General fidelity limit for quantum channels
Howard Barnum, Christopher A. Fuchs, Richard Jozsa, Benjamin W. Schumacher · Physical Review A · 1996
We derive a general limit on the fidelity of a quantum channel conveying an ensemble of pure states. Unlike previous results, this limit applies to arbitrary coding and decoding schemes. This establishes in full generality the quantum noiseless coding theorem, formerly obtained only for the special case of unitary decoding schemes. \textcopyright{} 1996 The American Physical Society.