Matthew Fisher

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ORAL HISTORIES
Image of Matthew Fisher

Credit: UC Santa Barbara Dept. of Physics

Interviewed by
David Zierler
Interview date
Location
Video conference
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Interview of Matthew Fisher by David Zierler on January 12, 2021,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
www.aip.org/history-programs/niels-bohr-library/oral-histories/47466

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Abstract

Interview with Matthew Fisher, professor of physics at UC Santa Barbara. Fisher recounts his early childhood in London as the son of a prominent physicist, and his upbringing in Ithaca where his father was on the physics faculty. He discusses his undergraduate experience at Cornell, where he started in engineering but gravitated toward physics, and he reflects on a conversation with a graduate student, which – more than any influene from his father or his brother, also a prominent physicist – sparked his interest. Fisher describes his initial graduate work at MIT, where he focused on experimental condensed matter research in the lab of Bob Birgeneau, before he transferred to the University of Illinois at Champaign-Urbana to re-focus on condensed matter theory, with a special interest in quantum mechanics under the direction of Tony Leggett. He explains the mental health issues he began to suffer from in graduate school, which extended into his postdoctoral, and then full time, work at IBM, until a psychiatrist prescribed him medication that essentially restored him to a state of mental health. Fisher describes the opportunities leading to his faculty appointment at UC Santa Barbara, and he discusses his newfound interests in high temperature superconductors, the fractional quantum Hall effect, and the localization of bosons. He discusses his ongoing interest in quantum mechanics, quantum spin liquids and quantum phase transitions, and he describes his long term collaboration with Charlie Kane. Fisher explains the singular advances Phil Anderson made to the field, and what supercomputing has allowed in the last twenty years that was not possible in the previous twenty years. He connects his mental health challenges with his recent interests in the concept of a quantum mind, or the possibility that the brain operates quantum mechanically. Fisher stresses that the field is nascent and that it is too early to tell if his preliminary ideas will be substantiated, and why a greater understanding of both evolution and the nature of consciousness is crucial to developing of this path of inquiry. He explains the implications of the notion of free will if the brain operates according to quantum processes, and he describes how this research may bear out experimentally. 

Transcript

Zierler:

This is David Zierler, oral historian for the American Institute of Physics. It is January 12, 2021. I am delighted to be here with Professor Matthew Fisher. Matthew, it’s great to see you. Thank you so much for joining me today.

Fisher:

It’s also my pleasure. Thank you for having me.

Zierler:

To start, would you please tell me your title and institutional affiliation?

Fisher:

I am a Professor of physics at UC Santa Barbara. I used to be a permanent member of the Kavli Institute for Theoretical Physics. Before UC Santa Barbara, I spent a number of years at IBM on the east coast, and I spent one year at Caltech in 2009-2010.

Zierler:

What year did you arrive at Santa Barbara?

Fisher:

It was in 1993.

Zierler:

Okay. Good. Well, let’s take it all the way back to the beginning. I know that your father was a physicist, so I want to hear all about him, and both of your parents. So, let’s start first with where they’re from.

Fisher:

My mother’s father is Spanish. My mother was born and brought up in Madrid. And when Franco took over in Spain, her family and she, at maybe 13 years old, had to flee to Geneva in Switzerland. And then when it looked like Hitler was about to invade Switzerland, they went to London. My mother’s mother was British. And so, they were in London during the Blitzkrieg. My father was born in Trinidad and Tobago, but — because his dad was working for Shell Oil, grew up in England. And during World War II, he was sent to South Africa with some relatives just to get out of the hot zone. And my parents met at a math club, while my mother was getting a master’s in mathematics, and my dad was working on his Ph.D. at that stage.

Zierler:

Was it uncommon — did your mom talk about — was she a bit of a trailblazer pursuing math at that level as a woman?

Fisher:

I think so. But I don’t think she was into it as much as my father. She was good at it, and enjoyed it, although she didn’t pursue it once she had a family. I remember when I was 18 years old, having learned some calculus, I took her aside, and said, you know: Mummy, how much math do you actually remember from 35 years ago? And she said, “Nothing. I remember nothing.” I said, “You must remember something.” And so I said, “I’m going to ask you a question.” And I asked her, “What’s the derivative of x2?” And she goes, “2x?” Which was the right answer. But she was unsure. So, she did have some recollection of some of the math that she’d learned.

Zierler:

What was your father’s training? What was his educational trajectory in physics?

Fisher:

His Ph.D. was not in physics, per se. It was in something to do with computing. He got into physics mostly after his Ph.D. You know, my mother’s brother was a theoretical physicist as well, so we had —

Zierler:

Both sides of the family.

Fisher:

Yes. So, us children were doomed, in a way. [laughs]

Zierler:

[laughs] Now, who’s older, you or your brother Daniel?

Fisher:

Daniel is three and a half years older.

Zierler:

Okay. And from your vantage point, did you grow up knowing what it meant to be a physicist? Did your father involve you at all academically or culturally in what he was doing?

Fisher:

I of course knew he was a physicist, and we met his grad students and postdocs. They would come and visit our house. For my father, physics was viewed as a higher calling, almost. We grew up with physics almost as a religion. And he had his inner sanctum, which was his study, and then the outer area. And if we children ventured anywhere close to that, we had to tiptoe, because he was doing such important work, or so we were told. And that had some impact on me when I started doing graduate research, and I realized that physics is a great profession, and it’s a wonderful endeavor, but it’s not the be-all, end-all of life. But he was very much into what he was doing. And there were four of us, four kids. I was the youngest of four. And Daniel, my brother — he was a child prodigy, absolutely a genius, right from the beginning. And he went to college at 15, graduated from college at 18, got his Ph.D. at 21, and started working at Bell Labs in their theory division. Shortly after that, he became a professor at Princeton and then Harvard and Stanford. So, I grew up — I wouldn’t say it was in his shadow, but you know, I saw the conversations that my brother and my dad were having about physics. But as a kid, I had to find something that I was good at, that the rest of the family wasn’t good at. That was sports, so I did a lot of sports as a kid.

Zierler:

Did your father have the same academic affiliation throughout your childhood, or did he move around?

Fisher:

He was mostly at Cornell University. He was a professor of math, physics, and chemistry there for many years, and after I had left and gone off to graduate school he moved to the University of Maryland . So, I grew up in Ithaca throughout my childhood, after moving from London to Ithaca when I was 6 years old, so basically I became an American kid.

Zierler:

Did the family move knowing that it was going to be a permanent move, or was there the sense earlier that you would go back to England?

Fisher:

Well, we did take a one-year trial run, with my father at Rockefeller University when I was 3 years old, and then we went back to England for a couple of years. The move to Cornell was viewed as a permanent move, and it was, until they moved many years later to Maryland.

