  Unlike the two-terminal device, in which the time-reversal invariant
spin-orbit interaction alone cannot polarize the spins, such a polarization can
be generated when electrons from one source reservoir flow into two (or more)
separate drain reservoirs. We present analytical solutions for two examples.
First, we demonstrate that the electrons transmitted through a "diamond"
interferometer into two drains can be simultaneously fully spin-polarized along
different tunable directions, even when the two arms of the interferometer are
not identical. Second, we show that a single helical molecule attached to more
than one drain can induce a significant spin polarization in electrons passing
through it. The average polarization remains non-zero even when the electrons
outgoing into separate leads are eventually mixed incoherently into one
absorbing reservoir. This may explain recent experiments on spin selectivity of
certain helical-chiral molecules.
