  The effective interaction between magnetic impurities in metals that can lead
to various magnetic ground states often competes with a tendency for electrons
near impurities to screen the local moment (Kondo effect). The simplest system
exhibiting the richness of this competition, the two-impurity Kondo system, is
here realized experimentally in the form of two quantum dots coupled through an
open conducting region. We demonstrate non-local spin control by suppressing
and splitting Kondo resonances in one quantum dot by changing electron number
and coupling of the other dot. Results suggest an approach to non-local spin
control relevant to quantum information processing.
