The ultimate limit for controlling electronic logic would be to use the
spin state of a single electron. Recher et al. address the problem of
controlling the spin dynamics in nanostructures by proposing a quantum dot
as the basic building block for single-electron controlled-spin systems. In
the presence of a magnetic field and in the Coulomb-blockade regime, the
highest, singly occupied energy level of the dot is spin polarized, so that
only electrons with opposite spin to that of the dot can pass through it,
thus creating an efficient single-spin filter. The dot can function as a
single-spin memory when its electrical contacts are also spin-polarized--
the electron occupancy being detected with electron spin resonance
techniques. -- ISO

Detains in: Phys. Rev. Lett. 85, 1962 (2000).