  It is shown that given two copies of a q-ary input channel $W$, where q is
prime, it is possible to create two channels $W^-$ and $W^+$ whose symmetric
capacities satisfy $I(W^-)\le I(W)\le I(W^+)$, where the inequalities are
strict except in trivial cases. This leads to a simple proof of channel
polarization in the q-ary case.
