Work

Mixed-State Phases from Local Reversibility

Year: 2026

Type: article

Abstract: We propose a refined definition of mixed-state phase equivalence based on locally reversible channel circuits. We show that such circuits preserve topological degeneracy and the locality of all operators including both strong and weak symmetries. Under a locally reversible channel, weak unitary symmetries are locally dressed into channel symmetries, a generalization of symmetry for open quantum systems. For Abelian higher-form symmetries, we show the refined definition preserves anomalies and spontaneous breaking of such symmetries within a phase. As a primary example, a two-dimensional classical loop ensemble is trivial under the previously adopted definition of mixed-state phases. However, it has nontrivial topological degeneracy arising from a mutual anomaly between strong and weak 1-form symmetries, and our results show that it is not connected to a trivial state via locally reversible channel circuits.

Source: Physical Review X

DOI: 10.1103/1kr5-jlcb

Authors: Shengqi Sang, Leonardo A. Lessa, Roger S. K. Mong, Tarun Grover, Chong Wang, Timothy H. Hsieh