Digging deep into diamonds, physicists advance quantum science and technology

Feb 14, 2010
A diamond-based nanowire device. Researchers used a top-down nanofabrication technique to embed color centers into a variety of machined structures. By creating large device arrays rather than just "one-of-a-kind" designs, the realization of quantum networks and systems, which require the integration and manipulation of many devices in parallel, is more likely. Illustrated by Jay Penni.

By creating diamond-based nanowire devices, a team at Harvard has taken another step towards making applications based on quantum science and technology possible.

The new device offers a bright, stable source of single photons at room temperature, an essential element in making fast and secure computing with light practical.

The finding could lead to a new class of nanostructured diamond devices suitable for and computing, as well as advance areas ranging from biological and chemical sensing to scientific imaging.

Published in the February 14th issue of Nature Nanotechnology, researchers led by Marko Loncar, Assistant Professor of Electrical Engineering at the Harvard School of Engineering and Applied Sciences (SEAS), found that the performance of a single source based on a light emitting defect (color center) in diamond could be improved by nanostructuring the diamond and embedding the defect within a diamond nanowire.

Scientists, in fact, first began exploiting the properties of natural diamonds after learning how to manipulate the , or intrinsic angular momentum, associated with the nitrogen vacancy (NV) color center of the gem. The quantum () state can be initialized and measured using light.

The color center "communicates" by emitting and absorbing photons. The flow of photons emitted from the color center provides a means to carry the resulting information, making the control, capture, and storage of photons essential for any kind of practical communication or computation. Gathering photons efficiently, however, is difficult since color-centers are embedded deep inside the diamond.

"This presents a major problem if you want to interface a color center and integrate it into real-world applications," explains Loncar. "What was missing was an interface that connects the nano-world of a color center with macro-world of optical fibers and lenses."

The diamond nanowire device offers a solution, providing a natural and efficient interface to probe an individual color center, making it brighter and increasing its sensitivity. The resulting enhanced optical properties increases photon collection by nearly a factor of ten relative to natural diamond devices.

"Our nanowire device can channel the photons that are emitted and direct them in a convenient way," says lead-author Tom Babinec, a graduate student at SEAS.

Further, the diamond nanowire is designed to overcome hurdles that have challenged other state-of-the-art systems—such as those based on fluorescent dye molecules, quantum dots, and carbon nanotubes—as the device can be readily replicated and integrated with a variety of nano-machined structures.

The researchers used a top-down nanofabrication technique to embed color centers into a variety of machined structures. By creating large device arrays rather than just "one-of-a-kind" designs, the realization of quantum networks and systems, which require the integration and manipulation of many devices in parallel, is more likely.

"We consider this an important step and enabling technology towards more practical optical systems based on this exciting material platform," says Loncar. "Starting with these synthetic, nanostructured diamond samples, we can start dreaming about the diamond-based devices and systems that could one day lead to applications in quantum science and technology as well as in sensing and imaging."

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maxcypher
not rated yet Feb 14, 2010
Can anyone explain -- in layman terms -- what a 'color center' actually is?
maxcypher
not rated yet Feb 14, 2010
Never mind, I looked it up and it's not that hard to understand.
seneca
not rated yet Feb 14, 2010
The diamond layers with implanted holes demonstrated superconductivity at room temperature already. The mechanical strength of diamond films enables to bind electrons to their surface in such strong way, the electrons will overcome their repulsive forces, so that they're behaving there in similar way, like atoms in boson condensate at low temperature.

http://www.iop.or...8/3/319/

This is extremely interesting result even with respect to quantum computing, because it would enable to maintain entangled states of electrons at room temperature. With respect to high price of diamond films such usage could become ever more significant, then the superconductivity applications.
seneca
not rated yet Feb 14, 2010
what a 'color center' actually is
Diamond is indirect band gap semiconductor, which means, electrons and holes cannot recombine in it mutually due their different crystal momentum in conductive and valence bands. By insertion of crystal lattice defects and/or foreign atoms we can create places, where such recombination could occur more easily. Such places therefore increasing absorbtion coefficient of diamond for photons, they give a color to it - so we can call them a "color centers".

For example, chemically pure carborundum (so called moissanite) is transparent and white - but technical carborundum based emery paper is green or red depending whether donors or acceptors of electrons (i.e. holes) are prevailing into it. If I remember well, Hope diamond is blue, because it contains boron color centers - whereas red diamond contains oxygen or fluorine (electron acceptors).
seneca
not rated yet Feb 15, 2010
IMO fluorine ions injected into diamond or bornitride could be the most effective system for demonstration of surface superconductivity by J.F.Prins method and definitely worth to study:

http://www.iop.or...8/3/319/

Fluorine is the most electronegative atom known so far and bornitride has a highest dielectric strength among common insulators.
mauinut
not rated yet Feb 15, 2010
now they just need a decent photon spin detector/target,perhaps an angled target will tell the spin via angular momentum in the spin resulting in a high/low strike signal?