Results of the numerical simulation for the spin-filtering device shown in Fig. 1b. The spin polarization P
of the output current in reservoir D1 is shown as a function of gate voltage V
g on the quantum dot. The height of the tunnel barriers is U
S = U
D1 = 0.9E
F, whereas (a) U
F = 0.9, (b) 0.8, (c) 0.7, and (d) 0.6.