Control over electron-spin states, such as coherent manipulation, filtering
and measurement promises access to new technologies in conventional as well as
in quantum computation and quantum communication. In this paper, we review
recent theoretical proposal of using electron spins in quantum confined
structures as qubits. We also present a theoretical proposal for testing Bell's
inequality in nano-electronics devices. We show that the entanglement of two
electron spins can be detected in the spin filter effect in the nanostructure
semiconductor / ferromagnetic semiconductor / semiconductor junction. In
particular, we show how to test Bell's inequality via the measurement of the
current-current correlation function in this setup.Comment: 7 pages, 5 figure
