  The study of quantum channels is the most fundamental theoretical problem in
quantum information and quantum communication theory. The link product theory
of quantum channels is an important tool for studying quantum networks. In this
paper, we establish the Stinespring dilation theorem of the link product of
quantum channels in two different ways, discuss the discrimination of quantum
channels and show that the distinguishability can be improved by self-linking
each quantum channel n times as n grows. We also find that the maximum value of
Uhlmann's theorem can be achieved for diagonal channels.
