  This brief article gives an overview of quantum mechanics as a {\em quantum
probability theory}. It begins with a review of the basic operator-algebraic
elements that connect probability theory with quantum probability theory. Then
quantum stochastic processes is formulated as a generalization of stochastic
processes within the framework of quantum probability theory. Quantum Markov
models from quantum optics are used to explicitly illustrate the underlying
abstract concepts and their connections to the quantum regression theorem from
quantum optics.
