Detection of long-range entanglement in gapped quantum spin liquids by local measurements

Abstract: Topological order, reflected in long range patterns of entanglement, is quantified by the topological entanglement entropy (TEE) $\gamma$. We show that for gapped quantum spin liquids (QSL) it is possible to extract $\gamma$ using two-spin local correlators. We demonstrate our method for the gapped $\mathbb{Z}_2$ Kitaev spin liquid on a honeycomb lattice with anisotropic interactions. We show that the $\gamma = \log 2$ for $\mathbb{Z}_2$ topological order can be simply extracted from local two-spin correlators across two different bonds, with an accuracy comparable or higher than the Kitaev-Preskill construction. This implies that the different superselection sectors of $\mathbb{Z}_2$ gauge theory determined by global Wilson loop operators can be fully reflected locally in the matter majorana sector.