Time: 10:00 am, Nov. 29 (Friday), 2024

Venue: No. 1 Meeting Rm, 3rd Floor, No. 6 Bldg, UCAS Zhong-Guan-Cun Campus (国科大中关村校区6号楼三层第一会议室)

Tencent Meeting: 724-645-584

Speaker: Prof. Shuo Yang (杨硕), Tsinghua University

Abstract

This study delves into the concept of quantum phases in open quantum systems, examining the shortcomings of existing approaches that focus on steady states of Lindbladians and highlighting their limitations in capturing key phase transitions. In contrast to these methods, we introduce the concept of imaginary-time Lindbladian evolution as an alternative framework. This new approach defines gapped quantum phases in open systems through the spectrum properties of the imaginary-Liouville superoperator. We find that, in addition to all pure gapped ground states, the Gibbs state of a stabilizer Hamiltonian at any finite temperature can also be characterized by our scheme, demonstrated through explicit construction. To illustrate the effectiveness of this framework, we apply it to investigate the phase diagram for open systems with Z_2^σ×Z_2^τ symmetry, including cases with nontrivial average symmetry protected topological order or spontaneous symmetry breaking order. Our findings demonstrate universal properties at quantum criticality, such as nonanalytic behaviors of steady-state observables, divergence of correlation lengths, and closing of the imaginary-Liouville gap. These results advance our understanding of quantum phase transitions in open quantum systems.

References:

[1] Yuchen Guo, Ke Ding, and Shuo Yang, arXiv:2408.03239.

[2] Yuchen Guo and Shuo Yang, arXiv:2410.13734.