Bohr’s 1938 formulation as a restatement of von Neumann’s S+M measurement description

Ascertain whether the emphasized lines in Niels Bohr’s 1938 paper “The causality problem in atomic physics,” which stress considering the entire experimental arrangement and the role of the quantum mechanical formalism, constitute a Bohrian wording of John von Neumann’s 1932 description of measuring an observable by treating the quantum system and the measuring apparatus jointly within a fully quantum S + M framework.

Background

In Section 4, the author compares Bohr’s 1938 analysis of the observation problem with von Neumann’s 1932 formal model of measurement. The suggested mapping is that Bohr’s insistence on including the whole experimental arrangement and fixing external conditions mirrors von Neumann’s joint system-plus-apparatus (S + M) treatment.

Validating this textual and conceptual correspondence would bolster the claim that Bohr’s measurement analysis coheres with von Neumann’s universal quantum-mechanical modeling, reinforcing the paper’s thesis that their positions are much closer than commonly portrayed.

References

My conjecture here is that the emphasized lines – with the non accidental reference to the ‘quantum mechanical formalism’ – represent a (typically idiosyncratic) Bohrian wording of the von Neumann description of a measurement of a physical quantity on a system S by an apparatus M in terms of the entirely quantum-mechanical joint system S + M.

— Bohr and von Neumann on the Universality of Quantum Mechanics: Materials for the History of the Quantum Measurement Process (2405.08722 - Laudisa, 13 May 2024) in Section 4, pages 23–24