Postquantum steering

TL;DR

This paper explores the possibility of postquantum steering, a form of nonlocal correlation beyond quantum mechanics, demonstrating its existence in tripartite systems and highlighting its fundamental differences from postquantum nonlocality.

Contribution

The paper proves the existence of postquantum steering in three-party systems, revealing a new form of nonlocality beyond quantum theory.

Findings

Postquantum steering exists in tripartite systems.

Postquantum steering is fundamentally different from postquantum nonlocality.

Provides new insights into multipartite quantum correlations.

Abstract

The discovery of postquantum nonlocality, i.e., the existence of nonlocal correlations that are stronger than any quantum correlations but nevertheless consistent with the no-signaling principle, has deepened our understanding of the foundations of quantum theory. In this work, we investigate whether the phenomenon of Einstein-Podolsky-Rosen steering, a different form of quantum nonlocality, can also be generalized beyond quantum theory. While postquantum steering does not exist in the bipartite case, we prove its existence in the case of three observers. Importantly, we show that postquantum steering is a genuinely new phenomenon, fundamentally different from postquantum nonlocality. Our results provide new insight into the nonlocal correlations of multipartite quantum systems.