  Calculations for two electrons in an elliptic quantum dot, using symmetry
breaking at the unrestricted Hartree-Fock level and subsequent restoration of
the broken parity via projection techniques, show that the electrons can
localize and form a molecular dimer, described by a Heitler-London-type wave
function. The calculated singlet-triplet splitting (J) as a function of the
magnetic field (B) agrees with cotunneling measurements. Knowledge of the dot
shape and of J(B) allows determination of the degree of entanglement in the
ground state of the dot, which is of interest for the implementation of quantum
logic gates. The theoretical value agrees with the experimental estimates.

Mesoscale and Nanoscale Physics;Strongly Correlated Electrons;Chemical Physics;Quantum Physics