  We investigate combined effects of spin-orbit coupling and magnetic field in
carbon nanotubes containing one or more bends along their length. We show how
bends can be used to provide electrical control of confined spins, while spins
confined in straight segments remain insensitive to electric fields. Device
geometries that allow general rotation of single spins are presented and
analyzed. In addition, capacitive coupling along bends provides coherent
spin-spin interaction, including between otherwise disconnected nanotubes,
completing a universal set of one- and two-qubit gates.