Zierler:

Who were some of the key collaborators that your father had on the Cornell faculty? What were some of the names that you would always hear as a kid growing up?

Fisher:

Well, Ben Widom and Ken Wilson, who was the founder of the renormalization group…

Zierler:

Right.

Fisher:

…which is a remarkable invention. It’s an incredible lens through which to look at physics and other scientific phenomena. And so, I heard about Ken Wilson and maybe met him a few times. There was another person who my dad was quite close to, who was Brian Josephson, who was at Cambridge. And he, in graduate school, discovered what’s now called the “Josephson junction,” which was a huge deal. And he won the Nobel Prize when he was pretty young. He would come over to our house a couple times a year to visit, and since he was a bit awkward, — the children and me, in particular, would be sent into the pool room to play pool with Brian, because you didn’t have to make conversation if you were playing pool.

Zierler:

When did the family achieve citizenship? Was that a drawn-out process, or that happened relatively quickly?

Fisher:

No, it was very, very drawn out. In fact, my dad just became a citizen a year ago.

Zierler:

Wow.

Fisher:

The 2020 election was his first election. And my mother never became a citizen. I became a citizen when I was in graduate school. My parents were very proud people, proud to be English. An amusing story was when I was in second grade, after we came to the states from England. I had a very strong English accent, of course, and was teased mercilessly at school. And so, I started evolving a little bit, and speaking a little bit more like an American child would. But then at home, while I was not quite teased, my parents would say, “In our house, we speak proper English.”

Zierler:

[laughs] You were caught between two worlds.

Fisher:

Yes, I was navigating these two worlds, finding some middle ground. And then when I was maybe 10 or 11, I discovered what physicists call a first-order transition. There are some words that when you pronounce in English-English and American-English, that it’s impossible to interpolate smoothly from one to the other. One such word is C-A-N-‘-T. An American would say “cant” and an English person would say “caan’t.” And you can’t go smoothly from “cant” to “caan’t”. At least I can’t! And so, I had to decide, do I abruptly, say tomorrow, start saying “cant.” I decided I couldn’t go across that divide, because it just felt too stilted — like I was trying too hard.

Zierler:

Matthew, to what extent did this serve as a microcosm to your overall identity as either an American kid or a British kid growing up in America?

Fisher:

It did impact me, and up to high school I was teased to some extent. Although, by then I was doing sports, so it wasn’t so bad. And, by the time I was ending high school and in college, I discovered to my delight that American women like an English accent. [laughs] And now, I say my accent is “Mid-Atlantic”, somewhere halfway across the ocean.

Zierler:

Matthew, did you have a strong science and math curriculum in high school?

Fisher:

It was pretty good. But I was basically doing everything I could to avoid going into academics, because my older brother was so precocious and so brilliant, and my dad was very brilliant. And I was just kind of your normal kid. So, I did things I’m not proud of now, but I would go a whole year in school without using a pencil or pen, except for taking tests. I’m not proud of it, but that’s kind of where I was at, at that stage.

Zierler:

Do you mean more out of rebellion, or to demonstrate that you were able to memorize all this stuff without notes?

Fisher:

Well, it was a bit of both. It was probably pride in part, and a bit of a rebellion. But I was getting good grades — but then when I went to college at Cornell, it was a shock, because I wasn’t really prepared. And I had to really hit the ground running in freshman year.

Zierler:

Now, as a student of a Cornell professor, I assume tuition was part of the equation for going to Cornell?

Fisher:

Yes. It was tuition-free. And so, of my siblings, three of the four of us went to Cornell, and my sister went to Brown.

Zierler:

At what point did you sort of come into physics on your own?

Fisher:

So, I basically started in engineering. And the reason I went into engineering — again, I’m not proud of this — was that there was no language requirement, and I’m terrible at foreign languages. And I’d taken French in high school, and I said: well, I’m good at math, so I might as well do engineering. But then what happened is by the end of my sophomore year I was doing engineering and physics — and I started really liking physics.

Zierler:

Now, correct me if I’m wrong, but the engineering physics program at Cornell, you were essentially taking as much physics as physics majors themselves.

Fisher:

Yes. So, I was being exposed to physics, and it was good. Cornell is a great school. It was a very good engineering physics program, really incredibly good professors. And I soon became inspired, especially by one TA, Michael Guillen, I believe was his name, who had a big impact on me. Towards the end of my sophomore year, he said: well, Matthew, in physics there’s so many things we don’t understand, like, what is time? How do we define time? Can we think about time in a scientific manner? And I was kind of blown away by that. I don’t have any insight into time, [laughs] of course. But I just thought that was pretty crazy. So, by the time I was a junior, I decided I would learn as much physics as I possibly could. I just threw myself into it.

Zierler:

Matthew, I can’t help but notice that between your father and your brother, it took a TA to blow you away in terms of a physics concept.

Fisher:

Well, I didn’t want to just follow my dad or my brother’s footsteps. They’re both extremely successful, and I wanted to find my own path.

Zierler:

Did you grow up having a sense that there was this binary in physics, between the world of theory and experimentation?

Fisher:

I did become aware of that. But physics in our household was theoretical physics. But once I was at college my dad frequently emphasized experimental physics. He would say, “Physics is an experimental subject.” And by the time I was a senior in college and thinking about: did I want to go to graduate school?, he tried to discourage me from doing theoretical physics, because he thought it was too competitive. And it is, perhaps, more competitive than experimental physics.

Zierler:

But there is this natural talent for math that runs in your family that you recognized in yourself as well.

Fisher:

Yes. By standards of the general population, I’m very, very good in math. But by the standards of theoretical physicists I’m only fairly good at math. It’s not absolutely my strength. My strength is more in conceptualizing - in pictures. I of course had to learn all the math, since math is the language of science. But I was going into physics not because I liked math. The fact that I was good at math gave me an entree into physics and theoretical physics. But then I started graduate school at MIT trying to do experimental physics. And I was in the lab of Bob Birgeneau, who has since been the chancellor at Berkeley, many years later. And I was in the basement in his lab, and my desk had dripping water from pipes, and it was totally miserable. And then you go and visit Professor Birgeneau in his office. He was up on a stage with his big desk, and you would be kind of standing down lower. And I said, geez, thinking to myself: I don’t want to have a career in the basement [laughs]. You know, I want to be like Bob Birgeneau, with a nice desk and a view out the window. So, I switched. But of course I also love theoretical physics, so I am partly being facetious here.

Zierler:

Matthew, to go back to Cornell for a second, was there ever the possibility that you’d have your dad as a professor?

Fisher:

I did have him.

Zierler:

Did you try to avoid it, and you couldn’t, or you wanted this experience?

