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Solid-State Quantum Memory for Light

Photonics.com
Jun 2010
CANBERRA, Australia, June 25, 2010 —  Using a technique pioneered to stop and control light from a laser by manipulating electrons in a crystal cooled to -270 degrees Celcius, a team from the Australian National University (ANU) say they have developed the most efficient quantum memory for light in the world.


Light passes through the crystal in the quantum memory experiment. (Image: ANU)

According to the team, the unprecedented efficiency and accuracy of the system allows the delicate quantum nature of the light to be stored manipulated and recalled, which they say could lead to super-fast computers and communication secured by the law of physics.

“Light entering the crystal is slowed all the way to a stop, where it remains until we let it go again,” said lead researcher Morgan Hedges. “When we do let it go, we get out essentially everything that went in as a three-dimensional hologram, accurate right down to the last photon.

“Because of the inherent uncertainty in quantum mechanics, some of the information in this light will be lost the moment it is measured, making it a read-once hologram. Quantum mechanics guarantees this information can only be read once, making it perfect for secure communication.”

The same efficient and accurate qualities make the memory a leading prospect for quantum computing, which has the potential to be many times faster and more powerful than contemporary computing.

In addition, the researchers say the light storage will allow tests of fundamental physics, such as how the bizarre phenomenon of quantum entanglement interacts with of the theory of relativity.

“We could entangle the quantum state of two memories, that is, two crystals,” said team leader Dr. Matthew Sellars. “According to quantum mechanics, reading out one memory will instantly alter what is stored in the other, no matter how large the distance between them. According to relativity, the way time passes for one memory is affected by how it moves. With a good quantum memory, an experiment to measure how these fundamental effects interact could be as simple as putting one crystal in the back of my car and going for a drive.”

Sellars’ team has previously performed an experiment that ‘stopped’ light in a crystal for over a second, more than 1000 times longer than was previously possible. He said that the team is now bringing together systems that combine the high efficiency with storage times of hours.

The research team included Dr. Jevon Longdell from the University of Otago and Dr. Yongmin Li from Shanxi University. The findings were published in the journal Nature.

For more information, visit:  www.anu.edu.au 




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.
quantum mechanics
The science of all complex elements of atomic and molecular spectra, and the interaction of radiation and matter.
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