量子信息交叉中心学术报告033
Title: Detecting Quantum Phase Transition and Deriving Order Parameter from the Reduced Density Matrix
Speaker: Professor Haiqing Lin (林海青院士/教授，北京计算科学研究中心）
Place: RM 101，Bulg. 2，Xixi Campus (西溪校区西二楼101室)
Date and time: 9:30，December 27th，2019 （12月27日上午9:30）
Abstract：We report works on detecting quantum phase transition (QPT) from quantum information perspectives and deriving order parameter from reduced density matrix. Firstly, due to its quantum nature, we show how quantum entanglement is connected to the QPT, with studies on several well known quantum many-body systems. Secondly, by establishing a connection between the mutual information and the long-range order of the system, we propose a scheme to derive the order parameters corresponding to some long-range correlations in the ground state, without any prior knowledge of the existing symmetries. We demonstrate our scheme on the one-dimensional Hubbard model and the spinless Su-Schrieffer-Heeger (SSH) model. All the derived order parameters and their possible corresponding quantum phases are verified by the entanglement entropy and electronic configuration analysis. In particular, the order parameter appropriate to the topological regions of the SSH model is proposed and further proved by calculating the Berry phase under twisted boundary conditions. Moreover, we found that the topological nontrivial phase is robust to the introduction of repulsive inter-site interactions and can appear in the topological trivial parameter region when appropriate interactions are added.