Portrait photograph of Nobel Prize winner Wolfgang Ketterle.

Picture: facesbyfrank/TUM.

Alumni doing research
TUM Alumni Prof. Wolfgang Ketterle
“Suddenly the Atoms Showed Their Wave Nature”
14. Oct 2011  |  
Reading time Min.
This interview is a republication of the original interview with Professor Ketterle from spring 2011.

At the age of 43, TUM alumnus Prof. Wolfgang Ketterle was awarded the Nobel Prize in Physics in 2001 “for the generation of Bose-Einstein condensation in dilute gases from alkali atoms and for early fundamental studies on the properties of the condensates”. Since 1993, the award-winning scientist has been researching and teaching at the Massachusetts Institute of Technology (MIT) in the United States. At the end of his seven-month stay in Munich, Ketterle took time to talk about his research, the city of Munich and endurance sports.

How did you spend the seven months in Munich?
I did 70% of what I would have done at MIT, which was write reports, submit research proposals, and supervise my research group via Skype and monthly visits. The only difference was that I didn’t have to give lectures. This gave me the opportunity to have discussions here at the Max Planck Institute in Garching, to watch in the lab, to discuss with PhD students and to learn about the research.
How would you rate your stay?
I am really excited about the possibility of taking a sabbatical. For over 20 years, I was never away from MIT for more than a few weeks. The distance makes me more aware of my own work and that of the group. The talks here in Garching and at other European research institutions gave me additional new impulses for my own research program. It was also great to be in Germany for a longer period of time after 20 years. In the last six months, I have been to the theater and museums very often, and have simply enjoyed Munich to the full. Several times a week I went jogging in the English Garden and in October I also ran the Munich Marathon.
Are you continuing to do research on Bose-Einstein condensates?
No, that’s exhausted. My current goal is to discover and research other new materials that require temperatures in the range of absolute zero.
What actually explains the name “Bose-Einstein condensation”?
This process, in which a new form of matter is formed, was only made possible by cooling processes that bring us to within millionths of a degree of absolute zero. Bose and Einstein described radiation and matter with their equations in the twenties. A singularity in the solution of the equations was interpreted by Einstein to the effect that here very many atoms march in step, so to speak. Thus he predicted an essential property of the Bose-Einstein condensates. However, it took a long time until it became clear that Einstein’s considerations could be realized in nature.
It was like the moment of truth. We are sitting in the lab and suddenly this wave pattern comes. Everything was just as we had imagined.

What was it like when you first observed the wave nature of the Bose-Einstein condensate?
When we first achieved this result, we had worked all night. We saw the wave nature of the Bose-Einstein condensate as a wave pattern on the computer screen. It was like the moment of truth. We’re sitting in the lab and suddenly this wave pattern comes. Everything was as we had imagined. And suddenly you know you’ve seen something that no one has ever seen before.
Do you keep such a research success secret for the time being?
On the contrary, one publishes as quickly as possible. Ideally, two to three weeks after a discovery, the paper is written and it appears a few weeks later. It is also most exciting and thrilling when new findings are served up with fresh momentum.
We often hear that researchers in different countries make the same discovery at the same time. Is that true?
This happens again and again and of course has to do with the fact that researchers talk to each other, influence each other. The discovery then hangs in the air, so to speak. Various groups have been working on Bose-Einstein condensation for several years. Then, within four months, two groups succeeded in proving it.
Your career in science began when you studied physics at TUM. Do you have any memories of that time?
Oh yes, of course. I did my diploma in theoretical physics with Prof. Wolfgang Götze, an excellent teacher and researcher. I learned a lot from him and the diploma thesis was my first research paper. You’re still proud of it afterwards.
How did you experience your graduation?
I did my diploma in 1982 and my doctoral thesis in 1986. In both cases there was no ceremony, no handing over. I went to some office in the main building and handed in my copies of the diploma or doctoral thesis. Then a clerk handed me the diploma and said “Congratulations”. Later, in the USA, I experienced what great events these can be.
Porträt Picture of Nobel Laureate Wolfgang Ketterle.

