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Interview of Marlan Scully by David Zierler on April 28, 2021,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
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Interview with Marlan Scully, Distinguished University Professor and Burgess Chair at Texas A&M and Distinguished Research Academician at Baylor University. The interview begins with Scully recounting his early experience contracting COVID-19 and how that informed his research into the virus. Then he describes growing up in Wyoming and recalls not being very interested in school until he fell in love with calculus while attending community college. Scully talks about his studies in physics at the University of Wyoming before eventually transferring to Rensselaer Polytechnic. He then discusses his decision to move to Yale to work with Willis Lamb on laser physics. Scully recounts his assistant professorship at MIT and the opportunity at University of Arizona, where he was involved with starting their Optical Sciences Center. He talks about his subsequent joint position between University of New Mexico and Max Planck Institute for Quantum Optics, as well as his work with Air Force weapons labs on laser applications. Scully details the events leading to his position at Texas A&M and the inception of the Institute for Quantum Studies, and his ongoing affiliations with Princeton. At the end of the interview, Scully reflects on the interplay between theory and experimentation throughout his career and in laser physics specifically, as well as the technological advances that have propelled laser research forward.
This is David Zierler, oral historian for the American Institute of Physics. It is April 28, 2021. I’m delighted to be here with Professor Marlan Scully. Marlan, it’s good to see you. Thank you for joining me today.
Thank you. It’s a pleasure to be here with you.
Marlan, to start, would you please tell me your titles and institutional affiliations? And you’ll note that I put an “s” on everything, because I know you have more than one.
[laughs] Right. Well, my main title and my first love is Texas “Atomic and Molecular” University. Right? Texas A&M. It used to mean something else, but that’s what it means today. I’m a Distinguished University Professor. I have the Burgess Chair, and I’m director of the Institute for Quantum Science and Engineering here at A&M.
At Baylor University up the road, a nice liberal arts school that I like a lot, I am a Distinguished Research Academician. You can only have one professorship. You can only be tenured at one University. I work with and have a major research activity at the Baylor Research Institute called BRIC: Baylor Research Innovation Collaborative.
A Princeton connection which has been ongoing for the last 20 years was a position which began as a visiting professor of chemistry, back in the day when we were trying to use lasers to detect anthrax. And that, of course, was a big problem back in the 2001-02 era. And then, I stayed on at Princeton as a lecturer with rank of professor. I’m very dedicated to the notion of teaching and research, especially at the graduate level. Textbooks and conferences — we have a conference, which we’ve had now for 50 years, at Snowbird, Utah, every winter—Physics of Quantum Electronics. So, that’s probably more than you wanted to know.
That’s everything. That’s great. Marlan, tell me about the Burgess Chair. Who was, or is, Burgess?
Burgess was a banker in Texas who was on the board of directors of Texas A&M, a regent, Board of Regents. And he did good things, and so they named a chair after him.
Marlan, tell me about your science during the pandemic, being remote, not seeing your colleagues, being away from the experiments. In what ways has this allowed you to get more work done that you might not otherwise have? And in what ways have some of the projects that you were working on had to be back-burnered to some degree?
I’m theoretical quantum optics, interested in general relativity, the foundations of quantum mechanics from the theoretical side more, and issues like lasing without inversion, slow light, experimentally. We were the first to see lasing without inversion here at Texas A&M, and slow light in hot gases, we were the first. Then came the anthrax problem, and we learned how to use quantum mechanical coherence to detect Anthrax in small amounts very quickly. So then when the pandemic came in early February 2020, we had just been to our PQE conference—our winter conference—and we had many of our wonderful Chinese friends; some from Wuhan. And sure enough, we picked up the bug. And it hit me and my wife and a couple of others who were there. It didn’t bother us a lot, but by the time that we were recovered—several people were locked down here in College Station—Volker Deckert from Jena, an expert in virus detection, using an application of lasers to studying virus and viral systems.
So, we switched over and began studying the COVID-19 virus. One virus and looking at the amino acids on the surface of that virus. That kind of precision is now possible using and extending the techniques that we developed to detect Anthrax. So, we began working on that aspect of the virus problem and other aspects, such as the ability to detect the antibodies associated with the virus. Here we used the technology used in pregnancy kits; you dip this strip in urine, you get a line, you’ve detected the hormone, and so forth. That’s what people were doing in 2020 and before to detect the antibodies, as we all know. What we did was to use a laser readout to improve the sensitivity of those measurements by factors of 10. So, all of that, seeing a single virus, improving on the readout kits, doing theoretical analysis of the viral statistical mechanics, those are things that we focused on; but we also were working on a black hole question—what happens when you drop atoms into a black hole. Well, they radiate, and we found some interesting results, which result in a school at Princeton—the Princeton Institute for Advanced Studies, entitled, I’m looking at it, “Unruh Acceleration Radiation Vacuum Entanglement on Relativity.” Unruh acceleration. Well, Bill Unruh has joined us here at Texas A&M now, and we’re very, very pleased that that type of activity is now being pushed here at the university. When I was at New Mexico, I had the good pleasure of hiring Carl Caves. That was 30 years ago, or more. It is really a pleasure to see these young people prosper and blossom.
Marlan, a general question ranging from your work from Anthrax to COVID-19: to what extent do you read up on biology and virology and things like that, and to what extent do you have collaborators who are more at-home in those areas of expertise?
The answer is both. We have — many of us have an amateur’s interest in biophysics and what we call biophotonics. We can use laser techniques to great advantage in probing crop health. And as a longtime amateur farmer, when my alfalfa fields are stressed, certain areas have not enough water, and others maybe too much water, so the drought-stressed plant emits something called salicylic acid. It’s a lot like aspirin, and you can detect that using our laser techniques of the type that I’ve been mentioning. Raman is the bottom line. Raman was a famous physicist in India and was one of the first to see the influence of molecular systems backscattering light. So, you send a laser in. It hits the molecule. If it’s Anthrax, you’re looking for a marker molecule, dipicolinic acid. And if it’s probing alfalfa crops, then you’re looking for some other molecule. So, it’s mostly that kind of physical spectroscopy directed toward a molecular, biological system.
But many of my people are quite competent as biologists, physicists, biophysicists, with — perhaps “physical biologists” is a better way to say it. But we have professional biologists in the group: John Walker and Bob Brick, Ph.D. biologists. And when we started in this, we found a guy named Ben Neuman, who was at one of the branch campuses, University of Texas A&M at Texarkana, an expert in the coronavirus problem. And so, we brought him down for the summer, and then the biology people hired him and kept him on. So, he’s now the Chief Virology expert at Texas A&M. And we’ve got a lot of depth in molecular biophysics here, of course, with the vet school and medical school, the ag college. And so, these people are friends who hire physicists, and frequently, they end up in a med school or the vet school. So, that’s kind of our back-and-forth on biophysics and bio-photonics.
Marlan, a very broad question: of course, we’re going to be spending most of our time talking about lasers, but I’m curious if, at any point in your career, masers were interesting to you.
At what point did I become interested in the laser?
No, at what point, if ever in your career, were masers — with an “m” — masers interesting to you?
Okay. Well, the maser was developed in the US in the ’50s by Charlie Townes and his graduate students. And then, in the early ’60s, the optical maser came into being. The person who made the first optical maser was a guy, Ted Maiman, who happened to have gotten his Ph.D. from Willis Lamb, who was my advisor–Nobel Prize for his work in quantum electrodynamics. So, when I was in graduate school at Yale, I had the good fortune to do my thesis with Willis Lamb. I started out doing experimental low temperature, but it turned out that I wanted to do more theoretical plus experimental. And so, Lamb was looking at the quantum nature of light and the quantum theory of laser radiation. That was back in ’65. So, that’s how I got interested. He gave me— that gave me the chance to work on that problem, and lucky for me, I cracked it with his guidance. He gave me the problem, did me the great favor of going away for the summer and letting me stew. So, when he came back we made real progress — it’s really wonderful to collaborate with a great physicist and a great thesis advisor.
