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Credit: Yale Quantum Institute
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Interview of Steven Girvin by David Zierler on 2020 July 2,Niels Bohr Library & Archives, American Institute of Physics,College Park, MD USA,www.aip.org/history-programs/niels-bohr-library/oral-histories/44930
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In this interview, David Zierler, Oral Historian for AIP, interviews Steven Girvin, Eugene Higgins Professor of Physics and Professor of Applied Physics at Yale University. Girvin recounts his childhood in Florida and then in a tiny town in the Adirondack region of New York, and he discusses his decision to attend Bates College as an undergraduate. Girvin explains some of the advantages he found studying physics in such a small program and he describes his early research on helicon waves. He discusses his dual interests in theoretical and experimental physics which he brought with him to his graduate work at Princeton, where he worked with John Hopfield, who introduced him to a problem from Bell Labs on optical fluorescence data from a semiconductor. Girvin describes his postdoctoral research with Jerry Mahan in Indiana and Sweden and explains the value he learned in doing diagram calculations. He discusses his work at National Bureau of Standards (NBS) and his involvement in neutron scattering and the quantum Hall effect. Girvin explains his research and teaching accomplishments at Indiana University, he discusses his contributions to superconductor insulator transitions, and he recounts the circumstances leading to him joining the faculty at Yale. At the end of the interview, Girvin describes his work for the Nanoscience and Quantum Engineering Institute and explains what excites him most about future prospects in quantum information.
This is David Zierler, oral historian for the American Institute of Physics. It is July 2nd, 2020. It is my great pleasure to be here with Professor Steven Girvin. Steve, thank you so much for being with me today.
Oh, it’s a pleasure. Thank you, for doing this.
To start, please tell me — and I know this might be a mouthful for you, but please tell me your title and institutional affiliation.
I am at Yale University, and my title is Eugene Higgins Professor of Physics and Professor of Applied Physics.
I think there’s more there, right? Deputy provost?
So for ten years, from 2007 to 2017, I was deputy provost for research at Yale. But I'm now back on the regular faculty.
To civilian life.
Civilian life, yes! [laugh] The so-called real world, which is maybe not so real — [laugh]
Let’s take it back to the beginning. Let’s start with your parents. Tell me first, where are your parents from?
My mom was born in Detroit, Michigan. My dad was born in Georgetown, Texas, which used to be a small village out in the country outside of Austin. Now it’s a [laugh] significant suburb.
And Girvin traces back to what country? Where’s the nationality of that name?
Well, we're pretty sure that it’s Scottish. Don’t actually know for sure. There is another spelling of Girvin — G-I-R-V-A-N. Mine is G-I-R-V-I-N. But there’s a Girvan in Scotland spelled with an “A” and family folklore has it that that’s where we're from. And the ancestors that I know about were in North Carolina and then moved to Texas. There’s a ghost town — Girvin, Texas — in the western part of Texas. It’s an interesting place to visit! [laugh] My uncle claims it was founded by the cattle-rustling branch of the family. [laugh]
Oh, I see. [laugh] Where did your parents meet?
Well, that’s an interesting story. On May 17th, 1947, I think, they met on a Greyhound bus going from Austin, Texas, to San Antonio. My dad said that he was in line to get on the bus, and he saw this pretty girl and kind of waited back and got on the bus, but then he didn't dare ask if he could sit with her, so he sat in another seat. But after a while, he got nervous that somebody else would sit down, so he worked up the nerve to ask if he could sit with her.
What was your mom doing in Texas? It’s clear why your dad was in Texas. How did your mom get down there?
Well, that’s a complicated story, but her parents had gotten divorced, and her mother had moved them to Texas to the hill country outside Austin. And yeah, so that’s how they met. I was born in 1950 in Austin, Texas, which at the time was a small town of 50,000 people. And the tuition at the University of Texas was $25 a semester. [laugh]
[laugh] And what were your parents’ professions?
My mom did some bookkeeping. My father was a handyman, a maintenance guy at St. Stephen’s Episcopal School in Austin, a private high school. We stayed there until after first grade, so 1957 we moved to Boca Raton, Florida. An old Army buddy of my dad’s wanted him to join a cabinet-making business. My father was an expert cabinet maker, pattern maker, woodworker. We were there for a couple of years. Then we lived for a summer on the Outer Banks of North Carolina, in Corolla. And then they got a job back with the Episcopal church, which was opening a retreat and conference center in a small village, Brant Lake, New York, in the Adirondack Mountains. So from 1959 through high school, that’s where I grew up. Beautiful place on a lake. Very small town; there were five kids in my high school class.
Two boys and three girls! [laugh] So I got all kinds of — when I applied to colleges, I got all kinds of letters from coaches saying, “Oh, I see you lettered in soccer and basketball and baseball, and we want you for our [laugh] college.” And I had to write back to them and say, “No, actually, you don’t! [laugh] I was on all those teams only because they were [laugh] desperate for enough people to make a team.”
Steve, to the extent that talent in math and science has a genetic component, is there anyone in your family that you can trace your aptitude?
Well, that’s an interesting question. Neither of my parents went to college, but my father had an amazing gift for all things mechanical. I mean, he was sort of a precision woodworker and liked to think about inventing things. His father had a few inventions for things like — [laugh] things to help wash cows, and things like that. So he wasn’t trained as an engineer, but he had a kind of engineering mindset. And my mom was quite good with numbers, and read voraciously. So I think between that genetic gift and the gift of a lot of time to do nothing so you could kind of use your imagination to explore the world — I think those were the main gifts from my parents.
Now, in high school, were you — I mean, out of five, I don’t know if it’s easy to stand out or not, but —
— how strong were you in math and science?
Pretty strong. I'm not quite sure the teachers knew [laugh] what to do with me. But I always knew I wanted to be a scientist, I mean, from a very early age, maybe age seven. And even somehow decided I wanted to be a physicist, even though I'm not sure I exactly understood what that was.
There must have been things in the cultural zeitgeist capturing your imagination, perhaps the Space Race?
Yeah, I vividly recall the Sunday morning stopping — my parents stopping at a store and getting the newspaper with the headline that there was this [laugh] — that the Russians had launched this object, and it was overhead. That was exciting. My father did simple experiments with us. Made a kind of camera obscura to project images in a dark space using a magnifying glass. And we made a simple telegraph with a nail and a wire and a couple pieces of tin can. I vividly recall — there was a person — you know, in your life, there are people that just — these moments where people help you out.
So I was seven or eight when we were living in Florida. And my father and his brother had played with crystal radios when they were kids. And I wanted to do that, and I went to this hobby shop, and they had a kit with a wire and coil and a crystal and ear phones and so forth. And it was $13, which in 1957 was a fortune, especially for [laugh] a little kid. And I don’t remember whether it was allowance money or — somewhere I had seven dollars. And I asked the guy how much it was, and he said 13. And I said, “Oh, I only have seven.” And he said, “Well, you're in luck. We have a special today! It’s a reduced price, for only $7.” And that made an enormous, huge difference in my life. What a gift from somebody to do that. And so we wound the coil and sanded off the varnish insulation and made a tunable radio, and you could hear local radio stations. And the magic of getting signals out of the air like that [laugh] was pretty amazing.
