Feynman rules for probability amplitudes

Abstract

Starting with very simple assumptions, Feynman rules for the quantum mechanical amplitudes and the associated probabilities are derived. These rules emerge as the only consistent rules for manipulating complex amplitudes assigned to processes. The probability of a process to which an amplitudex has been assigned is determined asp(x)=|x|^α, 0<α≤2. If virtual processes are allowed,α=2.