Quantum entanglement is usually the domain of exquisitely controlled experiments: a few trapped ions, a handful of photons, a small array of superconducting qubits. The idea that entanglement can exist in ordinary solid matter, a crystal you can hold in your hand, has been theoretically expected but extraordinarily difficult to prove.
Now researchers at the Vienna University of Technology (TU Wien), the University of Wuerzburg, and Rice University have done exactly that. Using neutron scattering data analyzed through the lens of quantum Fisher information, a tool from quantum information theory, they have shown that a centimeter-scale crystal of the strange metal Ce₃Pd₂₀Si₆ contains groups of at least nine quantum-entangled entities acting collectively. The result was published June 15 in Nature Physics.
“This is not a detail of one particular material, but a general physical principle,” said Fakher Assaad, a theoretical physicist at the University of Wuerzburg. “Strong entanglement appears to be directly linked to the unusual behavior of strange metals.”
Measuring the unmeasurable
The material in question, Ce₃Pd₂₀Si₆ (a compound of cerium, palladium, and silicon), is a “strange metal,” a class of materials whose electrical resistivity increases linearly with temperature, defying the conventional T² behavior of ordinary metals. Strange metals are found among high-temperature superconductors, heavy-fermion compounds, and twisted bilayer graphene, and their anomalous transport properties have puzzled physicists for decades.
The TU Wien team used the ThALES cold-neutron triple-axis spectrometer at the Institut Laue-Langevin (ILL) in Grenoble, France, to fire neutrons at the crystal and measure the dynamic spin correlations, essentially, how magnetic fluctuations in the material respond to energy transfer. From this data, they computed the quantum Fisher information (QFI), a quantity from quantum metrology that quantifies how sensitively a quantum system responds to a perturbation.
The logic is straightforward: independent particles can only produce a limited collective response. If the measured response exceeds that bound, the particles must be entangled. At a temperature of 60 millikelvin, just above absolute zero, the team measured a QFI value of 8.2, corresponding to an entanglement depth of at least nine particles. The true depth may be much greater: the authors note that their estimate is a conservative lower bound, and that the actual number of entangled entities could be orders of magnitude larger if the induced magnetic moment in the material is smaller than assumed.
“These are not just pairs of entangled particles,” said Federico Mazza, the study’s first author and a doctoral student at TU Wien. “This is multipartite entanglement, a genuinely collective quantum state involving many parties simultaneously.”
What it means for strange metals
The result provides a microscopic explanation for strange metal behavior. In a conventional metal, charge carriers (electrons) behave like independent particles, and their interactions can be treated perturbatively. In a strange metal, the strong entanglement discovered in this study means that the carriers lose their particle-like character, they are no longer independent entities but parts of a collective quantum state. This explains why strange metals exhibit such unusual properties, including ultra-low electrical noise, which the same group reported in 2025.
“This is the first direct measurement of strong multipartite entanglement in a macroscopic solid,” said Silke Paschen, the lead experimentalist at TU Wien. “It opens a completely new way of thinking about quantum materials.”
The work also validates a theoretical framework: the QFI approach to detecting entanglement in condensed matter was developed relatively recently (Hauke et al., Nature Physics, 2016), and this is one of its most striking applications. The researchers used quantum Monte Carlo simulations running on the SUPERMUC-NG supercomputer in Germany to confirm their experimental findings, showing that a Kondo destruction model, a specific theoretical framework for quantum criticality in heavy-fermion systems, reproduces the scale-free increase in QFI at the quantum critical point.
A new probe for quantum materials
The significance extends beyond a single material. The QFI-neutron-scattering technique can now be applied to other strange metal platforms: cuprate superconductors, iron-based pnictides, organic conductors, and moire materials such as twisted bilayer graphene. If strong entanglement is indeed a universal feature of strange metals, it would unify a disparate set of phenomena under a single quantum principle.
The caveats are typical of measurements at the frontier of condensed matter physics. The entanglement is inferred from the QFI analysis, not directly measured; the reported entanglement depth is a lower bound; the measurements were performed at a single wavevector, not mapped across the entire Brillouin zone; and the technique requires ultra-low temperatures and high energy resolution, making it far from a routine characterization tool.
Nevertheless, the result establishes that macroscopic quantum entanglement exists in ordinary solid matter, and that it can be detected and quantified. For a field that has spent decades building ever-larger entangled systems atom by atom, this is a reminder that nature may already be doing it at scale, in materials that have been sitting on laboratory shelves all along.
Source: Mazza, F., Biswas, S., Yan, X. et al. “Quantum Fisher information in a strange metal.” Nature Physics (2026). DOI: 10.1038/s41567-026-03298-0