Quantum discord - WikipediaIn quantum information theory, quantum discord is a measure of nonclassical correlations between two subsystems of a quantum system. It includes correlations that are due to quantum physical effects but do not necessarily involve quantum entanglement. The notion of quantum discord was introduced by Harold Ollivier and Wojciech H. Zurek[1][2] and, independently by Leah Henderson and Vlatko Vedral.[
