  We propose a device acting as a spin valve which is based on a double quantum
dot structure with parallel topology. Using the exact analytical solution for
the noninteracting case we argue that, at a certain constellation of system
parameters and externally applied fields, the electric current through the
constriction can become almost fully spin-polarized. We discuss the influence
of the coupling asymmetry, finite temperatures and interactions on the
efficiency of the device and make predictions for the experimental realization
of the effect.
