High-finesse optical quantum gates for electron spins in artificial molecules

We propose the storage of the quantum information (qubit) in the spin of an excess electron in two vertically coupled quantum dots and its all-optical manipulation through ps-laser pulses. The auxiliary levels of the artificial molecule allow the implementation of the logical gates solely by means of stimulated Raman adiabatic passages, and the consequent suppression of the environment losses. The mapping of the spin states onto the orbital degrees of freedom results in the switch on of the dipole-dipole interaction between neighbouring qubits and thus allows the conditional dynamics (two-qubit gates) to be performed.