The experiment was a variation on the celebrated double slit experiment that shows how photons are both particles and waves, at least in some interpretations of the universe. That’s freakish in a not-news kind of way, as is the fact that the same is true of good old atoms, which might seem more as though they should stay particular all the time.
One amusing view of the ANU experiment is that an atom can “decide” to be either particle-like or wave-like based on information from the future. Just like the restaurant at the end of the universe, that is, of course, impossible.
If I were a better physicist I could explain this to you, but in all honesty it was just the lack of intuitiveness about high energy physics (and maybe the contemporaneous demise of the Superconducting Super Collider) that turned me off to the subject as an undergraduate. Still, what a universe to live in, eh Horatio?