Von Neumann-Lueders projection, and its applicability to EPR experiments

TL;DR

This paper examines the conditions under which von Neumann's projection postulate can be validly applied to EPR experiments within a quantum measurement framework, treating projection as a form of conditional preparation.

Contribution

It clarifies the specific conditions where von Neumann's projection postulate is applicable to EPR experiments, addressing a longstanding foundational issue.

Findings

Identifies conditions for the validity of the projection postulate in EPR setups

Reframes projection as a special case of conditional preparation

Provides a theoretical framework for measurement in quantum mechanics

Abstract

Notwithstanding it is well known that von Neumann's projection postulate is inapplicable to most realistic measurement procedures, it keeps haunting the foundations of quantum mechanics. In particular its applicability to EPR experiments is often assumed. In the present contribution this problem is considered from the point of view of a quantum mechanical theory of measurement, allowing a treatment of projection in EPR experiments as a special case of conditional preparation. The conditions are spelled out under which the postulate may be applicable.