Against the Tyranny of ‘Pure States’ in Quantum Theory

Christian De Ronde, Cesar Massri

Research output: Contribution to journalArticle


We argue that the notion of pure sate within Standard Quantum Mechanics is presently applied within the specialized literature in relation to two mutually inconsistent definitions. While the first (operational purity) provides a basis-dependent definition which makes reference to the certain prediction of measurement outcomes, the latter (trace-invariant purity) provides a purely abstract invariant definition which lacks operational content. In this work we derive a theorem which exposes the serious inconsistencies existent within these two incompatible definitions of purity.
Original languageEnglish
Pages (from-to)27–41
Number of pages15
JournalFoundations of Science
Issue number1
Publication statusPublished - Mar 2022


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