  We show that the entanglement between two distant magnetic impurities,
generated via electron scattering, can be easily modulated by controlling the
magnitude of an applied external electric field. We assume that the two
magnetic impurities are fixed and located on an one-dimensional quantum wire. A
ballistic electron moving through the wire is scattered off by both impurities,
so the electron spin can be seen as a mediator between the spins of the
impurities. Heisenberg operators are used to describe the interactions between
electron and impurities spins. We use a wave guide formalism to model the
ballistic electron wave-function. Entanglement control is shown to be possible
for three different protocols of entanglement detection. The effect of
detection protocols on the entanglement extraction is discussed.
