  Using bosonization, which maps fermions coupled to a ${\mathbb{Z}}_2$ gauge
field to a qubit system, we give a simple form for the non-trivial 3-fermion
quantum cellular automaton (QCA) as a unitary operator realizing a phase
depending on the framing of flux loops, building off work by Shirley et al. We
relate this framing dependent phase to a pump of $8$ copies of a $p+ip$ state
through the system. We give a resolution of an apparent paradox, namely that
the pump is a shallow depth circuit (albeit with tails), while the QCA is
nontrivial. We discuss also the pump of fewer copies of a $p+ip$ state, and
describe its action on topologically degenerate ground states. One consequence
of our results is that a pump of $n$ $p+ip$ states generated by a free Fermi
evolution is a free fermion unitary characterized by a non-trivial winding
number $n$ as a map from the third homotopy group of the Brilliouin Zone
$3$-torus to that of $SU(N_ b)$, where $N_b$ is the number of bands. Using our
simplified form of the QCA, we give higher dimensional generalizations that we
conjecture are also nontrivial QCAs, and we discuss the relation to
Chern-Simons theory.
