Scientists look beyond diamond for quantum computing

Apr 30, 2010

A team of scientists at UC Santa Barbara that helped pioneer research into the quantum properties of a small defect found in diamonds has now used cutting-edge computational techniques to produce a road map for studying defects in alternative materials.

Their new research is published in the online edition of the (PNAS), and will soon be published in the print edition of the journal. The findings may enable new applications for semiconductors --materials that are the foundation of today's information technology. In particular, they may help identify alternative materials to use for building a potential quantum computer.

"Our results are likely to have an impact on experimental and theoretical research in diverse areas of science and technology, including semiconductor physics, materials science, magnetism, and quantum device engineering," said David D. Awschalom, UCSB physics professor and one of two lead investigators on this project. "Ironically, while much of is devoted to eliminating the defects that interfere with how today's devices operate, these defects may actually be useful for future quantum technologies."

According to PNAS, the researchers have developed a set of screening criteria to find specific atomic defects in solids that could act as quantum bits (qubits) in a potential quantum computer. As a point of reference, they use a system whose they themselves have recently helped to discern, the NV or nitrogen-vacancy center defect in diamond. This defect, which the team has shown can act as a very fast and stable qubit at room temperature, consists of a stray alongside a vacancy in the otherwise perfect stacking of in a diamond.

Electrons trapped at the defect's center interact with light and microwaves in a predictable way, allowing information to be stored in and read out from the orientation of their quantum-mechanical spins.

The drawback to using diamond, however, is that the material is expensive and difficult to grow and process into chips. This raises the question of whether there may be defects in other materials that have similar properties and could perform equally well.

In this week's publication, the researchers enumerate specific screening criteria to identify appropriate defects in materials that could be useful for building a quantum computer. Experimental testing of all the potential candidates might take decades of painstaking research, explained Awschalom. To address this problem, the UCSB group employed advanced computational methods to theoretically examine the characteristics of potential defect centers in many different materials, providing a sort of road map for future experiments.

UCSB's Chris G. Van de Walle, professor of materials and one of the senior investigators on the project, remarked: "We tap into the expertise that we have accumulated over the years while examining 'bad' defects, and channel it productively into designing 'good' defects; i.e., those that have the necessary characteristics to equal or even outperform the NV center in diamond." This expertise is backed up by advanced theoretical and computational models that enable the reliable prediction of the properties of defects, a number of which are proposed and examined in the paper.

Awschalom added: "We anticipate this work will stimulate additional collaborative activities among theoretical physicists and materials engineers to accelerate progress towards based on semiconductors."

Current computers are based on binary logic: each bit can be either "one" or "zero." In contrast, each qubit in a quantum computer is continuously variable between these two states and hence offers infinitely more possibilities to be manipulated and combined with other qubits to produce a desired computational result. "It has been well established that, in theory, quantum computers can tackle some tasks that are completely beyond the capabilities of binary computers," said Awschalom. "The challenge has been to identify real physical systems that can serve as qubits for future machines."

Explore further: Quantum holograms as atomic scale memory keepsake

Related Stories

Dark spins light up

Oct 25, 2005

Want to see a diamond? Forget the jewellery store - try a physics laboratory. In the November issue of Nature Physics, Ryan Epstein and colleagues demonstrate the power of their microscope for imaging individual nitrogen ...

Turning down the noise in quantum data storage

Jan 19, 2010

Researchers who hope to create quantum computers are currently investigating various methods to store data. Nitrogen atoms embedded in diamond show promise for encoding quantum bits (qubits), but the process ...

Pushing quantum mechanics to higher levels

Aug 11, 2009

Scientists at UC Santa Barbara have devised a new type of superconducting circuit that behaves quantum mechanically -- but has up to five levels of energy instead of the usual two. The findings are published ...

'Self-correcting' gates advance quantum computing

Mar 12, 2009

(PhysOrg.com) -- Two Dartmouth researchers have found a way to develop more robust “quantum gates,” which are the elementary building blocks of quantum circuits. Quantum circuits, someday, will be used ...

Recommended for you

Scientists develop compact medical imaging device

49 minutes ago

Scientists at the MIRA research institute, in collaboration with various companies, have developed a prototype of a handy device that combines echoscopy (ultrasound) with photoacoustics. Combining these two ...

User comments : 0