What Does the New Double-Slit Experiment Actually Show?

Quantum mechanics is one of the most successful theories in all of science; at the same time, it's one of the most challenging to comprehend and one about which a great deal of nonsense has been written. However, a paper from Science, titled "Observing the Average Trajectories of Single Photons in a Two-Slit Interferometer", holds out hope that we might be able to get closer to understanding how nature works on the smallest scales. The authors – Sacha Kocsis, Boris Braverman, Sylvain Ravets, Martin J. Stevens, Richard P. Mirin, L. Krister Shalm, and Aephraim M. Steinberg – have measured both the trajectory and the interference pattern from photons, a difficult feat to say the least, and one with interesting implications. (Scientific American also has a brief article on this experiment, republished from Nature.)