  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.
