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Updated 10:00 AM September 10, 2007
 

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Physicists establish 'spooky' quantum communication

Physicists at the University have coaxed two separate atoms to communicate with a sort of quantum intuition that Albert Einstein once called "spooky."

In doing so, the researchers have made an advance toward super-fast quantum computing. The research also could be a building block for a quantum internet.

Scientists used light to establish what's called "entanglement" between two atoms, which were trapped a meter apart in separate enclosures (think of entangling like controlling the outcome of one coin flip with the outcome of a separate coin flip).

A paper on the findings appears in the Sept. 6 edition of the journal Nature.

"This linkage between remote atoms could be the fundamental piece of a radically new quantum computer architecture," says Professor Christopher Monroe, the principal investigator who did this research while at U-M, but is now at the University of Maryland. "Now that the technique has been demonstrated, it should be possible to scale it up to networks of many interconnected components that will eventually be necessary for quantum information processing."

David Moehring, the lead author of the paper who did this research as a U-M graduate student, says the most important feature of this experiment is the distance between the two atoms. Moehring graduated and now has a position at the Max-Planck-Institute for Quantum Optics in Germany.

In this experiment, the researchers used two atoms to function as qubits, or quantum bits, storing a piece of information in their electron configuration. They then excited each atom, inducing electrons to fall into a lower energy state and emit one photon, or one particle of light, in the process.

By manipulating the photons emitted from each of the two atoms and guiding them to interact along a fiber optic thread, the researchers were able to detect the resulting photon clicks and entangle the atoms. Scientists could set the position of one qubit and know that its entangled mate will follow suit.

Entanglement provides extra wiring between quantum circuits, Monroe says. And it allows quantum computers to perform tasks impossible with conventional computers. Quantum computers could transmit provably secure encrypted data, for example. And they could factor numbers incredibly faster than today's machines, making most current encryption technology obsolete (most encryption today is based on the inability for man or machine to factor large numbers efficiently).

The paper is titled "Entanglement of single atom quantum bits at a distance."

For more information, go to focuspfc.physics.lsa.umich.edu.

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