Wave and particle realism in quantum delayed-choice experiments

Wheeler’s delayed-choice experiment, a scenario wherein a classical apparatus, typically an interferometer, is settled only after the quantum system has entered it, has corroborated the complementarity principle. However, the quantum version of Wheeler’s delayed-choice experiment has challenged the robustness of this principle. Based on the visibility at the output of a quantum-controlled interferometer, a conceptual framework has been put forward which detaches the notions of wave and particle from the quantum state.
In this talk, I will present our results concerning a quantum-controlled reality experiment, a slightly modified setup that is based on exchanging the causal order between the two main operations of the quantum Wheeler’s delayed-choice arrangement. We employed an operational criterion of physical realism to reveal a different state of affairs concerning the wave-and-particle behavior in this new setup. An experimental proof-of-principle will be presented for a two-spin-1/2 system in an interferometric setup implemented in a nuclear magnetic resonance platform. Finally, it will be discussed how our results validate the complementarity principle.