Well, Marlan, let’s take it all the way back to Wyoming. Let’s start first with your parents. Tell me a little bit about them and where they’re from.
My father was born on a homestead in Wyoming. His parents came to Wyoming in the early part of the 20th century. Homestead up in an area on the way to Yellowstone Park, from Casper. My mother’s people were homesteaders coming from Texas too, again, the oil fields in Wyoming. The parents of my excellent wife—soulmate—Judith Bailey Scully also homesteaded in Wyoming. The big hit in oil back in antiquity, when it was still used for kerosene lamps, came, of course, from Pennsylvania and then east Texas. And the east Texas technology for drilling and exploring for oil was what went a long way to making the Wyoming oil — Salt Creek Oil Fields work. In the early 20th century it was the biggest oil field in the world.
You wouldn’t have thought that, but it was, and that was what drew my people to Wyoming, homesteading and then working the oil fields. And then I had the good fortune to grow up in the town of Casper, Wyoming, which was a very wealthy community because of the oil. And good schools. Even though I was not a very interested student, my dad was a cattleman—minerals man, that studied a lot on his own—would take me out to go help him in the back woods. So, when hunting season came, I was gone. I saw my report card— third grade. Half the time, I was gone, and the teacher didn’t object. She said, “Marlan’s doing okay,” and didn’t mention the fact that I was gone most of the time. But those were the days. You couldn’t do that today, right?
So, I went to high school there. It was an okay high school. And then went to a junior college because what did I want to do? I wanted to be an oil field geologist. Right? That’s what you want to do. And you don’t go off to MIT and Yale to do that. You go to the University of Wyoming and get a degree. It was just a union card. They don’t teach you what you really need to know, I thought. Of course, they do.
But then I went to this small community college, Casper College, and it was excellent. And I took calculus. Little did I know that I would fall in love with the subject and with my teacher, Norman Ball. And boy, was it great. We had about 120 students in this class, most of them veterans of the Korean War, and then those of us who were trying to get a union card to go into the oil fields. And this was a great course, and by the end of that time, I decided, okay, I’ll try physics. Anyway, at the University of Wyoming I got a B.S. in physics and then went off to Rensselaer Polytech. RPI, back in the day, it was like Carnegie Mellon, like Case. There was MIT and Caltech, but RPI was very good. I enjoyed it. But then I got interested in the stuff that Willis Lamb was doing, and someone said, “You should leave and go to Yale.” So that’s how I ended up working with Lamb.
Marlan, what was your field of study at RPI? What were you working on there?
When I was at the University of Wyoming, after my junior year, I was invited to RPI to study materials science and skip my senior year. So, they had this program where they would go around the country and find kids who weren’t braindead and offer them a Ph.D. in what would have been essentially six years after getting out of high school. And so, I went there to study materials science and reactor engineering. But after that, I realized it wasn’t what I wanted to do, and that’s how they said, “Yeah, well, for what you want, Lamb is the guy to work with. Go to Yale.”
Was it physics specifically that you were getting more interested in?
Yeah. Yes, absolutely. But engineering physics. I still believe that students should be educated the same way that they’re educated at New Mexico State: in comes a bright young kid from the ranch, and he wants to study whatever. They make sure that he learns to weld. Learn a trade that you can always make a good living on. In my case, I learned laser gyro technology working with Lamb. It wasn’t what my thesis was about. My thesis was about the photon nature of laser light, a somewhat philosophical issue. But I watched these guys who graduated, and they were being snapped up by United Aircraft, by PerkinElmer. So, anybody who was able to do this kind of physics was really guaranteed a good job.
I was interested in physics—to answer your question—but I always kept an eye open for the equivalent to welding. Right? And I’d tell all my students, “It’s fine to be a theoretical physicist, but learn to do experiments, and in your learning to do experiments, watch out for a good opportunity to do applied work. It’s more fun, you’ll make more money, and people care.” That’s why it’s fun. You do a calculation. You go in in the morning, and the people there say at ‘Litton Industries, where I was working on laser gyros, care about your results.” For years I consulted for these various industries and it worked fine. It was a great opportunity. But of course, physics was my first love, yet the applications in this regard are, I think, what we really ought to emphasize, make sure that the students come out of here able to make a living and to make a contribution. So, that’s my soapbox. I think applied physics is where you really ought to put your money. Then if you want to spend time doing general relativity and the foundations of quantum mechanics, which I do, and that’s where I got my thesis—go ahead. But don’t send your children out to be theoretical physicists. [laughs]
Marlan, what was Willis Lamb working on when you first connected with him at Yale?
When I got to Yale, I had the opportunity to be a TA. I didn’t have to really do much of anything. I was also supported by research grants. But Lamb was teaching quantum mechanics, and I had always paid attention to quantum mechanics, even when I was an undergraduate at University of Wyoming. I had good teachers there. A man named Bob Bessey, who worked with Uhlenbeck, was an excellent physicist. He taught me quantum mechanics back in the day when people didn’t learn quantum mechanics until graduate school. And as a junior undergraduate, I had a good course. I got to RPI and had another good course.
So, when I got to Yale, Lamb gave me the opportunity to grade for him. Okay. So, I graded his quantum mechanics course, and then found out that I wanted to do more theoretical work in conjunction with experimental work. Lamb was working on laser physics. He was explaining questions that people were struggling with. A radio wave is a wave, and we understand that technology very well. The notion of photon physics, looking at aspects of the Hanbury Brown-Twiss effect, looking at the nature of light being both particle-like and wave-like, that was what Lamb was thinking about when I was hired by in with him. He said: “Well yeah, there’s this problem on trying to explain the photon quantum nature of the laser, but the laser’s a lot like a radio wave. It’s a wave.” So, electromagnetic waves, how do you explain that from a photon point of view? Roy Glauber of Harvard, one of my mentors throughout life, had written some beautiful papers on the way in which a radio wave or a coherent wave could be understood quantum mechanically. But that didn’t explain how the laser worked, especially at threshold, when below threshold, it looks like thermal light. Going way above threshold, it becomes so coherent it’s a lot like a radio wave. But what about in between? How does it make that transition? That was what Lamb was interested in.
So, he was leaving for Les Houches to give lectures there on fluctuations in lasers, on noise, photon physics. Remember, Einstein came to the photon concept studying fluctuations. So, Lamb explained what was going on, and he said: “You won’t be able to get this. You won’t be able to solve it. Schwinger has a paper on it, and it didn’t quite work out. You won’t be able to get it. But go ahead and try. There’ll be enough for a thesis.” So, I worked on it a little bit, and sure enough, didn’t get it. [laughs] But then he came back, and I started working, going along the lines that he would suggest. And I saw him a lot. I would go to see Lamb every morning. I’d just go into chat with him, and he never turned me away. I saw him turn students away, but he never turned me away. And I would talk to him, show him what I did, and I think he was impressed that I was working all night, every night. And that was the beginning of a love affair. I loved Lamb, and Lamb loved that I did problems fast. [laughs]
Marlan, was anybody working on general relativity when you were a graduate student at Yale? Did you have opportunities to study GR?
Yeah. Yeah. But it was sort of a bad thing to do.
