussed.