The GHZ paradox shows that quantum correlations cannot be explained by local realistic models. An international team used coherent light to encode GHZ-type correlations and produced photons whose quantum states span 37 internal dimensions, demonstrating exceptionally strong nonclassical behavior. Published in Science Advances, the work opens new research paths and potential applications for high-dimensional quantum communication, computation and cryptography.
Scientists Create Photons That Simultaneously Occupy 37 Quantum Dimensions
This Experiment Created Light in 37 DimensionsSAKKMESTERKE/SCIENCE PHOTO LIBRARY - Getty Images
Researchers have pushed the boundaries of quantum strangeness by engineering photons whose quantum states span 37 distinct internal dimensions. The experiment extends the Greenberger–Horne–Zeilinger (GHZ) paradox into much higher-dimensional territory and produces some of the strongest nonclassical effects observed to date.
The GHZ paradox, introduced by Greenberger, Horne and Zeilinger in 1989, reveals sharp contradictions between quantum mechanics and any model that insists particles are influenced only by their immediate surroundings (so-called local realistic models). In simple GHZ thought experiments, imposing locality and predefined outcomes leads to logical impossibilities—highlighting how quantum correlations cannot be reproduced by classical descriptions.
In a paper published in Science Advances, an international team encoded GHZ-type correlations into coherent light by exploiting properties such as color and wavelength. Instead of the familiar three spatial dimensions, the researchers prepared photons that require 37 internal reference levels to fully describe their quantum state. Producing and verifying entanglement across so many levels is technically demanding, but the team reports clear signatures inconsistent with any local realistic explanation.
“This experiment shows that quantum physics is more nonclassical than many of us thought,” said Zhenghao Liu of the Technical University of Denmark, a co-author of the study. “It could be that 100 years after its discovery, we are still only seeing the tip of the iceberg.”
The work combined established photon-generation and control techniques with a tailored, scalable GHZ-like scheme that operates across many internal states. By encoding correlations across color and wavelength channels in coherent light, the researchers could manipulate and test 37-dimensional quantum states with precise measurements.
Beyond its conceptual significance, the experiment points to practical opportunities. High-dimensional entanglement can carry more information per particle and may offer enhanced resilience, security, or capacity for quantum communication, computing and cryptography compared with two-level (qubit) systems. The authors suggest the approach opens several avenues for further research into both foundations and applications of high-dimensional quantum systems.
Reported in New Scientist and documented in Science Advances, the experiment represents a step toward richer quantum states and deeper tests of nonclassicality. If current experiments reveal only the "tip of the iceberg," as Liu suggests, exploring higher-dimensional systems may uncover still more powerful quantum phenomena.
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