Daniel Terno, Macquarie University
The debate on wave vs particle nature of light goes back to the days of Huygens and Newton. When used to model properties of quantum system these concepts lose their objective meaning and simply become the two aspects of wave-particle duality. Duality played a central role in Bohr—Einstein debates and prompted Bohr to formulate the complementarity principle. Complementarity leaves open the possibility that by adapting to the specific experimental sit-up a quantum system always behaves definitely either as a particle or as a wave. Delayed-choice experiments aim to exclude this possibility.
I review the history of delayed-choice gedanken experiments and discuss some of their realizations, particularly Wheeler's delayed choice experiment, delayed-choice quantum erasure and entanglement swapping. Introduction of quantum control allows for new theoretical and experimental opportunities. After discussing the effects of quantum control I present how the techniques we developed can be used in other problems of quantum foundations.