Universal compression of classically correlated stationary quantum sources

Abstract

For a real number r > 0, let F(r) be the family of all stationary completely ergodic quantum sources with von Neumann entropy rates less than r. We prove that, for any r > 0, there exists a blind, source-independent block compression scheme which compresses every source from F(r) to rn qubits per input block length n with arbitrarily high fidelity for all large n. As our second result, we show that the stationarity and the ergodicity of a quantum source {ρm}m=1∞ are preserved by any trace-preserving completely positive linear map of the tensor product form e⊗m, where a copy of e acts locally on each spin lattice site. We also establish ergodicity criteria for so called classically-correlated quantum sources.