And after we moved to Brant Lake in New York, I got interested in short wave radio, and somebody helped me out to get started with a transmitter and receiver. There was this company called Heathkit where you could order from Long Island these kits, electronic kits that you could assemble. And so I built the receiver and purchased the transmitter. And even though I, in the end, turned out to be a theorist, the time I spent hanging antennas in trees and playing with transmitters and receivers turned out to be ideal preparation for the work I do now on circuit quantum electrodynamics.
Steve, how did you land at Bates, of all places?
Well, I was from such a small place, I wanted to go to a small college. Our family doctor, Thomas Halliday, who just died about a month ago, had gone to Bates. And so that’s how I found out about it. So I applied, and then — my parents really didn't have much money, so I needed a scholarship to be able to go. I went on the bus to Maine and visited, and got an appointment with the dean of admissions, Milton Lindholm, and said, “I would really love to come here, but I can’t afford it without a full tuition scholarship.” And he kind of picked up my folder and kind of peeked under it for a second and said, “Well, I think we'll be able to do something.” And sure enough, I got a scholarship and was able to go there. That was another incredibly important thing in my life. There was a wonderful physics department.
Did you declare a major in physics right away?
Yeah. I knew [laugh] that’s what I wanted to do.
And there was a good physics program at Bates?
Yeah. It’s a small enough place that the professors know who you are.
And there’s no graduate students, I assume?
No, there’s no graduate students.
So undergraduates get all of the professors’ attention.
Right, right. On some level, they did research in the summer. It’s not the same as a research university, but they were very active in encouraging students to do thesis projects and so forth. So it was a very nice experience. [laugh] Two of my professors, Jack Pribram and George Ruff, retired now some years ago, and I went to the dinner and spoke there. And [laugh] I was taking freshman physics and came to the first exam, and the professor had told the story that he was extremely worried about this one kid, who wasn’t moving his pencil [laugh], was just sitting there, and he thought, “Uh-oh, this guy’s in trouble,” and then after a while, he [laugh] wrote one thing on the paper. [laugh] And it turned out it was me, and I didn't realize that [laugh] — I hadn’t heard this story. But it turned out that I was just proceeding in a different style of thinking about it before writing the answer down. [laugh]
Steve, were the physics professors at Bates primarily teaching, or were they involved in original research themselves?
It was a mix. But one of my teachers, George Ruff, was very involved in research. He had a system of every seven years going on a sabbatical to an atomic physics lab at MIT or other major research universities, and catching up on the latest stuff, and then bringing back the knowledge — building a new experiment at Bates to keep up with the state of the art. And actually interestingly, he attended a summer school at the Institute of Optics in Rochester in, I don’t know, sometime in the seventies. And George’s thesis in Princeton had been in optical pumping. In those days, you had a gas bulb with some sodium in it, and you got it to fluoresce by getting a tesla coil and [laugh] sparking it and having some RF coils there. And it would glow, and it would emit yellow radiation, yellow light, that could be absorbed by another bulb of sodium. And you could put circular polarizers and linear polarizers in the way and things. And just around this time, the dye laser was invented, which was the first laser where you could tune the frequency.
And George was at this summer school in Rochester, and the professor showed that you could tune the dye laser and make this bulb of sodium vapor suddenly fluoresce when you hit the right color. And George immediately stopped going to the course and asked if he could have some lab space. [laugh] And they gave it to him, and he did the first optical pumping experiment using a dye laser, ever, in a few days. [laugh] So he was a pretty amazing experimentalist, and a wonderful human being.
Steve, I wonder, on the social side of things, had the antiwar movement, the civil rights, women’s liberation, had those activities reached Bates during your time there?
Yes and no. The topics were in the air, but it wasn’t like being at Columbia or Berkeley where there were active major activities, riots, protests, and things going on.
Now, would you say that’s more just because of how small Bates is, or because it’s sort of more a culturally conservative kind of place? Or both?
Probably mostly to do with the size, I guess. I'm not really sure. But there were definitely activities around the Vietnam War and the draft. I was in I think the second year of the draft lottery. I was there in 1968, which was a truly horrible [laugh] year for the country.
Were you personally concerned about getting drafted?
Yes. But I was fortunate to get a very high draft number. So I was at the tail end of the draft for Vietnam. And friends of mine who got low numbers were drafted. But I got a high number and didn't have to worry about it.
Was there a senior thesis for you?
Yes. And I did something a little unusual. A friend of mine, David Riffelmacher and I decided to do a joint thesis. He was actually a math major also majoring in physics. And I've always been somebody that kind of worked more by intuition and sometimes struggled a little bit with formal mathematics. And he was the other way around, so I thought it would be fun to do a thesis together. So we petitioned the faculty to do that. And I don’t know whether it’s still the only one that has ever happened at Bates that was a joint thesis, but they gave us permission, and we did that. So we studied some experiments that were done at Cornell on a collective mode called helicon waves. So you take ultra, ultra-pure material like sodium metal, with a very long mean free path for the electrons at low temperature, and you put it in a high magnetic field. And because the conductivity is so high — it’s a kind of plasma physics problem, where if the — the magnetic field lines and the electrons have to travel together because if they didn't, there would be huge Lorentz forces or Faraday induction that would make gigantic currents, because the connectivity was so high. And that kind of loads the magnetic field lines with the inertia of the electrons and makes an extremely slow wave called the helicon wave, an electromagnetic wave that can travel through the metal. And I don’t remember exactly how I stumbled onto that topic as something I wanted to learn, but it seemed kind of cool, and so we wrote a thesis about the physics of that thing, and how you derive the equations for the resonance frequencies of these modes in a cubic sample.
Steve, would you say that your identity as a theorist was pretty well solidified as an undergraduate, or would that only come later on?
[laugh] That’s an interesting question. I was so impressed by the kind of experimental work that George Ruff was doing. I thought I wanted to do tabletop physics experiments like that, so atomic physics experiments. And when I went to Princeton, I thought I might do something like that, but Tom Carver, who was the great optical pumper there, and actually was George Ruff’s thesis advisor, was getting near retirement and wasn’t doing that anymore. And I was kind of, I don’t know, looking around for what to do, and I knew I didn't want to do particle experiments with thousands of people [laugh] on a giant team. And by chance — I don’t remember; I must have heard a talk or somehow I met John Hopfield. He was in the midst of making a transition from what in those days was solid state physics theory to biophysics and neural networks and hemoglobin and things. Kinetic proofreading and things like that.
Oh, this was when he was getting into biophysics?
Yes. In fact, he had basically already transitioned. But I was very impressed with his kind of intuitive style of doing science and decided, “Well, I'll just work for him and be a theorist.” But I wanted to do condensed matter theory. So even though his main focus was neural networks and people like Terry Sejnowski were working with him at that time, and some other things he was doing with biophysics were his main focus, he took me on as his last condensed matter student, and muttered something about, “We're thinking about hiring another theorist, and maybe you'll end up — you could transfer to him.” And the other theorist turned out to be P.W. Anderson, but in the end, John didn't say anything after Phil arrived, so I just kept working for John. [laugh]
And so in the end, I'm his last condensed matter student.
Now, you had a brief interlude — before Princeton, you were at the University of Maine. You got a master’s degree there.
