Title: Symmetry in open quantum systems: fromquantized response to long-range entanglement

Speaker:  Dr. Xiao-Qi Sun(孙孝奇),Max Planck Institute ofQuantum Optics

Time: 10:00 am, June 27 (Friday), 2025

Place: Room M830,IOP-CAS(中国科学院物理研究所M830)

 

Abstract:

Symmetry plays a central role in characterizing quantum phases. In openquantum systems, it arises in two distinct forms: weak symmetry, wherecharges are conserved only on average, and strong symmetry, with exactconservation laws. In this talk, I will explore their physical implications in1D open systems using a tensor network framework. For weak symmetry.will show that it enables a quantized response distinguishing mixed-statephases, including those without pure-state analogs, identifiable throughstring order parameters. For strong symmetry, I construct a broad class ofrenormalization fixed-point mixed states that exhibit zero correlationength and anomalous symmetry. Despite the absence of local correlationsthese states cannot be efficiently prepared, indicating intrinsic long-rangeentanglement.
Reference:
[1]ZM Huang,S Diehl, XO Sun, arXiv:2504.02941[2]XQ Sun, arXiv:2504.16985

 

About the speaker
Dr. Xiao-Qi Sun is currently a Humboldt Postdoctoral Fellow at theMax Planck Institute of Ouantum Optics, Before moving to Germany, heobtained his Ph.D. from Stanford University in 2020 and was a Gordonand Betty Moore Postdoctoral Scholar at the University of Illinois atUrbana-Champaign, His research lies at the intersection of quantuminformation and condensed matter physics, with a focus on topologicaphenomena in quantummanybodysystems, bothin and outoequilibrium.