Stronger two-observer all-versus-nothing violation of local realism.
We introduce a two-observer all-versus-nothing proof of Bell's theorem which reduces the number of required quantum predictions from 9 to 4, provides a greater amount of evidence against local realism, reduces the detection efficiency requirements for a conclusive experimental test of Bell's theorem, and leads to a Bell inequality which resembles Mermin's inequality for three observers but requires only two observers.
Cabello
Adán
A
Departamento de Física Aplicada II, Universidad de Sevilla, 41012 Sevilla, Spain.