 Quantum mutual information

The quantum mutual information of a bipartite state isIts nonnegativity is equivalent to Subadditivity of Von Neumann entropy.

Quantum mutual information is a concept from quantum information theory that generalizes the classical notion of mutual information to the realm of quantum mechanics. In classical information theory, mutual information quantifies the amount of information that two random variables share, representing how much knowing one variable reduces the uncertainty about the other. In the quantum context, consider a bipartite quantum system composed of two subsystems \( A \) and \( B \).