  TensorNetwork is an open source library for implementing tensor network
algorithms in TensorFlow. We describe a tree tensor network (TTN) algorithm for
approximating the ground state of either a periodic quantum spin chain (1D) or
a lattice model on a thin torus (2D), and implement the algorithm using
TensorNetwork. We use a standard energy minimization procedure over a TTN
ansatz with bond dimension $\chi$, with a computational cost that scales as
$O(\chi^4)$. Using bond dimension $\chi \in [32,256]$ we compare the use of
CPUs with GPUs and observe significant computational speed-ups, up to a factor
of $100$, using a GPU and the TensorNetwork library.
