Measuring a dynamical topological order parameter in quantum walks

• 作者: Xiao-Ye Xu Qin-Qin Wang Markus Heyl Jan Carl Budich Wei-Wei Pan Zhe Chen Munsif Jan Kai Sun Jin-Shi Xu Yong-Jian Han Chuan-Feng Li Guang-Can Guo
• 来源期刊: 光：科学与应用（英文版）
• 年，卷（期）: 2020,（1）
• 所属期刊栏目: Original Articles
• 页码范围: 60-70
• 页数: 11页
• 语种: 英文

摘要

Quantum processes of inherent dynamical nature, such as quantum walks, defy a description in terms of an equilibrium statistical physics ensemble. Until now, identifying the general principles behind the underlying unitary quantum dynamics has remained a key challenge. Here, we show and experimentally observe that split-step quantum walks admit a characterization in terms of a dynamical topological order parameter (DTOP). This integer-quantized DTOP measures, at a given time, the winding of the geometric phase accumulated by the wavefunction during a quantum walk. We observe distinct dynamical regimes in our experimentally realized quantum walks, and each regime can be attributed to a qualitatively different temporal behavior of the DTOP. Upon identifying an equivalent many-body problem, we reveal an intriguing connection between the nonanalytic changes of the DTOP in quantum walks and the occurrence of dynamical quantum phase transitions.