Quantum interference viewed in the framework of probability theory

An additivity equality of probability theory is suggested to define (relative) noninterference. Interference is deviation from this additivity. It is shown that two‐slit interference fits into this scheme. It is argued that the physical meaning of quantum interference is an observable deviation of quantum filtering from quantum occurrence of events. The expounded view should restore the essence of textbook treatment of interference in a precise and correct probability‐theoretic framework. The approach is essentially a continuation of a critical argument presented by Ballentine.