Picture: facesbyfrank/TUM.

So how is graduation celebrated at MIT?
The academic year celebration is the big event in the year of an American university. Parents come to see their children receive their diplomas. Many alumni come to reunite on this occasion. Because of the entrance of the professors in gown and mortarboard (doctoral hat) at the beginning of the event, the whole thing is called “commencement exercises”.
How many people come to the commencement exercises?
MIT has 1000 undergraduates and 1000 graduate students each year, each inviting two to three relatives. With faculty and alumni, there must be 10,000 people on campus. The ceremony is held in the open air on a large lawn on the Charles River Basin, which has been covered with chairs for the commencement exercises. The big event is the commencement address. A school of MIT’s quality gets distinguished public figures for that. We have had, for example, President Clinton, Koffi Anan (UN Secretary General) or the President (James Wolfensohn) of the World Bank.
My lectures are intended to convey enthusiasm for the research itself.

What is important to you in teaching?
I try to show students that the basic physics they are learning is alive and well in current research. My lectures are meant to convey enthusiasm for research itself and, of course, for basic research. At the moment, I have 13 graduate students working on different topics in my four labs.
Are German graduates welcome abroad?
Oh yes! Some of my best employees are from Germany. They are excellently trained.
Would you like to come back to Germany?
A return to Germany is not an issue at the moment. I feel very comfortable in the USA. My family is there, I have settled down. Ten years ago, I got a great offer to return to Munich, and it was a tough and very close decision to stay at MIT. But I have good mentors and colleagues there and the relationship is very family-like. I am equally rooted in Germany and the U.S., so to speak. It’s quite conceivable that if I had gone to Germany 15 years ago, things would have been similarly successful here and I would have felt just as comfortable. But unfortunately, you only have one life.
What would you like today’s students to take with them on their journey?
I would like to take the pressure off them that they have to decide today and now for their entire lives. My career also only came about in the course of life. It’s like sailing: You always have to focus on the next leg, assess the waves and the wind, and then do your best and give your best. When the wind and waves change, you correct your course. It has a lot to do with career and life. You have to figure something out about the water, the winds, about yourself. And you need a certain speed to navigate. If the sailboat is standing still, you can’t steer. To the students I would say: even if you don’t know what you want to do, you have to get out of the harbor! You must steer toward some goal, you must gain speed. By doing something, you evolve and get the experience and insights needed to make the next course correction. In the end, you often reach a goal that was unimaginable at the beginning.
Porträt picture of Nobel Laureate Wolfgang Ketterle.

Picture: facesbyfrank/TUM.

Wolfgang Kettlere

Diploma Physics 1982

Wolfgang Ketterle was born in 1957 as the second of three children and grew up in Eppelheim. After graduating from high school, he began studying physics at the Ruprecht Karls University in Heidelberg in 1976. After his intermediate diploma, he transferred to the TUM. He took the direction of theoretical physics and graduated in 1982 on spin relaxation of disordered materials, then moved to the Max Planck Institute of Quantum Optics in Garching and the Ludwig Maximilians University in Munich and received his PhD in 1986 with the thesis Spectroscopy on the helium hydride and the triatomic hydrogen molecule.

After his time in Garching, Ketterle moved back to Heidelberg to conduct research on combustion engines at the chair of Jürgen Wolfrum. In 1990, he moved to America to work on laser cooling problems in the group of David E. Pritchard. In 1993, he joined the Physics Department of the Massachusetts Institute of Technology (MIT) and now holds the John D. MacArthur Chair in Physics.

Wolfgang Ketterle received the Nobel Prize in Physics in 2001, jointly with Eric A. Cornell and Carl E. Wieman, for the generation of Bose-Einstein condensation in dilute gases of alkali atoms and for early fundamental studies of the properties of condensates.