Quantum Holism

TL;DR

Quantum holism reveals that composite quantum systems possess global properties incompatible with their parts, challenging traditional notions of physical objects and extending the concept of properties within operational probabilistic theories.

Contribution

This paper introduces the concept of mereological holism in quantum theory and extends the notion of properties to all operational probabilistic theories, highlighting differences between classical and quantum systems.

Findings

Quantum systems exhibit properties incompatible with their parts.

Classical theory is not mereologically holistic.

Operational probabilistic theories can be extended to include holistic properties.

Abstract

A composite quantum system has properties that are incompatible with every property of its parts. The existence of such global properties incompatible with all local properties constitutes what I call "mereological holism"--the distinctive holism of Quantum Theory. Mereological holism has the dramatic conceptual consequence of making untenable the usual understanding of the "quantum system" as being a "physical object", since composed objects have properties compatible with those of its parts. The notion of "property" can be extended in a unique way to the whole class of operational probabilistic theories (shortly OPTs), of which the most relevant cases are Quantum Theory and Classical Theory. Whereas Classical Theory is not mereologically holistic, we can now search for other OPTs that are so. Within the OPT framework the role of the "system" is that of an input-output connection between two objective events. In non holistic theories, such as Classical Theory, the system can still be regarded as an "object". On the contrary, in holistic theories interpreting "system" as "object" constitutes an hypostatization of a theoretical notion.