Fisher:

When I was an undergraduate at Cornell I took a graduate course in statistical mechanics from my father, which is what he had been teaching for many years. And I knew he would be a great teacher - and he was, fantastic. In hindsight I’m surprised that I was brave enough to dive into that course. But by then, I had realized how important it is to have physics explained to one in a way that’s conceptualized for the student. And so, when I was a junior and a senior, I would go back home and talk to my dad. And half an hour with him would be as valuable as three weeks of physics classes, because he would frame it just right, saying: these are the things you have to know. And so, the statistical mechanics class was fantastic, and I really enjoyed it. And I wasn’t too worried about the grade, but I did end up doing well, so I was kind of relieved at the end. But my dad already had one brilliant child doing physics so I didn’t think it was so important for him to have me as a successful physicist.

Zierler:

Why MIT? Where else were you thinking about?

Fisher:

[laughs] I’m really exposing myself, here. But I don’t like prestige, generally. I like doing things well and being at a good university, but I don’t like being at a university whose reputation is based on historical precedence. So, I got into Harvard, and the other top schools, for graduate school, but I didn’t want to go to Harvard, because I didn’t like the attitude so much at Harvard. I mean, obviously, the individual professors are great and so forth, but collectively, it wasn’t what I liked. But prestige was still important to me then, as it maybe shouldn’t have been as much, and so MIT was like — okay, that’s the second best place. It’s not Harvard. But I ended up transferring to University of Illinois in Champaign-Urbana.

Zierler:

Was this shortly after your realization about not wanting to be an experimental physicist?

Fisher:

Yes. At MIT, there was a professor, David Chandler, a theoretical chemist who was visiting MIT for the year on his sabbatical. And I started talking with him and got very excited about the kind of work he was doing. And he was visiting from University of Illinois, so it was natural for me to transfer there. And I started working with him on some problems, but after a while it didn’t work out. That was a bit of a difficult time, starting doing research in graduate school, because I realized that my professors either didn’t know the material as well as I thought maybe they might, or were doing work which seemed to me very narrow and pretty uninteresting — because one learns as an undergraduate quantum mechanics, electromagnetism, statistical mechanics, all these wonderful fields of physics which developed over decades, if not centuries. And then when you start your own research, it tends to be very, very narrow. And I’m a big-picture type of person, and so I didn’t really like that so much. And it was then that I also realized that physics research, while exceedingly interesting, is not the be-all, end-all in life. And that sort of harkened back to my father’s inner sanctum when we were growing up, and I was like: hmm. [laughs] I understand that now. That worked well for him.

Zierler:

Matthew, what was the process to get to theoretical condensed matter? In other words, did you go to MIT with that being the plan, or you were more open at that point?

Fisher:

Well, so I went to MIT to do experimental condensed matter.

Zierler:

Yeah.

Fisher:

So, my dad probably had a very big influence on me in condensed matter physics. And I like it when my theoretical physics has at least some relevance to, if not ongoing experiments, future experiments one could imagine. I really like that connection. And high-energy theory, at that stage and really ever since then, since my senior year in college, hasn’t really evolved at all. I did a senior thesis on the standard model of particle physics, and it’s still the standard model of particle physics. So, I knew the experiments were very slow to come, and so that wasn’t a field I wanted to look at.

Zierler:

And I love to historicize the term. So, by the time you were thinking about graduate school, was it still solid-state, or we had fully moved into condensed matter? Or, was it sort of in a transition at this point?

Fisher:

It was in the transition, actually. My father was emphasizing that solid state physics is just one part of condensed matter physics. Condensed matter physics is much broader, so solid state physics, in his view, at that stage — and this was in the late ’70s — was not really a good name for the field.

Zierler:

Right.

Fisher:

Condensed matter physics is not a good name, either. I mean, it’s —

Zierler:

And is that because there’s soft matter physics and rheology? Is that part of it as well?

Fisher:

Yes. Although back then, at least theoretical physicists, they weren’t working on just quantum condensed matter physics or soft condensed matter physics. They were doing theoretical physics.

Zierler:

Right. Right.

Fisher:

And so, I was as well. But I fell in love with quantum mechanics.

Zierler:

As an undergraduate, you mean?

Fisher:

As an undergraduate. By the time I was in graduate school, I was really smitten, continuing to this day.

Zierler:

Who taught you quantum mechanics at Cornell? Was it Mermin?

Fisher:

Yes, David Mermin.

Zierler:

Yeah.

Fisher:

I took a graduate class with him.

Zierler:

Anybody who learns quantum mechanics from Mermin is very lucky indeed.

Fisher:

Yes, so I was really lucky. I also had a quantum mechanics course from Kurt Gottfried, who was a high-energy theorist. He’s a wonderful teacher. And I took my first quantum mechanics course with Vinay Ambegaokar. What I liked about quantum mechanics is you can look at things from so many different angles, and the mathematical framework is very broad, even though the subject is just one subject. In graduate school, I decided to really specialize my research on quantum mechanics. I recall that my dad had gone to a conference which was in honor of Niels Bohr for the 100-year anniversary of his birth. And my dad gave a talk and submitted a paper with a title something like, “Why quantum mechanics is irrelevant in condensed matter physics.” [laughs] He was partly just being facetious, but mostly trying to be provocative. And I thought, “I don’t believe that!” So, I started seeking topics where the system is so quantum mechanical that there is no classical intuition to be had.

And this was soon after the discovery of the fractional quantum Hall effect. So, I had an argument with my father, and I said: well, in the fractional quantum Hall effect the particles are not condensing - they’re not behaving like in a superfluid, and they are not behaving like ordinary particles. Neither a particle representation nor a wave representation is valid. You really need to live between particles and waves to understand the fractional quantum Hall effect. And my father admitted that the fractional quantum Hall effect might be a special case, where you really did need quantum mechanics in a big way. So then I decided that I wanted to focus my research on quantum phenomena which have no classical analogue. This seemed not a bad way to try to frame my research path. And that’s when I started working for Tony Leggett, who I imagine you’ve probably heard of. And that was great.

Zierler:

Matthew, I’ll note editorially, perhaps the University of Illinois was perfect, in the sense that it doesn’t have the prestige of a place like Harvard, but when you look at condensed matter, it’s the best, or one of the best, hands-down. So, it had all of the substance without the name and whatever that might entail or not.

Fisher:

You’ve hit the nail on the head. That was exactly right. Illinois was - and still is - phenomenally good in condensed matter physics and in solid state physics, but it’s a state school. It didn’t have the prestige. It was just good. That’s where I wanted to be, in a place which is really strong, but where you don’t wear your successes on your shoulder.

Zierler:

And in terms of your budding interests in quantum stuff — I mean, today, talking to people like Dale Van Harlingen, there’s a quantum revolution that’s happening specifically at Illinois. Do you sense that going back to when you were there, this is really the origins of this?

