General fidelity limit for quantum channels
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.
Barnum, Howard; Fuchs, Christopher; Jozsa, Richard; and Schumacher, Benjamin, "General fidelity limit for quantum channels" (1996). Physical Review A 54(6): 4707-4711. Faculty Publications. Paper 260.
Physical Review A