<Articles>Modeling a Procedure for Providing the Ontology of Quantum Objects: Focussing on the Identity and Individuality of Single Particles in Individual Quantum Systems
Since the 2000s, studies on the ontology of quantum objects have developed relatively actively. However, few studies have thoroughly addressed not only theoretical and metaphysical perspectives but also experimental viewpoints within specific cases. This paper aims to clarify the ontology of quantum objects, focusing on the issues of identity and individuality. Specifically, it constructs a new model that represents a procedure for providing the ontology of quantum objects, with particular attention to single-particle experiments in individual quantum systems. The proposed model is developed by complementarily organizing, abstracting, and integrating the discussions of Bueno (2018), Imai (2024), and Chen (2016, 2018, 2023), which examine the ontology of microscopic objects from theoretical and/or experimental perspectives. Although this model cannot independently resolve the issues of identity and individuality for quantum objects in specific cases, it is a valuable tool for exploring the ontology of quantum objects from a broader framework.
Since the 2000s, studies on the ontology of quantum objects have developed relatively actively. However, few studies have thoroughly addressed not only theoretical and metaphysical perspectives but also experimental viewpoints within specific cases. This paper aims to clarify the ontology of quantum objects, focusing on the issues of identity and individuality. Specifically, it constructs a new model that represents a procedure for providing the ontology of quantum objects, with particular attention to single-particle experiments in individual quantum systems. The proposed model is developed by complementarily organizing, abstracting, and integrating the discussions of Bueno (2018), Imai (2024), and Chen (2016, 2018, 2023), which examine the ontology of microscopic objects from theoretical and/or experimental perspectives. Although this model cannot independently resolve the issues of identity and individuality for quantum objects in specific cases, it is a valuable tool for exploring the ontology of quantum objects from a broader framework.
Quantum entanglement remains one of the most counterintuitive and challenging phenomena in modern physics, with existing interpretations often struggling to reconcile its nonlocal correlations with a coherent ontological framework. This work presents a novel, ontological identity-based explanation for quantum entanglement, positing that entangled particles maintain an fundamental existential unity rather than exhibiting isolated spooky action at a distance. The proposed framework resolves key conceptual paradoxes by redefining the nature of quantum individuality, establishing a consistent metaphysical foundation for the interpretation of non-local quantum correlations. To validate this approach, equilibrium state interference experiments are conducted, and the results are shown to align precisely with the predictions of the identity-based model. These findings not only provide a robust theoretical underpinning for quantum entanglement but also offer new directions for the foundational research in quantum mechanics, bridging the gap between abstract mathematical formalism and concrete physical ontology.
While entanglement in the case of distinguishable particles is clearly understood, in the case of indistinguishable particles, there is still a wide debate regarding basic conceptual issues. Here, I will address two such issues. First, the debate almost always rests on a differentiated treatment of the cases of distinguishability and indistinguishability, even with respect to the definition of the concept of entanglement. Second, the fact that symmetrized and antisymmetrized states of indistinguishable particles are non-factorizable leads to certain perplexities about the very nature of entanglement. In the present work, both issues will be addressed from the perspective of an ontology of properties, which finds its natural expression in the algebraic formalism of quantum mechanics. The final goal will be to show that the proposed ontology allows a unified treatment of entanglement in the distinguishability and indistinguishability cases and offers a straightforward way out to perplexities. This article is part of the theme issue 'Identity, individuality and indistinguishability in physics and mathematics'.
This article critically examines the challenges of developing a metaphysics of non-individuals in the context of quantum mechanics. It investigates the Received View, which posits that quantum entities are non-individuals, and highlights several unresolved issues. Through these challenges, it is shown that a coherent metaphysics of non-individuals remains an ongoing project. Section 2 outlines the historical motivations behind a metaphysics of non-individuals in quantum mechanics, providing insight into how physics seems to necessitate such a framework. Section 3 discusses how these motivations have been articulated in the traditional approach (referred to here as the ‘non-reflexive proposal’), which characterizes non-individuality as a failure of the identity relation to apply. Section 4 situates the problem within a broader context, extracting methodological insights and clarifying the issue. Section 5 elaborates on the challenges that a metaphysics of non-individuals must still overcome, positioning this text as a prolegomenon to future formulations of such a metaphysics grounded in quantum mechanics, and section 6 wraps it all up.
This thesis examines the concepts of identity and individuality via scientifically-informed philosophical analysis. It has two parts. The first part deals with metaphysical claims that turn out to be, in effect, very general empirical claims extracted from our (supposed, but rationally-accredited) knowledge of the world. I here compare two approaches: a) the Leibniz-Quine view of identity as a derivative relation, and, relatedly, of individuality as dependent on the qualities of things; and b) the view that identity is a non-analysable primitive, and, relatedly, that the individuality of things is not reducible to anything else. The former position, based on the Principle of the Identity of the Indiscernibles as a criterion of individuation, might appear prima facie more plausible. However, I argue that it runs into difficulties both at the level of a priori analysis and in terms of 'fit' with the evidence described by our best science. It is, in fact, not even as compelling from the empiricist point of view as is commonly believed. I therefore argue that the position that identity and individuality are primitive may be preferred. In the second part of the thesis - under the assumption that the proper role of metaphysics is to characterise the best solutions to issues that are left open by current science - I deal with the question regarding whether and how the ultimate constituents of reality can actually be conceived of as primitive individuals. I argue in favour of an ontology of tropes, develop the view in detail and defend it against various criticisms. The fundamental tropes that constitute the basic 'building blocks' of reality are identified with the state-independent properties of elementary particles. The way in which these constitute complex particulars is described, and certain peculiarities having to do with quantum statistics are accounted for. I conclude by suggesting possible avenues for further research.
Abstract The issue about the nature of quantum systems usually hinges on the category of individual: the question is whether this category can be applied to understand the peculiarities of quantum behavior. However, some metaphysical subtleties are commonly overlooked in this discussion. What is the difference between the notions of object and of individual? What metaphysical principles are quantum systems supposed to fulfill? What ontological kinds of properties are involved in the quantum domain? These questions should be taken into account when the issue at stake is the ontological nature of quantum systems and, more generally, the structure of the quantum realm. In order to address these and other metaphysical questions, different ontological distinctions that are scarcely taken into account in the debate are brought to the fore in this chapter. In light of these distinctions, the ontological challenges that quantum mechanics poses to the ontological picture presupposed by traditional metaphysics will be discussed in the following chapter.
Several experiments have suggested that the complete indistinguishability of quantum systems is to be considered a real phenomenon. Experiments such as the HOM effect, the existence of BECs, the path identity cases, and many others are physical realities of today. Physicists `explain’ these phenomena using different models, such as Bohmian mechanics, relational quantum mechanics or the QBism approach. Most of these models are constructed within a standard mathematical framework, meaning standard mathematics, where all things can, even if only in principle, be distinguished from one another, so complete indistinguishability can only be mimicked. These approaches may work for physical purposes but are debatable regarding logical and metaphysical questions. If we accept that such questions are at least part of the philosophical aspect of quantum physics, then we are authorised to analyse them and try to offer an alternative. Looking for an alternative, we consider Alain Aspect’s and Anton Zeilinger’s views about quantum realism, opting for Aspect’s acceptance of some kind of reality behind the wave-function, while Zeilinger suggests that everything comes from information. In our opinion, the case is the opposite: it is information that comes from the existence of things. The aim of this paper is to justify why we think that the underlying reality (in Aspect’s sense) can be seen as a quantum ontology of non-individuals.