How to teach and think about spontaneous wave function collapse theories: not like before

Abstract

A simple and natural introduction to the concept and formalism of spontaneous wave function collapse can and should be based on textbook knowledge of standard quantum state collapse and monitoring. This approach explains the origin of noise driving the paradigmatic stochastic Schr\"odinger equations of spontaneous localization of the wave function $\Psi$. It reveals, on the other hand, that these equations are empirically redundant and the master equations of the noise-averaged state $\hat\rho$ are the only empirically testable dynamics in current spontaneous collapse theories.Comment: Almost the published version p3-11 in "Collapse of the Wave Function", ed.: S Gao, Cambridge University Press, 201