Classification of symmetry protected topological phases in quantum spin chains

Abstract: We consider the classification problem of symmetry protected topological (SPT) phases on quantum spin systems. SPT phases are gapped short-range-entangled quantum phases with a symmetry $G$. We explain that in one and two-dimensional quantum spin systems, there are $H^{2}(G, U(1))$/ $H^{3}(G, U(1))$-valued invariant, confirming a physicists conjecture.