  We study entanglement in the scattering processes by fixed impurity and Kondo
impurity. The fixed impurity plays a role as spin state filter that is employed
to concentrate entanglement between the scattering particle and the
unscattering particle. One Kondo impurity can entangle two noninteracting
scattering particles while one scattering particle can entangle two separate
noninteracting Kondo impurities.
