  We study two-color QCD with two flavors of Wilson fermion as a function of
quark chemical potential mu and temperature T. We find evidence of a superfluid
phase at intermediate mu and low T where the quark number density and diquark
condensate are both very well described by a Fermi sphere of nearly-free quarks
disrupted by a BCS condensate. Our results suggest that the quark contribution
to the energy density is negative (and balanced by a positive gauge
contribution), although this result is highly sensitive to details of the
energy renormalisation. We also find evidence that the chiral condensate in
this region vanishes in the massless limit. This region gives way to a region
of deconfined quark matter at higher T and mu, with the deconfinement
temperature, determined from the renormalised Polyakov loop, decreasing only
very slowly with increasing chemical potential. The quark number susceptibility
chi_q does not exhibit any qualitative change at the deconfinement transition.
We argue that this is because chi_q is not an appropriate measure of
deconfinement for 2-color QCD at high density.
