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Diamond-based quantum computing

Quantum computing is usually associated with extremely low temperatures. Now, physicists at Harvard University have shown that diamonds can be used to create stable quantum computing building blocks at room temperature. A nitrogen vacancy in diamond could lead to quantum registers able to store or retrieve data. One of the researchers wrote that 'these registers can be used as a basis for scalable, optically coupled quantum information systems.' But you will not see a computer using this technology before a long time.
Written by Roland Piquepaille, Inactive on

Quantum computing is usually associated with extremely low temperatures. Now, physicists at Harvard University have shown that diamonds can be used to create stable quantum computing building blocks at room temperature. A nitrogen vacancy in diamond could lead to quantum registers able to store or retrieve data. One of the researchers wrote that 'these registers can be used as a basis for scalable, optically coupled quantum information systems.' But you will not see a computer using this technology before a long time.

How to make diamond qubits

You can see above a diagram showing the experimental setup used to build these diamond-based quantum registers. This research effort has been led by Mikhail Lukin, professor of physics at Harvard, and the members of his Quantum Optics group (Credit for diagram: Mikhail Lukin's group, Harvard University).

Here are more details about what the group found.

They found that nuclear spins associated with single atoms of carbon-13 -- which make up some 1.1 percent of natural diamond -- can be manipulated via a nearby single electron whose own spin can be controlled with optical and microwave radiation. The excitation of an electron by focusing laser light on a nitrogen vacancy center, a stable defect in a diamond lattice where nitrogen replaces an atom of carbon and develops an electronic spin in its ground state, causes the single electron's spin to act as a very sensitive magnetic probe with extraordinary spatial resolution.
Using the nitrogen center as an intermediary, a single carbon-13 atom's nuclear spin is cooled to near absolute zero, creating in the process a single, isolated quantum bit with a coherence time that approaches seconds. The controlled interaction between the electron and nuclear spins allows the latter to be used as very robust quantum memory.

And here is one possible direction for future work.

The Harvard physicists also observed and manipulated coupling between individual nuclear spins, thus demonstrating a way to increase the number of qubits working in the quantum register. Because the electron spin and nuclear spin are controlled independently, the experiments lay the groundwork for development of larger, scalable systems in which such quantum registers are connected via optical photons.

This research work has been published by Science under the title "Quantum Register Based on Individual Electronic and Nuclear Spin Qubits in Diamond" (Volume 316, Issue 5829, Pages 1312-1316, June 1, 2007). Here is a link to the abstract. And this work will be presented at the 38th Annual Meeting of the Division of Atomic, Molecular, and Optical Physics of the American Physical Society which will be held in Calgary, Alberta, Canada, on June 5–9, 2007.

For more information, you also can read chapters 2 and 3 of the thesis of one Lukin's graduate students, Lilian Childress, "Coherent manipulation of single quantum systems in the solid state" (PDF format, 188 pages, 1.89 MB). The above illustration appears on page 26 of this document, which was used as one of the basis of the Science report mentioned above.

Sources: The Harvard University Gazette, May 31, 2007; and various websites

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