  We investigate the disorder-driven superconductor to insulator quantum phase
transition (SIT) in an interacting fermion model using determinantal quantum
Monte Carlo (QMC) methods. The disordered superconductor is modeled by an
attractive Hubbard model with site disorder chosen randomly from a uniform
distribution. The superconducting state which exists for small disorder is
shown to evolve into an insulating phase beyond a critical disorder. The
transition is tracked by the vanishing of (a) the superfluid stiffness, and (b)
the charge stiffness or the delta function peak in the optical conductivity at
zero frequency. We also show the behavior of the charge, spin, pair, and
current correlations in the presence of disorder. Results for the temperature
dependence of the dc conductivity, obtained by an approximate analytic
continuation technique, are also presented both in the metallic phase above
$T_c$ and the insulating phase. We discuss some of the complications in
extracting the resistance at the transition point.