Julian Schwinger, another of my mentors and dear friends in later life, he would say, “General relativity is a subject for the very young and the very old. I’m neither of those.” [laughs] And at Yale, there were a couple of guys—one excellent physicist, Dieter Brill, who worked on general relativity and left Yale, went to University of Maryland, where he spent his career. So, there were people working on relativity. But it wasn’t a hot topic. To my mind, it became a hot topic with Stephen Hawking and Bill Unruh, when they showed us that the black hole concept could be understood very deeply by doing a certain kind of—what amounts to quantum mechanics in curved spacetime—quantum field theory in curved spacetime. So, that was in the ’70s, ’75. But back in the time that I was a graduate student in the ’60s, it was a fun subject, and we all thought it was fascinating. Yeah. But given my philosophy of applied physics first, it was no place to spend your time.
Marlan, tell me about your work with Peter Franken.
Yeah. Exactly how did you phrase that? Say it again.
Tell me about your work with Peter Franken while you were at Yale.
[laughs] Okay. So, Franken passed through Yale while I was there, but I never knew him. I worked with Lamb. I followed David Lee, who got the Nobel Prize, and I hired David Lee here, by the way. He’s down the hall from me. Peter Franken was a big hero back in the early laser days, because he had, for the first time, demonstrated how you could take two red photons and get one green photon. Nonlinear optics. He was the first guy to see nonlinear optics.
Well, he was at Michigan, not Yale. And I may be wrong in emphasizing his connection to Yale, because I know he was at Oxford with Lamb before Lamb came to Yale. Lamb came to Yale about ’62, before that he had moved around a lot. After he got the Nobel Prize—he was at Columbia when he got the Nobel Prize—he went to Stanford and then Oxford.
Peter Franken, I went to visit him at Oxford and he told Lamb: “Hey, I’d like to use this laser to convert two red photons to one green one.” Lamb said: “No, it won’t work, because this requires two photons to be there simultaneously, and if you look at the density of photons coming out of a laser — it’s not high enough. Not high enough particle density, so it won’t work.” So luckily, Franken didn’t listen to him and went back to Michigan, tried it, and had a great student named Allen Hill, who is also on the IQSE staff here, by the way. But he showed that it worked, and Lamb, being the great scientist and dry wit guy that he is, said: “Okay, from now on, I will spend my time showing how to do these problems of laser physics in nonlinear optics at the interface between photon physics and wave physics.” Maxwell’s equations, wave physics, photon physics, quantum electrodynamics—which field Lamb opened, as you know.
Okay. So, after I got my degree—this is all about Peter Franken. I haven’t forgotten what you asked. But to get there, I have to take you through MIT. After I got my degree, I told Lamb I wanted to go to Bell Labs. Hey, there’s a good place. Learn applied physics. And he said: “No, you’re going to stay here. I got you a job as an instructor, teaching physics this fall.” So, I said, “Well, I want to work with Lax at Bell Labs.” He said, “Well, he’s teaching this summer at Brandis. You can go to him for two months this summer. That’s your postdoc. Then you get back here and get into your career.” [laughs] So, I did. I came to Yale, I taught for a year and another year, and by that time, I was getting more and more interested in other aspects. And MIT offered me an assistant professorship. I was an instructor at Yale. So, I went to MIT, and I liked it a lot, but somehow it wasn’t quite what I wanted, and Boston is a cold place. Winters are cold. The people are cold, too. So, I looked back at the west, which I love. People are friendly, and the summers aren’t cold. [laughs] Arizona was starting an optical sciences center. This was the home of the Kitt Peak Observatory, initiated by Aden Meinel. So, they offered me the position of coming there as one of the founders of the optical sciences center, starting the quantum optics laser physics section. So, I went to that…
Marlan, I’m curious: why Arizona? If you look at Rochester, it makes a lot of sense why they would be strong in optical science. But why, of all places, Arizona?
Why did I go there, or why did they…
Why would Arizona be a center place for optical science?
Oh, okay. Fair question. Because of Kitt Peak. After the war, World War II, Aden Meinel, who was a very famous guy within the context of the American government, is a scientist who went around and interviewed all of the Nazi scientists. So, they felt they owed him something. He wanted to build an astronomical observatory, so he put a telescope on his back, and hiked up Kitt Peak. It’s very dry and very high, and a very excellent place for an observatory. So, he founded Kitt Peak Observatory. So they had to make big lenses for their telescopes, and he was working on that, and then the government came back and said: “Well, how about optics for satellites?” And so Aden got involved in that, and he told the Air Force, “Okay, I’ll work on these things for you if you build me a big optical sciences center.” And it was Aden Meinel who started all this, he was a great guy. And when I was at MIT, I was hearing about these people, and it was very interesting. I told Lamb I wanted to go there, and he said, “No way. You can’t go there until you get promoted at MIT, because people will always say, ‘Oh, he didn’t make it at MIT.’” So I said, “Okay.” So, I worked hard, and I earned early promotion at MIT. After two years, I got promoted. So, I called him up and said, “Can I go to Arizona now?” And he said, “Yeah. And tell me more about Arizona.” So, after I was there for a couple of years, we hired Willis Lamb. Well, Peter Franken—don’t forget Peter Franken. Where does he come into all of this? Sorry. [laughs]
You’re a great interviewer. So, I got to Arizona just at the time that the physics profession was crashing. It was a depression. Tons of physicists out of work because the government shut down the Moon shots. We finished going to the Moon, and NASA laid off literally thousands of people. So, it was just at that time that I had accepted a position at Arizona, and I was hired as a full professor on the sunny side of 30, with a great salary, and I loved Arizona. Still do.
Marlan, what was your home department at Arizona?
Joint appointment between physics and optical science. But optical science is why I went there. The physics department at Arizona was a good, solid department, but the astronomy department was A-plus. It still is. The optical sciences center now is an A-plus. It’s a fine department. So, my appointment was joint, between physics and astronomy. But this physics depression business hit, and there were no jobs, and people were pulling their support back, so I actually went back to MIT after my first year at Arizona. I got a Guggenheim while I was at Arizona, and so I got a year to do what I wanted. So, I decided to roam around the country—I still had graduate students who were finishing up at MIT, so I went back there and finished with those guys, and they did very well. But at that time, money was tight. So, I came back to Arizona and learned how to bring money in. I went in to see Aden. And he said, “Tell me what you’re doing.” So, I told him about all the physics that I was doing. And he said, “Well, that’s important too.” And I said, “Too? What do you mean?” [laughs] I found out what he meant. He meant we’ve got to get enough money in here to run this place, and he was tired of it. He had brought the money in to make Kitt Peak. He had brought the money in to make the Optical Sciences Center. He didn’t want to do it anymore. And by then, he had 20 faculty. And so, I went out to the Kirkland lab over in Albuquerque and to Los Alamos, and I got good funding from those guys. And I came back, and Aden said, “Well, why don’t you be director of the Optical Sciences Center?” Well, here I am, still in what I think is— and was—the sunny side of my career. I don’t want to get involved in administration at this point. So I said, “Well, I don’t want to do that, but if you’ll let me be the chair of the hiring committee, I’ll get you somebody that we really want as the director of the Optical Sciences Center.” So he said, “It’s a deal,” so I hired Peter Franken. Yeah. And Franken was, of course, a big hero, because this was now the end of the ’60s, but he was the guy who started nonlinear optics, and many other things. And he was one of the directors of DARPA. Well, that’s really great, because the guy knew how to bring in money, and he had made a Nobel Prize contribution to physics, so it was a great hire. And that’s how I got involved with Peter Franken. I’m not sure that that’s quite the way you asked it, but that’s how it happened.
That’s how it happened. What were your major funding sources at Arizona? Was it the NSF?
