Earman, John (2026) Assessing POVMs (and povms). [Preprint]

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Abstract

For many decades the development of the quantum theory and its applications were guided by the framework laid out in von Neumann's Mathematische Grundlagen der Quantenmechanik (1932). The spectacular success of the theory was seemingly strong testimony to the resilience of this framework. In recent decades, however, a number of researchers working under the banner headlined "POVMs" have claimed that the von Neumann framework needs to be expanded in various ways. Some researchers claim that in order to be empirically adequate the theory has to recognize observables represented by maximally symmetric but non-selfadjoint operators. Other researchers, working under the same banner, stick with selfadjoint observables but claim that realistic quantum measurements which are "unsharp" have to be described not in terms of projection operators but "effects"---positive bounded (and, thus, selfadjoint) operators that are not projections. A critical examination of this program reaffirms the resilience of the von Neumann framework.

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Item Type:	Preprint
Creators:	Creators Email ORCID Earman, John jearman@pitt.edu
Keywords:	POVMs, observables in QM, quantum probability, unsharp measurements
Subjects:	Specific Sciences > Physics Specific Sciences > Probability/Statistics Specific Sciences > Physics > Quantum Mechanics
Depositing User:	John Earman
Date Deposited:	06 Apr 2026 12:36
Last Modified:	06 Apr 2026 12:36
Item ID:	28926
Subjects:	Specific Sciences > Physics Specific Sciences > Probability/Statistics Specific Sciences > Physics > Quantum Mechanics
Date:	6 April 2026
URI:	https://philsci-archive.pitt.edu/id/eprint/28926

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