Fisher:

In a way, it was. John Bardeen was still there, although being quite elderly was not so active. I think people at Illinois were rather forward-looking because of having professors like John Bardeen. And I became very close to Bill McMillan, another professor who you may not have heard of. But he was a condensed matter theorist who worked on superconductivity and worked on Helium-4 and other problems. And he was extremely creative. And then he died tragically in a bicycle accident.

Zierler:

Now, did you know Tony Leggett, either personally or by reputation, before you got to Champaign-Urbana?

Fisher:

Not personally. He was already somewhat famous, but he won the Nobel Prize quite a bit later. I was drawn to Tony because of his creativity, and because he loves quantum mechanics, very much enamored by quantum paradoxes, like the quantum measurement paradox. He was working on macroscopic quantum mechanics, asking whether a mesoscopic - that is a non-microscopic - degree of freedom can still be described quantum mechanically, or not? I joined in with the effort that he was undertaking, and that was a lot of fun.

Zierler:

But just so I understand the chronology, you did not go out to Illinois with the intention of working with Tony. That sort of happened when you arrived on the scene.

Fisher:

More or less. Initially I was working with David Chandler.

Zierler:

Right.

Fisher:

Then I worked with Michael Wortis, and with Eduardo Fradkin, too, who was just a new assistant professor then. And then I started working with Tony Leggett. But I also collaborated a lot with postdocs and other graduate students, which was really important in my development. I was trying to find my own path, trying to find a professor whose style suited me, because you want to find your own voice in physics. So, working with four different professors, I was exposed to a spectrum of styles.

Zierler:

And in terms of the confluence of interests, what exactly happened that drew you to Tony? What was he working on at that time?

Fisher:

He was interested in small superconducting rings with little weak links that are called Josephson junctions. And he was proposing the following experiment — which is, if you take your small superconducting ring and put on a magnetic field, and tune the magnetic field to a special value — it’s called one half of the flux quantum — then the electrical current doesn’t know whether to circulate clockwise or counter-clockwise. It’s energetically the same circulating either way. And he wanted to ask: can these clockwise and counter-clockwise circulating currents be placed in a quantum superposition, much like the spin of a single particle. And experiments done maybe 10 or 15 years later showed that this was possible! And these currents were something like a microamp. Not truly macroscopic, like Schrödinger’s cat. But it’s not an atom or a molecule that’s behaving quantum mechanically, either. So, I found that really super interesting.

Zierler:

Matthew, culturally, I wonder if it was a breath of fresh air for you to leave the MIT environment, which is known to be so cutthroat and competitive, and come out to Illinois, which I’ve heard so often described as such a supportive and kind place.

Fisher:

Exactly. I mean, you don’t really need to interview me, [laughs] because you know the answers, already —

Zierler:

But I’m saying, that worked for you personally. I mean, some people, they thrive in an environment like MIT.

Fisher:

Exactly. And so when I say, “Harvard doesn’t work for me,” it’s not because Harvard’s bad. It’s just maybe more competitive. Illinois was friendly, supportive. You know, the human endeavor, the human side of physics, is extremely important to me. And having collaborators who I like is critical.

Zierler:

Yeah.

Fisher:

At Illinois, there was just a lot of really great people who were warm and supportive, and that’s true to this day. I mean, different physics departments have different cultures. And Illinois had this great culture.

Zierler:

And how much course work did you have to take at Illinois, or were you coming in enough where you could essentially jump right into the thesis research?

Fisher:

I had to take maybe one year of courses. I’d taken some graduate courses as an undergraduate.

Zierler:

What was Tony’s style as a mentor? In other words, did he essentially hand you a problem to work on that was relevant to his research, or he let you develop that mostly on your own?

Fisher:

He was somewhat hands off. We called it “sink or swim.” At that time he had something like eight graduate students working with him. So, basically the students needed to find some problem that was close to Tony’s interest, and then try to get involved with that. So, a slightly removed advising style — but it suited me then, because there were postdocs I was talking with and other graduate students. But Tony was always available to talk, whenever you wanted. He is a very warm and kind individual. So, I have nothing but good things to say about Tony.

Zierler:

Was there a cultural connection with Tony at all?

Fisher:

A bit. He is from England, and so there was that. And he would have graduate students and postdocs over to his house sometimes, where he proudly offered a bowl with Reese’s peanut butter cups, which is a very American snack. I mean, they don’t have Reese’s peanut butter cups in England. And he was enamored by the small cups, because the surface to volume ratio was higher, so you got more chocolate than peanut butter. We all found that very amusing: this British man eating Reese’s peanut butter cups.

Zierler:

And how receptive was Tony to these ideas that you had about integrating quantum mechanics? Did this work in terms of what he was able to offer — the kind of mentorship that he was able to give you?

Fisher:

Yes, definitely. After all, quantum mechanics is Tony’s thing. I remember there was a time — probably fourth year in graduate school — when Tony suggested one problem he was interested in, and I thought about it for a while. And I realized that even though it was well posed, there wasn’t a clean yes/no answer. The best physics questions for me are those where the answer is either “yes” or “no.” And there’s no “maybe” or something in between. So, the problem he was suggesting wasn’t of that yes/no form, and I tried to sort of talk about that with him. But you know, that didn’t bother him, so I was finding my own voice at that stage already.

Zierler:

And what was the process for you, sort of intellectually, in establishing your niche academically, to develop your thesis research?

Fisher:

Taking inspiration from Tony was crucial, but seeking to find those yes/no questions that most appealed to me was also critical.

Zierler:

How did you know that you were ready to defend? At what point did you feel like you had enough where you can talk about it and introduce it to the scholarly community?

Fisher:

Okay. Well, this is where I’m going to be extremely open about one of the challenges in my life. But it’s been a central part of my life and my career. I was going to defend in June of that year, but I had already lined up a postdoc at IBM in January. So, things were looking good. But then on February 15, 1986, I woke up in the morning, and I felt like I hadn’t slept in a week. I felt like I had jetlag. My brain was in a fog. I felt ill. And I went to the doctors, and they tested this and tested that, and they couldn’t find anything wrong. This mental fog lasted for two years, and I could hardly function. It was hard just to put together a sentence. And I discovered eventually, through medications, that I was suffering from depression. But depression — I had somehow thought of as sort of a sadness, you feel blue. For me, it was like I had pain over my whole body, basically, and my brain just wouldn’t function.

But that was back when there weren’t as many medications for mood disorders. Lithium was around for bipolar disorder, and a relative was on lithium. So I knew about the craziness of mania. But I wasn’t crazy, because I could behave perfectly normally, and I could hide what was going on inside me. So, my thesis defense was through this haze. It was horrible. It was really, really tough. I simply didn’t know what was wrong. I didn’t feel like talk therapy would have helped me. And the first psychiatrist I went to said, “I don’t think I can help you.” The second one said, “Just try this pill. Take this pill - it is a tricyclic antidepressant” And he said, “Wait three weeks and see what happens.” And it blew my mind, it was as if I was reborn.