Yeah. Yeah, good question. I got funding from every place that you could get funding. The NSF, the DOE, the DOD, NASA, NIH and so forth. And the Air Force at that time was trying to decide what they could do with this Star Wars project, and Los Alamos was involved in high-powered lasers. So, I would serve as a kind of consultant with these guys. I was on the Physics Division Advisory Council at Los Alamos for many years, and I got funding from all those places. Now, we got money from the NSF, but the NSF was not the kind of funding source, in those days, that you could use to fund an Optical Sciences Center. It is now. They fund JILA. They fund many of the different Institutes, like University of Maryland Atomic Physics Institute. But not then. So, I had NSF grants, sure. But I also had NIH grants, etc.
I was working on trying to measure pressure in the heart by putting little air bubbles in the blood, and the frequency of ringing of the air bubbles told you the pressure of the ambient fluid. This doesn’t kill you. You have to put a slug of air into the system to kill you, but if you just have a froth in there, which you can inject, then that gives you a measure of the heart pressure without putting the cable in, and NIH supported this.
So, we had funding from everywhere, and it was a useful exercise, because I’m convinced that we as scientists are not different from our colleagues in the English department or the Art department. They’re doing beautiful things that contribute to our civilization and to our ability to function in the best way, the highest most human way. But they’re all starving to death. Why is that? Because they can’t do something that people are willing to support, and that is the essence, I think, of what we must show our students. You’ve got to be a physicist comprised, first of all, of a research scientist, and secondly, you’ve got to be a good teacher and a good professor, and finally, you’ve got to be a businessman. You’ve got to be able to go to Washington or to wherever it is that your customers are and get funding for your project, because these graduate students need a paycheck, and this machine runs on money. Now money is not the main thing. Let’s not forget that. But it is a major part of what we have to do.
Marlan, an overall question about the research mission of the Optical Science Center. What was the balance between basic research and applied research?
Right. Good question. 50/50. I would say even right now, during the pandemic, I was working on the general relativity associated with black holes. David Lee asked me: “How come the entropy is proportional to the area of a black hole? Shouldn’t it be the volume?” So I said: “Well, I’ll work it out a different way, and show you this way, and see what you think.” Well, it turned out that it was very interesting, and so interesting that these guys like Unruh, who is the heir apparent of Hawking—in my mind—took a position at the TAMU Hagler Institute and spent a year with us, and we had a great time. Then he joined us, and I love the guy. That’s fundamental physics, no question. Covid detectors, then improving Covid detection, well hey, that’s the essence of applied physics. Both these things. The Unruh problem—I think I mentioned—we were invited to run a workshop by Princeton Institute for Advanced Studies, last year. We’re working now on various aspects of Covid, and that isn’t the only thing we’re working on. We’re working on other applications to biology and quantum optics. 50/50. That’s the answer.
Tell me how the opportunity to work at the Max Planck Institute came about for you.
Yeah. Boy, you really know everything. Well, after being at Arizona for a decade, maybe a little less—well, I had a great postdoc—Pierre Meystre. And Pierre left Arizona and went to Munich, where they were starting this Max Planck Institute for Quantum Optics. And this was around 1980. Well, at that time, I was working more and more closely with the Air Force at Kirtland Air Force Research Lab and Los Alamos and Sandia. Those were some of my closest colleagues in New Mexico. And so, New Mexico offered me a “distinguished professorship,” and very good funding. But I didn’t want to go there and do just that, and yet when they heard that I had an offer from the Max Planck Institute, they said, “Well, we’ll pay you, and you can go to the Max Planck Institute for half time.” Wow, that’s a good deal. So, that’s what I did. I went to New Mexico, bought a ranch there—which we still own—and went to Munich, where we spent the summer and part of the fall term for several years, and loved it.
Herbert Walther was the guy who really made that institute work. And I was called there as the head of the theory group. There were four groups in the Institute. I won’t bore you with the details, but I had a great theory group. Pierre Meystre was there, and we got money to run schools, at the school where we invited all the people who were interested in this gravity wave detection crazy idea back in the early ’80s. Young people like Carlton Caves and his advisor, Kip Thorne, came to us. My friends back at MIT—the people at MIT—were much involved in that, and that really sparked my interest. That was when—some years after the Hawking black hole work—Ray Weiss at MIT, one of my good buddies, we were two assistant professors working late at night, and he would say: “You know, I think I can make some pretty good gravity wave measurements here with these lasers.” And we’d all say: “Yeah, but not in your lifetime. Look how hard that is to do. That’s going to take 50 years.”
Well, lucky for him, it only took 40 years. [laughs] He got the Nobel Prize. And so, Carlton was a very bright guy, and we invited him to our school, along with his boss, Kip Thorne, who also got the Nobel Prize for this stuff. And that was the connection with the Max Planck. My student, Wolfgang Schleich, who is now the number one guy in quantum optics in Germany, really has done some wonderful things and got good funding — billion Euro funding — for quantum mechanics in Germany and probably in Europe at large, European community. Yeah, so I loved the Max Planck Institute. Best job I ever had. I would go there, spend some time. They funded me. No questions asked. One workshop for three days at the end of two years. We had to present our work. That was fun. But now, look, they’ve got Ted Hänsch, Nobel Prize, and others who are going to get the prize. That’s a great place.
Was there an expectation to pick up German at the Planck Institute, or everything was in English?
Yeah, well, I started that way. I took Goethe courses, so I learned a little German the first year I was there. And then I found out that the only time I was using German was on the streets. So, I learned a little street German. “Ich sprechen nur Straßen Deutsch.” And I’d go to the Institute, and the people wouldn’t speak German. They wanted to speak English. They wanted to improve their English. And I was more interested in the physics than the German, that’s for sure. So, to my disappointment and chagrin, I never learned German, really. So, street German is all I spoke. The epitome of my German career? I’m in the subway, and this lady asked me a question, in German, of course. So, I answered her, and she said, “Sind sie Deutscher?” “No.” “Sind sie Hollander?” [laughs] It was a great time. I loved Germany, and I loved the Germans. When they get into something and focus on it, they do it right. It’s a great country.
Marlan, tell me if you were ever involved with any of the weapon’s laboratories in the 1980s and their interests in laser applications.
Yeah. In the ’80s, of course, that was the height of the Cold War, and it looked bad to all of us, who watched the JFK Cuban crisis. We thought: “okay, it’s going to happen.” And I still worry about that, of course. But we need to really be paying attention. And so, when it seemed like the laser could be used to defuse a missile threat, and it was something that looked like we ought to work on, I began working at the Air Force lab as a consultant for people like General Don Lambertson and laboratory director Pete Avizonas. Then going up the hill at Los Alamos, they were working on laser fusion, using lasers to compress tritium. And so, I worked with those guys. There was a strong connection between Los Alamos and the Air Force weapons lab in Kirtland. And I felt at the time that if we could do something to knock missiles out before they got to cities, that would be a very wonderful accomplishment. And we almost made it.
What happened is we never got to the point where we could control laser beams well enough. Adaptive optics now allows you to do that. So, these days, it’s possible. The problem, of course, is that in the ’80s, we worked on these things. The ’90s, well, not so much. After the demise of the U.S.S.R., we kind of lost our interest in developing these defensive weapons. And I’ve let my clearance lapse, and then began working on these other problems—biology problems, which I’d always been interested in.
My nephew, David Sandison, a bright kid, came to me and said: “I want to go to Arizona and work for Willis Lamb.” He got his bachelor’s at University of New Mexico, where I was. He went there and did a wonderful job. Straight A student. He said, “I want to go to Arizona and work with Willis Lamb.” I said, “No, you’re going to Cornell and do biophysics. That’s what you should do.” So, he did. He went to Cornell and did bio-physics and came back and went to Sandia Labs in New Mexico, and he’s now one of the directors of Sandia. Dr. David Sandison is a very successful physicist. So, these activities—Kirtland, Sandia, Los Alamos—were a major focus in the ’80s.
