Robustness of entanglement as an indicator of topological phases in quantum walks
Qinqin Wang, Xiao-Ye Xu, Weiwei Pan, Si-Jing Tao, Zhe Chen, Yongtao Zhan, Kai Sun, Jin‐Shi Xu, Geng Chen, Yong‐Jian Han, Chuan‐Feng Li, Guang‐Can Guo · Optica · 2019
How to reveal topological phases and their boundaries is an intriguing issue in various systems. Entanglement, which plays a fundamental role in quantum information, has been found profoundly related to topological phases. However, experimentally exploring this relation is precluded by the limited ability to obtain entanglement in many-body systems. In this work, we propose and experimentally demonstrate that the robustness of entanglement, quantified by the von Neumann entropy, can be used to reveal the topological phase with winding number W = 1 and topological phase with W = 0 in quantum walks. With the different robustness of entanglement against perturbations of a parameter, the phase boundaries between the distinct topological phases can be further determined. As a result, our work not only offers a new perspective for quantum walks but also exhibits the deep connection between entanglement and topological physics.