Density matrix renormalization group

Summary

The density matrix renormalization group (DMRG) is a numerical method that finds low-energy states of quantum lattice systems, above all one-dimensional chains. It was introduced by Steven White in 1992. In modern form it minimises the energy over matrix product states of a fixed bond dimension, optimising one or two sites at a time. It keeps, at each cut of the chain, the states of largest weight in the reduced density matrix, which is where its name comes from.