Experiments on entangled particles turned a philosophical puzzle into the foundation of quantum technology.
A challenge to completeness
Quantum mechanics predicts that entangled particles share correlations stronger than classical physics allows, even when measured far apart. Einstein, Boris Podolsky, and Nathan Rosen used this strangeness to argue that the theory might be incomplete.
In 1964, physicist John Bell turned the philosophical dispute into an experimental question. Bell’s inequalities defined a limit that local hidden-variable theories must obey.
Experiments close the loopholes
John Clauser’s early experiments and Alain Aspect’s later refinements found violations consistent with quantum mechanics. Anton Zeilinger expanded the work into multi-particle entanglement and quantum-information experiments.
Later ‘loophole-free’ tests strengthened the conclusion: nature does not fit the combination of assumptions captured by local hidden-variable models.
The experiment did not make quantum mechanics less strange. It made the strangeness testable.
From paradox to technology
The 2022 Nobel Prize in Physics recognized Clauser, Aspect, and Zeilinger for experiments that established the foundations of quantum information science.
Entanglement now underpins work on quantum communication, sensing, and computation. A question once used to expose quantum theory’s discomfort became a resource for building new tools.