Physicists used Bell’s test across 73 qubits to prove that large quantum systems genuinely follow quantum mechanics. The breakthrough confirms real quantum correlations, paving the way for more secure communication and advanced quantum computing.
For decades, scientists have wondered: do large quantum systems truly obey the strange laws of quantum mechanics, or do they just appear to? Now, an international team of physicists has found the answer. Using an advanced version of Bell’s test, they proved that even large systems with up to 73 qubits display genuine quantum behavior that cannot be explained by classical physics.
The researchers describe their work as building a “quantum lie detector”—a tool that exposes whether a machine, like a quantum computer, is authentically quantum or merely imitating one.
The Bell Test: Quantum Truth Serum
Bell’s test, first proposed by physicist John Bell, is a cornerstone of quantum theory. It checks for nonlocal correlations—the spooky connection between particles that Einstein once called “spooky action at a distance.”
The experiment, led by Jordi Tura, Patrick Emonts, and PhD candidate Mengyao Hu from Leiden University in collaboration with Tsinghua University (Beijing) and Zhejiang University (Hangzhou), pushed this concept further than ever before. By running Bell tests on 73 superconducting qubits, they confirmed deep, nonclassical correlations beyond any statistical doubt.
A Clever Experiment with Big Results
Instead of directly measuring Bell correlations—a nearly impossible task in large systems—the team used a clever shortcut. They focused on minimizing energy within the quantum system, a process that quantum computers already excel at.
The results were dramatic. The researchers measured energy levels 48 standard deviations below what would be possible in any classical system, providing overwhelming evidence of authentic quantum behavior.
Even more impressively, they confirmed genuine multipartite Bell correlations, where all qubits in the system are involved simultaneously. This type of correlation is both rare and difficult to verify, yet the team managed to certify it in systems of up to 24 qubits.
Quantum Computers Are Getting “More Quantum”
This achievement shows that quantum computers aren’t just growing in size—they’re becoming more authentically quantum in nature. It’s the first time scientists have verified such deep quantum correlations in a system this large.
Beyond pure physics, the implications are immense. Understanding and harnessing Bell correlations could lead to more secure quantum communication, stronger encryption, and faster quantum algorithms.
A Leap Toward Quantum Trust
This breakthrough marks a major step toward building trustworthy quantum technologies. As quantum systems grow more complex, tests like this will ensure they behave according to quantum rules—not just classical approximations.