Zierler:

Matthew, before this fateful morning in February 1986, had you experienced symptoms of depression? Was this a new feeling altogether for you, or was it happening earlier, but you didn’t think much of it, because it wasn’t as severe?

Fisher:

Well, it really was qualitatively different than anything I’d experienced. So, it really did turn on in one day.

Zierler:

Have you ever investigated why? Perhaps the pressures of defending the thesis, or you don’t know?

Fisher:

You know, we always look for external reasons, but it’s likely in the genes, I think. Mental illness runs rampant on my mother’s side of the family.

Zierler:

What did you do for those two years? I mean, you were on this momentum. You were going to defend. You were pursuing postdocs. What did you do, and where did you live during this time?

Fisher:

Well, from February through August of that year, I was still in Illinois. I got married in August, but it was through my fog. It was just getting through one day at a time. I really didn’t know what was going on. We then moved to IBM, where I was a postdoc, and for the first year and a half, I could barely function. I only wrote one or two papers, but it was lucky that people at work really didn’t notice. After the postdoc at IBM, I started interviewing for junior faculty positions, and I remember some of the interviews, where they were asking a question, and I couldn’t understand the question. I simply couldn’t focus on it.

Zierler:

And you were not medicated yet at this point. That came later?

Fisher:

I was not medicated. It was after my postdoc ended and I got hired on by IBM as a member of the technical staff, and it was after that that I started taking the medications. And you know, the medications are mind-blowing. I mean, they saved my life. I took this pill for a week, nothing happened. Two weeks, nothing happened. By the beginning of the third week, a miracle happened, that the metaphorical fog, which had so enshrouded me that I didn’t even realize it was there — it had a bit of a light area, where I could see that maybe there was a sun behind, and I just started metaphorically swimming towards the light. And over the next three or four weeks, I came out of the clouds, and I started seeing the sun. And it was just this one pill. It wasn’t changing who I was, but it was changing how I felt and how I could function, and qualitatively, it’s just a huge difference. And I burst out of that depression into what was a pretty healthy mental state — physical state as well.

And my research just took off, because to really do good scientific research, you have to, in my view, be somewhat optimistic. You have to think: if I try this, there’s at least some chance that it’s going to work. And in the beginning, if you’re saying: I can’t even imagine this working, well then, you’re not going to try, and you’re not going to do anything interesting. But when I came out of my depression - being literally reborn - I was very optimistic and looking forward. And my research just flourished.

Zierler:

Matthew, when you came out of the depression, do you feel like you returned to your old self, or looking back, were you always depressed, and this was actually a new life?

Fisher:

I didn’t return quite to my old self. I was like, 90 percent. So it was almost back to the way I was before.

Zierler:

Here’s an impossible counterintuitive, counterfactual question: do you feel that as a result of going through this challenge, that you had a burst of creativity and optimism that might not have been available to you, looking at all that you would go on to accomplish?

Fisher:

Yes. Coming through that and coming out into the light with the burst of optimism was crucial in my creative life and in the physics that I accomplished in the next four or five years. So, I owe my life to medications, and I certainly owe my physics career to medications. You can’t function — doing theoretical physics unless your brain is working extremely well, because you need to be right on the outer reaches of complex conceptual thinking - impossible for me to do while in this metaphorical fog.

Zierler:

Matthew, I’d like to return for a minute to the opportunities that were available to you when you were considering postdocs. So, my first question is: given that your brother was at Bell Labs, was pursuing a career, or at least a postdoc in an industrial research environment — was that something that was just sort of intrinsically interesting to you?

Fisher:

Yes it was intrinsically attractive, for a number of different reasons. One was that I knew if you have a postdoc at Bell Labs or IBM, if you do fairly well, you get hired on, and you are essentially tenured two years out of your Ph.D. And I wasn’t relishing the thought of, after a postdoc, becoming an assistant professor and struggling with all of the things that you would have to struggle with. And IBM was a godsend. I mean, IBM was to Bell Labs what Illinois was to Harvard. [laughs] It was really top-quality, a lot of exciting things going on, a lot of experiments. And a very supportive environment. I can’t say enough good things about IBM Watson Lab at that stage.

Zierler:

Matthew, at this point, culturally, depression is still very much — in the late 1980s, it’s still very much taboo. Did you make efforts to conceal your illness, or were you open about it?

Fisher:

No, I was concealing it.

Zierler:

And yet, you were still able to write papers and work with collaborators.

Fisher:

Well, during that two-year period, before I got on the meds, the one or two papers I wrote were not inspired, and haven’t got many citations, either!

Zierler:

This does suggest that there was not a sink-or-swim culture at IBM, if you were able to continue on and get by.

Fisher:

Exactly. IBM was very supportive. And I was able to start collaborating, especially with Geoff Grinstein, who became a mentor to me, a postdoctoral mentor, and he was a very, very warm individual, extremely supportive. But I didn’t open up about my depression, partly because I didn’t know it was a depression. I just knew I couldn’t function properly. I mean, what are you going to say? “I can’t function properly”? I mean, tough luck. You know?

Zierler:

Yeah.

Fisher:

But as the years have gone by, I’ve become more and more open. So what happened is when Prozac came out, I switched over to Prozac.

Zierler:

Which was even better for you.

Fisher:

Well, it had less side effects, but it wasn’t quite as good, actually, for the mental acuity. But it was certainly fairly good. And I was on Prozac for about five or six years.

Zierler:

Matthew, let’s go back to IBM, where you made that interesting comparison with Bell Labs. Was your sense culturally, at that time, that basic science was really what the lab was all about, that you were not necessarily —

Fisher:

Yes.

Zierler:

There was no interest in you needing to contribute to IBM’s bottom line.

Fisher:

Well, not to the bottom line. I mean, they liked it if you were working on problems which had something to do with some of the experiments that were going on. But it was basically like a university research environment.

Zierler:

Yeah.

Fisher:

But you didn’t have to write grant proposals. Just do your science. And there were amazing experimentalists at IBM. I mean, there’s 2,000 scientists, mathematicians, physicists, and chemists. But about a year before I left, it started changing. Bell Labs started changing. IBM started changing. And the bottom line started becoming more important. I remember we were asked to brainstorm about new business directions IBM might take. And I was working on the fractional quantum Hall effect. I didn’t want to be at a place where I wasn’t fulfilling expectations. It was soon after that I moved to California, to UC-Santa Barbara.

Zierler:

Matthew, it’s so difficult to disentangle your academic interests at this point from the mental health issues that you were going through. But when you got to IBM, did you see this more as an opportunity to refine and improve upon your interests from your thesis research, or did you want to pursue new avenues of inquiry at this point?

