Variational methods for contracting projected entangled-pair states

Projected entangled-pair states (PEPS) provide excellent variational wave functions for ground of strongly correlated quantum systems in two dimensions. Determining the expectation value such a PEPS function requires contraction two-dimensional tensor network. Here, authors show that this can itself be formulated as problem, allowing one to compare accuracies commonly used schemes. The find good agreement between different schemes, demonstrating robustness simulations.