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  • New Switch Could Scale Up Quantum Computing

Photonics.com
Apr 2014
CAMBRIDGE, Mass., April 11, 2014 — A new technique to connect particles could assist in development of quantum computing systems.

Scientists at MIT and Harvard University have coupled a lone atom of rubidium with a single photon, an interaction that allows each to switch the quantum state of the other. This coupling can serve as a quantum switch through which information can be transmitted and quantum-level computing operations can take place.


A new method of trapping rubidium atoms in a lattice of light could help the development of quantum computing. Courtesy of Christine Daniloff, MIT.


Placing many atoms within the same field of light could enable networks that process quantum information more effectively. The new technique could increase the number of useful interactions occurring within a small space, thus scaling up the amount of quantum computing processing available.

That would create a hybrid quantum system, in which the individual atoms are joined to microscopic fabricated devices, and in which atoms and photons can be controlled in productive ways. The researchers found that this new device can also serve as a router to separate photons from one another.

Although the research is still in the early stages, "this is a major advance of this system," said Dr. Vladan Vuletic, a professor in MIT's Department of Physics and Research Laboratory for Electronics (RLE), a lead researcher.

The researchers used a laser to place the rubidium atom within 100 to 200 nm from the surface of a photonic crystal cavity, or lattice of light. Such a short distance prompts a strong attraction between the atom and the surface of the light field, which traps the atom in place. This has given the researchers much more control over the particles than previously studied techniques.

"In some sense, it was a big surprise how simple this solution was, compared to the different techniques you might envision of getting the atoms there," Vuletic said.

The Max Planck Institute of Quantum Optics in Germany has also been developing a method of producing atom-photon interactions that uses mirrors to form quantum gates to change the direction of motion or polarization of photons, the researchers said.

The MIT-Harvard team’s work was funded by the National Science Foundation, the MIT/Harvard Center for Ultracold Atoms, the Natural Sciences and Engineering Research Council of Canada, the US Air Force Office of Scientific Research and the Packard Foundation. Their research is published in Nature. (doi: 10.1038/nature13188

For more information, visit: www.mit.edu


GLOSSARY
photon
A quantum of electromagnetic energy of a single mode; i.e., a single wavelength, direction and polarization. As a unit of energy, each photon equals hn, h being Planck's constant and n, the frequency of the propagating electromagnetic wave. The momentum of the photon in the direction of propagation is hn/c, c being the speed of light.
polarization
With respect to light radiation, the restriction of the vibrations of the magnetic or electric field vector to a single plane. In a beam of electromagnetic radiation, the polarization direction is the direction of the electric field vector (with no distinction between positive and negative as the field oscillates back and forth). The polarization vector is always in the plane at right angles to the beam direction. Near some given stationary point in space the polarization direction in the beam...
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