Isometric Tensor Network States on an Infinite Stripe

Contraction of standard 2D tensor network ansatzes relies on approximation schemes, as tensor contractions costs scale exponentially with system size. Recently, the Isometric Tensor Network (isoTNS) ansatz was introduced for 2D finite quantum systems on a square lattice, allowing for exact $\mathcal{O}(1)$ evaluation of expectation values provided we can efficiently move the orthogonality center throughout the network. Here we generalize this isoTNS ansatz to strip geometries, in which the networks are infinite by finite and consist of translationally invariant rows of tensors. We demonstrate several algorithms for the infinite Moses Move (iMM), which moves the orthogonality hypersurface between columns of infinite length in the network. Using these iMM algorithms, we perform imaginary time evolution to identify the ground state of our 2D system, where the cost of optimization scales linearly with strip width rather than exponentially.