---

Phil Ponce talks with Steven Chu, one of the three Nobel Prize winners in Physics, about his collaborative effort in developing a way to cool and trap atoms with laser light. Professor Chu shares the prize with fellow American William Phillips and Claude Cohen-Tannoudji, a French colleague.

---

PHIL PONCE: The last of the Nobel prizes were announced this morning, and today's winners were in the sciences. In Physics two Americans, Steven Chu and William Phillips, and a French colleague, Claude Cohen-Tanoudji, won the prize. The scientists developed ways to cool and trap atoms with laser light. To explain that and its implications we're joined by one of the winners, Steven Chu of Stanford University. Prof. Chu, first of all, congratulations.

STEVEN CHU, Nobel Laureate, Physics: Thank you.

PHIL PONCE: Did you have any inkling that this prize might be in the works, or did it come as a complete surprise?

STEVEN CHU: Perhaps not a complete surprise but because every time about this time friends who mean well might say, well, here's hoping, and so there's a bit of agitation that I try very much to ignore these things and just proceed with my life.

PHIL PONCE: Professor, what is it exactly, the work that you did, that precipitated the prize?

STEVEN CHU: We--meaning my colleagues at Bell Labs and also Bill Phillips and his group and Claude Cohen-Tanoudji and his group had developed techniques to cool atoms in a gas phase. Now, let me explain what that means. First, I have to explain what temperature means. In this sense we talk of temperature as some average random velocity of these gaseous atoms. And by cooling the atoms we're reducing the average velocity of the atoms in this gas phase. So at room temperature, molecules, atoms are moving at speeds comparable to that of supersonic jet planes, and by using laser techniques we were able to cool these atoms, that is, reduce the velocities down to speeds comparable to the speed that an ant might be walking, and so there's a great reduction in the velocity.

PHIL PONCE: Using lasers, you trap atoms, you slow them down, they cool down; you can study them and measure them. So where does this lead you in terms of applications?

STEVEN CHU: There are numerous things you can do. For example, you can improve the precision of atomic clocks and hopefully the accuracy of atomic clocks. Atomic clocks now form the basis of many things from the global positioning satellites that circle the Earth that tell you where you are to a meter, that also tell you whether the ocean levels are going up and down with respect to land mass, so if in issues of global warming you want to measure that. They also tell you how land masses' tectonic plates are moving and building up of stresses in earthquakes.

PHIL PONCE: So the kind of work you're doing can make for a much more accurate clock that will give people better information about what is happening on Earth because of their use in satellites, for example.

STEVEN CHU: Potentially because there are other issues that might cloud the accuracy of these measurements. So what I'm trying to stress is that the new, improved accuracy that we will see from these cooling entrapment techniques have been going to atomic clocks; whether that particular application will emerge is yet to be known. So it's a wonderful thing about science. When we were doing these early experiments, we didn't know what the applications were. We knew about that one, but we didn't know about some of the others.

PHIL PONCE: I understand that it's almost an accident that you came across this, that you started this area of inquiry.

STEVEN CHU: Well, in a certain sense, yes, it was. What ones decide to do in science and how one goes into research is a mixture of accidents, not that you sit alone and think of grand designs and important issues. In this particular case it was a mixture of talking socially to Arthur Ashkin, a colleague of mine at Bell Labs, who had made many early proposals on trapping and cooling--trapping of particles and atoms, and also a post-doc, Leo Hulberg, who had just joined me--

PHIL PONCE: Was this a eureka moment, or was it more of a step-by-step kind of a thing?

STEVEN CHU: There were few eureka moments, but there were a series of experiments that--speaking for myself--that we did first in demonstrating what we call optical molasses, the initial cooling experiments, then there was another experiment that demonstrated you can actually hold onto these atoms with laser light, another experiment demonstrating a different kind of trap, that it's now the mainstay cooling, trapping trap used in the world today, another experiment that demonstrates how you can split atoms apart, bring them back together again, and how we use that to make very sensitive measurements of let's say the acceleration due to gravity. So it's actually a series of experiments that extended from the published work, which extended from 1985, to the present, so it's a long series of things.

PHIL PONCE: Prof. Chu, so many people try go get away from Physics. What attracted you to Physics in the first place?

STEVEN CHU: Well, that's a good question. It's a variety of things. First, I was blessed. I had a terrific high school Physics teacher and it was in public school in Garden City Long Island, New York, and I had Physics as a junior, and then had Advanced Placement Physics as a senior. It was absolutely wonderful, in fact, nationally recognized. I grew up in a science background. My older brother was at that time majoring in Physics in college. And then there was the inherent simplicity and beautifulness of Physics that--that's not really a word--but it's a sort of thing where you can take nature and you describe nature in terms of mathematical models. And the mathematical models allow you to reach far reaching conclusions, and you can test these conclusions by going back in the lab.

The whole structure of making progress in this way seems so appealing it's--you really say if I really understand it, then I should make a quantitative prediction of what's going on, and you can go in the lab and check it. And so it's a no-nonsense sort of thing. You can't in the end fool yourself. You have to make a prediction, go in the lab and test it. And that's a very satisfying feeling because in the end it means that once you've established this connection between experiment and the model of how nature works you can believe to believe it, and then from there you build on to the next step and the next step. And so in this process of going very slowly, building very slow, little steps from the time let's say of Galileo, when modern Physics really began, we've come a long way, by making incrementally little steps.

PHIL PONCE: How do you think this award is going to change your life?

STEVEN CHU: Well, I'm hoping it doesn't change it too much. After this hullabaloo dies down, I intend to go back in the lab. There's different directions that my group--my students and I are going in, in addition to working with atoms and the like, we're also now working with molecules. We're manipulating molecules of DNA both for Palmer experiments and also for Biology. You know, I've been told by my colleagues at Stanford that things calm down after a year. They award the prize to someone else, and then the limelight goes on them.

PHIL PONCE: Well, Professor Chu, again, congratulations, and I thank you for joining us.

STEVEN CHU: All right. Thank you.

REGIONS TOPICS RECENT PROGRAMS ABOUT US FEEDBACK SUBSCRIPTIONS / FEEDS:

Support the kind of journalism done by the NewsHour...Become a member of your local PBS station.
PBS Online Privacy Policy Copyright ©1996- MacNeil/Lehrer Productions. All Rights Reserved.