Mesoscopic Stern-Gerlach device to polarize spin currents

Spin preparation and spin detection are fundamental problems in spintronics and in several solid-state proposals for quantum information processing. Here we propose the mesoscopic equivalent of an optical polarizing beam splitter. This interferometric device uses nondispersive phases (Aharonov-Bohm and Rashba) in order to separate spin-up and spin-down carriers into distinct outputs and thus it is analogous to a Stern-Gerlach apparatus. It can be used both as a spin preparation device and as a spin measuring device by converting spin into charge (orbital) degrees of freedom. An important feature of the proposed spin polarizer is that no ferromagnetic contacts are used.