A minimal example of quantum non-classicality without freedom of choice

Abstract:Bell's theorem is often considered the most stringent notion of non-classicality. The generalization of Bell's theorem to causal networks offers interesting new perspectives on the phenomenon of quantum non-classicality and prompts us with a fundamental inquiry: What is the simplest scenario leading to the incompatibility between quantum correlations and the classical theory of causality? Here we demonstrate that quantum non-classicality is possible in an entanglement swapping network consisting of only three dichotomic variables, without the need for the locality assumption or external measurement choices. We also show that interventions, a central tool in the field of causal inference, significantly improve the noise robustness of this new kind of non-classical behavior, making it feasible for experimental tests with current technology.

10.1103/PhysRevLett.135.090201

arXiv:2404.12790 [quant-ph]

(or arXiv:2404.12790v2 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2404.12790 Focus to learn more arXiv-issued DOI via DataCite

Phys. Rev. Lett. 135, 09020 -- Published 26 August, 2025

https://doi.org/10.1103/3854-r395 Focus to learn more DOI(s) linking to related resources

arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website.

Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy. arXiv is committed to these values and only works with partners that adhere to them.

Have an idea for a project that will add value for arXiv's community? Learn more about arXivLabs.