Solid-state Stern-Gerlach spin splitter for magnetic field sensing, spintronics, and quantum computing.

We show conceptually that the edge of a two-dimensional topological insulator can be used to construct a solid-state Stern-Gerlach spin splitter. By threading such a Stern-Gerlach apparatus with a magnetic flux, Aharanov-Bohm-like interference effects are introduced. Using ferromagnetic leads, the setup can be used to both measure magnetic flux and as a spintronics switch. With normal metallic leads a switchable spintronics NOT-gate can be implemented. Furthermore, we show that a sequence of such devices can be used to construct a single-qubit SU(2)-gate, one of the two gates required for a universal quantum computer. The field sensitivity, or switching field, , is related to the characteristic size of the device, , through = /(2π), with being the unit of electric charge.