【时 间】2023年5月10日 下午：4:30-6:30
【地 点】保定校區 数理系 教7楼406
【主 讲 人】刘全城 博士 Bar-Ilan University
刘全城，以色列巴伊兰大学博士生，2020年本科结业于山东大学泰山学堂。主要从事量子行走，量子丈量，非厄米量子力学，量子信息等方面的研究，在Physical Review Letters, Physical Review Research, Physical Review A 等期刊宣布多篇研究论文。
Recurrence in the dynamics of physical systems is an important phenomenon that has many far-reaching consequences. In classical physics, Poincare&/xshd/39;s recurrence theorem states that a complex system will return to its initial state within a finite time when left alone. This theorem has been extended to the quantum case and has been observed experimentally. In this work, we investigate quantum recurrence for a quantum system that interacts with periodic measurements. Specifically, we consider interacting spin systems where the measurements are performed on one spin. We ask the question: if the monitored spin is initially prepared in the upstate (for example), how long will it take to measure the spin for the first time in the upstate again? We show that the mean recurrence time is fractionally quantized and characterized by the number of dark states, which are eigenstates of the spin system where the monitored spin and the surrounding bath are not entangled. The mean recurrence time is invariant when changing the sampling rate, and this invariance is topologically protected by the quantized winding number.