Snapshots of Anderson localization beyond the ensemble average

We study (1 + 1)D transverse localization of electromagnetic radiation at microwave frequencies directly by two-dimensional spatial scans. Since the longitudinal direction can be mapped onto time, our experiments provide unique snapshots of the buildup of localized waves. The evolution of the wave functions is compared with semianalytical calculations. Studies beyond ensemble averages reveal counterintuitive surprises. Oscillations of the wave functions are observed in space and explained in terms of a beating between the eigenstates.