A team in Australia turned thought experiment into lab reality by using lasers. Their subject matter was not a photon but a helium atom. The lasers they used served as a pair of grates, one before the other, with the second grate randomly dropped in.
What they found is weirder than anything seen to date: Every time the two grates were in place, the helium atom passed through, on many paths in many forms, just like a wave. But whenever the second grate was not present, the atom invariably passed through the first grate like a particle. The fascinating part was, the second grate's very existence in the path was random. And what's more, it hadn't happened yet.
In other words, it was as if the helium particle "knew" whether there would be a second grate at the time it passed through the first.
Also covered at: phys.org. An abstract is available; full report is pay-walled. The original news article is at Australian National University
(Score: 4, Informative) by draconx on Thursday June 11 2015, @02:54PM
The secondnexus.org article is rather sensationalist, with statements like "one thing is clear: This new wrinkle adds more questions than answers.".
The phys.org article says the experimental results were predicted by quantum theory. So this serves to validate what we already know (which is important!). The news is that nobody had done this particular experiment before.