Product states, entanglement, and measurement

TL;DR

This paper clarifies that product states in quantum systems should be interpreted as correlations rather than independent properties, resolving fundamental issues in the measurement problem and aligning theory with experimental observations.

Contribution

It provides a new interpretation of product states as correlations, addressing the measurement problem and reconciling theory with non-local interferometry experiments.

Findings

Product states are better understood as correlations.

This interpretation resolves the measurement problem.

Experimental results support the correlation interpretation.

Abstract

A product state of a composite quantum system AB is customarily interpreted physically to mean subsystem A has property A1 and subsystem B has property B1. But this interpretation contradicts both the theory and observed outcomes of non-local interferometry experiments on the momentum-entangled state of two photons. These experiments demonstrate that product states must be interpreted physically as correlations, i.e. the product state means A has property A1 if and only if B has property B1. This clarification resolves the problem of definite outcomes and, with it, the measurement problem.