The story
Named after John Stewart Bell (1928–1990), Irish physicist.
Etymology from Wiktionary, CC BY-SA 4.0.
Bell state
Today it means: One of a set of four entangled states, namely |Φ⁺⟩=1/√2(|00⟩+|11⟩), |Φ⁻⟩=1/√2(|00⟩-|11⟩), |Ψ⁺⟩=1/√2(|01⟩+|10⟩), and |Ψ⁻⟩=1/√2(|01⟩-|10⟩), where |xy⟩:=|x⟩⊗|y⟩; these are the simplest examples of entangled states. Full definition →