  We prove that the minimal Renyi entropy of order 2 (RE2) output of a
positive-partial-transpose(PPT)-inducing channel joint to an arbitrary other
channel is equal to the sum of the minimal RE2 output of the individual
channels. PPT-inducing channels are channels with a Choi matrix which is bound
entangled or separable. The techniques used can be easily recycled to prove
additivity for some non-PPT-inducing channels such as the depolarizing and
transpose depolarizing channels, though not all known additive channels. We
explicitly make the calculations for generalized Werner-Holevo channels as an
example of both the scope and limitations of our techniques.