Yeah. [laugh] So my wife is from Lewiston, Maine, which is where Bates is. I met her on a blind date when she was in high school, and a Bates friend of mine who was from Lewiston was dating a girl that was a friend of hers, and they were each looking for a tall person to [laugh] fix up another tall person with. So we met on a blind date. And she went to the University of Maine. I had a kind of — like when I went to college, the transition to college from this small village in New York was not that hard for me. I mean, actually Bates was a huge place. There were more students there than people lived in my town. But I found the transition to graduate school somehow suddenly difficult. I don’t know why. And Princeton has this infamous exam in two parts — the preliminary exam and the general exam. And I took the preliminary exam at the end of the first year and failed. And I had gotten married on New Year’s Day, January 1st, 1972, and decided I would take — my wife had one year to go at U Maine, so I spent a year there, boning up on the physics I needed to pass the exam in Princeton. And when she graduated, then we went back — I got a master’s degree in that year and then went back to Princeton.
So Maine was all about setting the stage for Princeton? That was the plan the whole time?
Yeah, yeah. And so that worked out quite well, actually.
Did you feel, coming from a small school — how well prepared were you, relative to your cohort at Princeton coming in? I assume most of your fellow students were coming from places like Harvard, MIT, Princeton undergraduate.
Yeah, yeah. It was actually quite a small class. I think there were only, hmm, seven of us, or eight of us. But yeah, there were people who just seemed much more advanced than me. They knew what vector spherical harmonics were and knew much more quantum mechanics. I felt a bit lost. But what I didn't — it took me a long time to realize that yes, those people knew what vector spherical harmonics were, but if you asked them to draw the dipole radiation pattern from an antenna or from a sodium atom that had been excited by linear polarization, they had no idea what it looked like, and I knew. [laugh] So eventually I realized I had just a different skill set, but I was still able to do OK. It took me a while to realize that.
How did you go about putting together your dissertation topic?
Well, [laugh] [pause] so as I said, Hopfield was focused on neural networks and biophysics and things, and he had some, I don’t know, consulting, or some kind of part-time arrangement with Bell Labs. And I wanted to do a condensed matter problem. So he came back from Bell Labs with some data, some optical fluorescence data from a heavily doped semiconductor, and said, “Why don’t you explain this?” [laugh] So it wasn’t a super exciting phenomenon, but it turned out — you had to think about all kinds of different many-body effects and electron-phonon coupling, and electron-electron interactions, and screening, and all kinds of stuff, to explain the shape and position of the fluorescence spectrum. So I worked and worked and worked, and I don’t know, just wasn’t getting anywhere. [laugh]
And so John said, “Well, why don’t you try this?” So then I worked on another problem, an x-ray edge problem, absorption of soft x-rays in a metal where a core electron comes up to the Fermi level, and there’s some funny singularities related to the Kondo problem. And I managed to make some progress on that. And then I went back to the original problem and just was able to plow through it and do it. I don’t know, somehow I had gotten — I knew enough now what to do, and plow through it, and get it done. There weren’t any other condensed matter theory students for a good part of the time I was there, until Phil Anderson started developing a group. So there was a guy in the class behind me named Ed Witten, who seemed to be a pretty good theorist. [laugh] So sometimes I’d go and ask him questions, like, “What does this Feynman diagram mean?” or something. And he was amazing. I mean, he would say things like, “Well, in QED, this is an utterly negligible effect, but I wonder what it’s like in silicon.” [laugh] Or, you know. And he didn't really know a lot of condensed matter physics, but he knew a lot of physics, and those were [laugh] — those were helpful conversations.
Who was on your committee?
Let’s see. So I'm visualizing the signatures on the bottle of champagne. So Phil Anderson, and Pam Surko was a particle experimentalist, and Steve Schnatterly who was a condensed matter experimentalist were on the committee. And other signatures of people that were there — Elihu Abrahams was there. And I don’t think he was on my committee, however. I think it was just those three people. And [laugh] I remember my wife had a job in the Princeton archives, and one of the other graduate students that was a couple years behind me — several graduate students came to the defense. And she was horrified — you know, she had to do her defense in another year or something, and she was horrified by the level of grilling [laugh] that I was getting. So then when the public part was over, we had arranged for her to call my wife and tell her it was time to come down. And [laugh] my wife said, “Did he pass?” And she said, “I have no idea! It was horrible!” [laugh] Then of course my wife was terrified. But it was fine. They liked to really ask wide-ranging questions and [laugh] just see what you could do. So there’s a strategy. You don’t want to answer the questions too quickly. You want to try to run out the clock if you know the answer. So I remember [laugh] Steve Schnatterly — there was this giant book on the table, some big book. And it was like volume 27 of Landolt and Börnstein, the properties of materials or whatever. It was some German series that took up about two meters of space on the library shelves. And he said, “Open this book to a random page —
— and find a graph, and explain all the physics.” [laugh] So, you know, I open up the book, I find a page with a graph, I notice that the book is in German. [laugh] So a momentary panic. I was actually in the last class at Princeton for two things — one was mandatory academic robes at dinner, and the other was two foreign languages. And I had had French in college; that was fine. But I hadn’t — no other language. So I took a German course [laugh] the summer before I started in Princeton. Didn't — it was terrible. I didn't really learn anything. I remembered one word, afterwards — klapperschlangenbiss, a rattlesnake bite — because there was some story about a rattlesnake bite.
But, you know, I couldn't read German. But I looked at the graph, and I could see it — there was an “Fe,” so it had something to do with iron, and there was temperature on the horizontal axis. And I realized it was the magnetization of iron as you cooled that through the Curie temperature. I tried to say those words. So the question came up, “Well, where’s the magnetization above the Curie temperature?” And I said, “Well, there are magnetic domains, and they're all randomly oriented.” And they asked me, “Well, how thick — how wide is the domain wall in a ferromagnet like that?” “Well — ” You know, I had no idea. I knew it wasn’t — it would have to be gradual…spins would turn over gradually, but I didn't know, you know, what the distance was. So I was temporizing, and I said, “A few — uh — a few — ” [laugh] And about the fourth time I said “a few,” John Hopfield said, “That’s right, a few thousand angstroms!” [laugh]
Nice. That’s great.
[laugh] So [laugh] — anyway. I managed to get through. I remember the question from Pam Surko. She had a superball, one of those super bouncy balls, and she spun it and dropped it on the table, and it bounced back and forth in an arc repeatedly. And I had to explain what was going on there. I struggled with that one, a little bit. It’s actually kind of tricky! [laugh]
Now, was your postdoc one postdoc in two places, or was Indiana and Sweden two separate programs?
So that was one postdoc in two places. It was with Jerry Mahan, who it turns out was John’s first PhD student.
Was that the connection?
No, I can explain the connection in a second. But [laugh] one funny story is — you know, John was at Berkeley in the sixties, for not very long I don’t think, but he had two students while he was there, Jerry Mahan and Bert Halperin. And I heard him say once [laugh] in public, in front of those guys — “Why did you leave Berkeley?” And he said, “I couldn't get any good students.” [laugh]
[laugh] Anyway, he had these two luminaries for students. But the way that I got this postdoc was there was an x-ray conference that Dick Deslattes organized at the Bureau of Standards, now NIST, in Gaithersburg, Maryland. And that was the first conference I went to, and I gave a talk about this x-ray edge work. And Jerry Mahan, who formulated the x-ray edge problem and partially solved it, was in the audience. And that’s how I — I mean, I didn't know him, didn't know who he was. But by chance, he was looking for a postdoc, and contacted me afterwards and made me an offer. So he was at Indiana University, but he was going on sabbatical for a year at Chalmers University in Gothenburg in Sweden. And that seemed like an awesome [laugh] opportunity. So we moved in January of ’77 in an incredibly bitter cold winter storm, drove out to Bloomington, and we were there until the summer, and then spent a year in Gothenburg. It was a wonderful experience, and I made lasting friends there and have many connections, and actually go back to Sweden even now quite frequently, for various scientific advisory boards and other kinds of things that I do there.
