Observation of multipartite spin entanglement in a cuprate chain

Year: 2026

Type: article

Abstract: Quantum materials are believed to host highly entangled states of matter, but probing and quantifying such entanglement has long remained experimentally elusive. Here, we use resonant inelastic X-ray scattering (RIXS) as a probe of multipartite spin entanglement. By projecting the RIXS cross section onto the appropriate spin excitation channel, we show that the Quantum Fisher Information can be extracted directly from the measured spin fluctuation spectrum. We detect at least 7-partite spin entanglement in the model one-dimensional cuprate Sr$_2$CuO$_3$, revealing one of the largest entanglement depths yet reported in a solid. The observed entanglement depth agrees with Hubbard-model expectations and persists to elevated temperatures. Our results establish RIXS as an experimental probe of many-body spin entanglement and provide a platform for extensions to charge and orbital sectors and nonequilibrium settings.

Source: Physical Review X

DOI: 10.1103/q6gw-zk1k

Language: English

Topic: Quantum many-body systems

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $4,200

Funders: U.S. Department of Energy, Research Corporation for Science Advancement, Oak Ridge Associated Universities, Deutsche Forschungsgemeinschaft, Office of Science, Oak Ridge Institute for Science and Education, Basic Energy Sciences, Workforce Development for Teachers and Scientists, Brookhaven National Laboratory, Lawrence Berkeley National Laboratory

OpenAlex ID: W7212014093