Bell's Theorem
A mathematical theorem proving that no physical theory incorporating local hidden variables can reproduce all predictions of quantum mechanics.
Governing formula
|E(a, b) - E(a, b')| + |E(a', b) + E(a', b')| ≤ 2
SI unit
Dimensionless Inequality
In depth
Formulated by John Stewart Bell, the theorem establishes experimental criteria (Bell inequalities). Quantum mechanics predicts correlations that violate these inequalities, proving that nature is non-local or that physical properties do not exist prior to measurement.
Examples in the real world
Experimental verification of Bell inequality violations using polarization-entangled photons, earning the 2022 Nobel Prize in Physics.