Researchers at Rice University and TU Wien have experimentally measured quantum entanglement within a quantum critical metal, extending beyond theoretical predictions about these unusual materials and providing concrete data on electron behavior. The collaborative study, published in Nature Physics, characterized quantum materials that defy conventional electrical rules to determine the entanglement state of their electrons. “In quantum critical metals, electrons act so collectively that they lose their individual identity,” said Qimiao Si, the Harry C. Wiess Professor of Physics and Astronomy and director of Rice’s Extreme Quantum Materials Alliance. The team discovered the “spin quantum Fisher information” was at its highest at the quantum critical point, indicating a peak in entanglement as the material shifts between phases, and Si hopes this work will enable further exploration of quantum information capacities.
Quantum Entanglement Characterization in Strange Metals
A peak in quantum entanglement within strange metals occurs precisely at the point where the material transitions between distinct phases; researchers discovered this phenomenon while characterizing these unusual substances. Physicists at Rice University, led by Qimiao Si, partnered with Silke Paschen at TU Wien to experimentally measure this entanglement, moving beyond theoretical models of these materials. Si, the Harry C. Wiess Professor of Physics and Astronomy, said, “Experimental determination of the enhanced quantum entanglement in strange metals is really gratifying,” highlighting the significance of the empirical data. This research received funding from the U.S. Department of Energy, the Air Force Office of Scientific Research, the Robert A. Welch Foundation, and the Vannevar Bush Faculty Fellowship.
They found that a particular characteristic of entanglement, called the spin quantum Fisher information, was at its highest at the quantum critical point, a phenomenon that allows quantum materials to move in between two different phases.
Spin Quantum Fisher Information at the Quantum Critical Point
Characterizing these unusual metals, which exhibit electrical properties outside conventional norms, allowed the team to define the degree of quantum connection between electrons. This measurement of spin quantum Fisher information provides a concrete metric for understanding how strongly electrons are linked in these materials, offering insights into their collective behavior. Si envisions leveraging this research to create a new framework for exploring quantum information capabilities, stating, “We want to use this work as a launching pad to develop a framework that uses entanglement to explore ways to advance new…” The research received funding from the U.S.
This new collaborative work shows that in a highly collective quantum material, like strange metals, the electrons are particularly highly entangled.
Source: https://news.rice.edu/news/2026/physicists-measure-quantum-entanglement-quantum-critical-metal