In the ’90s, more Max Planck. And for me then, phasing on into the Anthrax times. I was, ah 15-years at Princeton. But all of those times, I had a permanent position—Texas A&M, University of New Mexico, someplace in the West, in addition to some jobs at the Max Planck and jobs at Princeton.
Marlan, tell me about your decision to join the faculty at A&M.
Yeah. That’s a fun story. We learned at the Max Planck Institute in Munich that a certain kind of coherence was important in laser physics, and if you could use this to advantage, you could actually cancel noise. Well, other people, especially in Russia, were learning how to cancel absorption. A very bright young graduate student there named Olga Kocharovskaya, showed lasing without inversion—none of us knew it, but I’m sorry, I’m losing the timeline. Somewhere around 1990, she did her thesis on aspects of cancelling absorption using quantum coherence to make lasers without inversion. And we picked up on that problem from another point of view. Steve Harris was a professor at Stanford and introduced me to this at one of our PQE conferences. He didn’t know about Olga. Neither did I. But when I heard about this stuff from Steve, I quickly did the theory from another point of view and found we could, in principle, make a whole new class of lasers without using all the energy that it took to drive high-powered lasers. This was very exciting, so I came to Sandia and showed them what I was doing. And they said, “Oh, that’s great.” So, they worked for a year and couldn’t make it work. So, I went to Washington, got the money, and then became involved with a hotshot group in atomic physics at the University of Texas, Austin. So, I went there and met a guy named Manfred Fink, and said, “Look, I’ve got the money. I’ve got the theory. Will you do the experiment and make a laser without inversion?” So he says, “Yeah, just give me the money.” So, I went there in May, made the deal, transferred the money, then I went back to Munich and spent the summer. I came back in the fall, and he hadn’t been able to do it. And so, that was a disappointment. But during that intervening period, I met a TAMU guy here named Ed Fry, and I told him what I was thinking about, and he said, “Well, that’s interesting.” I told him about how we had tried at Sandia, and we tried it at the University of Texas. Couldn’t make it work. And he said, “Well, I think I can make it work.” So I said, “Okay. If you can make it work, I’ll take a sabbatical, come to Texas A&M, and we’ll try.” Came to Texas A&M, and using support from George Mitchell—the guy who pioneered fracking, by the way—he may not have invented it, but he made it work. He gave us some money, and Ed Fry and I, working together, within six weeks we had the first laser operating without inversion. I said, “Wow. That’s a university! I want to stay with these guys.” So, I never left, and I’ve never been sorry, because this is an amazing place. It’s really a great institution which has grown a lot since I came here.
The graduate students are dedicated, hardworking. One of my graduate students left here, and after four years was a professor at Harvard. Mikhail Lukin was his name. And others have done very, very well. So, the students are great. The colleagues—they gave me money to hire people like Dudley Herschbach, David Lee, Leonid Keldysh and Olga Kocharovskaya. I got her here early on. So, I’m Aggie through and through.
Marlan, when did the first ideas for the Institute for Quantum Studies begin?
The Institute for Quantum Science and Engineering. Is that your question?
No, the Institute for Quantum Studies at A&M.
Yeah, at A&M. Well, that was—after we made a laser without inversion, and after we made a hit with the Anthrax problem, DARPA gave us $10 million to study these problems. And so, I made the proposal here that we should have an institute for quantum studies. And we took it to the regents, and they agreed. Great research, great funding, great student success stories. And about that time, the university, Texas A&M, had a competition for getting megabuck funding from the university to build activities that they thought would be transformational. So, we wrote a proposal, and they gave us money for the quantum engineering, and I changed the name from the Institute for Quantum Studies — yeah, IQS — to the Institute for Quantum Science and Engineering. And that’s where we are. We do both fundamental science, and applied science engineering.
The idea there was that you would broaden out the expertise.
Yeah. We made possible this business of working in the lab, doing the theory, going to the lab, doing the experiments, and really doing science the way it should be done. Physics is an experimental subject. That is the emphasis here at A&M. Can I check to see if I’m not missing this thesis exam? I’m not sure I am. Just a sec. Well, I don’t see them. I’m sitting here waiting for them to show up. But I think we have a better—I think I can go until 11 if you want to.
Absolutely. We should be able to wrap up by then.
Tell me about your—what was initially a visiting professorship at Princeton. How did that come about for you?
Okay. Good. When the Anthrax poisoned letters were posted in Princeton, it became clear that we needed to be able to detect Anthrax in the mail or in small samples and do it quickly. So, I began looking at ways to do this. Well, it turns out that in Princeton, back in the ’70s, a guy named Tom Spiro had shown that you can use lasers to detect Anthrax by looking at this marker molecule; 17 percent by weight of Anthrax is this simple molecule. It’s simple. It has about a dozen atoms. It’s essentially benzene with carboxylic acid.
So, I worked on the problem a little bit, studied what Tom Spiro had done. But he’s doing Raman studies again. You know, it took about five minutes, when you have an Anthrax sample, this molecule you’re looking at. Send in light, and you get back red scattered light. And the frequencies of the backscattered light tell you what molecules you have there. Okay, that’s the Raman effect, a famous, well known effect, but it’s very weak. So, it would take five minutes. Letters go through in, what, a fraction of a second, so you don’t have five minutes, if you’re trying to do things quickly. Or, if you look in the air, 100 kilograms of Anthrax endospores upwind from Washington, D.C., will kill more people than an atomic bomb. Wow.
Well, what if we could detect that and give everybody a shot of penicillin? Yeah, that would save them. So, let’s try to come up with a way to improve on the Princeton work. So, we used the same ideas that made lasing without inversion work: “Quantum Coherence.” And we convinced ourselves that we could look at, and detect, Anthrax much quicker than Tom Spiro was back in his laboratory, using coherence — it’s called “Coherent Anti-Stokes Raman Scattering: CARS.” And so anyway, there are reasons that won’t work either—but I put together a variation on CARS, and the theory looked kind of good. And so, I went to Washington and presented the idea to DARPA, and they said: “Well, we don’t think it’ll work, but it’s an important problem, so here’s a million dollars. Go find out why it won’t work.”
Okay. So, to do what we wanted to do required these femtosecond pulses, which Strickland and Mourou got the Nobel Prize for. Well, there were only a few places in the country where you could get those lasers: for example, Michigan and Princeton. Okay. So, I called Michigan; because I had some friends there. I called my friend and told him what I wanted to do, and he said: “Well, that sounds like a speculative solution to an important problem. Okay. We’ve got our lasers booked up. Sorry.” So, I called Princeton. Well, Princeton had a different point of view, and I explained what I wanted to do, and they said: “Well, come and give us a colloquium.” So, I came. I started giving the colloquium, and this guy jumped up in the back of the room, and he says, “You can’t do that, and here’s why.” And he starts rattling off the DARPA killer. Okay? Well, I knew all that stuff, but I didn’t want to fight with this guy. I wanted to use his lasers. So, I said, “Well, thank you. I want my strongest criticism from my friends in private, not my enemies in public.” Good line, right? And this guy, a tough guy, he says, “I count 200 people in this room. This is not private, and we’re not your friends.”
[laughs] Wow! So, I said, “Okay, in that case, I’ll just have to say, ‘You’re wrong,’ and here’s why you’re wrong.’ ” So, I explained it to him. And he came up after the talk and said, “I shot you down.” I said, “No, you didn’t. You didn’t shoot me down. You tried to shout me down, and that didn’t even succeed at that.” So, he laughed. Then we exchanged mail for a couple of weeks, and he said, “Okay, I see there’s a chance that this will work.” So, we kept working, and we convinced ourselves it really would work, and DARPA then said, “Okay, here’s $10 million. Go make this work.” So, Princeton had these lasers, and we worked with Princeton. They invited me in as a visiting professor of chemistry. Right? You can only have a professorship one place, and I’m not going to leave A&M. But I had the good fortune to work with those guys for a while and then come back to A&M, and by then, we knew how to make these lasers. Made the lasers, Alexei Sokolov is still here. And we made it work.
