Analogs of absolutely maximally entangled states in nonlocal correlations via the sheaf-theoretic framework and its applications

Abstract

The foundational work by Bell led to an interest in understanding non-local correlations that arise from entangled states shared between distinct, spacelike-separated parties, which formed a foundation for the theory of quantum information processing. We investigate the question of maximal correlations analogous to the maximally entangled states defined in the entanglement theory of multipartite systems. In this work, we define the maximality of nonlocal correlation as being analogous to the absolutely maximally entangled state. To formalize this, we employ the sheaf-theoretic framework for contextuality, which generalizes non-locality. This provides a metric for correlations called contextual fraction (CF), which ranges from $0$ (non-contextual) to $1$ (maximally contextual). Using this, we have defined the absolutely maximal contextual correlations (AMCC), which are maximally contextual and have maximal marginals. The Popescu-Rohrlich (PR) box serves as the bipartite example, and we construct various extensions of such correlations in the tripartite case. An infinite family of various forms of AMCC is constructed using the parity check and the constraint satisfiability problem (CSP) construction. We also demonstrate the existence of maximally contextual correlations, which do not exhibit maximal marginals, and refer to them as non-AMCC. Furthermore, we showed that GHZ correlations in the $(n,2,2)$ setting give rise to AMCCs for the particular choice of measurement settings. The results are further applied to secret sharing and randomness extraction using AMCCs.