Collapse of the quantum wavefunction and Welcher-Weg (WW) experiments

TL;DR

This paper analyzes the wavefunction collapse and Welcher-Weg experiments within quantum mechanics, discussing how measurement, complementarity, and interference relate to the reality of quantum states before measurement.

Contribution

It provides a quantum mechanical analysis of wavefunction collapse and Welcher-Weg experiments, clarifying the role of superposition and interference in measurement.

Findings

Wavefunction collapse can be understood through pure quantum mechanics.

Welcher-Weg effect relates to complementarity and wavefunction orthogonality.

Superposition states lack definite reality prior to measurement.

Abstract

The 'collapse' of the wave function in a general measuring process is analyzed by a pure quantum mechanical (QM) approach. The problem of the delayed choice and Welcher-Weg (WW) experiments is analyzed for Mach-Zehnder (MZ) interferometer. The WW effect is related to complementarity principle and orthogonality of wavefunctions although it produces small momentum changes between the electromagnetic (EM) field and the beam-splitters (BS's). For QM states for which we have a superposition of states and interference effects there is no reality before measurement, but by excluding such effects the system gets a real meaning already before measurement.