August 16, 2011 — University of Tübingen researchers are making surface plasmons interact with cold atoms by illuminating gold nanowires with lasers. The laser light concentrates the light field at the surface of the wires, generating surface plasmons. These bound light fields could lead to optical computing advances and quantum computing.
The surface plasmons (data transfer) must be coupled to data storage, such as atoms. The research team, lead by Dr. Sebastian Slama and Prof. Claus Zimmermann are developing techniques for positioning cold atoms very close to surfaces so they interact with bound light waves. They collaborated with the nanotechnology group of Prof. Dieter Kern and Dr. Monika Fleischer, who fabricated the gold structures.
Atomic gases are cooled to a few hundred Nanokelvin in vacuum chambers. The temperatures force atoms to act unlike classical gases. They form a Bose-Einstein condensate, in which all atoms are in the same quantum state. The condensate can be regarded as a single huge super-atom and can be shifted by external magnetic fields to the surface, where it feels the influence of the plasmon. Some plasmons attract atoms and others repel them. "By structuring the surface we can tailor almost arbitrary potential landscapes for the atoms," says Dr. Slama.
Christian Stehle, PhD thesis candidate, measured the data together with Helmar Bender, who is now postdoc at the University of Sao Carlos in Brazil.
Results are published in Nature Photonics. Christian Stehle, Helmar Bender, Claus Zimmermann, Dieter Kern, Monika Fleischer, and Sebastian Slama, "Plasmonically tailored micropotentials for ultracold atoms," Nature Photonics 5, 494-498 (2011), www.nature.com/nphoton/journal/v5/n8/full/nphoton.2011.159.html and News and Views: James P. Shaffer, "Marriage of atoms and plasmons," Nature Photonics 5, 451-452 (2011), www.nature.com/nphoton/journal/v5/n8/full/nphoton.2011.174.html
The researchers are aiming to build hybrid devices for optical computing and quantum information, says Dr. Slama.
Learn more at Universität Tübingen, www.uni-tuebingen.de