QUANTUM SOURCES AND A QUANTUM CODING THEOREM

We define a large class of quantum sources and prove a quantum analog of the asymptotic equipartition property. Our proof relies on using lo cal measurements on the quantum source to obtain an associated classic al source. The classical sourer provides an upper bound for the dimens ion of the relevant subspace of the quantum source, via the Shannon-Mc Millan noiseless coding theorem. Along the way we derive a bound for t he von Neumann entropy of the quantum source in terms of the Shannon e ntropy of the classical source, and we provide a definition of ergodic ity of the quantum source. Several explicit models of quantum sources are also presented. (C) 1998 American Institute of Physics.