Work

Topological Response in Open Quantum Systems with Weak Symmetries

Year: 2025

Type: article

Abstract: In open quantum systems, the interaction of the system with its environment gives rise to two types of symmetry: a strong one, where the system's symmetry charge is conserved exactly, and a weak one, where the system can exchange symmetry charge with the environment but still preserve symmetry at the ensemble level. While generic open quantum systems feature weak symmetries only, the symmetry-protected topological response for bosonic (spin) systems has only been considered in the stricter setup with additional strong symmetries. Here, we address the generic case and demonstrate that weak symmetries alone can protect topological responses that distinguish different phases of matter. For bosonic systems, focusing on one-dimensional mixed states described by locally purifiable density operators, we propose a quantized response characterizing qualitatively distinct phases. It is detectable via the decay behavior of different string order parameters. We illustrate our general results through a noisy Affleck-Kennedy-Lieb-Tasaki model. In particular, we show that the coupling to the environment can induce a phase transition to a state protected by weak symmetries, without a pure-state or strong-symmetry analog.

Source: Physical Review Letters

DOI: 10.1103/qg2g-nz88

Authors: Ze-Min Huang, Sebastian Diehl, Xiao-Qi Sun

Institutions: University of Cologne, Max Planck Institute of Quantum Optics, Munich Center for Quantum Science and Technology

Language: English

Topic: Quantum many-body systems

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,750

Funders: Alexander von Humboldt-Stiftung, Deutsche Forschungsgemeinschaft