Lyapunov Exponent of a Quantum Many-Body System Measured for the First Time through Theory–Experiment Collaboration

The theoretical proposal was put forward by Tiangang Zhou, Pengfei Zhang, and Hui Zhai. Using dissipaton theory, they clarified the role of noise in measurements of out-of-time-ordered correlators, a key diagnostic of quantum many-body chaos. In collaboration with the groups of Prof. Xinhua Peng and Prof. Jiangfeng Du at the University of Science and Technology of China, the proposal was realized experimentally in a solid-state nuclear magnetic resonance system. The experiment not only provided the first verification of the central predictions of dissipaton theory, but also enabled noise effects to be systematically removed, leading to the first experimental extraction of the Lyapunov exponent in a quantum many-body system. The collaborative work was recently published in Physical Review Letters as an Editors’ Suggestion. APS Physics also published a commentary on the work by Prof. Xiao-Liang Qi of Stanford University.