Researchers at the University of Tübingen are working on next
generation’s computer: They made cold atoms interact with
miniature gold wires as small as a thousandth of a millimeter.
Illuminating the wires with laser light in a special way, the
physicists concentrated the light field at the surface of the wires
and, by that, generated so-called surface plasmons. These are bound
light fields which might enable the construction of devices for optical
computing and for quantum information. Circuits based on these devices
would be much faster and more efficient than present technologies.
In order to build an optical computing device the surface plasmons,
which are useful for data transfer, must be coupled to data storage
elements, such as atoms. This is what the research team lead by Dr.
Sebastian Slama is working on. The junior scientist developed
techniques at the chair of Prof. Claus Zimmermann which are crucial for
positioning cold atoms very close to surfaces such that they can
interact with bound light waves. For that atomic gases are cooled in a
vacuum chamber down to temperatures as low as a few hundred Nanokelvin.
At such low temperature the atoms no longer behave as a classical gas.
They form a so-called 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. “We can
generate plasmons which attract the atoms and others which repel them.
By structuring the surface we can tailor almost arbitrary potential
landscapes for the atoms”, says Dr. Slama.
Recently, the scientists published their results in Nature Photonics
magazine. First author Christian Stehle, who is working on his PhD
thesis and has measured the data (together with Helmar Bender, who is
now postdoc at the University of Sao Carlos in Brazil) is enthusiastic:
“Our results had a great impact. We managed to get on the title
page of the August issue, and the magazine values our work in a
comment.” However, with this success the scientists’ work
is not terminated. “Our goal is to build hybrid devices for
optical computing and quantum information. We were now able to set a
milestone, but there is still a lot to do”, says Dr. Slama. In
his opinion these goals can only be achieved in cooperation with other
scientists. Beside already existing cooperations like the one with the
nanotechnology group of Prof. Dieter Kern and Dr. Monika Fleischer, who
fabricated the gold structures, Slama has made contact to further
scientists in Tübingen, Europe and in Brazil.Publication: 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
More inforamtion at www.uni-tuebingen.de/