  The spin-dependent localization of electrons in quadruple quantum dots (QD's)
has been studied by the configuration interaction method. We have investigated
two nanodevices that consist of laterally coupled quadruple QD's. We have shown
that -- in both the nanodevices with suitably chosen parameters -- the
exclusive OR (XOR) logic gate can be realized by all-electrical control with
the readout of output via the spin-to-charge conversion. We have determined the
nanodevice parameters that are optimal for the performance of the XOR logic
gate.
