Superconductivity in correlated wave functions

We describe a new method to numerically evaluate the properties of correlated superconducting wave functions. We have applied it to the resonating-valence-bond (RVB) wave function for the Hubbard model on the square lattice. For the half-filled case we find that the $d$-wave RVB state and the antiferromagnetic ordered state have the same energy within numerical accuracy. At 10% doping we find $d$-wave superconductivity, consistent with previous studies. We show that the superconducting order parameter is proportional to the number of holes, for small hole concentrations.