A qubit is the quantum equivalent of the 'bit', which can have the values, or 'states' of zero or one. However, because of their quantum nature, qubits can be in both states at once, due to a property called entanglement, the "spooky action at a distance" so disliked by Einstein. It's this remarkable property that gives quantum computers their huge processing power, such as the ability to crack all encryption schemes based on classical methods. If only mankind could build them. Quantum computers are still very much in an embryonic research phase and have been stuck there for decades, due to the difficulty of producing and working with entangled particles. The best that scientists have been able to do so far is to entangle just a few particles at extremely low temperatures, to reduce thermal noise corruption, to create qubits and research their behaviour. Now, it looks like mankind is a tiny step closer to building such quantum computers and this is where diamond comes in.A team of scientists at Oxford University, England, lead by Ian Walmsley, have managed to put two three millimetre-sized bits of diamond, separated by a distance of 15 mm in an entangled state. They used a complex arrangement of lasers and beam splitters, such that any given photon could be in either diamond, thereby entangling them. Now, there's two amazing parts to this extraordinary feat: the diamond particles being entangled are gigantic, being big enough to be easily visible to the naked eye, plus they were at room temperature! Normally, this kind of thing needs to be done at near absolute zero, because heat gives the particles so much energy that they fall out of entanglement, ruining the experiment. The team have had their work published (paywall) in the prestigious journal Science, which shows us this abstract:

Quantum entanglement in the motion of macroscopic solid bodies has implications both for quantum technologies and foundational studies of the boundary between the quantum and classical worlds. Entanglement is usually fragile in room-temperature solids, owing to strong interactions both internally and with the noisy environment. We generated motional entanglement between vibrational states of two spatially separated, millimeter-sized diamonds at room temperature. By measuring strong nonclassical correlations between Raman-scattered photons, we showed that the quantum state of the diamonds has positive concurrence with 98% probability. Our results show that entanglement can persist in the classical context of moving macroscopic solids in ambient conditions.

However, this cautionary note was sounded by Californian quantum mechanics research scientist Andrew Cleland: "I am not sure where this particular work will go from here. I can't think of a particular use for entanglement that lasts for only a few picoseconds" in rival journal Nature. However, Walmsley insisted that "diamond could form the basis of a powerful technology for practical quantum information processing".

And it might well do. History has shown us that the path to useful inventions which can be used in practical applications is never a linear one and is full of setbacks, accidents and surprises. The next few years are sure to be very interesting indeed - especially for fans of quantum computers...