Detecting topological order in a ground state wave function

A large class of topological orders can be understood and classified using the string-net condensation picture. These topological orders can be characterized by a set of data (N, d(i), F-lmn(ijk), delta(ijk)). We describe a way to detect this kind of topological order using only the ground state wave function. The method involves computing a quantity called the "topological entropy" which directly measures the total quantum dimension D = Sigma(i)d(i)(2).