  We describe a simple real space renormalization group technique for two
dimensional classical lattice models. The approach is similar in spirit to
block spin methods, but at the same time it is fundamentally based on the
theory of quantum entanglement. In this sense, the technique can be thought of
as a classical analogue of DMRG. We demonstrate the method - which we call the
tensor renormalization group method - by computing the magnetization of the
triangular lattice Ising model.
