Department of Mathematical Sciences
QIT Thinking Seminar
Wednesday, November 19th, 2025
4:00PM-14:50PM
Stratton Hall 207
Speaker: Qucheng Gao, Boston College
Title: Scrambling Transition in Free Fermion Systems Induced by a Single Impurity
Abstract: In quantum many-body systems, interactions are often responsible for the rapid and chaotic spreading of information—a process known as scrambling. In this talk, I will discuss a surprising scenario where such scrambling emerges even when particles interact only through a single interaction impurity. By mapping the operator dynamics of random free-fermion systems to a random-walk–like process, we identify an “escape-to-scrambling” transition controlled by the impurity strength. The result connects concepts from random walks, nonequilibrium dynamics, and quantum information, and provides a universal picture for how local defects can trigger global information mixing.