The energy states in semiconductor quantum dots are discrete as in atoms, and quantum states can be coherently controlled with resonant laser pulses. Long coherence times allow the observation of Rabi-flopping of a single dipole transition in a solid state device, for which occupancy of the upper state depends sensitively on the dipole moment and the excitation laser power. We report on the robust preparation of a quantum state using an optical technique that exploits rapid adiabatic passage from the ground to an excited state through excitation with laser pulses whose frequency is swept through the resonance. This observation in photoluminescence experiments is made possible by introducing a novel optical detection scheme for the resonant electron hole pair (exciton) generation. Photon correlation measurements along with resonant laser scattering have established the atom-like character of the interband transitions in quantum dots [1][2][3]. Excitation of a two level system by a short, intense laser pulse can induce an oscillation of the system between the upper and lower state during the pulse, at the Rabi frequency Ω(t) = µA(t)/ where µ is the dipole moment of the transition and A(t) the electric field envelope of the laser pulse. Any quantum state (qubit) manipulation scheme benefits from the long coherence times in quantum dots [4] and necessitates fast and robust initial state preparation [5][6][7]. In principle a two level system can be initialised in the upper state with a maximum fidelity of 100% if the laser power is optimised in order to induce exactly half a Rabi oscillation during the pulse duration, a so-called π pulse [8][9][10]. Although Rabi oscillations observed in a single dot or for individual atoms [11] are a beautiful example of strong coupling between laser light and a single dipole, this commonly used technique presents two major drawbacks: (i) the upper state population is highly sensitive to fluctuations in the system, such as laser power, and (ii) in measurements on dot ensembles, an inhomogeneous distribution of dipole moments and transition energies among dots requires different laser intensities and frequencies for inducing a population transfer of the dot ensemble.Here we show that these drawbacks can be overcome by inducing an adiabatic passage with frequency-swept laser pulses. Unlike Rabi cycling, adiabatic passage is robust against small-to-moderate variations in the laser * Corresponding author : urbaszek@insa-toulouse.fr intensity, detuning, dipole moment and interaction time [12]. Chirped radiofrequency (RF) pulses are commonly used in nuclear magnetic resonance (NMR) based imaging [13]. In the context of semiconductor quantum dots adiabatic population transfer has been induced by a slow variation of the electrostatically defined confinement potential [14]. For applications in atomic physics and chemistry for quantum states separated by frequencies in the optical domain, chirped laser pulses, in strong analogy to NMR, have been used to induce complete population transfer via...