Optimal compression for mixed signal states - art. no. 052309

We consider the problem of the optimal compression rate in the case of a so urce producing mixed signal states within the visible scheme (where Alice, who is to compress the signal, can know the identities of the produced stat es). We show that a simple strategy based on replacing the signal states wi th their extensions gives optimal compression. As a result we obtain a cons iderable simplification of the formula for an optimal compression rate with in a visible scheme.