We were able to do it. And at that point, the people at Princeton wanted to be in on this too, and they said: “Why don’t you come back to Princeton, and we’ll make this kind of a special professorship? A lecturer, with rank of professor.” So, I took a part-time salary from A&M, a part-time salary from Princeton, and went there for essentially a decade. And I love the place. It’s a great school. The applied science engineering college is a lot of fun, but it’s not the powerhouse financially that Texas A&M is. Princeton probably has the highest endowment per professor of any place in the country, but they don’t have very many professors. [laughs]
And they are dedicated to the Ivy League kind of liberal arts tradition. I had grants at Princeton, but to spend a dollar at Princeton, I have to bring in two dollars. At Texas A&M, to spend a dollar, I had to bring in 50 to 75 cents, because there were these other funds that were supporting us and helping us do what we were doing. So, between A&M and Princeton, there was a good run for many years.
Marlan, how did you get involved in Bose-Einstein condensate research?
[laughs] Yeah. You know everything. So, the laser—back in the day when Lamb and I were working on lasers, Roy Glauber had said: “This is a tough problem to do this quantum theory of the laser. And it was going to require a better treatment of the nonlinearities than we have. This is not a simple problem, and it’s not going to be solved very fast. And I told you all that stuff.”
Well, comes 1995, people at MIT generally and people at JILA, the University of Colorado, worked on and developed the super-cold rubidium gas where—I don’t remember the dates, I’m sorry. But anyway, they made this work. By the way, MIT is where it all started. MIT, Dan Kleppner was the guy who was saying: “You can make Bose condensates by cooling atoms using lasers.” And that was back in the day when I was there, and we all said: “No, it won’t work, because what’ll happen is you’ll get little snowflakes of rubidium. The interaction is too strong, and it won’t work.”
And fortunately for us, we were wrong. Unfortunately, we missed some of the physics. But Lamb called me, because Kleppner had written an article in which he talked about the Bose condensate, laser-cooled gases, as being like an atom laser. These atoms are in a coherent kind of configuration, and it’s just like a laser, except instead of photons, you have atoms. So, Lamb read this article, and he called me up, and he was angry. And he said: “This is nonsense. I want you to go work out the quantum theory of Bose condensate and show that it’s not like a laser. You never get away from your thesis advisor.”
I of course, still kept working with him after I left Arizona. He stayed there for the rest of his life, and we had some nice papers. So, I worked it out, and lo and behold, it was exactly like the laser. Wow! The same density matrix equations, the same statistical distribution that I found for the photons applied to the atoms in a Bose condensate. I was stunned. Tickled at the same time, of course. So, I called Lamb and said, “Willis, they’re right. It is an atom laser.” And he said, “No. You’re wrong.” So, I flew over to Tucson, spent a couple days with him, and finally he said, “No, this isn’t right, and it’s stupid what you’re saying, and I don’t want to hear any more about it.” So, I said one of the few times that I had to talk back to the old man, I said, “Lamb, you know, the only way to have a friend for 40 years is to know somebody for 40 years. I wager you don’t have very many 40-year friends.” And he laughed, and he said, “Yeah, that’s right. You go ahead and publish this by yourself, and we’ll stay friends.” [laughs] I was wanting to publish it with him. Well, that was the beginning, and we were — I did that first paper, and Lamb didn’t want to publish it with me, so I wrote it up by myself and published it. But then the guys here at Texas A&M saw what I was doing, and a great physicist, Vitaly Kocharovsky, Olga’s husband—hired Olga, and then her husband came—and I got to know him. And he’s a great physicist. So, we hired him, too. He saw what I was doing, and we got involved in more and more of this problem. Still working on it. Interesting problem. Good example of how it is that this quantum theory of the laser stuff is so useful. Here, right now, we’re applying it to the study of Covid antibodies. What’s the statistical number of antibodies necessary to kill off the Covid virus? Well, you say: “Oh, it’s about 1010 per milliliter. Okay, but is it 1010 plus or minus the square root of 1010, or 1010, plus or minus 1010. What are the statistical characteristics?” So, that’s my soapbox on statistics. Fluctuations are very important.
Marlan, we talked at the beginning of our discussion about your work over the past year, but more recent — more broadly than that, over the past five years, what have been some of the major projects you’ve been involved in?
Right. Right. Let me tell you my favorite paper over the last decade. Let me have a decade. Can I?
So, it turns out when I was at Princeton, I ran the colloquium series for a while. And a guy named Dudley Herschbach at Harvard had shown that by using certain aspects of quantum chromodynamics, elementary particle theory, you can solve problems in many body theory—an atom with a hundred electrons around it—without solving the same differential equations that we usually have to solve. Dudley Herschbach then came and gave us his talk, and I thought: “Well, how about molecules? Can I take two atoms, use the Bohr picture of the atom and put atoms together and make a molecule.” And so, with this Dudley Herschbach elementary particle hybrid, we (Anatoly Svidzinsky, Dudley and I) tried it, and it worked. It worked like gangbusters. We sent off a Phys. Rev. letter, and the referee says, “Well, yeah, this is interesting, and it probably should be published.” Phys. Rev. Letters is our high-water mark in some ways. It’s my favorite journal. “But you’re overreaching. You’ll never go very far with this.” So, we did the problem that he was suggesting, which is higher lying states. It worked. So, this business of doing quantum mechanics using what’s called dimensional scaling, a hybrid of molecular physics on the one hand, and particle physics, quantum chromodynamics, on the other—turned out to be a really fun problem, and after we worked on that for a while, we got Dudley Herschbach to come out here and take a position at Texas A&M. And so, we worked on this problem for 10 years, with Dudley.
He would be here, but his family and friends were all at Harvard, and he still went back to Harvard. So, that was one of my favorite problems. And a young guy, Anatoly Svidzinsky; was one of my bright young postdocs and solved problems right and left. He’s now a research associate professor. I don’t want him to have to teach. I want him just to solve problems. So, that’s what he’s working on. Now, working on the applying the quantum theory of the laser to biophysics is something that we’ve been doing over the last few years. And that’s a problem that we are very excited about and are continuing to work on. Now, the general relativity—the David Lee/Unruh problem—that was something that started about five years ago, and we’ve really spent a lot of time on that. Also biophysics using laser techniques mathematically to solve for the fluctuation properties in certain biophysical problems.
So, those are the sorts of things we’ve been doing, and we’ve also enjoyed problems in which we’re trying to make systems that have a better detectivity, less noise—and this is kind of halfway in between quantum fundamental physics and really applying it making better detectors.
Marlan, for the last part of our talk, I’ll ask some really big questions about your career and your research, sort of in a reflective mode. So, the first one is: “Your style is equally comfortable in theoretical and experimental physics. You operate well, fluidly I would say, in both of these areas. So, I wonder if you can reflect on when in laser physics the theory was leading the experimentation or informing the experimentation, and when in your career the experimentation was really leading or informing the theory.”
Yeah, good question. To begin with, the laser was more of an experimental effort, I would say. Art Schawlow got the Nobel Prize for a paper he wrote with Charlie Townes, the Shawlow-Townes article; showed how you could make a laser work. People didn’t think lasers would work, because the atoms decay so fast. You pump an atom or a molecule in a maser up into some excited state, and it’ll live for milliseconds or maybe even longer. With atoms, when you pump them into the excited state they decay very quickly—a nanosecond. And so, people didn’t think that this kind of optical maser would work, but Shawlow and Townes wrote an article which encouraged people to think it might work. Then the experiment was done in semiconductor crystals.
