Locality and classicality: role of entropic inequalities

Abstract

The use of the so-called entropic inequalities is revisited in the light of new quantum correlation measures, specially nonlocality. We introduce the concept of classicality as the nonviolation of these classical inequalities by quantum states of several multiqubit systems and compare it with the nonviolation of Bell inequalities, that is, locality. We explore—numerically and analytically—the relationship between several other quantum measures and discover the deep connection existing between them. The results are surprising due to the fact that these measures are very different in their nature and application. The cases for n=2,3,4 qubits and a generalization to systems with arbitrary number of qubits are studied here when discriminated according to their degree of mixture.