Which features of quantum physics are not fundamentally quantum but are due to indeterminism?

Flavio Del Santo; Nicolas Gisin

doi:10.22331/q-2025-04-03-1686

Which features of quantum physics are not fundamentally quantum but are due to indeterminism?

Flavio Del Santo and Nicolas Gisin

Group of Applied Physics, University of Geneva, 1211 Geneva, Switzerland
Constructor Institute of Technology, Geneva, Switzerland
Constructor University, 28759 Bremen, Germany

Published:	2025-04-03, volume 9, page 1686
Editor:	Thomas Elliott
Eprint:	arXiv:2409.10601v3
Doi:	https://doi.org/10.22331/q-2025-04-03-1686
Citation:	Quantum 9, 1686 (2025).

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Abstract

What is fundamentally quantum? We argue that most of the features, problems, and paradoxes – such as the measurement problem, the Wigner's friend paradox and its proposed solutions, single particle nonlocality, and no-cloning – allegedly attributed to quantum physics have a classical analogue if one is to interpret classical physics as fundamentally indeterministic. What really characterizes non-classical effects are incompatible physical quantities, which, in quantum quantum theory are associated to the fundamental constant $\hbar$.

Popular summary

Richard Feynman once made the famous claim that “nobody understands quantum mechanics." Even a hundred years later, this might still be the case. But is this confusion truly unique to quantum physics, or do similar deep-seated mysteries also exist in classical physics, just in a less apparent way? Put differently, are the features that define quantum mechanics—and are often seen as marking a radical break from classical physics—actually exclusive to the quantum realm?
In this paper, we show that a number of supposedly genuine quantum features –-such as the measurement problem, the Wigner’s friend paradox and its proposed solutions, single particle nonlocality, and no-cloning-– can already be found in classical physics, if one interprets the latter as fundamentally indeterministic.

► BibTeX data

@article{DelSanto2025whichfeaturesof,
  doi = {10.22331/q-2025-04-03-1686},
  url = {https://doi.org/10.22331/q-2025-04-03-1686},
  title = {Which features of quantum physics are not fundamentally quantum but are due to indeterminism?},
  author = {Del Santo, Flavio and Gisin, Nicolas},
  journal = {{Quantum}},
  issn = {2521-327X},
  publisher = {{Verein zur F{\"{o}}rderung des Open Access Publizierens in den Quantenwissenschaften}},
  volume = {9},
  pages = {1686},
  month = apr,
  year = {2025}
}

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Cited by

[1] Bartosz Jura, "Negation of the Separatedness-Based Framework as a Methodological Principle", (2026).

[2] Flavio Del Santo and Nicolas Gisin, "Was Schrödinger ever a determinist?", Nature Reviews Physics 8 8, 472 (2026).

[3] Bartosz Jura, "Negation of the Separatedness-Based Framework as a Methodological Principle", (2025).

[4] Bilal Khalid and Sabre Kais, "Classical analog of entanglement for a kicked top", Physical Review A 112 1, 012201 (2025).

[5] Bartosz Jura, "Negation of the Separatedness-Based Framework as a Methodological Principle", (2025).

[6] Bartosz Jura, "Negation of the Separatedness-Based Framework as a Methodological Principle", (2026).

[7] Shibdas Roy, Filippo Caruso, Srushti Patil, and Anumita Mukhopadhyay, 2025 IEEE International Conference on Quantum Control, Computing and Learning (qCCL) 65 (2025) ISBN:978-1-6654-5782-8.

[8] Nicolas Gisin, Flavio Del Santo, and Sean Bailly, "La physique intuitionniste rapproche les mondes classique et quantique", Pour la Science n° 586 8, 28 (2026).

[9] Bartosz Jura, "Negation of the Separatedness-Based Framework as a Methodological Principle", (2025).

[10] Amrapali Sen and Flavio Del Santo, "Superluminal transformations and indeterminism", New Journal of Physics 28 7, 074514 (2026).

[11] Alexey Golovnev, "Is there any Trinity of Gravity, to start with?", arXiv:2411.14089, (2024).

[12] Barnabas Gall, Sacha B. Pulsford, Dana Matthews, Matthew A. Spence, Joe A. Kaczmarski, John Z. Chen, Mahakaran Sandhu, Eric Stone, James Nichols, and Colin J. Jackson, "Protein Evolution as a Complex System", arXiv:2412.06115, (2024).

[13] Samuel Schlegel, Borivoje Dakić, and Flavio Del Santo, "Entanglement without Quantum Mechanics: Operational Constraints on the Quantum Signature", arXiv:2512.14834, (2025).

[14] Samuel Schlegel, Borivoje Dakić, and Flavio Del Santo, "Classical and quantum mechanics across representations: an operational reading of the Wigner Weyl correspondence", arXiv:2607.13135, (2026).

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