The Many Inconsistencies of the Purity-Mixture Distinction in Standard Quantum Mechanics

Abstract

The distinction between pure states and mixed states is a kernel ingredient of what is considered to be the standard formulation of quantum mechanics and plays today a kernel role in foundational debates about the meaning of quantum probability, the separability of quantum systems, the definition and measure of entanglement, etc. In this work we attempt to expose the many inconsistencies introduced by this distinction and the serious consequences this has for many ongoing research programs within quantum physics which apply these notions uncritically.