Electronic entanglement in the vicinity of a superconductor

A weakly biased normal-metal-superconductor junction is considered as a potential device injecting entangled pairs of quasi-particles into a normal-metal lead. The two-particle states arise from Cooper pairs decaying into the normal lead and are characterized by entangled spin- and orbital degrees of freedom. The separation of the entangled quasi-particles is achieved with a fork geometry and normal leads containing spin- or energy-selective filters. This solid state entangler is characterized by noise cross-correlations which are identical to the noise in one lead, a signature consistent with entanglement. A connection to Bell-type experiments is envisioned (cond-mat/0009193).