I’m sorry. I’m getting way off. Ruby crystals, not semiconductor. And Maiman—Willis Lamb’s Stanford graduate student—went to Hughes Aircraft. He actually did it, and that was when the theory really opened up, so Lamb said: “Oh. This is interesting.” And he did his famous work on the semiclassical theory of the laser. He says: “Treat the laser as a classical device, in the sense that microwaves are classical. Radio waves are classical. They’re wavy. Maxwell fields. Maxwell, 1870, taught us all we need to know about this stuff. But use the Schroedinger quantum equation for the atoms.”
Lamb developed the semiclassical theory for gas lasers, helium neon lasers. And this was work which went on at Bell Labs—Javan and Bennett and others back at Bell Labs—made these gas lasers work. Lamb wrote the theory while he was at Oxford. At Oxford, they wouldn’t let you do theory and experiment. If you were hired to do experiment, you do experiment. If you were hired to do theory, you do theory. Lamb was hired to do theory. So, we worked at Oxford for a few years and did this beautiful theory, 1964 paper, “The Semiclassical Theory of an Optical Maser” [https://journals.aps.org/pr/abstract/10.1103/PhysRev.134.A1429 Title is “Theory of an Optical Maser”]. That’s what he called it. And he predicted things that experimentalists had not thought to look for. It’s called the “Lamb dip,” and it — I won’t bore you with the details—but when you tune the laser to a point that you would expect to see a maximum, you actually see a minimum. It was a very exciting time, and then people like Bennett went off and started looking for this “Lamb dip”, and he found it. And Lamb said that his laser paper had many more references than his Lamb shift paper, which was what he got the Nobel Prize for. So, he said that the Lamb dip is what he likes best, not “sheep dip,” but the “Lamb dip.”
So, Lamb predicted this neat stuff, and it was all the rage during the time that I went to MIT. One of the reasons that I had such good luck at MIT is I hit there at a time when Ali Javan was doing these experiments, and Lamb had done the theory. And I had, of course, done the quantum theory. So, it was just the time when theory was really coming into its own — e.g. Roy Glauber’s famous papers. So, for the period of time from, say, 1970 until maybe the ’80s, it was theory leading. But then along came Haroche and Walther building the single-atom maser. These two guys showed how to make a device work with a single atom in this maser cavity. Because the photon lives so long in the cavity, it could do that. It’s a wonderful result. And in particular, then it got a lot of us theorists thinking about these experiments. And then in the 90’s came the Bose condensate, and wow, that was a real barnburner.
So now, you’ve got theory playing catch-up, and in an exciting time. Then came the business of quantum coherence, lasing without inversion, ultraslow light. We can now freeze light. We can make it go centimeters a second rather than the “super-fast” 186,000 miles a second. So, then we sort of morph into an era when the laser has been used to see the first gravity wave, and that’s an example of a combination of theory and experiment—hand in hand. When Ray Weiss first explained this, his idea, to Kip Thorne, Kip didn’t agree. He said it won’t work. And Einstein, you remember, had first said that you’ll never see gravitational radiation, because what is gravitational radiation? You’re warping space. You warp space, you warp your meter stick, too, so you can’t tell that there is a gravity wave there. And so, then he sent a paper off — maybe Phys. Rev., or maybe the Franklin Institute, anyway it was rejected. It’s a well-known story. And you know it, I’m sure. But then somebody asked him a couple years later if he still thought that, and he said, “Well, it’s an interesting problem.” So, here’s theory, way behind. Right? And the experimentalists catch up, and then it turns out that some of the techniques that Carlton Caves developed in his thesis—namely the essence of squeezed light. I mentioned squeezed light. We’re working to make better detectors this way, but not for the purpose of gravity, but for the purpose of microscopy. But now, people are looking at Carl Caves’ theory using squeezed light in gravity wave detection, and it’s about theory and experiment—kind of hand-in-glove. That’s a long-winded answer to the question.
It’s a complicated question. Marlan, looking back at your formative partnership, your intellectual partnership with Lamb, what was it about that partnership—what allowed for the intellectual breakthrough that would become the quantum theory of the laser?
Right. Right. Well, of course, Lamb in the days when he was coming to Yale, was not just on a pedestal, but he was on the apex of the pyramid. When he came to Yale, we talked about the first order Lamb shift and the second order Lamb shift; because people were moved out of their offices and then those people had to bump other people out of their offices. So, the Lamb shift was office-bumping. And Lamb taught his graduate course, and I was lucky to be able to grade it. It was a great time. And then somehow, he was leaving for the summer, and I wanted to get involved, and it was encouraged by my friends in low temperature physics to do something more like theory. I was not doing enough experiment. And they were right. I got a hold of Murray Sargent, a guy we wrote a book with Sargent, Scully, and Lamb. I brought him to Arizona after I went to Arizona. He was a student of Lamb’s, and Lamb really liked Sargent. Sargent was a true-blue Yalie and a great guy. He had the Yale veneer. Lamb liked that. And Sargent was a friend of mine—because I was, you know, we had study sessions—solving problems together. And he said: “I’m going to help you get a job with Lamb.” So, I got the job with Lamb. Lamb said: “Okay, here it is, the quantum laser theory. You can work on it. You won’t get very far, but I’m leaving, and I’ll see you in the fall.” So, he left me for the whole summer. Good idea. That’s what you should do. Give a student enough rope and let him hang himself, and then come and get him just before he expires. So, he came back, and I had worked all summer long from a particular point of view, using the density matrix techniques.
Lamb didn’t like it. He came back, and he did not like it. He wanted to use wave functions. And so, we argued, and at one point, he said: “Well, we can keep on a little longer like this, but I’m not willing to support you if you’re not going to do what I tell you.” So, then he gave me a problem which was a little easier—which was the decay of photons in a cavity. And I got that one. So, I went in—and I’ll never forget—I went in, showed it to him, and he said—the best that you ever got from Lamb was: “Nobody can argue with that.” But I showed him the solution to this problem, and he said: “Well, I’m fascinated. If you don’t do anything else, that’s enough for your thesis.” Well, I’d only worked for him for about—you know, two months in the summer and a month in the fall—so it’s only three months. That’s not enough for a thesis. So, he said: “Go ahead and go back and try these ideas using the density matrix, with the lasers.” So I did. And by Christmas we had it—because I would show him what I was doing, and he would say: “Well, I don’t like this. Try that.” And I would try it, and I would come back, and I would say it worked, or it didn’t work. He didn’t do calculations at that point. He was a great theoretical physicist. He did calculations, and he was really able to do complicated calculations. But at that point—he was busy, and he was sort of out of it—but I would do them, so he would tell me what he was thinking about. I would do the math, and I know he said to people that the thing he liked about Scully is that he solved problems fast. He didn’t really like me, but he got to like the fact that there was this give and take. I would go see him—he’d spend time with me—I’d come back with the problem done. So, by Christmas, we had it. And I wanted to keep working, and we did.
Then this developed into a friendship, a good kind of mentor/student relationship. And he would take me with him when he went places. Once he said: “Okay, come pick me up tomorrow morning, and we’ll go to Bell Labs together.” So, he said: “Have breakfast with us.” So, I went in, and had breakfast with his wife, Ursula, and she’s feeding us a good breakfast. And as we get ready to go out the door, she says: “Bring him back in the same condition you found him. Take care of him.” And he says to her: “It’s none of your damn business.” I said: “Well, of course it’s her business. If it isn’t her business, whose business is it?” And he says: “Okay. Let’s go.” [laughs] He’d make outrageous statements, and mostly people didn’t argue with him. And of course, when I began, I didn’t argue with him. But spending days on days with him, it became a chance to really see how an excellent physicist functions. And that was the great! Later on, we kind of fell out. He didn’t like the photon concept, and he went over-board saying: “there are no photons.” And he went too far, and I argued with him a lot on that. But we stayed close, even at that point. Yeah.
