University of Science and Technology China Studies Hydrodynamic Breakdown

Researchers in China are challenging a fundamental assumption in the study of quantum dynamics, with findings released on July 2, 2026, suggesting established theories of charge transport may be incomplete. The team, affiliated with the Laboratory of Quantum Information, University of Science and Technology of China, and the Anhui Province Key Laboratory of Quantum Network, states that Kardar-Parisi-Zhang (KPZ) dynamics emerge in an open integrable model, the B3 model, rather than diffusion. According to the research, the B3 model functions as two interacting asymmetric XXZ spin chains, and the prevailing approach only captures the influence of interactions between these chains. The authors state that this work motivates a re-evaluation of the theory of charge transport in open systems beyond the approach based on spontaneous symmetry breaking, potentially reshaping our understanding of non-equilibrium quantum systems and their universal behaviors.

Kardar-Parisi-Zhang Dynamics in the B3 Model

This research, originating from the Laboratory of Quantum Information, University of Science and Technology of China, in Hefei, Anhui, represents a significant investment in unraveling complex quantum behavior. The license for their work was issued on July 2, 2026. The core of their work questions the widely accepted spontaneous symmetry breaking approach, a framework used to describe charge transport in open quantum systems. The researchers state that, contrary to predictions made by this approach, the B3 model exhibits KPZ dynamics rather than the diffusive dynamics typically expected. “When the initial state is appropriate, the asymmetric XXZ structure dominates the dynamics, which gives KPZ scaling behavior even when the hopping rate becomes negative.” This finding is significant because it suggests that relying solely on spontaneous symmetry breaking is insufficient for a complete understanding of emergent hydrodynamics in open systems.

The researchers utilized the Lindblad master equation to model the system, focusing on the charge dynamics. Through detailed analysis, they observed that the charge density, denoted as G(x,t), deviates from the diffusive behavior predicted by the spontaneous symmetry breaking approach. Rescaled data presented in their work shows a -2/3 exponent for short times, and a -1/2 exponent.

The study of quantum many-body systems increasingly focuses on identifying universal behaviors, particularly when these systems are driven away from equilibrium. Researchers are striving to understand how macroscopic properties emerge from microscopic interactions, and a key approach has been the spontaneous-symmetry-breaking approach. This framework, applied to open quantum systems modeled using the Lindblad master equation, offers a streamlined method for predicting charge transport properties. However, the limits of its applicability remain a crucial question, prompting investigations into whether deviations from this approach reveal more complex underlying dynamics. Guo-Qiang Wang, Chang-Ling Zou, Guang-Can Guo, and Xu-Bo Zou, affiliated with the Laboratory of Quantum Information, University of Science and Technology of China, and the Anhui Province Key Laboratory of Quantum Network, are challenging the widespread acceptance of this approach. Their work, with a license issued on July 2, 2026, centers on the B3 model, an open integrable system.

Researchers in China are intensely focused on understanding the intricacies of Kardar-Parisi-Zhang (KPZ) dynamics, a complex area of non-equilibrium physics with implications for diverse systems exhibiting fluctuating interfaces. This research challenges a widely accepted framework for describing charge transport in open quantum systems. Detailed analysis revealed that the spontaneous symmetry breaking approximation, while successful in many scenarios, fails to fully capture the emergent hydrodynamics of the B3 model.

Researchers within the Laboratory of Quantum Information are meticulously investigating Kardar-Parisi-Zhang (KPZ) dynamics, revealing a nuanced understanding of open quantum systems. This concentrated effort, spanning multiple affiliated key laboratories within the university and the Hefei National Laboratory, points to a focused approach to unraveling complex physical phenomena. Detailed analysis of charge density, denoted as G(x,t), revealed a scaling behavior inconsistent with spontaneous symmetry breaking approach predictions. Rescaled data shows a clear alignment with the KPZ scaling function.

The B3 model, rather than exhibiting diffusion as predicted by the spontaneous symmetry breaking approach, displays KPZ scaling behavior. This suggests that under certain conditions, the inter-chain interactions become negligible, and the system’s behavior is dictated by the individual asymmetric XXZ chains. The implications extend beyond the B3 model itself, prompting a re-evaluation of how charge transport is understood in open systems. Rescaled data presented in the study aligns with the characteristic scaling function of KPZ dynamics, confirming the deviation from diffusive behavior. This approach allowed them to observe the charge density. The findings, originating from Hefei, Anhui, suggest a shift in perspective regarding the fundamental mechanisms governing charge transport in these complex quantum environments.

The team’s findings suggest that the spontaneous symmetry breaking approach’s predictive power isn’t universal, and under certain conditions, fails to accurately capture emergent hydrodynamic behavior. Crucially, when the system begins in a specific initial state, the inter-chain interaction becomes negligible, and each chain behaves as an independent asymmetric XXZ model leading to the observed KPZ dynamics. This discovery is significant because it highlights the limitations of relying solely on spontaneous symmetry breaking to understand complex quantum phenomena. The researchers utilized detailed analysis of the charge density, observing deviations from spontaneous symmetry breaking approach predictions. The team’s approach involved modeling the system using the Lindblad master equation. They found that the spontaneous symmetry breaking approach neglects the effects of terms in the master equation that drive wavefunctions out of the variational subspace, and questioned whether this approximation is valid.