No Bipartite-Nonlocal Causal Theory Can Explain Nature's Correlations

TL;DR

This paper proves that certain quantum correlations cannot be explained by any bipartite nonlocal causal theory, establishing that Nature's nonlocality is inherently multipartite across all physical theories.

Contribution

It introduces a new, theory-agnostic definition of genuine tripartite nonlocality based on LOSR, challenging previous bipartite explanations of quantum correlations.

Findings

Certain tripartite quantum correlations are incompatible with bipartite nonlocal causal models.

A new framework for defining genuine multipartite nonlocality is proposed.

Quantum correlations violate device-independent inequalities, certifying inherently multipartite nonlocality.

Abstract

We show that some tripartite quantum correlations are inexplicable by any causal theory involving bipartite nonclassical common causes and unlimited shared randomness. This constitutes a device-independent proof that Nature's nonlocality is fundamentally at least tripartite in every conceivable physical theory - no matter how exotic. To formalize this claim we are compelled to substitute Svetlichny's historical definition of genuine tripartite nonlocality with a novel theory-agnostic definition tied to the framework of Local Operations and Shared Randomness (LOSR). A companion article [PRA. 104, 052207 (2021)] generalizes these concepts to any number of parties, providing experimentally amenable device-independent inequality constraints along with quantum correlations violating them, thereby certifying that Nature's nonlocality must be boundlessly multipartite.