NIST researchers have achieved a major milestone in quantum physics by conducting the first loophole-free test of Bell’s theorem. The experiment, led by NIST’s Physical Measurement Laboratory (PML) and Information Technology Laboratory (ITL), used entangled photon pairs to demonstrate that quantum theory is complete and that Einstein’s 1935 “EPR” paradox cannot be explained by local hidden variables.
The team closed three major loopholes that had previously undermined earlier tests:
1. Detection loophole: NIST developed ultrafast single-photon detectors to ensure nearly perfect detection efficiency
2. Fair sampling loophole: They used a novel source of entangled photons to ensure fair sampling of all possible measurement outcomes
3. Locality loophole: The experiment was conducted with space-like separated measurement settings to ensure locality
The experiment, published in Physical Review Letters, provides clear evidence against local hidden variable theories and supports the quantum mechanical description of reality. The achievement was recognized with a Gold Medal Award from NIST.
Keywords: Bell’s theorem, entangled photon pairs, loophole-free test, quantum theory, single-photon detectors
