Compressibility of quantum mixed-state signals - art. no. 017902

We present a formula that determines the optimal number of qubits per messa ge that allows asymptotically faithful compression of the quantum informati on carried by an ensemble of mixed states. The set of mixed states determin es a decomposition of the Hilbert space into the redundant part and the irr educible part. After removing the redundancy, the optimal compression rate is shown to be given by the von Neumann entropy of the reduced ensemble.