Optimal Inequalities for State-Independent Contextuality

Contextuality is a natural generalization of nonlocality which does not need composite systems or spacelike separation and offers a wider spectrum of interesting phenomena. Most notably, in quantum mechanics there exist scenarios where the contextual behavior is independent of the quantum state. We show that the quest for an optimal inequality separating quantum from classical noncontextual correlations in a state-independent manner admits an exact solution, as it can be formulated as a linear program. We introduce the noncontextuality polytope as a generalization of the locality polytope and apply our method to identify two different tight optimal inequalities for the most fundamental quantum scenario with state-independent contextuality.

Figure 1

Graph of the compatibility relations between the observables for the Yu-Oh scenario. Nodes represent vectors $|v_i⟩$ [or the observables $A_i$ defined in (5)] and edges represent orthogonality (or compatibility) relations.