  Conjugate degradable channels are channels whose quantum capacity is
calculable. They were defined and studied in [1] where, however, only channels
that are both degradable and conjugate degradable were found. In this paper we
bring the very first example of conjugate degradable channels that are not
degradable. We also identify the physical origin of these channels and show
that they belong to the class of optimal universal asymmetric cloners. We thus
not only positively answer the question whether conjugate degradable channels
form a new class of channels with a single-letter capacity formula but as a
side result we also calculate the quantum capacity of the optimal asymmetric
1->1+1 cloning channels.
