Based on the Bardeen Cooper Schrieffer (BCS) theory of superconductivity, the
coherent splitting of Cooper pairs from a superconductor to two spatially
separated quantum dots has been predicted to generate nonlocal pairs of
entangled electrons. In order to test this hypothesis, we propose a scheme to
transfer the spin state of a split Cooper pair onto the polarization state of a
pair of optical photons. We show that the produced photon pairs can be used to
violate a Bell inequality, unambiguously demonstrating the entanglement of the
split Cooper pairs.Comment: 11 pages, 9 figures, v3 with added reference
