Colloquium on July 26, 2010

Götz S. Uhrig
Technische Universität Dortmund, Fakultät Physik

Coherent Control of Quantum Bits: Ideas against Decoherence

To exploit the special phenomena of quantum mechanics for information processing is a dream which stimulates physicists and engineers already for quite some while. Since about ten years the research on this field is booming. Instead of encoding a bit (0 or 1) in a classical variable it is stored in a quantum two-level system (quantum bit or qubit) which also allows for the superposition of the states $|0\rangle$ and $|1\rangle$. On the one hand, this is the basis for the humongous potential of quantum information processing: exponentially many classical computations can be carried out in parallel! On the other hand, it is also its Achilles' heel because it renders quantum information fragile. If the coherence of the quantum states is lost (decoherence) its very special character and hence its particular assets are lost.

Therefore it is an important objective to suppress decoherence. Fundamental concepts to do so are presented in this talk. The focus lies on physical methods which effectively reduce the coupling between quantum bits and their environment. In this way, the decoherence rate can be reduced by almost two orders of magnitude.