Diamond imperfections could be key to advancing quantum computing


Scientists say a defect found at the atomic scale in diamonds could offer a significant advance on the road to quantum computing.

Carefully controlling and taking advantage of a technologically beneficial defect in diamonds known as a nitrogen vacancy center could bring quantum computers and nanoscale sensors one step closer, they say. 

University of Chicago physicist David Awschalom explains that an NV center consists of one nitrogen atom that sits immediately next to a vacant spot, with the pair taking the place of a pair of carbon atoms within the crystal of diamond.

That leaves an electron that is unpaired, and a property of such an electron known as spin can be used to hold and then transmit qubits, which is the quantum equivalent of a traditional computing bit.

Particularly significant is that the qubit can be written, read and transferred at room temperature, the researchers say.

A problem in trying to use NV centers as quantum information handlers lies in the difficulty encountered in attempting to put them in a location Awschalom refers to as functioning “sweet spots” within a quantum device.

Another obstacle is how to increase the density of NV centers without reducing the lifetime of their spins, which must be of sufficient duration within a system to extract useful information.

The key, Aswchalom’s team reported in the journal Applied Physics Letters, is creating the vacancy and nitrogen defects separately then bringing them together within a diamond crystal film.

The technique allowed the researchers to place NV centers in a localized cavity in the film around 180 nanometers wide, a small enough volume to be well-suited for use in experimental quantum computing systems.

The researchers were able to achieve spin duration in the NV centers of 300 microseconds and above, an order of magnitude improvement over what has been achievable with other methods.

The researchers say one goal for using the new technique will be to gauge the spin of hydrogen atom nuclei, one of the smallest magnetic signals in nature, in biological molecules to gains insights into the function of vital biological processes such as photosynthesis.

“Our research impacts diverse fields of science and technology,” Awschalom says. “Technological advancements always open new avenues of scientific research.”

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