Making spin states last with nitrogen-flecked diamonds

Synthetic diamonds are laced with impurities thanks to the manufacturing process. One of these, nitrogen, turns them an attractive shade of nicotine-stain-yellow.

Synthetic diamonds are laced with impurities thanks to the manufacturing process. One of these, nitrogen, turns them an attractive shade of nicotine-stain-yellow. These stones might not be pretty enough to grace a jewellery store window, but new research suggests this nitrogen “flaw” might make them extremely valuable: as pieces in quantum computers.

When a nitrogen atom is next to a hole in the diamond’s carbon lattice, one of its electrons occupies the vacancy. For a few years, researchers have been able to use microwaves to manipulate the spin state of the electron with enough control to allow it to function as a qubit.

But now researchers at the University of California have found a way to link the spin state of the electron to that of the nucleus of its donor nitrogen atom. Even at room temperature, the nuclear spin state is stable for around 100 nanoseconds, long enough for it to function as quantum memory.

Speaking at a meeting of the American Physical Society in Dallas last week, David Awschalom of the University of California, Santa Barbara said: "Oddly enough, perfection may not be the way to go. We want to build in defects."

According to Science News, he told the meeting the technique has a fidelity of 85 to 95 per cent.

From the Science News report: In contrast to some other quantum systems under development, which require temperatures close to absolute zero, this diamond memory works at room temperature. The spins inside the diamond can be both changed and measured by shining laser light into the diamond. This could make diamond an attractive material for scientists developing nanophotonic systems designed to move and store information in packets of light.