The test with neutrinos involves correlations between measurements separated not in space, but in time. Last year, physicists in the Netherlands and the United States performed the best demonstrations yet of those correlations, nixing such hidden variables.

That quantum connection produces correlations between the particles that are stronger than hidden variables allow, Bell showed. In quantum theory, two photons in two-way states can be 'entangled' so that a measurement on one instantly determines not only its polarization but that of the other photon as well, even if it's light-years away. theorist John Bell devised a way to test that notion. To salvage 'realism,' some physicists argued that the result of such a measurement is predetermined by some 'hidden variable' within the photon. Albert Einstein disdained that idea, arguing that a physical property of an object has to be 'an element of reality' that exists independently of measurement. Still, according to quantum theory, the photon's polarization doesn't exist until it's measured. Measure, say, a particle of light or photon that is simultaneously polarized both horizontally and vertically and it will randomly 'collapse' one way or the other.

Those two-way 'superposition' states are fragile, however. Unlike an apple, a subatomic particle can be in two places or of two different types at once. 'The result is utterly unsurprising and yet utterly attractive because it tells us that there's a new system for testing quantum foundations.'Īccording to quantum theory, minuscule things behave nothing like everyday objects. Lucia, in Brisbane, Australia, who was not involved in the work. 'If you had told me 10 years ago that we would use neutrinos to study quantum foundations, I would have said that you'd been smoking something very exciting,' says Andrew White, a physicist at the University of Queensland, St. But it's the sort of thing typically shown with highly controlled quantum optics experiments and not with nearly undetectable neutrinos. Data from a massive neutrino experiment show that the elusive subatomic particles must literally be of two mutually exclusive types at once-poking a hole in our intuitive sense of reality.

Neutrino particle