Fisher:

Let me talk about after I was reborn. I then wanted to find new directions. High-temperature superconductors had just been discovered, and I was getting really interested. And I did some work on vortex lines in high-temperature superconductors, and I was thinking about bosons, localization of bosons, and the superconductor-insulator transition. And these were completely new things. And I started working on edge states in the fractional quantum Hall effect. And one-dimensional quantum wires, where there were some experiments going on. I hooked up with a brilliant postdoc, Charlie Kane, who much later was the discoverer of topological insulators. He may well win a Nobel Prize. In fact, my successes then, and any since, have largely, if not completely, been due to the fact that I’ve had junior collaborators who are truly fantastic. And I’ve also had amazing senior collaborators, like Steve Girvin. I don’t know if you’ve heard of him.

Zierler:

Of course.

Fisher:

Steve is a wonderfully warm person, and I was drawn to him. Not to mention he’s a brilliant physicist. Steve was in Indiana at that stage, and I was still at IBM. With Steve, I was not worried about working with a well-established senior collaborator, because I had full confidence that he was going to give me the credit that I deserved. Once, when I had a little physics idea I brought it to Steve. And there’s nothing that a senior person likes better than when a junior person brings them an idea, especially if it is viable. [laughs] We became very close friends.

Zierler:

Yeah. Yeah.

Fisher:

I was blessed to have other amazing senior collaborators, too. I collaborated with Peter Young, who was at Santa Cruz. But then I started collaborating with postdocs who were younger than me, and I realized the most important thing was to encourage them and to help them find their own style. So, when I was at Santa Barbara, we would get these brilliant postdocs coming in who had just finished their Ph.D. And they were imprinted by their thesis advisor, quite naturally. That’s what they’ve seen. So, I would try to get them to spread their wings. I would encourage them, and we would talk physics for six, seven hours a day. I was benefitting tremendously. They were, I think, benefitting tremendously, too. And I will say the thing I’m most proud of in my career is the junior people that I’ve…

Zierler:

Mentored.

Fisher:

…mentored.

Zierler:

Yeah.

Fisher:

Yes. Amazing group.

Zierler:

When you talk about sort of coming out of the shadow and into the light, right — because you came with all of your physics education, it was already there.

Fisher:

Exactly.

Zierler:

Was there any clarity in terms of what was important to you, almost even on a spiritual level in terms of what you wanted to contribute, what you were most curious in, what you thought your legacy would be, long-term — that you might not have otherwise, without having gone through this significant experience?

Fisher:

Well, it was mostly just enjoying being alive, and I wasn’t really thinking about long-term, and I don’t generally plan long-term. But I was thinking about: what can I find that’s exciting, and to follow that.

Zierler:

After those one or two initial papers, what do you see as your most significant work coming out of IBM?

Fisher:

Work on fractional quantum Hall effect edge states, point contacts in the fractional quantum Hall effect — and, quantum wires and electrical transport in quantum wires. I was involved with proposing a vortex glass phase in high-temperature superconductors in a magnetic field, where the vortices are pinned by impurities, and at low temperature they simply can’t move and the material superconducts, whereas at high temperatures, the vortices start moving around and dissipate energy, and it becomes resistive. That’s called a vortex glass transition.

Zierler:

And either by virtue of what you were working on, or the environment in which you were working, was the world of experimentation particularly relevant to any of the research you were doing?

Fisher:

Yes, really, it was. I would say particularly at that stage, and because there were so many interesting experiments going on, and there were so many great experimentalists. In fact, this vortex glass work was directly inspired by experiments that were going on 10 corridors down at IBM. The edge states and the quantum Hall effect were inspired by experiments that people were doing on quantum Hall systems 20 corridors down.

Zierler:

Was your term at IBM undefined? Did you have a specific time where you had to make a decision about whether to stay or leave?

Fisher:

After my two year postdoc I got hired on at IBM as a permanent employee. I was there for 5 more years. It was just a phenomenal environment. But then things changed, and basic research became less important to IBM. It was in the mid-’90s and the bottom line became much more important, and the CEOs started caring only about their stock options. At IBM, they basically came in and said, “We’re going to disband the 200 people in this physics area.” So, it was a conscious choice to really ramp down in a big way. And that was going on at Bell Labs as well, around the same time. I think it’s a real tragic loss for the country that these big companies are not doing basic research on hardware and solid-state physics, on other materials physics.

Ironically, today, the only hardware experiments that are being supported by the big companies are at the software companies, which are supporting quantum computing hardware. [laughs] It’s a good thing that they’re doing that, but it’s certainly changed.

Zierler:

Did you feel, at IBM, that you were well-integrated with the broader academic community? Were you going to the same conferences?

Fisher:

Yes.

Zierler:

Were you co-writing papers with your peers in academic departments?

Fisher:

Yes, definitely, I was very integrated in the academic community.

Zierler:

And to what extent did IBM — there’s so much more that’s known about the changing culture at Bell as a result of the breakup of the monopoly, but there’s a broader story about American corporations just not being as supportive into the 1990s about basic science.

Fisher:

Yup.

Zierler:

Was that part of your reasoning as well, that IBM’s culture was changing?

Fisher:

Yes, that’s why I left.

Zierler:

Yeah.

Fisher:

And then I had a great opportunity out in California as well, but I was looking to leave.

Zierler:

Was that a gradual process at IBM, or was that new leadership, and this is really a sudden change?

Fisher:

It came on pretty quickly, within a year or two.

[BREAK]

Zierler:

So, when you were starting to put feelers out, what opportunities were available to you? What looked attractive to you?

Fisher:

I had an offer from three universities: Indiana University, Berkeley, and UCSB.

Zierler:

Now, was Steve Girvin still at Indiana at this point?

Fisher:

Steve Girvin and Allan MacDonald, who I have also collaborated with. There was a great atmosphere in the Indiana physics department, thanks in no small part to Steve and Allan. And I also had a nice offer from Berkeley. But at Santa Barbara, I got an offer from what was then the Institute for Theoretical Physics, with a reduced teaching load. It has great postdocs, a lot of support, and Santa Barbara is an extremely friendly environment as well. And it’s a great place to live, and it’s nice, and good for the family. Ultimately, it wasn’t that hard a decision to come to Santa Barbara and the Institute for Theoretical Physics.

Zierler:

Now, people like Doug Scalapino — had you worked with him, or you knew him?

Fisher:

I knew him fairly well. But I hadn’t worked with him. Doug has had a big impact on me, by the example that he sets and how he does his work, and the integrity that he shows, and also the warmth and support that he gives to junior people generally. He’s very much been like a father to me. And he’s truly an American gentleman.

Zierler:

And you came on at the associate level?

Fisher:

No, I came on as a full professor. And I was only 33.

Zierler:

Right. That’s pretty young

Fisher:

Yes. Well, you know, if you’re reborn — [laughs]

Zierler:

[laughs] Fair.

