How does light move?: Determining the flow of light without destroying interference

Abstract

Young's two-slit experiment constitutes the paradigm of quantum complementarity. According to the complementarity principle, complementary aspects of quantum systems cannot be measured at the same time by the same experiment. This has been a long debate in quantum mechanics since its inception. But is this a true constraint? In 2011, an astounding realization of this experiment showed that perhaps this is not the case, and the boundaries to our understanding of the quantum world are still far away.