Diamonds demo quantum entanglement on a macro scale

Researchers working in the UK’s Clarendon Laboratory at Oxford have demonstrated long range quantum entanglement in two synthetic diamonds, at room temperature.

Those last words are the really important ones, because quantum entanglement is a very fragile thing, and generally needs a super chilly environment to be stable. Generally it has only been demonstrated on a very small scale, too, and using single atoms in gaseous clouds.

Quantum entanglement is one of the weirder properties of the very small, quantum scale world. In effect, it means that events at one location can affect events at another. Scaled up (which it doesn’t – this is a metaphor) it would be as if the roulette wheels in a casino determined each others outcomes. If table one shows red, the table two will show black, for instance.

It also lies at the heart of the nascent science of quantum computing. Entangled particles would theoretically allow instant communication between two locations, and can be exploited in cryptography as well.

This time, the researchers used two solid pieces of diamond, separated by 15cm, and showed that the manipulating the vibrations of one crystal affected the vibrations in the other, even though it had not been touched.

"We used short pulse lasers with pulse durations of around 100 femtoseconds (a quadrillionth of a second). A femtosecond is to a second as a nickel is to the debt of the federal government generally speaking," said Ian Walmsey, professor of experimental physics at Oxford's Clarendon Laboratory.

The light pulses affected the phonons in the crystal, which since diamond is transparent to visible light was easily measurable. The phonon modes in the other diamond responded as well, even though it had not been stimulated with pulsed light, demonstrating entangelment.

The work is published in Science.