Quantum physics, the science governing the universe at the smallest scales, is full of mind-bending concepts that challenge our everyday intuition. One such concept is the Greenberger-Horne-Zeilinger (GHZ) paradox, which explores the strange phenomenon of quantum entanglement and non-locality. A recent experiment, conducted by scientists at the University of Science and Technology of China, has taken this paradox to an unprecedented level, testing it in a remarkable 37 dimensions.
Imagine checking your mailbox for a letter. In our everyday experience, we assume the letter exists in a definite state – either it’s there, or it isn’t – regardless of whether we’ve looked. This is the principle of “local realism,” where events are linked through cause and effect across space and time. However, quantum physics throws a wrench into this seemingly straightforward picture.
Before you open the mailbox, quantum mechanics suggests the letter’s existence is uncertain, existing in a superposition of possibilities. This uncertainty is called “context,” and the interconnectedness of these contexts is “entanglement.” The GHZ paradox demonstrates how entangled contexts can lead to outcomes that contradict local realism, suggesting that the letter might somehow appear in your mailbox without the postman ever having visited.
The Chinese researchers pushed the boundaries of this paradox by creating an experiment with three quantum contexts (analogous to the letter, the postman, and the mailbox) and exploring their relationships in a staggering 37 dimensions. Instead of a physical letter, they used photons, the particles of light. Their “mailbox” was a sophisticated system of fiber optics and detectors. By carefully analyzing the correlations between the photons, they demonstrated a GHZ-type paradox, showing that even with just three contexts, our classical understanding of reality breaks down.
This experiment’s key innovation was the use of 37 dimensions. While we experience reality in three spatial dimensions and one time dimension, quantum mechanics allows for the exploration of additional, abstract dimensions. The researchers designed a set of relationships between their three contexts that required 37 states, each representing a different dimension, to describe. This high-dimensional approach allowed them to probe the GHZ paradox in a more extreme and nuanced way than ever before.
The implications of this research are profound. It not only deepens our understanding of the fundamental principles of quantum mechanics but also has potential applications in quantum technology. By manipulating and understanding entanglement in higher dimensions, we may be able to develop more powerful and robust quantum computers and communication systems.
Furthermore, this work raises fundamental philosophical questions about the nature of reality, the limits of our intuition, and the meaning of these extra dimensions. While the experiment doesn’t explain why Aunt Judy might have forgotten your birthday (that remains a mystery!), it does illuminate the strange and wonderful world of quantum mechanics, a world far stranger than we could have ever imagined.
Reference: Zheng-Hao Liu et al, Exploring the boundary of quantum correlations with a time-domain optical processor, Science Advances (2025). DOI: 10.1126/sciadv.abd8080
