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Posted: June 4, 2009

Stable quantum bits - experiment proves theory of Dortmund Physicist Uhrig to be right

(Nanowerk News) As early as 2007 the physicist Prof. Dr. Götz S. Uhrig, chair holder of Theoretical Physics I at TU Dortmund, devised a method to keep the fragile states of quantum bits stable for as long as possible. The method is based on a universal optimization of a sequence of pulses controlling the quantum bit. But until now it was not possible to experimentally prove his theoretical proposal.
Now scientists from the National Institute for Standards and Technology (NIST) have conducted an experiment to verify the theory of their Dortmund colleague. In the latest edition of Nature they describe how they were able to keep the specifically induced states in atomic nuclei stable longer than before by means of a sequence of laser pulses calculated by Uhrig.
An American science team around J. Bollinger from the National Institute for Standards and Technology examined Uhrig’s calculations, published in the renowned magazine Physical Review Letter (vol. 98, page 100504) in 2007. They exposed 1000 beryllium atoms, which were held together by a strong magnetic field, to a sequence of laser pulses calculated by the Dortmund physicist. The result: measurements showed quantum bits which kept the desired state stable for a much longer time than ever before. Therefore the experiment, reported about in the latest edition of “Nature” (vol. 458, page 996), the world-wide most-respected magazine for natural sciences, proves the theoretical ideas of the Dortmund physicist to be right.
Both sides are eager to continue the successful German-American cooperation of theoretic and experimental physicists. At the invitation of the American team, Uhrig will present his theory at an international conference in Boulder, Colorado in October. Beyond that he wants to further optimize the control pulses together with his colleagues in Dortmund. Although the American experiment showed clearly prolonged quantum stability, the theoretician Uhrig has already ideas to enhance the potential of his optimized sequences.
Source: Technische Universität Dortmund