And then Jerry moved back to Indiana at the end of the year, and I spent another year in Bloomington. And a student at Chalmers, Mats Jonson came back to also be a postdoc with Jerry, and we were office mates and became lifelong friends as a result of that. And Jerry was writing his book on many-body physics during his sabbatical, and it was amazing to me to watch him crank out page after page, night after night, on a typewriter. And I learned how to do diagram calculations from sort of proofreading that rough [laugh] draft of the textbook. It was funny, because Hopfield wasn’t very big on all these techniques and so forth. Most of the things he did in condensed matter physics involved solving the harmonic oscillator in clever ways. Although he said when he started doing neural networks, he had gone horribly non-linear. So he had a very different style — John said to me, “Never do a calculation until you know the answer.” Which I found extremely good advice.
[laugh] The purpose of a calculation is after you understand the physics, you want to know the size of some dimensionless number, whether it’s 0.3 or three or whatever, you do a calculation. But you can’t do the calculation until you know the physics. Jerry was the other way around. He was amazingly good and quick at doing calculations. So he would calculate two or three things and then think about which one was the right model, or which one made physical sense, afterwards. So it was an interesting difference in style.
In what ways did the experience in Sweden sort of further your career?
[laugh] Well, another completely random coincidence occurred, which led to my first regular job. So I had been there two thirds of the year, and one of the people there, Göran Wendin, was teaching a class, and he said something to me about would I like to give a guest lecture. And I said, “Sure.” And I started preparing something on — the renormalization group was sort of a thing happening in those days, and so I wrote up a lecture on the scaling in the Kondo problem based on things that Phil Anderson had done. And somehow, I don’t know, Göran forgot he said I should do this, or something, but Stig Lundqvist, who was the head professor there, somehow said, “Oh, no, you should definitely give a talk.” So I gave a couple lectures on this, these notes I had typed up. And by sheer coincidence, Bill Gadzuk, who was a theorist in the surface science division at the Bureau of Standards happened to be visiting, and went to the lecture. And when I was looking for a job after my postdoc, as my postdoc was ending, I interviewed at — there weren’t very many jobs. This was 1979. I got a few interviews at the few jobs there were, academic jobs, but no offers. And I ended up with an offer of a second postdoc at Bell Labs or a job in this surface chemistry division at NBS. And we had a new baby, and I decided even though surface science wasn’t exactly my thing, a permanent job would be the right course.
Even though Bell Labs is probably a much more prestigious appointment, even if it’s not a permanent job?
Right, right. It was the same year that they hired Bob Laughlin as a postdoc, and later didn't keep him. So [laugh] I don’t think I would have managed to stay. The other thing that happened as a result of being in Gothenburg — Jerry Mahan was invited by Stig Lundqvist to visit there, as was — Elias Burstein, who was a wonderful human being who died one or two years ago now, was a friend of Stig’s and happened to be visiting. So I met him. And he was famous for organizing conferences and just a very energetic guy, but a real gentleman. And so I met him, and I think he was the first person to invite me to speak at a conference after my postdoc. So that also was a happy coincidence in my trajectory.
Did the National Bureau of Standards have a basic science component to it? Were you able to pursue kind of your own interests there, or was it strictly, “Here’s what we're doing, and you're going to jump in on that”?
Well, that’s an interesting question. I was supposed to be working in a certain general area of surface science and various kinds of spectroscopy and, you know, many-body dynamics and things, generally defined. But there weren’t a large number of theorists. And so I kind of — I had a fair amount of autonomy. I took it to be part of my job to kind of go around and poke my head in labs and find out what was going on, and being somebody that tried to break down the silos between different parts of the place. And so I found that interesting. I met Bill Phillips, now a lifelong friend, and he was busy building his Zeeman slower and getting ready to do his [laugh] experiment with laser cooling of atoms, which turned out to work better than theoretically predicted, which led to his Nobel Prize. And I met people in other divisions doing — there was an electron physics group doing interesting things. Neutron scattering. There was a lot going on. So I started in the summer of 1979, and then — but I was, I don’t know, I often think actually if I had gotten an academic job, that I don’t know how well I would have done. I could have been overwhelmed by the teaching and being on committees and being conscientious about doing all those things.
And maybe, I don’t know, I think I was a late bloomer in sort of getting good at research. And this turned out to be a perfect environment for me. There were no committees [laugh] and no teaching. Even though now, teaching is like my favorite activity. And so I kind of had time to learn how to do research. So I started in the summer of 1979, and in the summer of 1980, Barry Taylor, who was in charge of all the fundamental constants that had an “e” in them, so to speak [laugh], said to me, “You know, this guy von Klitzing has found something interesting and he talked about this quantum Hall effect at a conference recently.” And so this was like a miracle which completely changed my life. [laugh] So it had metrology implications, so it was fine for me to work on it, even though it wasn’t exactly surface chemistry. And it turned out that Barry Taylor was actually a referee of von Klitzing’s Phys Rev Letter, and he might deserve some credit with Klaus ending up with the Nobel Prize, because Klaus’s original title was something like “A New Resistance Standard” or something, and Barry said, “No, this is a new way to realize a measurement of the fine structure constant.” [laugh] So I found out about this just after it became public, and was extremely excited. I mean, it was like — I mean, how often — this felt like a once in a lifetime thing, this amazing experimental discovery that something was super precisely quantized in a horrible-looking, ugly, solid state sample with blobs of solder on it and, you know, [laugh] wires connected to it. You know, it was amazing.
But I didn't know anything. I didn't know what a Landau gauge was or a symmetric gauge or even what a Landau level was. I had a lot of catching up to do. And this became my focus. And by happy coincidence, Dick Prange, Richard Prange, who was at the University of Maryland, which is not too far away from Gaithersburg, wrote an early paper on the subject where he solved exactly the problem of a single impurity scatterer in a Landau — two-dimensional electron gas in a high magnetic field with Landau levels, and showed that the current that flowed was not diminished by the presence of this scatterer, which was unusual, and was kind of a toy model that led, eventually, to understanding what was going on through work by Laughlin and Halperin and others, fleshing that out in much more detail.
Steve, was your sense that your time at NBS, were you fairly well connected with the academic physics community?? Were you collaborating with people who had university appointments? Were you presenting at conferences? Were you publishing papers? Or was NBS sort of more a world unto itself as far as the physics was concerned?
Well, it was a mix. I ended up connecting with Dick Prange, and we held a series of lectures by people working on the quantum Hall effect over the next — I mean, a few years later. And we edited those lectures into a book. So I had that connection. I did collaborate with some academic colleagues on the outside. But what I didn't have was a kind of — that you would have had at an academic place would have been a condensed matter theory seminar, with people coming in with the latest results and so forth. That, I missed. On the other hand, when I later was thinking of moving to Indiana University, I went and talked to John Cahn, the famous metallurgist and thermodynamicist, who had been at MIT for many years. And his wife had gotten a job in the State Department at a level that until the Reagan administration was not considered a political appointment, and so they thought it was a permanent situation, but [laugh] the Reagan administration changed that. I went to talk to him, because I knew he had been at MIT for many years, and said, “Oh, I'm thinking of moving to academia.” And he laughed and said, “Oh, you'll find the Bureau of Standards to be a much more scholarly and academic place than any university.”
