Optical control of excitons in a pair of quantum dots coupled by the dipole-dipole interaction

We demonstrate coherent nonlinear-optical control of excitons in a pair of quantum dots (QDs) coupled via dipolar interaction. The single-exciton population in the first QD is controlled by resonant picosecond excitation, giving rise to Rabi oscillations. As a result, the exciton transition in the second QD is spectrally shifted and concomitant Rabi oscillations are observed. We identify coupling between permanent excitonic dipole moments as the dominant interaction mechanism, whereas quasiresonant (Forster) energy transfer is weak. Such control schemes based on dipolar interaction are a prerequisite for realizing scalable quantum logic gates.