Entangled Electrons in Quantum Space

Quantum Quirks: Are Subatomic Particles Individuals or Indistinguishable Entities?

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Avery Sinclair in Science & Nature June 2025 • 5 min read.

"Explore the mind-bending world of quantum mechanics, where the very nature of individuality is questioned. Are quantum particles unique individuals, or are they part of an indistinguishable collective?"


Quantum mechanics, the theory governing the subatomic world, presents some truly bizarre concepts. One of the most perplexing is the question of whether the particles that make up our universe—electrons, photons, and the like—are truly individuals in the classical sense. Do they have unique identities, or are they essentially interchangeable, indistinguishable entities?

This question isn't just a matter of abstract philosophy. It has deep implications for how we understand the fundamental nature of reality and how we interpret the mathematical formalism of quantum mechanics. The standard equations of quantum mechanics are compatible with both interpretations: particles as individuals and particles as non-individuals, without theory choosing or signaling decisively which assumption we must embrace.

The debate arises because quantum mechanics often describes particles in ways that seem to defy our everyday intuition. Unlike macroscopic objects, quantum particles can exist in multiple states at once (superposition) and can be linked together in strange ways, so that measuring the properties of one instantly influences the properties of the other (entanglement). These phenomena challenge our classical notions of identity and individuality, leading some physicists and philosophers to question whether these concepts even apply at the quantum level.

The Core of Individuality in Quantum Mechanics

Entangled Electrons in Quantum Space

The concept of individuality is deeply ingrained in our everyday experience. We perceive ourselves and the objects around us as distinct entities, each with its own unique properties and history. This intuitive understanding of individuality is formalized in classical physics through the principle of identity, the PII: if two objects share all the same properties, they are identical.

However, quantum mechanics throws a wrench into this neat picture. Consider two electrons in an atom. According to quantum mechanics, these electrons are indistinguishable. They have the same mass, charge, spin, and other intrinsic properties. Moreover, because of the phenomenon of quantum entanglement, it's impossible to assign a definite trajectory or history to each electron. This raises a fundamental question: if two electrons are completely indistinguishable, can we really say that they are two separate individuals?

  • The Leibniz’s Principle of Identity of Indiscernibles: This principle states that if two objects have all the same properties, they are the same object. Quantum mechanics challenges this, as particles can have identical properties yet still be considered distinct.
  • Quantum Statistics: Quantum particles obey different statistical rules than classical objects. For example, bosons (like photons) can occupy the same quantum state, while fermions (like electrons) cannot. This difference in statistical behavior reflects the underlying indistinguishability of quantum particles.
  • The Role of Observation: In quantum mechanics, the act of measurement plays a crucial role. Some interpretations suggest that it is only when we observe a quantum system that its properties become definite. This raises questions about whether particles have definite identities when they are not being observed.
The orthodox interpretation of quantum mechanics suggests that quantum objects lack individuality. As put by French and Krause, the identity of electrons is lost. We can know how many electrons are in an atom of Helium (He), but we can’t distinguish the qualities of each. Shrödinger stated, “one cannot mark an electron, one cannot paint it red”. This problem is one that is not epistemic (relating to knowledge), but ontological (relating to being).

The Metaphysical Implications

The question of quantum individuality has profound implications for our understanding of reality. If quantum particles are not individuals, then our classical notions of identity and existence may need to be revised. This could lead to new ways of thinking about the relationship between the quantum world and the macroscopic world we experience every day. Embracing the concept of non-individuality is more plausible as it opens up the possibilities for ontological pluralism. This exploration into the quantum world calls into the question not just how reality is created at a subatomic level, but also what our reality is as an object in space.

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Everything You Need To Know

1

In quantum mechanics, are subatomic particles like electrons truly individuals with unique identities, or are they indistinguishable entities?

Quantum mechanics introduces the idea that particles like electrons and photons might not be individuals with unique identities in the way we understand macroscopic objects. They could be indistinguishable entities. This challenges our classical understanding of identity because in the quantum realm, particles can exist in multiple states at once (superposition) and become entangled, where the properties of one instantaneously influence the other. This contrasts with classical physics, where objects have definite properties and histories.

2

How does Leibniz's Principle of Identity of Indiscernibles relate to quantum mechanics, and what is the role of Quantum Statistics in understanding particle indistinguishability?

Leibniz's Principle of Identity of Indiscernibles (PII) states that if two objects have all the same properties, they are the same object. However, quantum mechanics challenges this principle. Quantum particles can have identical properties such as mass, charge, and spin, yet still be considered distinct. The concept of Quantum Statistics also plays a role, where bosons and fermions behave differently due to their underlying indistinguishability. Bosons (like photons) can occupy the same quantum state, while fermions (like electrons) cannot.

3

What are the broader metaphysical implications if quantum particles are not considered individuals, and how might this affect our understanding of reality?

The concept of non-individuality in quantum mechanics has significant metaphysical implications. If quantum particles are not individuals, our classical notions of identity and existence may need revision. It may change the way we think about the relationship between the quantum world and our macroscopic reality. This opens the door to new perspectives, such as ontological pluralism, and impacts our understanding of reality at both subatomic and spatial levels.

4

How does the role of observation in quantum mechanics influence our understanding of whether particles have definite identities?

Observation plays a crucial role in quantum mechanics. Some interpretations suggest that the properties of a quantum system become definite only when we observe it. Before observation, particles exist in a superposition of states. This leads to questions about whether particles possess definite identities when they are not being observed, challenging our classical intuition that objects have inherent properties regardless of measurement. This is an ongoing point of discussion among interpretations of quantum mechanics.

5

What does the orthodox interpretation of quantum mechanics say about the individuality of quantum objects, and how does it differ from classical notions of identity?

The orthodox interpretation of quantum mechanics suggests that quantum objects lack individuality. This means that individual electrons, for instance, cannot be distinguished from one another. As Shrödinger said, “one cannot mark an electron, one cannot paint it red”. Although we can determine the number of electrons in an atom, we cannot differentiate each electron's qualities. This issue isn't epistemic (related to knowledge) but ontological (related to being).

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