And he said, “You know, if you need another six months to do something exactly right, to really dot all the i’s and cross the t’s, you can do that at the Bureau of Standards. And it’s very different in the supposedly scholarly ivory tower, where you're spending a lot of time getting grants, and there’s more deadline pressure.” The Bureau of Standards, you were expected to take as much time as was needed to do it right. And that was eye-opening for me. [laugh] There was some truth to it. So in some ways, it was great. It was a great way for me to build up some experience doing research — that was my full-time job — and kind of get the hang of it. At the same time, I think if I hadn’t accidentally been connected to the quantum Hall effect, which was of great interest to people in academia and of interest to people in metrology, I might have just kind of disappeared from doing things of interest in academia.
And why was the quantum Hall effect so compelling at this point?
Well, two reasons. One is it actually was a way to measure the fine structure constant in a way that was totally different than the high-energy physics g-2 experiments from the QED corrections of the gyromagnetic ratio of the electron or the muon. Totally different solid state system. But the fact that it seemed to give this universal result, independent of the fact that the — in fact, it wouldn't work unless the sample was dirty. I mean, that was amazing! [laugh] And then of course only I think three years later, Dan Tsui and Horst Stormer and Art Gossard and friends discovered the fractional Hall effect. And that was like, “Who ordered that?” I mean, [laugh] — you know, what in the world were you doing with fractional quantum numbers? What does that even mean? That was the second like once in a lifetime gift [laugh], only a few years later. And actually — so I was working hard on that, and going down various roads which eventually led to understanding some of the collective excitations, but not understanding the ground state. [laugh] And I recall sitting at my desk and calling Bob Laughlin to, I don’t know, I forget whether it was to bug him about his chapter [laugh] in this lecture series, or something else. I forget why. But I called him and I said, “Hi, Bob, how are you doing?” And he said, “I think I've got it.” And he laid out, over the next — we talked for an hour — he laid out, over the next hour, his picture of the Laughlin wave function and the ground state and the fractionally charged excitations and the plasma analogy. And it was simultaneously the most exciting and most depressing hour [laugh], because you know, I instantly knew that this was an amazing breakthrough, and it just had to be right. It was so simple and beautiful and elegant. And fortunately, psychologically, it’s one of those things where you can’t say to yourself, “Ah, if I had just worked a little harder, I could have thought of that” and you feel bad. It was so amazing and so original and so like bolt out of the blue that you couldn't feel bad. [laugh] You just say, “Wow, that was miraculous!” [laugh] And you know, there was still lots of interesting work to do, and I continued working in that area for many years. And it was really, really wonderful.
Were you looking at a certain point to reenter academia, or did the opportunity at Indiana just sort of come out of the blue for you?
Yeah, I wasn’t actively looking, although — there was many things that I enjoyed about being there, the people and the chance to do research and interact with all kinds of efforts. But I think I did realize that I wasn’t getting exposed to the kind of weekly theory seminars that — there wasn’t anything like that at NBS. So I was thinking it would be nice to have those kind of connections, but I wasn’t actively looking. And because I had been a postdoc in Bloomington, I was contacted when they had an opening. Actually, it was [laugh] the departure of my former postdoc advisor, Jerry Mahan, for Oak Ridge, that occasioned the opening.
Oh, wow. Small world.
Yeah. Small world, yes. [laugh] So I decided I would move there. There were other reasons. It was kind of — we couldn't afford in Gaithersburg to live in a place where we wanted to raise our kids. Bloomington was pretty nice in that respect. And I had a colleague, Allan MacDonald, who had a kind of mirror image position in Ottawa, and so we moved together to Bloomington and had a tremendous long run of fruitful collaboration. I really enjoyed my time in Bloomington. A wonderful place to raise kids and a wonderful town, and lots of nice people doing interesting physics to interact with.
Did you look at this opportunity as a chance to take your career in new directions? Or was your research agenda at NBS pretty well-established, and you wanted to continue on with that same line, just in a new environment?
I think it was more the latter. One thing — at NBS, they had these NRC postdoctoral fellows. That was the only way that you could get a postdoc. And it wasn’t so easy and reliable. So I didn't ever — I didn't have a steady group of postdocs that I could work with, and in that manner, that was kind of another thing that I was looking for. So I didn't really — I was busy working on the fractional quantum Hall effect, and that was what I was doing for some years further on. So I was just continuing in that direction. But I decided, partly for family reasons, and partly for just a chance to be in academia, that I would move.
Did you take on graduate students right away, when you got to Indiana?
Yes. So I had graduate students and postdocs, and my colleague Allan MacDonald, the same. We had a joint NSF grant, and we tried to build up an active group of young people to interact with. It was a lot of fun.
What were the most interesting research questions to you during your time at Indiana?
Well, there was a lot going on experimentally by people like Jim Eisenstein and Mansour Shayegan, on the bilayer quantum Hall effect. So you have two electron gases that are so close together that the distance between the layers is comparable to the distance between the electrons within each layer. So they're more strongly correlated with electrons in the same layer, but nearly as strongly correlated with electrons in another layer. And that leads to all kinds of fascinating physics, and spontaneously broken symmetries, and peculiar collective excitations, and there was a whole bunch of things that we did there. You could define a pseudospin, which was the layer index, and you could have a pseudospin ferromagnet transition. There was a version of it where you changed the magnetic field and you get skyrmion excitations. You get — how to describe it? — it’s not a coplanar ferromagnet. The spins are turning in more than one direction. So you would get these topological defects in the spin orientation, which would carry fractional charge and have funny statistics. And I think one of the things I really got excited about was specific heat data that Mansour Shayegan and collaborators in Europe had, where when you were in this funny state, which we later decided was one of these sort of “Meron” crystals, the specific heat rose five orders of magnitude. Well, that’s crazy. [laugh] What could that be? And the hypothesis was that it was the nuclei coming into equilibrium with the refrigerator, because something was dramatically shortening the nuclear spin lattice relaxation time.
Normally, electrons equilibrate fairly well, but the nuclei are so isolated they don’t equilibrate well. And they could equilibrate by a flip-flop transition with an electron, due to exchange, where the nuclear spin flips and the electron spin flips. But they differ in Zeeman energy by a factor of a thousand. So that transition doesn't conserve energy. And you don’t have any energy available at low temperatures to sort of make that happen. But it turns out that the peculiar magnetic structure of the electrons in this funny quantum Hall region, there’s a kind of Bose condensation of spin flips. The spin gets some coherence in a direction transverse to the magnetic field. And the spins can flip without paying the Zeeman price, in some sense. They get very low energy spin-flip excitations. And those, we calculated, would dramatically shorten the nuclear relaxation time and bring the nuclei into equilibrium. And it agreed beautifully with the experiment. And it’s not often that you get like a [laugh] five order of magnitude mystery with a really novel and interesting explanation. And yeah, Sean Barrett at Yale later had some direct NMR kind of measurements of these things. So that was one topic that I really liked.
When did you get involved in superconductor insulator transitions?
