ADS seminar

Organizers：数学物理团队

Speaker：Shuo Yang (Tsinghua University)

Time：

Thur., 13:30-14:30, May 14, 2026

Venue：

B627, Shuangqing Complex Building A

Title:

Quantum Phase Transitions in Open Quantum Systems

Abstract:

Characterizing quantum phases and phase transitions in open quantum systems is a key problem in modern physics. Standard methods based on real-time Lindbladian steady states cannot properly describe quantum phase transitions in open systems. We introduce a new framework based on imaginary-time Lindbladian evolution. It defines gapped quantum phases in open systems through the spectrum of the imaginary-Liouville superoperator. The closure of this gap signals phase transitions by relating to the divergence of the Markov length. We apply this framework to open systems with Z_2 x Z_2 symmetry and observe universal critical properties. We also construct new phases, including double average symmetry-protected topological (ASPT) phases unique to open systems. In addition, we briefly introduce complementary approaches for classifying mixed-state phases, including the locally purified density operator method and a purification-based framework. These results improve our understanding of quantum phases and criticality in open quantum systems.

[1] Y. Guo, K. Ding, and S. Yang #, Rep. Prog. Phys. 88, 118001 (2025).

[2] Y. Guo and S. Yang #, Phys. Rev. B 111, L201108 (2025).

[3] Y. Guo *, J.-H. Zhang *, H.-R. Zhang, S. Yang #, and Z. Bi #, Phys. Rev. X 15, 021060 (2025).

[4] Y. Guo and S. Yang #, arXiv: 2602.21979.