  The goal of this paper is to generalize classical d-separation and classical
Belief Propagation (BP) to the quantum realm. Classical d-separation is an
essential ingredient of most of Judea Pearl's work. It is crucial to all 3
rungs of what Pearl calls the 3 rungs of Causation. So having a quantum version
of d-separation and BP probably implies that most of Pearl's Bayesian networks
work, including his theory of causality, can be translated in a straightforward
manner to the quantum realm.