So that was at Indiana, and I guess I — my memory is a little fuzzy, but I guess it started by seeing talks by Allen Goldman at the University of Minnesota on data where as you varied — if you evaporated atoms of some superconductor on a thin film and it got thicker and thicker, the way the resistance behaved as a function of temperature changed from an insulating behavior, where the resistance goes to infinity, to a superconducting behavior where it goes to zero. And right on the boundary, the resistance kind of became independent of temperature. And curiously, it wasn’t very far away from the quantum of resistance, or at least the quantum of resistance for Cooper pairs. So h, Planck’s constant over the Cooper pair charge (2e) squared, which is one fourth of the von Klitzing quantum of resistance from the quantum Hall effect. So that was a number I was familiar with and liked. [laugh] So I started thinking about that and developed some very vague ideas about if there were a transition and there were some kind of self-duality where the Cooper pairs and the vortices were equally mobile, that could describe the critical state. But it was kind of vague, and I didn't — you know.
But I started interacting with Matthew Fisher, who immediately turned it into a calculation. [laugh] That was amazing. And so I did work with him and with Peter Young and other people, doing quantum Monte Carlo calculations to try to get a more precise number for this universal resistance right at the critical point separating the superconductor and the insulator. And with Matthew and others, we wrote this paper [laugh] with the title, “Presence of Quantum Diffusion in Two Dimensions,” which was a takeoff on the Gang of Four paper, “Absence of Quantum Diffusion in Two Dimensions” from Localization. [laugh]
Steve, who were some of your most successful graduate students and postdocs during your time at Indiana?
[pause] Well, my first student was Carlo Canali, a wonderful Italian guy who is now a professor in Sweden. I had two excellent Korean students, Min-Chul Cha who worked on the superconductor-insulator transition and Kyungsoon Moon who worked on the bilayer quantum Hall effect. One very successful student was Kun Yang, who is now at the National High-Field Magnet Lab and Florida State, and coauthor with me on our condensed matter textbook. He was one of the last in the second wave of CUSPEA students from the CUSPEA program from China, and was at Columbia, I think, for a year, but his wife was a graduate student in Bloomington, so he transferred to Bloomington. Another happy coincidence for me. And we did some work on both quantum Hall effect together, and also frustrated magnets. Then he went on to a postdoc with Rhavin Bhatt at Princeton, and then a postdoc at Caltech and then a professorship at Florida. I had a talented student, Patrik Henelius, from the Swedish speaking minority in Finland. I must be getting old because he is a Dean now! Jairo Sinova was a remarkable student from Spain who went to high school in the US. He now runs a big group in Mainz. For his thesis defense celebration we asked him to cook because he is an amazing chef. Another student I especially enjoyed working with was Aditi Mitra who is now a Professor at NYU.
Overall, was the physics department at Indiana a good place to be?
Yeah. I enjoyed it. It was a very friendly place, and good colleagues, and there were some interesting experimentalists. Like John Carini who did some of the first microwave experiments on quantum Hall systems. We really enjoyed our time there.
And how did the opportunity at Yale come about?
So I was invited to give a colloquium — must have been Sean Barrett who invited me, because he was doing NMR experiments on quantum Hall systems. And that led eventually to an offer. Our kids had left for college, and my long-time collaborator, Allan MacDonald, had taken a chaired position in Austin. And my wife and I both had aging parents at the time on the East Coast, so decided that was a good time to consider a move. On this visit to Yale — well, OK. So [exhale] — this was — I'm losing track of the exact time. But in 1999, there was a paper by Yasunobu Nakamura showing basically the first qubit experiment where you could see Rabi oscillations in a superconducting qubit. I didn't even know there was a field of quantum information or quantum computing. There were a few — [laugh] apparently a few crazy people working on it at the time. I had never heard of it, didn't know anything about it. And I saw this paper with this real tour du force difficult experiment, and I got extremely excited about it. And when I visited Yale, I met Rob Schoelkopf while I was going around to different offices and talking to people. And I knew who he was. I had even — Chris Monroe had arranged for us to be on a grant proposal together, even though I had never met Rob. The proposal didn't succeed [laugh].
But anyway, we met in his office, and we had this incredible conversation for 45 minutes at his blackboard, where we started laying out the idea of how you could use the ideas from atomic physics and optics and cavity QED to do something with superconducting qubits. And so that was the opportunity to change fields and be at a place where you had great experiments starting up on quantum computing with superconducting qubits and excellent condensed matter theorists — Subir Sachdev, R. Shankar and Nick Read — and experimentalists doing quantum Hall NMR and things — Sean Barrett. Just decided that it was a great opportunity. So I moved to Yale a few days before 9/11, actually, in 2001. And that was a disturbing experience, moving from sort of the distant Midwest to close to New York. But it was a fantastic move, and a chance to completely redirect my research program and learn — I mean, I didn't know anything about quantum optics or that kind of stuff, so I had to spend several years learning. And that was fun to do, and the first thing one discovers is that atomic people know a lot more quantum mechanics than condensed matter people. The only dynamics that we know about is Fermi’s golden rule and irreversible decay. But there’s all these concepts of coherence and Ramsey fringes, and open quantum systems, and quantum trajectories, and things that just were really a chance to just learn much, much more quantum mechanics, and finally understand what is a quantum measurement, and how do you think about them. It has just been — and then Michel Devoret arrived a few months after me, in January of 2002, another incredible experimentalist. And it just blossomed into this amazing opportunity to develop this whole field, which when we started, there were a few talks at the March meeting, and now there are many parallel sessions. [laugh] It’s hard to keep up!
Steve, why was this an opportunity for you to change up your research agenda?
Well, I feel like I do my best work interacting with experimentalists. I've done some formal theory — you know, order parameter for the fractional quantum Hall effect and things that are not connected to experiment. But most of the things I do are maybe related to the fact that I really wanted to be an experimentalist but never did! [laugh] So having people that you run into every day that are working on experiments and have amazing ideas and bring you amazing questions to think about, and keep you honest where you have to make suggestions that aren’t experimentally unrealistic for them to try — that’s just my favorite space to work in. And I like to — I tell students, “You don’t want to be 100 years ahead of your time. [laugh] You'll never see the experiment that says you were right. And you don’t want to be two weeks ahead of your time, because there’s too much competition. So there’s some sweet spot around two years or something, where you want to be. And you can be in that place more easily if your experimentalist friends are next door.”
What were your impressions when you came to Yale? Was physics done differently there? Was the culture of the physics department different than at Indiana?
Well, not wildly different, but there were really extremely high-quality scientists working really at the frontiers of the field. And there were more theorists and experimentalists for me to talk to. So it was a little more lively environment, despite the fact that condensed matter physics arrived late at Yale, shall we say.
What is your sense of that? Why was Yale late to the scene on condensed matter?
I don’t really know. But when they finally decided to — I mean, they had a long history of fundamental science, and particle and nuclear physics and so forth. They had R. Shankar working on condensed matter theory but he had been hired in particle theory and converted. But when they decided to hire in condensed matter theory, they hired two — Nick Read and Subir Sachdev, who are just amazing world-beating theorists. But most of the experiment was still in Applied Physics. It’s starting to build up now in physics, but that’s another sign that it has been late coming to Yale, is the commitment to experiment. But I don’t really know like the history much before I arrived, so I'm not quite sure what the origins of all this was.
Who were some of your most fruitful collaborators when you got to Yale, on the Yale faculty?