Fisher:

The most remarkable thing about Santa Barbara were the postdocs - Leon Balents, Chetan Nayak and Senthil, just to name a few. All of the postdocs have done extremely well. They make me proud.

Zierler:

Where did you see your field headed? What were some of the most exciting things to work on, as you made this transition out to California?

Fisher:

I was still looking for problems where quantum mechanics was absolutely central, and I started working on quantum magnets, so-called Mott insulators. These are materials which don’t conduct electricity, because each of the electrons is stuck on their respective atoms. But the spin of the electrons can fluctuate around. Sometimes the spins all align, and you get what’s called an antiferromagnet. But we knew from playing with toy models that you could also get much more interesting behavior, the so-called quantum spin-liquids. Phil Anderson was really the originator of the idea of a spin liquid, that quantum spins could fluctuate around and be in a liquid even down to zero temperature. So, I was working actively on quantum spin liquids from the late ’90s on.

At that stage, the theroretical work was further removed from experiment, and the Santa Barbara community was kind of viewed as “la la land,” doing such crazy disconnected physics. But things have changed since then, thanks to new materials and experiments. And quantum spin liquids are incredible - a quantum soup of spins fluctuating around which can organize themselves in a way that hosts excitations that behave like particles that carry fractions of an electron - something called fractionalization. And Xiao-Gang Wen at MIT was emphasizing that many of these spin liquids have an underlying topology, some sort of topological order. So, there’s sort of a robustness there. And topological order in spin liquids was also tying in with the fractional quantum Hall effect, where electrons in two-dimensional systems when placed in a magnetic field support quasi-particle excitations which carry one third of the charge of the electron. So, another example of electron fractionalization.

Zierler:

Matthew, in the early years, would you find — just in terms of the most exciting place to be intellectually, in terms of having conversations — would that be more at the ITP or more in the department, for you?

Fisher:

Well, it was really more at the ITP, because of the postdocs and because of the visitors.

Zierler:

Yeah.

Fisher:

And the programs for visitors— if there was a program in one’s field, it’s just an amazing experience. In some ways the ITP was the heart and soul of theoretical physics.

Zierler:

And was the culture of the ITP such that you were encouraged to, at minimum, at least have conversations and get to know people outside your immediate field?

Fisher:

Yes. So, when I first moved to the ITP, it was much smaller.

Zierler:

Right.

Fisher:

Because of that, one tends to look more sideways at other people, doing other things. There were the high-energy theory postdocs that I got to know really well. And I collaborated with Joe Polchinski, who died tragically from brain cancer four years ago. Joe was in a different field completely from me. He was in string theory and high energy theory. So collaborating together was really fantastic.

Zierler:

Matthew, I’m curious. In terms of the mid-1990s, if you look at the overall history of the ITP, from its early days in the 1960s to when it became the KITP and to this enormous institute that it is now — was your sense when you came in that it was still in growth mode, that it was sort of closer to its origins than where it is now, or how would you situate that time in the overall narrative?

Fisher:

Yes, it was probably something like a third the way along its trajectory to what it is now. It started in 1978 and this was ’93. So, it was much smaller, and perhaps was closer in spirit to the founding of the institute. Now it is amazingly strong, with great programs, but it’s a much bigger operation.

Zierler:

At what point did you have the more traditional responsibilities of being a professor? When did you take on your own graduate students? When did you start to teach undergraduate courses?

Fisher:

I started taking on graduate students and teaching graduate classes immediately, but have not taught so many undergraduate courses.

Zierler:

Is that because you simply didn’t like it, or it was difficult for you? It took you away from your research?

Fisher:

Certainly it did. But teaching cuts both ways, also feeding into research as well. And I love working with graduate students, working with postdocs, and that’s a form of teaching as well.

Zierler:

Where was your research on quantum phase transitions at this point? How well developed was it?

Fisher:

It was pretty well developed, since that started for me in the late 1980s, right after I was reborn. The superconductor insulator transition is a very nice example of a quantum phase transition, that has been much further explored by Subir Sachdev who wrote a book on the topic. Since then new types of quantum phase transitions have been explored, quantum phase transitions that have no classical analog. For example, you can get transitions from a quantum spin liquid into an antiferromagnet, and those transitions are very rich with an intricate structure.

Zierler:

Did you keep up your collaborations with Charles Kane?

Fisher:

We kept them up. After I moved out to California, we worked together for about three more years, and then I started pulling away a little bit for his sake. He almost didn’t get tenure at Penn. I had to really go to bat and emphasize that Charlie was the driver behind the work that we did together, he was the genius behind it. I think they’re glad they gave him tenure. [laughs]

Zierler:

Given that your collaboration with Charlie was so fundamental, just as a matter of partnership, what did each of you bring to the partnership?

Fisher:

My strength is probably coming up with ideas, most of which are not well-formulated, and some of them are just plain wrong.

Zierler:

So you’re saying, you brought a sense of adventure to this.

Fisher:

I brought a sense of adventure, and he brought a sense of ability and talent. [laughs] And you know, once he could formulate some vague idea, he could then take it and push it in all sorts of creative directions.

Zierler:

And so, would that include him not being afraid to tell you if one of your ideas was half-baked? [laughs]

Fisher:

Totally. Yes. To collaborate closely with someone in theoretical physics, there’s a certain amount of trust that you need, because you have to be able to say to the person: look, I don’t understand — I’m lost — please help. And if that person says, well, “How could you be so stupid?” that’s the end of the collaboration.

Zierler:

Yeah.

Fisher:

So, you need to trust them and to be patient. And it goes both ways. If you’re two or three people, you have to be patient with one another. So, with my closest collaborators, I have developed tremendous trust, and Charlie is one of those.

Zierler:

So, a question that has more of a thematic basis, because it comes in and out of your academic career so frequently — and that’s superconductivity. What would you say, in terms of the chronology, are the years where you’re most focused on superconductivity?

Fisher:

My interest in superconductivity started in graduate school, and continued through the mid 1990’s. And there was a period from the late 1990s to the early 2000s when I was thinking a lot about possible relevance of spin liquids to superconductivity. In 2000, my collaborator Senthil, designed and proposed a remarkable experiment for the high temperature superconductors. It involved a yes/no question. The experiment was: either you find this effect, or you don’t, and when the experiment was performed it was not found. And so we learned that the idea was wrong, and that’s important. You don’t get famous for a wrong idea, but you move forward, and it’s helpful. But I haven’t really worked on superconductivity that much in the last 10, 15 years.

Zierler:

And it’s a general question that’s probably most relevant to superconductivity, but it would also be a window into your larger perspective on these things. And that’s the extent to which you have any interest at all in the possible industrial or practical applications of the things you’ve been involved in. I mean, there’s varying perspectives on that. Some people either preternaturally, they just say, “I want nothing to do with that,” and some people, even though you’re operating in a world of theory, there’s a certain satisfaction of seeing a connection to the possibility that this could actually solve real-world problems.

