Academy of Mathematics and Systems Science, CAS
Colloquia & Seminars

Speaker:	Dr. Zhenning Cai, National University of Singapore
Inviter:
Title:	Diagrammatic Monte Carlo Methods for Open Quantum Systems
Language:	Chinese
Time & Venue:	2023.06.01 15:00-17:00 N202
Abstract:	In reality, all quantum systems are coupled to the environment, causing the system to exhibit some classical behavior. In this talk, we consider the open quantum system coupled to a harmonic bath. In the case where coupling is weak, we can mimic Feynman’s methodology to represent the dynamics as the sum of infinite diagrams, each of which stands for an integral after expanding the observable with respect to the small coupling parameter. Furthermore, bold diagrams can be defined as the sum of many diagrams with similar structures. We will discuss how we can use the diagrammatic representation to accelerate the computation of observables in open quantum systems. In particular, we will consider a specific diagrammatic method called the inchworm method and study its application to the spin chain models. Through this application, we will also reveal the limitations of the current method and point out some future directions.