Maximal Non-Classicality in Multi-Setting Bell Inequalities

Abstract

The discrepancy between maximally entangled states and maximally non-classical quantum correlations is well-known but still not well understood. We aim to investigate the relation between quantum correlations and entanglement in a family Bell inequalities with $N$-settings and $d$ outcomes. Using analytical as well as numerical techniques, we derive both maximal quantum violations and violations obtained from maximally entangled states. Furthermore, we study the most non-classical quantum states in terms of their entanglement entropy for large values of $d$ and many measurement settings. Interestingly, we find that the entanglement entropy behaves very differently depending on whether $N=2$ or $N> 2$: when $N=2$ the entanglement entropy is a monotone function of $d$ and the most non-classical state is far from maximally entangled, whereas when $N> 2$ the entanglement entropy is a non-monotone function of $d$ and converges to that of the maximally entangled state in the limit of large $d$.