It's one of the oddest tenets of quantum theory: a particle can be in two places at once -- yet we only ever see it here or there.
One could write several pages on what's wrong with that introductory sentence.
I shall restrict myself to one point: it is not a tenet of quantum theory (by which I think is meant "quantum mechanics") that "a particle [sic] can be in two places at once"; that is, rather, a tenet of one epistemological interpretation of quantum mechanics, albeit the one that is most commonly taught (and therefore learned).
There is at least one other interpretation, in fact in some ways a more powerful one in that it is ontological, that is based on quite a different model of what goes on "under the hood" of QM. I direct the interested reader to: https://en.wikipedia.org/wiki/..., or the book "The Undivided Universe" by Bohm and Hiley. In Bohmian Mechanics, there is no collapse of the wave function, and particles have well-defined positions; in particular, they are not in a superposition of states. All the standard experimental results are reproduced by Bohmian Mechanics, just as in the interpretation that is most-commonly taught.
I regard it as a travesty of modern pedagogy of physics that students often are never exposed to the fact that while the experimental results are solid, the underlying model of what is going on to cause those results is merely (at best) an hypothesis. QM, in its current state, provides a wonderful set of rules for making the most accurate predictions ever; but it provides no explanation of why those rules are the correct ones or how the way that the universe operates can be the way it appears to be. At this point I resist the temptation to blather on about non-locality, or any of the other things wrong about the summary's introductory sentence.
Note that I am not commenting on the physics of the paper on which the summary is based: that appears to be paywalled.