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Ultra-pure synthetic diamonds offer advances in fields from quantum computing to cancer diagnostics.
he 'magic Russian diamond', as some researchers have come to call it, was just 2 millimetres square, very clear and of a quality any jeweller would be happy to set in an expensive ring. Jörg Wrachtrup, a physicist at the University of Stuttgart in Germany, had spent much of 2005 looking for something just like it; his group finally found it by trawling through journals from the Russian Academy of Sciences, reading descriptions of the physical properties of such rare gems. But Wrachtrup wasn't interested in this diamond's beauty: what intrigued him was that the stone was very pure and perfectly flawed.
Inside the Russian gem, the regular diamond lattice of carbon atoms was interrupted on rare occasions by a nitrogen atom, with a neighbouring carbon atom also missing. Within each such hole, an extra electron could become trapped (see 'A useful hole'). Such impurities are not in themselves unusual. But Wrachtrup and others had theorized that, in some specific cases, electrons in these holes could prove the perfect medium for storing information for quantum computing - an effort to vastly speed up computing calculations by exploiting the fuzzy world of quantum mechanics. Unlike other candidates for such information storage, these defects in diamond should do their job at room temperature. To test the idea, Wrachtrup's lab split the diamond and sent half of it to Mikhail Lukin, a physicist at Harvard University in Cambridge, Massachusetts. By the end of 2006, both groups had shown that the Russian stone proved the theory correct1,2. "This diamond showed behaviour we had never seen before," says Wrachtrup.
Since then, the field has exploded. In 2005, just a handful of groups worldwide were working on the quantum possibilities of diamond; there are now about 75 in on the action. The Russian diamond has been cut up and divided between teams. Despite much searching, no other natural gems quite like it have been found. So researchers have turned their attention to making synthetic versions that are even better.
As more teams have entered into the game, so have ideas for potential applications. The same properties that make diamonds useful for storing quantum information also make them...