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  • Efficient and Tunable Entanglement Method Developed
May 2012
INNSBRUCK, Austria, May 25 — To construct a viable quantum network, individual computers will need a way to reliably transmit information to each other. This will require an understanding of how light and matter interact at a quantum level, an understanding that is now much more robust.

A research team at the University of Innsbrook's Institute for Experimental Physics, led by Rainer Blatt, Tracy Northup and Andreas Stute, trapped a calcium ion in a Paul trap, a device that uses DC and oscillating AC electric fields to trap ions, and placed it between two highly reflective mirrors. By shining a laser on the ion, the researchers induced the ion to emit a photon, which was reflected back and forth between the mirrors up to 25,000 times, becoming entangled with the ion. The entanglement can be tuned by adjusting the frequency and amplitude of the laser so that the target collective state of the photon and ion is reached.

At the core of the experiment lies an optical resonator consisting of two highly reflective mirrors. (Image: C. Lackner)

“The efficiency with which we produce entangled photons is quite high and in principle could be increased to over 99 percent,” Northup said. “But above all, what this setup lets us do is generate any possible entangled state.”

“Along with an efficient entanglement process, we’ve demonstrated an entangled quantum state between an atom and a photon with the highest precision measured to date,” Stute explained.

The results of this research are an important building block for quantum computing. All of the recent advancements in quantum networking would be useless if the individual parts of the network could not interface with each other and exchange data. Since, according to quantum mechanics, information about a quantum state cannot be transmitted without becoming corrupted, a reliable method to entangle matter and photons is necessary.

Rainer Blatt (third from right) and Tracy Northup (fourth from right) with their team at the Institute for Experimental Physics of the University of Innsbruck. (Image: University of Innsbruck)

“Whenever we have to transfer quantum information from processing sites to communication channels, and vice versa, we’re going to need an interface between light and matter,” Northup said.

The research was published in the May 24 issue of Nature; it was supported by the Austrian Science Fund and the European Union.

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