  We report selective injection of both spin-up and spin-down single electrons
into a quantum dot (QD) from spin-polarized non-equilibrium quantum Hall edge
channels (ECs) generated by selective transmission of spin-resolved ECs using a
surface gate placed at a distance from the QD. We change the spin polarization
of non-equilibrium ECs by changing the bias voltages applied to different
source Ohmic contacts. The efficiency of spin-up electron injection reaches
0.5, which is approximately 0.2 higher than that induced by spin-dependent
tunnel coupling between QD and ECs. On the other hand, the efficiency of
spin-down electron injection reaches 0.4. In addition, we rectify the
underestimation of the efficiency of spin filtering for equilibrium ECs by
numerically subtracting the contribution of the excited states in the QD. The
obtained spin-filtering efficiency is higher than that evaluated from the raw
experimental data and increases with magnetic field as expected with the
increase in the spatial separation between ECs.
