  We present a study of a simple model antiferromagnet consisting of a sum of
nearest neighbor SO($N$) singlet projectors on the Kagome lattice. Our model
shares some features with the popular $S=1/2$ Kagome antiferromagnet but is
specifically designed to be free of the sign-problem of quantum Monte Carlo. In
our numerical analysis, we find as a function of $N$ a quadrupolar magnetic
state and a wide range of a quantum spin liquid. A solvable large-$N$
generalization suggests that the quantum spin liquid in our original model is a
gapped ${\mathbb Z}_2$ topological phase. Supporting this assertion, a
numerical study of the entanglement entropy in the sign free model shows a
quantized topological contribution.