Well, my primary collaborators have been Rob Schoelkopf and Michel Devoret. But I've also written papers with my fellow theorists and Leonid Glazman and Subir Sachdev, for example. But my main focus has really been on how do we get superconducting circuits to actually work for processing information. And in some sense, it’s kind of applied. I mean, there was a deeply fundamental aspect of how does quantum mechanics work at macroscopic scales of electrical circuits. But the applied aspect of how do we actually try to build a quantum computer and do computations — that really required close collaboration with experimentalists doing that. So they're my main collaborators. And we have a joint group meeting every Monday, the Monday lunch seminar, and students — Rob and Michel basically have one group, and then there are other experimentalists there, and other theorists and their students. So we probably have 50 people at each seminar. It’s an amazing large collection of students. You know, not that many faculty, but lots of grad students and postdocs and also faculty there that are all really excited about this amazing topic. So it’s just a lot of fun.
When you were named Higgins professor, was your sense that this was sort of a general recognition of your contributions, or was there one particular project that may have connected to this honor?
Well, I wasn’t really told it was for something specific. I think the thing that I became known for inside Yale was my collaborations on quantum information processing with the experimentalists, Rob and Michel. So I assume it was based on that.
Can you talk a little bit about two years later when you become associate director for the Nanoscience and Quantum Engineering Institute? How did that come about, and in what ways was this appointment — how well did it jive with your ongoing research?
Well, so this center was established — there was interest from Paul Fleury, who was the dean of engineering at the time and interested in nanoscience. And we were interested in quantum — well, mesoscopics and quantum circuits and quantum information processing. So I didn't actually have a sort of major role in the formation, but I was associate director at the beginning. It has kind of evolved. The landscape has evolved a little bit, that that center has now become primarily a kind of core facility for nanoscience and quantum engineering. It does have a seminar series. And the Yale Quantum Institute was formed, well, almost six years ago now, to focus more directly on the quantum information processing aspects of the field. So my office is there. It’s partway between physics and applied physics, so it’s convenient for me to interact with the experimentalists, my colleagues who are in applied physics. And it’s the venue which hosts our interdisciplinary group meetings. And it’s the venue for us starting to interact, over the last year, with quantum chemists who were interested in can our small quantum computers run simulations of chemical dynamics, problems that are of interest to them. So it’s a kind of an opportunity to get collaborations going despite the existence of separate departments. [laugh]
And is this really an opportunity to work with engineers in a way that you might not otherwise be able to?
Yes. So we are starting to interact with computer architects and with electrical engineers who are building sort of hybrid devices that can transduce quantum information from microwave frequencies to optical frequencies, using some combination of our superconducting qubit and microwave technology with optical — integrated optics kind of technologies. And we're very interested in trying to expand more into — well, I just mentioned chemistry, but we're very interested in also expanding into computer science, which of course they're very busy with machine learning and deep neural networks and AI and all the other things that computer science is on fire with right now. But we're starting to get a lot of interest in if real quantum computers start happening at larger scales, what kind of computer science opportunities are there. And that’s an area where I need to learn a bunch, and they of course need to learn a little bit about quantum. And so that’s an interesting communication gap that we're trying to learn how to cross. I teach a freshman physics course called Intensive Introductory Physics, a kind of honors course. And I gave up the historical introduction to quantum mechanics with atoms and waves and particles, and just teach quantum information processing. So sort of throw out a lot of the physics, and just teach quantum mechanics using linear algebra, no partial differential equations. Because they're first year undergraduates. And I give them homework on the IBM Q system that’s available in the cloud, and [laugh] they really get excited about that, and think it’s cool. And you know, the challenge with freshman physics is that we're teaching Galileo and Newton. [laugh] And unlike 300-year-old biology, 300-year-old physics is not wrong.
[laugh] But it’s not that exciting, rolling balls down inclined planes and stuff. So we think it’s very important to try to give students a taste of the frontier without like — even though they're not ready yet with all their physics and math knowledge. It’s ironic that all these modern developments in quantum information theory have given us a completely new and actually simpler and better way to introduce quantum mechanics. Because all the paradoxes about entanglement and measurement and so forth, they all have to do with information and who has what information, when. And so you can jump directly to — you can teach first-year undergraduates about Bell inequalities and quantum dense coding and quantum error correction with very, very little mathematics. Whereas the traditional course, you start solving this partial differential equation for the hydrogen atom and things, and it’s, you know, very technical and confusing. So even though this is like a frontier topic, in some ways it has given us a whole new way to talk to beginning students and get them excited about it.
And probably in this field, students are sort of primed to be excited about this kind of thing.
Yeah, there’s a lot of interest. They follow — two years ago, when I started teaching this class again, [laugh] the first day, the students walked in and they did a double take, and they said, “Oh, you're the guy in the YouTube video!” [laugh]
So that was fun. Yeah, so they've heard about it, and they've seen stuff on YouTube or whatever. And they're really eager to get involved and learn more.
Steve, so these academic provost titles, they're so opaque, right? They don’t really tell you anything of what you're actually doing in these roles. You served for quite a long time. A decade is a pretty long time to be serving in these roles. So let’s start with the first one. What exactly did you do as deputy provost for science and technology?
So, yeah, this is an interesting question. The title eventually evolved to deputy provost for research, and today it’s vice provost for research.
Oh, so that was essentially the same position.
It’s the same position, but it turns out that at most places, the title is vice provost or vice president for research, so we eventually just harmonized it with that. So I kind of did it on a lark, I have to say. [laugh] And I didn't fully appreciate how insane these jobs are. But I did it for ten years, and enjoyed it. So what is the job? It’s essentially the chief scientist job at the university. And the interesting parts of the job are having a very broad view of all the science investments across the university, and all the who’s doing what, and making strategic investments in different areas, which you have to learn a few sentences about. So one of the last things I did was make a very large investment in cryo-electron microscopy with these very expensive aberration-corrected electron microscopes for looking at individual molecules. And you have to build up — you have to understand the size of the community that would use this. And sadly, you have to think about the financial model, of how will you pay for these very expensive things. But it’s interesting to think about “This is a moment in time when this technology will help advance a large swath of medicine and biology at Yale.” The other portfolio that I eventually had was the research administration. That’s the grants and contracts office that brings in more than three quarters of a billion dollars a year in external grants and contracts. So you don’t want to [laugh] mess that up! It’s a highly regulated environment, so you have to learn a whole bunch of new stuff. I suddenly found myself the institutional official for human subjects research and animal research. I had to learn all the ethical principles behind those kinds of research, which was very interesting. But also you have to [laugh] — you're authorizing people to inject things into people to see what they do, to see if it cures a disease, or do clinical trials. So you really have to [laugh] pay attention to these things. And, you know, there’s all kinds of less interesting things that involve the administration of science. Another interesting area, though, was recruitment and retention of faculty. Just negotiating start-up packages. I tried to be strategic there. That was interesting. But these are very demanding jobs, and physically taxing. Because you're outnumbered 3,000 to one by the faculty, all of whom just need a tiny slice of your time and your budget. But the opportunity to interact with academic leaders at Yale — you know, the president and the provost and the dean of the graduate school, the dean of Yale College, the dean of FAS — I mean, these are all amazing people. And the quality of conversation and debate about important issues that — and getting into the habit of thinking on hundred-year time scales, which I learned from Rick Levin when he was president — I mean, it’s an amazing experience. Like I thought — and the president and the provost are always saying, “Never let the urgent crowd out the important.” There’s just all kinds of urgent stuff. But you have to spend some time thinking strategically. What’s the big picture? How can we advance science and medicine and engineering at Yale, with strategic investment, strategic hiring, improving the efficiency of research administration and so forth. And when I started the job, I thought, “OK, I've learned — ” You'd be in these meetings with the president about some endowment indenture, and he would say, “OK, a hundred years from now, is this field going to exist? Can you really word the indenture this way? And you just get into this habit of thinking institutionally, and on really long time scales. So I thought, “Well, what can I do?” So I said, “Oh, I've got an idea. We should do a sea level rise study to think about what’s going to happen a hundred, 200 years from now, to Yale, and where we're situated on Long Island Sound.” I knew Long Island Sound was rising faster than mean sea level for various technical reasons. And so I went to talk to the relevant people in facilities about this. And they were in the middle of their second such study! [laugh] Already! So you’re just dealing with interesting people who were thinking very big, very long-term, and very strategically about this wonderful institution, and how to make it better and survive. So I really enjoyed that. And but it is demanding, and it was starting to eat seriously into my research time as I got more and more responsibilities.