Marlan, how do you see your work on the quantum eraser effect as deepening our understanding of quantum mechanics?
Right. The business of observation and state reduction is something that for a long-time people thought that; the mind of the observer was important. You’ve got to have a living observer make an observation and by simply knowing something in your mind—they argued—you determine the state of the atom. Eugene Wigner used to take that point of view very seriously. So, Wigner wrote a paper, and he said: “Well, when does this state reduction influence on the atom take place? Is it when my friend tells me the information, or what if it’s in the soundwave on the way to my head?”
So, I worked on this Wigner problem a little bit and showed that it’s the mere presence of a detector that rubs out coherence i.e. that makes state reduction. You don’t ever have to look at the detector, let alone put the state of the detector in your mind. It’s the entanglement, the combination of field and atoms, the combination of measuring system and system being measured. Okay. So, I published papers like that—some with Julian Schwinger, by the way. And I could tell you more about that if you give me a chance. But at some point, I said: “Well, if all you’re doing is putting the detector there and it doesn’t influence the system, what if I take the detector away or erase the information that’s in the detector? Will the system come back to its original configuration?” And so I worked it out, and the answer is: “Yes, it does.” You get this strange quantum eraser result. So, I had a lot of fun with that—well anyway, that answers your question.
But tell me about Schwinger. Tell me about your work with Schwinger more.
Okay, Schwinger and a guy named Berthold Englert—a bright physicist, very bright—they were friends, and I knew Schwinger through Lamb, and I invited him to New Mexico, and invited him to Wyoming, and invited him to our summer and winter schools. And one day, Julian and I were hiking, and I kept telling him about this quantum eraser stuff. And so he said: “Okay, I’ll come over to Munich and spend the summer with you, and we’ll show that what you’re saying isn’t right. This quantum eraser can’t be right.” So, we worked for the summer, Schwinger, Englert, and I, and we got it. And as we’re hiking one day, Julian says: “You’ve convinced me. I’ve changed horses in midstream.”
The published paper is called “Humpty Dumpty.” And Humpty Dumpty, when he falls, the egg shatters, and you can’t put it back together again. You can’t erase the event. But in a quantum system you can. And so, we published three papers with this Humpty Dumpty theme.
Marlan, a really big question that surveys your entire career, research career, in lasers: “When have there been major technological advances that have really propelled the field forward? And is there such a thing as a Moore’s Law for lasers?”
Okay, so let me ask. Now, are you saying, what has happened to push the field of laser physics forward, or what have lasers done that pushed something else forward?
No. Advances in the technology that makes lasers possible. What have been some advances in the surrounding technology in lasers that have been most fundamental for your research? And are there diminishing returns, such as a Moore’s Law, or something like that, that might limit what lasers can do at some theoretical point?
Yeah. Good. So for example, technology has been developed with semiconductor systems. So, the semiconductor laser is what is in all the supermarket scanners that you look at. And that technology came—laser technology came from being able to handle electrons in semiconductor configurations better. And then after the diode laser, positive and negative, p-n junction, after that, people at Bell Labs, Federico Capasso, and Al Cho, and others showed how to stack these systems together and make the quantum cascade laser—which gives us the ability to make a tunable system all through the infrared. This is an example of technology which impacted laser physics. Semiconductor technology impacted laser physics. Now, I’ll go to the frontiers of laser physics. Today, what we would like to do is make an X-ray laser. If you had an X-ray laser, you take one X-ray picture of a substance and move the film, and you don’t have to take lots of pictures and expose the patient to a heavy dose of X-rays. So, an X-ray laser would be great. Well, we are continuing to push our understanding of plasmas, and the people at Princeton—an excellent physicist named Suckewer, Szymon Suckewer—has now pushed the plasma physics and laser combination to the point that he can get a laser working at 4.2 nanometers. We’re collaborating with him on this. And that’s very exciting, because even now we can now use laser based techniques to scan out a DNA sequence—the nucleotides. Well, those nucleotides are only half a nanometer apart—10 angstroms apart, 5 angstroms apart. Well, if I can get an X-ray laser working down here at a 4-nanometer range—that’s getting close to where I would like to be—and it’s in the water window. It’s in the window where water doesn’t absorb. So, this kind of plasma physics technology is enabling new kinds of lasers, and that’s going to make an impact on biophysics. There’s no question about it.
Marlan, when do you know in your research, when you have an idea that’s worth patenting?
Yeah. Well, you do and you don’t. So, my experience with patents is that I have always allowed people to patent the stuff that I was working on. My name goes on the patent and in principle; I get some royalties someday, maybe. But people don’t necessarily think that the area that I want to move into is the area that we should move into. So, they aren’t going to patent it. And I think it’s a crapshoot. I don’t think that there’s the kind of enthusiasm for patents that there ought to be. In the universities, we have a National Academy of Sciences. I get elected to that, and people have dinners for me. And oh, that’s a big deal. What about inventions? I post patents, do people like that? Not really. There’s a National Academy of Inventors. I got elected to that. And my colleagues came around a few years afterward, and they said: “You know, we should nominate you for the National Academy of Inventors.” And I said: “Thanks, guys. Been there, done that.” [laughs] So, I don’t really know what the answer is. I think that we ought to spend more time—I frequently write my own patents, the first cut—and then give it to a lawyer. That way, I can do it for a few thousand bucks, not tens of thousands, maybe. So, I don’t know. That’s a hard question. I don’t know.
Marlan, my last question, looking to the future: “For as long as you want to remain active, what are you most interested in? What do you want to contribute to, and what are you most optimistic about future fundamental breakthroughs in your field?”
Relativity and entanglement. Entanglement and quantum eraser is an interesting problem. And general relativity, Unruh, entanglement—that’s very interesting.
Doing quantum optics, doing laser—quantum theory of the laser type physics on biological systems—that’s important. I’d like to work on that. I’d like to build a better detector for antibodies. We don’t detect antibodies very well, say you have Covid. You get over it. How many months later can these tests—these pregnancy-type kit tests—show you that you still have the antibodies? Not very long. We need better tests there. But the problem that I’d really like to get back to is the problem of life and quantum mechanics, quantum biology. We’ve made some minor advances in quantum thermodynamics and quantum biology. But I believe that the deep question, as Schroedinger said: “What is life? And what are the issues that would help us understand better the questions of life and matter, of life after life?” As Yang said: “We conserve momentum. We conserve energy. Why shouldn’t we conserve life?” So, I would like to study theology a little more. But that’s a deep, hard question that I’m going to save until I get old.
[laughs] And by studying theology, that means that you see some clear distinctions between science and spirituality.
Yeah, I see some distinctions, and I see a lot of commonality. I see the faith that there is a solution, that problems are soluble, and the faith that there is more to this business than meets the eye. I’ve always asked: “Consider the Chinese—they’re super smart—why didn’t they get science?” 1600s, 1700s, we got science. The Chinese didn’t get it. And one of the answers comes from—I won’t attribute it to Frank Yang, who is a Nobel Prize winner and one of my favorite people—but the answer that came was: “Well, the Chinese didn’t believe in law. They believed that everything was random.” They said look around you: Hurricanes, tornadoes, drought. It’s all random. There’s no laws. So, when they heard about Newton and his laws, they laughed. They didn’t believe it. So the West got science and religion, and the East got neither, for the same reason. They didn’t believe in law. So, there are a lot of subtle questions and it behooveth us to be more open-minded.
Hey, it’s a pleasure to talk to you.
Marlan, it’s been a pleasure to talk to you. Thank you so much.