  Strong electron and spin correlations in a double-quantum-dot (DQD) can give
rise to different quantum states. We observe a continuous transition from a
Kondo state exhibiting a single-peak Kondo resonance to another exhibiting a
double peak by increasing the inter-dot-coupling (t) in a parallel-coupled DQD.
The transition into the double-peak state provides evidence for
spin-entanglement between the excess-electron on each dot. Toward the
transition, the peak splitting merges and becomes substantially smaller than t
because of strong Coulomb effects. Our device tunability bodes well for future
quantum computation applications.
