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nanotimes News in Brief

10-05/06 :: May/June 2010

Quantum Interface // Controlled Coupling of Light and Matter

University Mainz, Germany, have developed a quantum interface which connects light particles and atoms. The interface is based on an ultra-thin glass fiber and is suitable for the transmission of quan- tum information. This is an essential prerequisite for quantum communication which shall be used for secure data transmission via quantum cryptography.

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„Our quantum interface might also prove useful for the realization of a quantum computer,“ adds Pro- fessor Dr Arno Rauschenbeutel from the Institute of Physics at Mainz University.

The central part of the work in Mainz is a glass fiber which has been heated and stretched until it measures only one hundredth of the diameter of a human hair. Remarkably, this nanofiber is thinner than the wavelength of the light it guides. As a conse- quence, the light is no longer restricted to the inside of the nanofiber but laterally protrudes into the space surrounding the fiber. Using this so-called evanescent field, the scientists trapped cesium atoms after they have been cooled to a few millionth of a degree abo- ve absolute zero by irradiation with suitably chosen laser light. When trapped, the atoms are arranged in a regular pattern and are levitated 200nm above the surface of the nanofiber. This distance might seem very small but it indeed is big enough to protect the atoms from the spurious influences of the fiber

group of physicists led by Professor Arno Rauschenbeutel at the Johannes Gutenberg

The Mainz quantum interface. Using laser light which travels through a tapered glass fiber, cesium atoms are trapped along its ultra-thin waist. The central part of the fiber is thinner than the wavelength of the light itself. As a consequence, the latter protrudes into the space surroun- ding the fiber and couples to the trapped atoms. © QUANTUM, JGU Mainz

surface. At the same time, the atoms reside in the evanescent field and thus interact with the photons propagating through the nanofiber. Further possible applications of the Mainz quantum interface include the connection of different quantum systems.

E. Vetsch, D. Reitz, G. Sagué, R. Schmidt, S. T. Dawkins, and A. Rauschenbeutel: Optical Interface Created by La- ser-Cooled Atoms Trapped in the Evanescent Field Sur- rounding an Optical Nanofiber, In: Physical Review Letters, Volume 104(2010), Issue 20, Article 203603 [4 pages], DOI:10.1103/PhysRevLett.104.203603: http://dx.doi.org/10.1103/PhysRevLett.104.203603

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