  Time-resolved electron dynamics in coupled quantum dots is directly observed
by a pulsed-gate technique. While individual gate voltages are modulated with
periodic pulse trains, average charge occupations are measured with a nearby
quantum point contact as detector. A key component of our setup is a sample
holder optimized for broadband radio frequency applications. Our setup can
detect displacements of single electrons on time scales well below a
nanosecond. Tunneling rates through individual barriers and relaxation times
are obtained by using a rate equation model. We demonstrate the full
characterization of a tunable double quantum dot using this technique, which
could also be used for coherent charge qubit control.
