Which Way?

Abstract: I report the result of a which-way experiment based on Young's double-slit experiment. It reveals which slit photons go through while retaining the (self) interference of all the photons collected. The idea is to image the slits using a lens with a narrow aperture and scan across the area where the interference fringes would be. The aperture is wide enough to separate the slits in the images, i.e., telling which way. The illumination pattern over the pupil is reconstructed from the series of slit intensities. The result matches the double-slit interference pattern well. As such, the photon's wave-like and particle-like behaviors are observed simultaneously in a straightforward and thus unambiguous way. The implication is far reaching. For one, it presses hard, at least philosophically, for a consolidated wave-and-particle description of quantum objects, because we can no longer dismiss such a challenge on the basis that the two behaviors do not manifest at the same time. A bold proposal is to forgo the concept of particles. Then, Heisenberg's uncertainty principle would be purely a consequence of waves without being ordained upon particles.