题 目：Time-crystal phase transition and quantum correlations in an emitter-waveguide system with feedback
报告人：Igor Lesanovsky (Professor of UNIVERSITY OF TÜBINGEN)
主持人：黄国翔 教授
时 间：2021年6月18日下午3:00
地 点：腾讯会议 ID：556 815 442 （光学大楼B225会议室）
报告人简介：
Igor lesanovsky, Professor of University of Tübingen in the Germany. His research interests are including: Strongly correlated spin systems, Relaxation and thermalization of closed quantum systems, Trapping and manipulation of highly excited (Rydberg) atoms, Collective phenomena in ultracold atomic gases, Creation of non-classical states of light and matter, Quantum Information with atoms and trapped ions, Non-equilibrium in open quantum systems.
Igor lesanovsky，德国图宾根大学教授。他的研究兴趣包括：强关联自旋系统，封闭量子系统的弛豫和热化，高激发（里德堡）原子的囚禁和操纵，超冷原子气体中的集体现象，原子和囚禁离子系统中的量子信息，量子开放系统中的非平衡物理问题等。
报告内容简介：
We investigate the creation and control of emergent collective behaviour and quantum correlations using feedback in an emitter-waveguide system using a minimal model. Employing homodyne detection of photons emitted from a laser-driven emitter ensemble into the modes of a waveguide allows to generate intricate dynamical phases. In particular, we show the emergence of a time-crystal phase, the transition to which is controlled by the feedback strength. Feedback enables furthermore the control of many-body quantum correlations, which become manifest in spin squeezing in the emitter ensemble. Developing a theory for the dynamics of fluctuation operators we discuss how the feedback strength controls the squeezing and investigate its temporal dynamics and dependence on system size. These results allow to quantify spin squeezing and fluctuations in the limit of large number of emitters, revealing critical scaling of the squeezing close to the transition to the time-crystal.