%0 Journal Article %T Topological properties of a Valence-Bond-Solid %A Hui Shao %A WenAn Guo %A Anders W. Sandvik %J Physics %D 2015 %I arXiv %R 10.1088/1742-6596/640/1/012048 %X We present a projector quantum Monte Carlo study of the topological properties of the valence-bond-solid ground state in the $J$-$Q_3$ spin model on the square lattice. The winding number is a topological number counting the number of domain walls in the system and is a good quantum number in the thermodynamic limit. We study the finite-size behaviour and obtain the domain wall energy density for a topological nontrivial valence-bond-solid state. %U http://arxiv.org/abs/1501.00237v1