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Bell tests: nature really is non-local (Nobel 2022)
1982· Discovery / experiment
ProvenTested many times; part of working physics.
Experiments from 1972 onward showing entangled particles break Bell's limit, ruling out the local hidden instructions Einstein hoped for.
See it on the Science map →How it works
A source makes entangled photon pairs and sends them to two distant detectors whose settings are chosen at the last moment. Clauser (1972) and Aspect (1982) found correlations beyond Bell's limit, matching quantum theory. Critics noted loopholes, such as missed detections or settings that could have influenced each other. In 2015 teams in Delft, Vienna and Boulder closed both at once. A 2018 test used settings from about 100,000 volunteers' choices.
Why it matters
They settled experimentally that nature is not locally pre-scripted, and made entanglement a dependable engineering tool. Nobel Prize 2022 to Aspect, Clauser and Zeilinger.
How we know
Repeated by many labs with photons, atoms, electrons and superconducting circuits, with significance far beyond chance. The 2015 Delft test used electrons in labs 1.3 km apart.
Still a mystery
'Non-local' is one reading. The tests rule out local pre-set values, but whether nature is non-local or simply lacks definite values before measurement remains debated.
Connections (2)
▸Bell's theorem was checked by Bell tests: nature really is non-local (Nobel 2022)Proven
The relationship
Bell's theorem gives a number: local hidden-value theories cannot exceed a certain correlation score. Experiments measure many entangled pairs at several detector-setting combinations and compute the score. Every serious test has exceeded the limit, matching quantum predictions.
How the link was found
Freedman and Clauser at Berkeley (1972), Aspect at Orsay with rapidly switched settings (1982), Zeilinger's group in Innsbruck (1998), and loophole-free tests in 2015.
Why it's proven
Results break Bell's limit by many standard deviations, repeated in many labs with different technologies. The 2015 tests closed the main loopholes together.
Open questions and mysteries
The 'superdeterminism' loophole, where detector settings are secretly correlated with the particles since the Big Bang, cannot be fully excluded, though most physicists find it implausible.
▸Bell tests: nature really is non-local (Nobel 2022) confirmed Quantum entanglementProven
The relationship
Bell tests confirmed that entangled particles share correlations no pre-arranged plan could explain. That moved entanglement from a debated theoretical oddity to a confirmed physical fact, and then to a working tool in quantum encryption, teleportation of quantum states and quantum computers.
How the link was found
Clauser in 1972, Aspect in 1982, Zeilinger from the 1990s, sharing the 2022 Nobel Prize. Loophole-free tests in 2015 by Hensen, Giustina, Shalm and colleagues.
Why it's proven
Consistent results across decades, technologies and continents, including entanglement distributed by the Micius satellite over 1,200 km in 2017.
Open questions and mysteries
The tests confirm entanglement but do not say what mechanism, if any, underlies the correlations.