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Ulf Leonhardt
Credit: TEDx Brussels/Scorpix

Follow your star

Theoretical physicist Ulf Leonhardt is not afraid to pursue audacious scientific ideas. Leonhardt is best known for his work on how metamaterials can be used to fashion invisibility devices and how fiber optics can be used to produce analogs of the event horizon, the point of no return in black holes. Last December at the TEDxBrussels conference, Science Careers asked Leonhardt, a professor of physics at the Weizmann Institute of Science in Rehovot, Israel, to share his thoughts about his research and career. The interview was edited for brevity and clarity.

Q: What qualities are necessary to be successful in academia? 

What I have observed in some very good young scientists is that they think too much about their careers.

—Ulf Leonhardt

A: Be stubborn. Believe in yourself. Follow your star. Don’t do what others are saying. Also very important is to stand up again and again. You will fall all the time. There will be disasters, small and great.

Each step in my career began with disasters. I studied for 1 year at Moscow State University to become a specialist in high-energy physics. But then I didn’t really like that, so I started all over again. I then did my master’s degree in half a year, so I almost caught up.

For my Ph.D., I started a project in the atomic physics of hot, dense plasmas during a very difficult time. This was just after the breakdown of former East Germany, and so the new academic system was being built. I was at Humboldt University of Berlin at the time, and my supervisor was under a lot of pressure to prove himself. He had very little time, and I suffered.

Also, I realized that atomic physics was not really what I wanted to do. I was interested in other questions. I worked for 2 years in this subject, but then I decided to write off these 2 years of my life, of my work, and start again.

So, instead, I did a Ph.D. in quantum optics, in one of the newly founded Max Planck Research Groups. This time around, I was in a position to take advantage of the changes in the system, embracing new opportunities, and that paid off. I did the Ph.D. in 1 year and 3 months, so at the end I was really on time for a Ph.D., even though I had failed the initial phase. Plus, I got an award from the Senate of Berlin: My thesis was, according to the committee, the best Ph.D. of all universities for all subjects in Berlin.

And so it went, on and on like this. Usually the first attempt fails, but you learn from it. Maybe you don’t even learn all the time, but from the beginning, you should somehow not be afraid of failure and learn how to stand up and start again.

Q: How did you find a permanent position?

A: Of course it was difficult, and my strategy won’t work for everyone; it only works for theorists. So most of the time I had research fellowships, which means I had my own money. I was independent. I could go where I wanted to and not where I had to. I had fellowships until the point when I got a full professorship, so I never went through the hurdles of a tenure-track or lecturer position. This keeps you independent and active, and you’re not forced to adjust to the academic system at an earlier stage. Also, I moved from country to country every 1 or 2 years, and this is not possible if you do experimental work, because you can’t move around with a lab. But for theorists, I think this is an approach that people should think about. 

Q: What idea did you think would be hardest to pull off?

A: This is not really what happens. I’ve always felt that if I have an idea, it’s going to work. Only when it fails do I realize that it doesn’t. And then comes, usually, a long period of desperation, but the idea is still lingering in my mind. Then suddenly a possible solution comes to mind.

An example is the idea about how to make analogs of black holes. I started this in 1999, and it became concrete in 2000, when our theoretical framework for making optical black holes in the laboratory was published and made a big splash in The New York Times. Our method was based on slow light, and I continued to work on it, but then I realized that it’s not going to work in practice, so this was a dead end. For a while it was still in my mind, but I didn’t actively pursue it anymore. Then, suddenly, I realized that it can be done, not with slow light but with optical fibers and laser light. The idea and a first experimental test of it were then published in Science in March 2008. This is an experiment that we are still doing, and we are now trying to measure interesting quantum phenomena in the laboratory.

So this is what usually happens. It’s not that you think it’s crazy at first. You may think that there is a chance that it works, and it may not completely work, but you should always believe in it. It’s surprising if something works the first time—usually it doesn’t—so then you need to be persistent and try to correct it to make it work.

Q: Have people tried to dissuade you from following your ideas?

A: Of course, all the time. Whether it affects me or not depends on the people and the style of the discussion. If people criticize me in a nonscientific way, I completely ignore them because it’s not an argument. If it’s a scientific attack I take it seriously, and then I respond and I learn from it.

Q: Any advice for young scientists?

A: What I have observed in some very good young scientists is that they think too much about their careers. They’re very keen on fitting the mold of a successful scientific career, so they’re building their CVs. This is all wrong: Build yourself, not your CV. Otherwise, of course you succeed in the short term, but then you may just burn out and you lose the fun in science. It’s so sad to watch that in talented people, when they just subscribe to the ideas of others. People are saying, this is what you need for your CV, you need to go to that prestigious place, do this and that, and publish these sorts of papers at that age. This is advice from others that doesn’t necessarily fit your needs. Young scientists should first think about what they want to do or are interested in doing. This is within limits, of course; you should not do complete rubbish. Know how science and the scientific establishment works, but don’t take it too seriously. Listen to what other people are saying, but don’t apply it automatically. The rationale is that other people may see some aspects of your situation, but they don’t have the knowledge of it all. Only you have that.

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