Bell's theorem without inequalities and without alignments.
A proof of Bell's theorem without inequalities is presented which exhibits three remarkable properties: (a). reduced local states are immune to collective decoherence; (b). distant local setups do not need to be aligned, since the required perfect correlations are achieved for any local rotation of the local setups; (c). local measurements require only individual measurements on the qubits. Indeed, it is shown that this proof is essentially the only one which fulfills (a). (b). and (c).
Cabello
Adán
A
Departamento de Física Aplicada II, Universidad de Sevilla, 41012 Sevilla, Spain. adan@us.es