A groundbreaking experiment on quantum entanglement puts the final nail in the coffin of our ordinary view of the universe, settling an argument that has raged for nearly a century.

(from the NewScientist | 5 September 2015 pp 8-9)

To understand the experiment, we have to go back to the 1930s, when physicists were struggling to come to terms with the strange predictions of the nascent science of quantum mechanics. The theory suggested that particles could become entangled, so that measuring one would instantly the measurement of the other, even if they were far apart.

Einstein famously proclaimed that God does not play dice with the universe and called entanglement "spooky action at a distance". He and others favoured the principle of local realism, which broadly says that only nearby objects can influence each other and that the universe is "real" - observing it doesn't bring it into existence by crystallising vague probabilities.

They argued that hidden variables at some deeper layer of reality could explain quantum theory's apparent weirdness. On the other side, physicists like Niels Bohr insisted that we accept the new quantum reality, because it explained problems that classical theories of light and energy couldn't handle.

In this set-up, Alice and Bob sit in two laboratories 1.3 kilometres apart, far enough to close the locality loophole. Each laboratory has a diamond containing an electron with a property called spin. The team hits the diamonds with randomly produced microwave pulses. This makes them each emit a photon that is entangled with the electron's spin. These photons are sent to a third location, C, where a device clocks their arrival time. If photons arrive from Alice and Bob at exactly the same time, the two electron spins become entangled with each other. The result was clear: they detected more highly correlated spins than local realism would allow. (For the Abstract, click here). The weird world of quantum mechanics is our world.

This raises the bar for other possibilities; Is the brain a quantum computer?

Professor Stuart Hameroff