Atomic impurities, or defects, in natural diamond lead to the colour seen in pink, blue and yellow diamonds. One such defect, a negatively-charged NV centre, occurs when a nitrogen atom and an empty (carbon) lattice site find themselves close to each other in diamond. When illuminated with laser light of a certain colour, or frequency, the NV centre emits light of another colour.

Although most work on the NV centre until now has focused on its optical and spin properties, being able to control its charge would allow it to store long-term information.

Researchers led by Carlos Meriles have now proved that this is indeed possible using NV-rich type-Ib diamond.

Atomic-sized defect can trap and release electrons

“In the world of big data, for example, there are limitations on how to store large volumes of information,” explains team member and lead author of the study Siddharth Dhomkar. “Typical hard disk drives (HDDs) like you find in your computer consume a lot of power and are limited to a few terabytes per drive.

"Optical data storage devices like digital-video-disk (DVD) and Blu-Ray are power efficient and cheap, but because of the planar nature of the medium as well as the intrinsic diffraction limit of light, their storage densities are very low.

“By exploiting the charge state and spin properties of the NV centre in diamond, we are able to circumvent these problems,” he says “Our bit is no longer some diffraction-limited bump on the surface of a DVD, but it is an atomic-sized defect that can trap and release an electron when excited with laser light of a certain wavelength.”

Competing with Blue-Ray technology

As a proof of principle, the CUNY–CCNY researchers used optical microscopy in which they beamed differently coloured light onto NVs to read, write and reset information in a diamond crystal.

“The crystal is equivalent to a rewritable memory storage device that hardly degrades over time – if kept in the dark,” says Dhomkar. “We also extend our technique over multiple planes to allow for 3D information storage without affecting the already-written data. And we show that by controlling the NV’s spin state using precisely-shaped multicolour beams and radio-frequency sources, we could achieve bit sizes much smaller than the optical diffraction limit.”

To achieve such precision, the researchers say they are now busy developing protocols that combine aspects of super-resolution microscopy and nuclear magnetic resonance to control NV centres. “If we succeed here, the resulting storage densities possible in this system could then be hundreds of thousands of times larger than existing Blue-Ray technology,” says Dhomkar.

The present work is detailed in Science Advances DOI: 10.1126/sciadv.1600911.