# Evaluating the Maximal Violation of the Original Bell Inequality by Two-Qudit States Exhibiting Perfect Correlations/Anticorrelations

## TL;DR

This paper investigates the maximum violation of the original Bell inequality by symmetric two-qubit and two-qutrit states with perfect correlations or anticorrelations, establishing an upper bound of 3/2 and exploring its implications.

## Contribution

It introduces a class of symmetric two-qubit states with perfect correlations and bounds the Bell inequality violation, extending analysis to two-qutrit states with an open question.

## Key findings

- Maximum violation bound of 3/2 for two-qubit states.
- Identified states where the bound is attained.
- Upper bound of 3/2 for two-qutrit states, with open questions.

## Abstract

We introduce the general class of symmetric two-qubit states guaranteeing the perfect correlation or anticorrelation of Alice and Bob outcomes whenever some spin observable is measured at both sites. We prove that, for all states from this class, the maximal violation of the original Bell inequality is upper bounded by 3/2 and specify the two-qubit states where this quantum upper bound is attained. The case of two-qutrit states is more complicated. Here, for all two-qutrit states, we obtain the same upper bound 3/2 for violation of the original Bell inequality under Alice and Bob spin measurements, but we have not yet been able to show that this quantum upper bound is the least one. We discuss experimental consequences of our mathematical study.