  Spin-helical states, which arise in quasi-one-dimensional (1D) channels with
spin-orbital (SO) coupling, underpin efforts to realize topologically-protected
quantum bits based on Majorana modes in semiconductor nanowires. Detecting
helical states is challenging due to non-idealities present in real devices.
Here we show by means of tight-binding calculations that by using ferromagnetic
contacts it is possible to detect helical modes with high sensitivity even in
the presence of realistic device effects, such as quantum interference. This is
possible because of the spin-selective transmission properties of helical
modes. In addition, we show that spin-polarized contacts provide a unique path
to investigate the spin texture and spin-momentum locking properties of helical
states. Our results are of interest not only for the ongoing development of
Majorana qubits, but also as for realizing possible spin-based quantum devices,
such as quantum spin modulators and interconnects based on spin-helical
channels.
