Exact entanglement renormalization for string-net models

We construct an explicit renormalization-group transformation for Levin and Wen's string-net models on a hexagonal lattice. The transformation leaves invariant the ground-state ``fixed-point'' wave function of the string-net condensed phase. Our construction also produces an exact representation of the wave function in terms of the multiscale entanglement renormalization ansatz (MERA). This sets the stage for efficient numerical simulations of string-net models using MERA algorithms. It also provides an explicit quantum circuit to prepare the string-net ground-state wave function using a quantum computer.