Popper's experiment realized again--but what does it mean?

(Phys.org)--Like Einstein, the philosopher Karl Popper was a realist who was deeply bothered by some of the odd implications of quantum mechanics. Both Popper and Einstein disliked the idea in Heisenberg's uncertainty principle, for instance, that precisely measuring one property of a particle means that the particle's conjugate property is completely undetermined. This idea undermines the basic principle of common-sense realism: that every particle's properties must have precise pre-existing va...