Large spin entangled current from a passive device

We show that a large entangled current can be produced from a very simple passive device: a cluster of three resonant quantum dots, tunnel coupled to one input lead and two output leads. Through a rapid first-order resonant process within the cluster, entangled electron pairs are emitted into separate leads. We show that the process is remarkably robust to variations in systems parameters. The simplicity and robustness should permit experimental demonstration in the immediate future. Applications include quantum repeaters and unconditionally secure interfaces.