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arXiv · 2512.14834

Entanglement without Quantum Mechanics: Operational Constraints on the Quantum Signature

Samuel Schlegel·Borivoje Dakić·Flavio Del Santo
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Abstract

Entanglement is often regarded as an inherently quantum feature. We show that this does not have to be the case: under restricted operational access, classical correlations can appear nonseparable when expressed in the formalism of quantum mechanics. If an observer is limited to a constrained set of measurements and transformations, certain classical phase-space distributions can mimic entanglement-like behaviours. Imposing positivity of the associated Hilbert space operator as a physicality requirement removes some of these representational artifacts, revealing a regime in which nonseparability is genuine but still reproducible by classical models. Only when the operational restrictions on the observer are lifted further--allowing operational tests of measurement incompatibility or other nonclassical signatures--does one obtain entanglement that can no longer be captured by any classical description. This operational hierarchy distinguishes classical artifacts, classically reproducible nonseparability, and genuine entanglement.

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Samuel Schlegel, Borivoje Dakić, Flavio Del Santo. 2025-12-16. Entanglement without Quantum Mechanics: Operational Constraints on the Quantum Signature. https://arxiv.org/abs/2512.14834

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