Steve, we're only a few short weeks away from #ShutDownSTEM, and obviously part of the goals of a day like that is not to isolate that as just another day on the calendar but to keep that conversation going.
I actually talked to Meg Urry yesterday, and she made it quite clear that issues of underrepresentation are not faraway concepts at a place like Yale.
And I'm curious if, in your role, in this administrative role, if you saw diversity and inclusion campaigns as sort of part of your portfolio, and if there were any particular opportunities for you to increase representation in STEM at Yale, of underrepresented groups?
Yeah. So there were various efforts made by the provost and president and deans in this direction. Of course in the STEM fields, women and persons of color are both underrepresented. And so my more direct interactions had to do with — you know, you have annual meetings with the department chairs and we’d talk about budgets and hiring and retention and recruiting, and of course diversity was always one of the topics. We thought about questions around startup packages for recruitment and retention. Is there any gender bias in the nature of those negotiations or startup packages and retention packages? I did some statistical analysis to kind of check myself to see where things stood there. Of course the number of women is actually sufficiently small that you have [laugh] — there’s not good statistical data. But it was a question that I asked myself and looked at. And there are a number of formal programs to help departments recruit and retain underrepresented groups on their faculty. It’s a constant struggle. And while retaining a person from an underrepresented group at Yale is maybe good for Yale, it doesn't increase the total number of people in the population. So you have to think about the training environment and the pipeline. Are you making sure that people are comfortable in their training environment, both in formal training programs like biology training groups and individual groups. So it was — I mean, thinking about those things was certainly part of the job. We've made a little progress, but we still have, I think, quite a ways to go.
When it was time for you to return to faculty civilian life, I'm curious, were you looking to sort of pick right back up where you had left off, full time, or was this another opportunity for new engagement, new projects?
No, I think — I mean, there’s so much going on in circuit QED and quantum information theory and experiment. I just wanted more time to keep up with it, basically. And so I did not change directions again. Which gets a little harder, I have to say, [laugh] as one gets older. I've got a lot of expertise built up in this area, but I was falling behind just by lack of bandwidth to keep up with all of the experiments inside Yale, never mind in the rest of the world. So I decided to not rock the boat and just stick with [laugh] what I knew, because it’s so active.
Steve, now that we're up to present day, I think just for my last question, I want to ask you a forward-looking question. And that is, in the world of physics — you're still a young guy. Physicists never retire. You can have many decades ahead of you, if you so choose. So I'm curious, both for yourself personally and for the fields that you represent, what are the most exciting areas in research and discovery that you see? What are the fields or the subfields that when you're talking to both undergraduates and graduate students about, “Here are the really exciting areas where the most impactful careers can be made in the 21st century,” what are some of those standout fields and research interests that really jump out at you?
Well, OK. So there’s much more to quantum information than just quantum computing, but I think the question of whether we can solve the problem of fault tolerance and build a large-scale system that can produce complicated entangled quantum states possibly useful for computation, and have it be reliable even though it’s built out of imperfect parts — that’s an amazing subtle question that’s much much more subtle than the corresponding question in electrical engineering for classical circuits, where it has been solved so well that most computer scientists don’t think about fault tolerance anymore. They're up here working with Python, and they don’t remember what the electrons are doing down here. We're still down here in the mud with the electrons. So that to me is the grand challenge if we're going to get quantum computers to work. The thing I like about this field is that there are lots of atomic physicists thinking with their systems and cold atoms and Rydberg atoms and optical lattices, how could they build a processor. And I give talks at DAMOP and I interact with Bill Phillips, Mikhail Lukin, and Jun Ye and other atomic physicists, and it’s great — we have a language in common now that we can — because we're both — we're all thinking about quantum coherence and computation and information. And there are many exciting things going on in cold atom physics. And cold atom physics starting with the BEC discovery, 25ish years ago now, they've discovered temperature and many-body physics and entropy and things that are near and dear to condensed matter physicists’ hearts. And we've discovered coherence, which is near and dear to them. So the coming together of these fields is very fruitful and is still an ongoing direction for — let’s say the common theme is maybe quantum simulation of many-body systems with one person using superconducting circuits, another person using Rydberg atoms or atoms in optical lattices. There’s a lot to do there that brings together these fields. Then particle — well, I don’t know what to call it — astrophysics — both kind of particle astrophysics like using — looking for dark matter — that’s a huge, interesting problem. There’s an experiment — the HAYSTAC experiment at Yale, which is using ideas from our superconducting quantum circuits and quantum optics techniques to beat down some of the quantum noise that’s limiting the rate at which you can search for axion particles, which turn into microwave photons. And so quantum sensing ideas applied to searches for dark matter — that's super interesting. The quantum sensing that’s now improving the rate at which LIGO can see black hole mergers using a similar technique. So the HAYSTAC experiment and the LIGO experiment are the only ones in the world that are using squeezed light — one is optical, one is microwave — to improve detection efficiency for these incredibly feeble signals. That’s amazing. That’s a different — LIGO is a big team and many people working together over a long period, but the physics opportunities for understanding neutron stars and black holes and [?] all these crazy [laugh] physics of these mergers seems extremely interesting. And finally, in the condensed matter physics, I would say all these twisted bilayer van der Waals materials where you see by having two layers that are twisted at a slight angle, and you can get a magnet or a superconductor or a strange metal — those are extremely exciting new opportunities because one thing that the atomic physicists have is the ability to like tune the parameters in their effective Hamiltonians. We tend to be stuck with synthesizing some material and there’s nothing to adjust. But now, with this ability to twist — assemble twisted layers with different twist angles, we've got another knob to turn. And if you change the Hamiltonian and understand the changes, you can learn a lot more. So ultimately, physics is an experimental science, and the thing that powers us is the unexpected surprises that come along. And we theorists tend to do a lot of post-diction and not a lot of prediction.
Occasionally, we get lucky and make a prediction.
But this virtuous cycle where new sensitive quantum technologies are allowing new measurements and discovery of completely new phenomena, which in turn may allow us to invent new measurement technologies, that’s just making this — I mean, the last 30 years have been — even 40 years — have been a very fruitful time for many areas of physics. To me, it’s all interesting!
I could have been happy doing almost anything! Although I do prefer finite size collaborations [laugh] over giant ones. But there are just so many interesting directions right now.
Steve, it has been so fun talking with you. I really want to thank you for the time you spent with me today.
Oh, it’s a great pleasure, and I'm glad you're doing this project.