  Using an approach that allows us to probe the electronic structure of
strongly pinched-off quantum point contacts (QPCs), we provide evidence for the
formation of self-consistently realized bound states (BSs) in these structures.
Our approach exploits the resonant interaction between closely-coupled QPCs,
and demonstrates that the BSs may give rise to a robust confinement of single
spins, which show clear Zeeman splitting in a magnetic field.
