  We consider sequences of random quantum channels defined using the
Stinespring formula with Haar-distributed random orthogonal matrices. For any
fixed sequence of input states, we study the asymptotic eigenvalue distribution
of the outputs through tensor powers of random channels. We show that the input
states achieving minimum output entropy are tensor products of maximally
entangled states (Bell states) when the tensor power is even. This phenomenon
is completely different from the one for random quantum channels constructed
from Haar-distributed random unitary matrices, which leads us to formulate some
conjectures about the regularized minimum output entropy.
