  Preparation of a specific quantum state is a required step for a variety of
proposed practical uses of quantum dynamics. We report an experimental
demonstration of optical quantum state preparation in a semiconductor quantum
dot with electrical readout, which contrasts with earlier work based on Rabi
flopping in that the method is robust with respect to variation in the optical
coupling. We use adiabatic rapid passage, which is capable of inverting single
dots to a specified upper level. We demonstrate that when the pulse power
exceeds a threshold for inversion, the final state is independent of power.
This provides a new tool for preparing quantum states in semiconductor dots and
has a wide range of potential uses.
