QUANTUM COMPUTATION

Jens Siewert

Quantum mechanics provides new ways of computation which - for certain problems - are more efficient than any known conventional (``classical'') scheme of computation.

An intuitive example for this observation goes back to Feynman (R. Feynman, Simulating physics with computers, Internat. J. Theoret. Phys., 21 (1982), pp. 467-488). He pointed out that there appears to be no efficient way of simulating a quantum mechanical system on a classical computer while a computer based on quantum-physical principles might be able to do it - a quantum system is able to simulate its own behavior in real time!

Quantum computation has developed into an extremely exciting and rapidly growing field of investigation. An increasing number of researchers with a whole spectrum of different backgrounds, ranging from physics, via computing sciences and information theory to mathematics and philosophy, are involved in researching properties of quantum-based computation.

What we are doing

Our research is focussed on implementations of simple quantum operations and also complete algorithms with qubits made of Josephson-junction circuits.

This is of interest also beyond the field of quantum computation: Josephson junction networks are macroscopic objects. Macroscopic quantum coherence is one of the long sought for phenomena in mesoscopic physics which has been observed experimentally only very recently (i'll add a few links). Entanglement in such systems remains still to be detected.

We are studying:

- dynamics and other properties of qubit implementations,
- realization of quantum algorithms for Josephson-junction qubits,
- holonomic quantum computation in solid-state devices, i.e.
a different way to implement a quantum computer by
using geometric phases.