HERBERT WALTHER, SCIENTIST EXTRAORDINAIRE (January 19, 1935 — July 22, 2006)

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PIERRE MEYSTRE College of Optical Sciences, Department of Physics and B2 Institute The University of Arizona, Tucson, AZ 85721, USA

People who have a transforming influence on science come in many vari- ations: there are of course the extraordinary researchers whose discoveries help open and define a new field of investigations; the great teachers who can inspire generations of students; and the visionary administrators who provide the financial and infrastructure support needed to carry out our work. Many physicists excel at one of these tasks, significantly less at two of them, and only very few at all three. Herbert Walther was one of these rare few. As a researcher, he produced advances and insights of the highest value. Amongst his many achievements, he helped define the field of cavity quantum electrodynamics, a field that is in turn pivotal to the emerging science of quantum information; as a teacher, he not only distinguished himself in the classroom, but trained and mentored an extraordinary palette of graduate students who went on to pursue highly distinguished academic careers — Nobel Prize winner Wolfgang Ketterle and Max-Planck direc- tors Gerd Leuchs and Gerhard Rempe immediately come to mind — or alternatively became influential industry leaders, and here I am thinking for instance of Rainer Schlicher and Andreas Dorsel. Last, but not least, starting from an empty leased building and a couple of “theory contain- ers”, he built a world-leading quantum optics research institute, producing Nobel-quality research and a mecca for both very senior scientists and bud- ding young researchers from all over the world. By attracting to Garching the likes of Marlan Scully and Ted Haensch and hosting a palette of scientific world stars, the absolute who-is-who of our field, he made the Max-Planck February 16, 2009 14:30 WSPC - Proceedings Trim Size: 9in x 6in icap2008

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Institute for Quantum Optics an undisputed center of gravity for AMO science, a must-stop destination. Herbert Walther’s scientific career took him from his PhD studies at the University of Heidelberg to Hannover, where he obtained his Habilitation in 1968. After extended foreign stays at JILA in Boulder and at the Lab- oratoire AiméCottoninOrsay,hebecameaProfessor at the University of Bonn, followed soon thereafter by a move to Cologne, where he stayed until 1975. He then became a Professor at the University of Munich, be- coming at the same time a founding Director of the Projektgruppe fuer Laserforschung with Siegbert Witkowski and Karl Kompa. This research group then morphed into the permanent Max-Planck Institute for Quan- tum Optics in 1981. The record indicates that during his Munich years, Herbert Walther graduated 94 PhD students, and had 10 of his collaborators receive their Habilitation. He is the author or coauthor of over 600 publications, covering topics from applications of narrow linewidth dye lasers to spectroscopy, a field where he was a true pioneer, to multiphoton processes; from the study of Rydberg atoms to cavity QED and micromasers; from trapped ion research to molecular spectroscopy; and from surface physics to more February 16, 2009 14:30 WSPC - Proceedings Trim Size: 9in x 6in icap2008

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applied topics such as the development of techniques to monitor the ozone layer in the atmosphere. Herbert Walther’s impact on science policy is just as remarkable: he served on a number of national and international committees, where he profoundly influenced the development and support of science in Germany, Europe and worldwide. These activities notably included a stint on the Sci- ence Council of the German Federal Republic as well as membership on the Executive Council of the European Science Foundation. Most importantly perhaps, in his role as Vice-President of the Max-Planck Society he was charged with the difficult and enormously challenging task of initiating the reorganization of science in the former East Germany following the reunifi- cation of Germany. This was without a doubt a task that would have fully consumed lesser mortals, but that he accomplished tirelessly with grace, fairness and good taste, while at the same time continuing all of his other activities. I remember once asking him how he could possibly carry out es- sentially three full-time jobs, while still finding time to be an extraordinary host and mentor, always giving the impression of having all the time in the world for his visitors. His answer was that “yes, one can turn any job into a full-time job, but there is no reason why this should be the case”. He February 16, 2009 14:30 WSPC - Proceedings Trim Size: 9in x 6in icap2008

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also explained to me one of his important rules, which was to touch any piece of paper that landed on his desk only once. Still, I remain immensely impressed by the fact that whenever I would talk to him, he gave me the impression that I was the most important person in the world and that he had unlimited time to talk and listen to me. To this day, I still don’t know how he did it. Herbert Walther had such a profound impact on so many aspects of science that it is not surprising that a long list of prestigious rewards, awards, and honors were bestowed upon him. They include the Max Born Prize, the Charles Townes Award, the King Faisal Prize in Physics, the Michelson Medal, the Humboldt Medal, the Stern-Gerlach Medal, the Verdienstkreuz 1. Klasse des Verdienstordens der Bundesrepublik Deutschland, the Willis E. Lamb Medal for Laser Physics, the Quantum Electronics Prize of the European Physical Society, the Alfred Krupp Prize for Science, the Or- der of Merit of the State of Bavaria, and the Frederic Ives Medal/Jarus W. Quinn Endowment. He was also a Member or Honorary Member of Academia Sinica, the Bavarian Academy of Sciences, the Akademie der Naturforscher Leopoldina, the Roland Eötvös Physical Society of Hungary, the American Academy of Arts and Sciences, the Heidelberg Academy of Sciences, the Romanian Academy, the Nordrhein-Westflische Akademie der Wissenschaften, Academia Europaea, the Russian Academy of Sciences, the Hungarian Academy of Sciences, the Convent for Technical Sciences of the German Academies, the German Physical Society, and the Belarusian Physical Society. But as impressive as they may be, these lists don’t even come close to expressing the impact that Herbert Walther has had on AMO science and most importantly, on generations of students and colleagues worldwide. When confronted with a difficult situation or a thorny problem, I still find myself asking “how would Herbert deal with that?” And this, for me, is the biggest compliment I can make to this unforgettable mentor. I still miss him terribly, and I know that there are very many of us who feel that way. Last but not least: As the saying goes, behind every great man there is a great woman. In Herbert Walther’s case, everybody who knew him also knows how very true that was. It is very difficult indeed to imagine that he could have achieved even a fraction of what he did without the support and love of his wife Margot. Not to mention her wonderful hospitality and her great dinners, which many of us have enjoyed so much! February 16, 2009 14:30 WSPC - Proceedings Trim Size: 9in x 6in icap2008

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Acknowledgements I am thankful to Dr. T. W. Haensch for providing me with a number of pictures of Herbert Walther, including those shown here.