Multiple Rabi rotations of trions in InGaAs quantum dots observed by photon echo spectroscopy with spatially shaped laser pulses

The authors investigate Rabi rotations, arising in photon echoes from an ensemble of InGaAs quantum dots. To overcome the dephasing of the Rabi rotations imposed by the inhomogeneity of laser intensities, a spatially flat intensity profile is introduced. This allows to observe robust Rabi rotations and to identify efficient coupling to acoustic phonons as the dominating channel of decoherence. The insights gained are crucial for the realization of optical quantum memories based on photon echoes from semiconductor quantum dots.