This subsection focuses on entropy measures and information-theoretic structure in classical and quantum settings.
Reading path — advanced, off the critical path. This block develops quantum Shannon theory: Shannon entropy, von Neumann entropy, and strong subadditivity. It is numbered here so it stays grouped with quantum information, but it is not a prerequisite for Quantum Computation (III), Quantum Error Correction (IV), or Programming (V). On a first pass, read it after III — the algorithms there make the operational meaning of these entropy measures concrete. Every quantum-computing textbook surveyed places this material after the algorithms; the numbering keeps the topical grouping while this banner keeps the reading order honest.
Use the sequence below as the local map for this branch. The subtopics are organized to keep the historical arc and the formal properties of entropy in the same frame.