Diamonds boost processing speeds in quantum computers

Scientists at UC Santa Barbara have made important advances in the field of spintronics by demonstrating the ability to electrically manipulate, at room temperatures, the quantum states of electrons trapped in the atomic structural defects of diamond crystals. Despite previous indications to the contrary, such quantum states can be manipulated very quickly, even at gigahertz frequencies, paving the way to significantly faster quantum computing.

Mass-production of a true general purpose quantum computer is perhaps still decades away, but it is certainly impressive to see the amount of effort that universities around the globe are putting into researching this field, and the subsequent speed at which scientists are tackling and gradually solving the remaining issues one by one, week after week.

We've looked at an all-electronic quantum processor before, and although it was capable of performing approximately one quantum operation every 10 nanoseconds, it had one minor issue — namely, its quantum bits completely disintegrated after a single microsecond.

The world's first programmable quantum computer, which we covered last week, didn't have endurance problems but averaged a simple 10-to-15-instructions-long program run in 37 milliseconds, by no means close to the standards of today's microprocessors, whose performance has long passed the tens of billions of floating point operations per second (FLOPS).

Finally, just under two months ago, researchers at MIT had discovered that nitrogen impurities in diamonds could be effectively exploited to detect and precisely manipulate atomic scale magnetic fields, leading the way to its deployment in spintronics - the subfield of quantum computing that represents digital information by the spin of electrons - and in medical research, where it could be used as an ultra-sensitive MRI device.

Building on these results, the researchers at UCSB patterned electromagnetic waveguides on a diamond-based chip, and through them were able to generate magnetic fields strong enough to consistently manipulate the state of nitrogen defects in a diamond crystal in just under one nanosecond, by purely electrical means.

The technique doesn't appear to have the qubit stability problems encountered elsewhere, and allows for very fast data processing; in other words, it might soon make it possible to run much more sophisticated algorithms on an all-electric chip in a fairly contained time.

"We set out to see if there is a practical limit to how fast we can manipulate these quantum states in diamond," lead author of the related paper Greg Fuchs explained. "Eventually, we reached the point where the standard assumptions of magnetic resonance no longer hold, but to our surprise we found that we actually gained an increase in operation speed by breaking the conventional assumptions."

The microwave techniques used in the experiment are analogous to those that power magnetic resonance imaging (MRI), although the group's results are unlikely to find immediate applications to the medical field. The quantum computing community, however, has just received one more valid reason to get excited over what could be the next developments, which in all likelihood won't be late to follow.

The work was performed at UCSB's Center for Spintronics and Quantum Computation, directed by Prof. Awschalom. A paper detailing the experiments was published on the online edition of Science magazine.