INTRODUCTION

Abstract

Coherence, condensation, and phase transitions are central concepts in physics. Several of the recent Nobel Prizes in Physicshave been given to pioneers of these fields. Systems can condense to condensates where particles act coherently, that is inexactly the same way. Photons in a laser is a well known example. Another example is the recent experimental realizationof a Bose Einstein condensate (BEC) in dilute gases where the wave functions of atoms overlap and form a coherent stateat low temperature, where all condensed atoms move together. BEC's are similar to superfluid and superconducting systems.Related phenomena occur in these condensates. For example, vortices of different kinds appear under rotation in BEC andsuperfluid 3He and 4He and correspond to quantized fluxons in superconductors under magnetic fields. Macroscopic quantumphenomena, another token of coherence, are typical of superconductors and occur also in the superfluids, includingBEC. Coherence is of utmost importance in so called quantum computers, a new concept based upon the probabilityof a two state system to be in one or the other of the states and where a number of operations have to be performedwithin a decoherence time.A Nobel Symposium provides an excellent opportunity to bring together a group of outstanding scientists for a stimulatingexchange of ideas and results. The Nobel symposia are small meetings and participation is by invitation only,typically 20-40 participants. In 2001, the Nobel Foundation celebrated the 100th anniversary of the first Nobel Prize and allprevious Nobel laureates were invited to attend the Nobel ceremonies in Stockholm. This gave an excellent opportunity forarranging jubilee symposia with topics that would attract several of the laureates. Our chosen subject of Condensation andCoherence in Condensed System (CoCoCo) attracted sixteen Nobel laureates and another thirty-five leading scientists whomet in Göteborg during four days before leaving for the festivities in Stockholm. The program had to be concentrated tocertain aspects and we apologize to all prominent scientists in the field that could not be invited due to space limits.Our idea was to bring scientists together from several related sub-disciplines: atomic physics, quantum optics, condensedmatter physics, for cross breeding of ideas, concepts and experience. Subject like phase transitions in strongly coupledsystems, Bose-Einstein condensation in weakly coupled systems, macroscopic quantum phenomena, coherence inmesoscopic structures, and quantum information were intensively discussed from different points of view. Coherencephenomena in condensed systems were emphasized. A special session was devoted to the emerging field of quantumcomputing with experimental and theoretical results reported for different types of qu-bits. The 2001 Nobel Prize to EricCornell, Wolfgang Ketterle, and Carl Wieman, "for the achievement of Bose-Einstein condensation in dilute gases of alkaliatoms, and for early fundamental studies of the properties of the condensates" gave an extra flavor to the theme of theCentennial Symposium.The Symposium was sponsored by the Nobel Foundation through its Nobel Symposium Committee. Lectures were givenat Ågrenska Villan, a former merchant mansion that was donated to the Göteborg University, at the MicrotechnologyCenter of Chalmers, and at Universeum, the new science center in Göteborg. Several of the sessions were open to invitedscientists or to a broader audience, which could enjoy reviews of central topics. High school students and His Majesty theKing of Sweden had the possibility to meet and interview many of the laureates during the visit at Universeum. Receptionswere sponsored by the City of Göteborg and Chalmers University of Technology and gave participants opportunities tomeet local scientists, students, and industrialists as well as to enjoy music and a guided tour of arts. The symposium wasorganized by Sune Svanberg, Mats Jonson, and Tord Claeson. Valuable hints were given by Anders Bárány, the secretary ofthe Nobel Committee of Physics. Many of the participants gave valuable comments regarding the planning of the CoCoCosymposium. Special thanks are due to our "sounding board": Anthony Leggett, Hans Mooij, Doung Osheroff, Bill Phillips,and Stig Stenholm. Per Delsing had the responsibility of editing the Proceedings. Our secretary, Ann-Marie Frykestig, andtechnician, Staffan Pehrson, did outstanding jobs organizing practical matters. Several of the members of our local universitycommunity helped with odds and ends. Mariana Ravneva ivanova and Madeline Claeson directed an appreciatedcompanions program.The Proceedings contain most of the material presented at the Symposium. A few contributions that summarized resultspublished elsewhere are exempted. We hope that these Proceedings will convey to the reader some of the excitement felt bythe participants during the Symposium. We also want to express our thanks to sponsors and contributors to the successfulscientific event.