  We show that the 2x2x2 interference channel, i.e., the multihop interference
channel formed by concatenation of two 2-user interference channels achieves
the min-cut outer bound value of 2 DoF, for almost all values of channel
coefficients, for both time-varying or fixed channel coefficients. The key to
this result is a new idea, called aligned interference neutralization, that
provides a way to align interference terms over each hop in a manner that
allows them to be cancelled over the air at the last hop.
