Indistinguishability and improper mixtures

Abstract

All quantum mixtures are what d'Espagnat has termed "improper." His "proper" mixture cannot be created -- if welcher weg, or distinguishing, information exists, an improper mixture results, while in the absence of such information, the resulting "mixture" is a pure state. D'Espagnat has claimed that an interpretation of the improper mixture in terms of subensembles leads to logical inconsistency; this claim is shown to be incorrect, as d'Espagnat's argument fails to account for the indistinguishability of the pure-state subensembles.

4 pages. v2: Improved introduction and presentation of theorem of section 5; other small corrections; theorem nicknames changed

References in corpus (3)

• On mechanisms that enforce complementarity
• "Quantal" behavior in classical probability
• Reply to Aharonov and Anandan's "Meaning of the Density Matrix"

Cited by in corpus (6)

• On the lattice structure of probability spaces in quantum mechanics
• Proper and Improper Separability
• Reply to K A Kirkpatrick
• Measurement: still a problem in standard quantum theory
• A Quantum Field Approach for Advancing Optical Coherence Tomography Part I: First Order Correlations, Single Photon Interference, And Quantum Noise
• Formalization of the distinguishability heuristics