A demonstration showing that the rise of conventional stochastic methods in the Heisenberg picture to describe a light beam produced by a statistical ensemble of classical (c-number) sources is equivalent to representing the statistical state of the light beam by a density matrix having a Glauber P-representation. The relation between the classical and quantum statistical descriptions implied by Sudarshan's probability functional approach is shown to be purely formal and without physical meaning. Sudarshan's statement that the probability functional method can be used to prove that all correlation functions of the beam determine its density matrix is shown to be incorrect. 21 pp.
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