The aim of this thesis was to highlight the possibility of using semiconductor quantum dots as the realization of quantum bits, building blocks of quantum information. We have demonstrated the feasibility of establishing a two-level system, which can be initialised and control ed using picosecond light pulses and then determined the time during which we were able to maintain its coherence. Rabi oscillations between the ground state and the excited level allow us to initialize the system in a coherent superposition which can then be manipulated by a second pulse in coherent control experiments. The system coherence time T2 is not only limited by the radiative lifetime T1 and remains well below the theoretical value T2 = 2T1. Different mechanisms of decoherence taking place were therefore studied, in particular the role of acoustic phonons, reponsible of a strong Rabi oscillations damping and a decrease of the coherence time for some of the quantum dots studied. However, in some cases we found proof of additional mechanisms related to the dots fluctuating electrostatic environment. In addition, a detailed study of dots emission polarization showed a tilt of eigenstates of the fine structure of the exciton, as well as a modification of their emission intensity, indicating a strong mixing in the valence band, between heavy holes and light holes
Coherent manipulation under resonant excitation of a single quantum dot state