Self-normal and biorthogonal dynamical quantum phase transitions in non-Hermitian quantum walks

• Published in: Light, science & applications Vol. 14; no. 1; pp. 253 - 11
• Main Authors: Zhang, Haiting, Wang, Kunkun, Xiao, Lei, Xue, Peng
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 26.07.2025; Springer Nature B.V; Nature Publishing Group
• Subjects: 639/766/400/3925; 639/766/400/482; Lasers; Microwaves; Optical and Electronic Materials; Optical Devices; Optics; Phase transitions; Photonics; Photons; Physics; Physics and Astronomy; Quantum physics; RF and Optical Engineering; Symmetry
• ISSN: 2047-7538; 2095-5545; 2047-7538
• DOI: 10.1038/s41377-025-01919-6

Dynamical quantum phase transitions (DQPTs), characterized by non-analytic behavior in rate function and abrupt changes in dynamic topological order parameters (DTOPs) over time, have garnered enormous attention in recent decades. However, in non-Hermitian systems, the special biorthogonality of the bases makes the definition of DQPTs complex. In this work, we delve into the comprehensive investigation of self-normal DQPTs (originally used in Hermitian systems) to compare them with their biorthogonal counterpart, within the context of non-Hermitian quantum walks (QWs). We present a detailed analysis of the behaviors of Loschmidt rate functions and DTOPs under these two distinct theoretical approaches. While both self-normal and biorthogonal methods can be used to detect DQPTs in quench dynamics between different topological phases, we theoretically present their differences in the definition of critical momenta and critical times by analyzing the Fisher zeros and fixed points. Finally, we present an experiment that observes both types of DQPTs using one-dimensional discrete-time QWs with single photons. The article performs a detailed analysis of self-normal and biorthogonal dynamical quantum phase transitions, presenting characteristics of their physical quantities both theoretically and experimentally.