Tangent-space methods for truncating uniform MPS

Understand

A central primitive in quantum tensor network simulations is the problem of approximating a matrix product state with one of a lower bond dimension.

• This problem forms the central bottleneck in algorithms for time evolution and for contracting projected entangled pair states.
• We formulate a tangent-space based variational algorithm to achieve this for uniform (infinite) matrix product states.
• The algorithm exhibits a favourable scaling of the computational cost, and we demonstrate its usefulness by several examples involving the multiplication of a matrix product state with a matrix product operator.