[..]Lucien Hardy proposed a thought experiment that makes nonsense of the famous interaction between matter and antimatter—that when a particle meets its antiparticle, the pair always annihilate one another in a burst of energy. Dr Hardy’s scheme left open the possibility that in some cases when their interaction is not observed a particle and an antiparticle could interact with one another and survive. Of course, since the interaction has to remain unseen, no one should ever notice this happening, which is why the result is known as Hardy’s paradox.
[..]This week Kazuhiro Yokota of Osaka University in Japan and his colleagues demonstrated that Hardy’s paradox is, in fact, correct.
They managed to do what had previously been thought impossible: they probed reality without disturbing it. Not disturbing it is the quantum-mechanical equivalent of not really looking. So they were able to show that the universe does indeed exist when it is not being observed.
The reality in question—admittedly rather a small part of the universe—was the polarisation of pairs of photons, the particles of which light is made. The state of one of these photons was inextricably linked with that of the other through a process known as quantum entanglement. [..]