  The recent article "Entropic Updating of Probability and Density Matrices"
[1] derives and demonstrates the inferential origins of both the standard and
quantum relative entropies in unison. Operationally, the standard and quantum
relative entropies are shown to be designed for the purpose of inferentially
updating probability distributions and density matrices, respectively, when
faced with incomplete information. We call the inferential updating procedure
for density matrices the "quantum maximum entropy method". Standard inference
techniques in probability theory can be criticized for lacking concrete
physical consequences in physics; but here, because we are updating quantum
mechanical density matrices, the quantum maximum entropy method has direct
physical and experimental consequences. The present article gives a new
derivation of the Quantum Bayes Rule, and some generalizations, using the
quantum maximum entropy method while discuss some of the limitations the
quantum maximum entropy method puts on the measurement process in Quantum
Mechanics.
