Professor Alain Aspect, the reciever of the Niels Bohr Gold Medal 2013:
Wave-particle duality for a single photon: Bohr's complementarity brought to light
8 October 2013
— Since the early days of quantum mechanics, interference between spatially separated trajectories of a single particle has not ceased to fascinate physicists. I will present a realization in optics of that GedankenExperiment, which is based on a true single photon source. It has allowed us to illustrate the concept of wave particle duality, a striking example of Bohr's complementarity. It has even been possible to implement the famous "Wheeler's delayed choice experiment", emphasizing the fact that Bohr's complementarity should not be understood too naively.