  Electronic energies are calculated for a Hubbard model on the $C_{60}$
molecule using projector quantum Monte Carlo (QMC). Calculations are performed
to accuracy high enough to determine the pair binding energy for two electrons
added to neutral $C_{60}$. The method itself is checked against a variety of
other quantum Monte Carlo methods as well as exact diagonalization for smaller
molecules. The conclusion is that the ground state with two extra electrons on
one $C_{60}$ molecule is a triplet and, over the range of parameters where QMC
is reliable, has a slightly higher energy than the state with electrons on two
separate molecules, so that the pair is unbound.
