  We study a single-species polarized Fermi gas tuned across a narrow p-wave
Feshbach resonance. We show that in the course of a BEC-BCS crossover the
system can undergo a magnetic field-tuned quantum phase transition from a
p_x-wave to a p_x+i p_y-wave superfluid. The latter state, that spontaneously
breaks time-reversal symmetry, furthermore undergoes a topological p_x+ i p_y
to p_x+ i p_y transition at zero chemical potential \mu. In two-dimensions, for
\mu>0 it is characterized by a Pfaffian ground state exhibiting topological
order and non-Abelian excitations familiar from fractional quantum Hall
systems.
