Graduate School in Nonlinear Science

Sponsored by the Danish Research Academy

MIDIT                               OFD                           CATS
Modelling, Nonlinear Dynamics       Optics and Fluid Dynamics     Chaos and Turbulence Studies
and Irreversible Thermodynamics     Risø National Laboratory      Niels Bohr Institute and 
Technical University of Denmark     Building 128                  Department of Chemistry
Building 321                        P.O. Box 49                   University of Copenhagen 
DK-2800 Lyngby                      DK-4000 Roskilde              DK-2100 Copenhagen Ø
Denmark                             Denmark                       Denmark


by Klavs Hansen
Department of Physics
University of Jyvæskylæ
Jyvæskylæ, Finland

Thursday December 7, 2000, 14.00 h
at FYS, Bldg. 309, Room 250, DTU,

Abstract: Computing has to date been a technology based exclusively on information stored and processed as classical bits. Recently it it was realised that quantum information and processesing are very different from their classical counterparts and that a quantum computer can perform tasks that are virtually impossible for a classical computer. This understanding has triggered a large activity to present the first physical realisation of the qubit, the quantum bit, and to design and operate the logical elements to read out and manipulate it. Two particularly interesting candidates are the solid state system of a small superconducting island coupled weakly to the surroundings through Josephson junctions, the so-called Single Cooper Pair Box, and the flux qubit which is based on persistent currents in a superconducting loop. In the talk I will discuss the basic principle of the quantum computer, review ongoing attempts to construct qubits and present results from the work in Jyvæskylæ on the Cooper Pair Box and the decoherence time which is the time available for computing with these devices.