Where does quantum weirdness end?
Answers
Explanation:
WE DO not find, at breakfast, that the milk is simultaneously poured onto our cornflakes and not,” says Andrew Briggs, a physicist at the University of Oxford. Nor can you be in two places at the same time, no matter how hard you try. None of which is even remotely surprising. Until, that is, you consider that the laws of quantum mechanics insist that subatomic particles such as electrons routinely pull off such a feat.
So if electrons can pop up in multiple places at once, why can’t milk and humans – essentially collections of fundamental particles – do the same?
Here we have to start small. This particular brand of quantum weirdness is best illustrated by the double-slit experiment, where you fire a beam of electrons, one after another, at a screen containing two slits. You would expect the electrons to pass through one slit and hit the detector placed behind the screen at a single point every time. But reality isn’t always that straightforward.
When researchers don’t keep track of each electron’s path, the beam passes through both slits simultaneously in the same way as a light wave, creating a pattern of bright and dark stripes on the detector that is characteristic of two overlapping wavefronts. So electrons can exist as both waves and particles at the same time – a phenomenon known as wave-particle duality.
As if that wasn’t weird enough, when researchers monitor one of the slits, the interference pattern disappears. Electrons suddenly abandon their wave-like behaviour, preferring to travel through one slit and produce a single spot on the detector.
Physicists explain this by invoking …