The Trouble with Weak Values

• URL: http://arxiv.org/abs/2602.09380v1
• Date: Tue, 10 Feb 2026 03:49:42 GMT
• Title: The Trouble with Weak Values
• Authors: Jacob A. Barandes,
• Abstract summary: Weak values first appeared in the research literature in a pair of papers in 1987 and 1988.<n>Papers on weak values have produced a number of important practical spin-offs.<n>This paper challenges these interpretational claims by arguing that they involve several forms of fallacious reasoning.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: In quantum theory, a weak value is a complex number with a somewhat technical definition: it is a ratio whose numerator is the matrix element of a self-adjoint operator and whose denominator is the inner product of a corresponding pair of state vectors. Weak values first appeared in the research literature in a pair of papers in 1987 and 1988, and were originally defined as the results of a special kind of experimental protocol involving non-disturbing measurements combined with an explicit form of post-selection. In the years since, subsequent papers on weak values have produced a number of important practical spin-offs, including new methods for signal amplification and quantum-state tomography. The present work is not concerned with those practical spin-offs, but with historical and ongoing attempts to assign weak values a transparent, single-system interpretation, as well as efforts that invoke weak values to make a number of exotic claims about the properties and behavior of individual quantum systems. This paper challenges these interpretational claims by arguing that they involve several forms of fallacious reasoning.

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