Fisher:

I would love for the work I do to be helpful in solving real-world problems, but at best it’s been a trickle down effect. The theory would have some relevance to experiments, and the experiments would be relevant to technology, conceivably, down the road. But I think it was partly wanting to be more impactful on real world problems that got me started thinking about the quantum brain, but that was in 2013.

Zierler:

So, to go back to the decade where you were most intensively involved in superconductivity, what were some of the most exciting developments at that time?

Fisher:

Well, initially, it was the vortex glass phase describing the magnetic field induced vortices fluctuating throughout a high temperature superconductor. Later, it was working on trying to understand the origin behind the high temperature superconductivity itself. But that’s a challenging subject, and I think to this day, we don’t really have a full theoretical framework for the high temperature superconductors.

Zierler:

By the 2000s, what were the most interesting projects for you to work on?

Fisher:

Well, in 2000, it was quantum spin liquids, and also some fractional quantum Hall effect problems.

Zierler:

And what were some exciting developments in the field at this point?

Fisher:

Well, we were finding toy models, which we could analyze enough to convince ourselves that they exhibited a new type of exotic quantum spin liquid — quantum fluctuating liquid behavior that we hoped might be there in physical systems.

Zierler:

And sort of a reflective question: in terms of what Phil Anderson contributed many decades ago, what were some of his insights that allowed for all of this subsequent research to happen?

Fisher:

Well, I mean, they were singular.

Zierler:

Yeah.

Fisher:

In 1973, Phil Anderson proposed a spin liquid in a particular model, a triangular-lattice antiferromagnet, but this was largely unexplored for 15 years. And then when high-temperature superconductors came along in 1987, Phil tried to start framing them in terms of doping a Mott insulator, removing carriers from the Mott insulator, and the Mott insulator was in some sort of quantum spin liquid. So, in some sense, what we were looking at in the late ’90s was the natural progression coming out of Phil’s early ideas on these things. I can’t emphasize enough how important Phil’s contributions were to the field. And he was inspirational, because some of his best work he did when he was my age, which is not so young anymore. [laughs]

Zierler:

And the research in 2D and 3D — is this happening concurrently, or sequentially?

Fisher:

In lower dimensions things are less rigid and quantum fluctuations are more important. For a one-dimensional quantum wire — and these are things I did with Charlie Kane in the early ’90s — if it’s thin enough, the electrons effectively splinter apart, and it’s rather exotic. In two dimensions, things are a little bit more rigid, and the quantum fluctuations are less dramatic typically, but in some instances they can be dramatic enough to have a quantum spin liquid. And in three dimensions, it’s a little harder still to liberate the quantum spins, but quantum spin liquids are still possible, although less common.

Zierler:

Matthew, a very broad question that perhaps connects your initial interest of going all the way back to undergraduate, and that is: when you had this idea from your inspiration in quantum mechanics, that you really wanted to take an out-of-the-box approach in terms of where quantum might take you intellectually, not even in terms of career or academics. Just sort of like, the adventure of seeing where this goes.

Fisher:

Yes.

Zierler:

How clear a line does that initial interest and ambition get you to quantum spin liquids, specifically?

Fisher:

It’s a long trajectory. But there is an unmistakable thread. Indeed, seeking entirely non-classical phenomena in systems with many quantum mechanical degrees of freedom has been a thread that’s gone through my entire career, really, and will surely continue.

Zierler:

And in terms of the advances that made this possible, relatively recently — both from a theoretical and an experimental perspective, what happened that allowed for this research to proceed, that would not have been possible in the ’80s or even earlier ’90s?

Fisher:

That’s a good question. Some of it was the development of fast computers.

Zierler:

Right.

Fisher:

The fact that you could do computations on complicated quantum mechanical models and obtain non-trivial information was coming into its own since 2000 or so. In the last 10 or 15 years, many of my graduate students have been using the computer to explore new phenomena.

Zierler:

Yeah.

Fisher:

Running a computer program as a type of an experiment. You’re given a model, and you run the program, and you see what comes out, and you try to understand it a bit, and then you change the program or the model. Usually you want some idea of what you’re trying to look for, not just shooting in the dark. Not only have the computers gotten so much more powerful, but the algorithms have improved enormously. And in part this has been due to the development of a new field called quantum information theory. Quantum information theory has breathed new life into quantum condensed matter physics, and, to some extent, vice versa. As developed, quantum information theory is theory. There were no experiments.

Zierler:

Right.

Fisher:

However, with quantum computers coming along, we’re starting to get some experiments. And quantum information theory has given us new codes that can be run on quantum computers.

Zierler:

Matthew, it’s impossible not to assume that there’s some deep connection between you coming out of your illness and later on, your interests in this idea of a quantum mind and the human brain, right?

Fisher:

Yes.

Zierler:

Why, though — there seems to be this lag. This is obviously not something that you take up right away. Is part of it that there needs to be more intellectual maturity on your part? Is some of it careerist, where this is sort of way out there kind of thinking, where you need to better establish yourself academically before you pursue this? How do we connect the dots in this regard?

Fisher:

It’s both. I wasn’t intellectually mature enough to even start going there. If I had been, I probably would have tried. But if it wasn’t for a successful career up to 2014 and ’15, working on the quantum brain could have been problematic. I mean, this is far and away the boldest exploration that I’ve been on. And I vacillate between thinking it’s fallacious - a fallacy that we don’t have any quantum mechanics going on in the brain, to thinking — it seems like we just might. I have hoped that we can do enough experiments to try to at least answer the question - do we have quantum mechanics going on in the brain, or not? The last three or four years we have some experiments going, but experiments are hard, and they go slowly. But you know, some of my colleagues, like T. Senthil, who is a dear friend was worried about me — he’d thought I’d lost it. So, he didn’t actually want to talk with me about the quantum brain, because he didn’t want to have to tell me I was full of shit, basically. [laughs]

Zierler:

Yeah. [laughs]

Fisher:

But, I’ve talked with him enough about it, and while he is very skeptical, he does acknowledge that it’s worth exploring conceptually and experimentally, that there are experiments to be done.

Zierler:

And as a sort of chicken-and-the-egg kind of question: did you develop, sort of organically, a broad interest in neuroscience, and then you landed on quantum information processing? Or, were you already thinking about quantum information processing, and this got you to start thinking about the brain in a sustained way?

Fisher:

I was starting to think about quantum fluctuations in water, and the role of solvated ions such as sodium, or potassium, or lithium. And I knew lithium, despite its simplicity, is very effective at treating bipolar disorder. I mean, lithium is not a molecule. It’s not like Prozac, which is a molecule with 20 atoms. In fact the lithium ion is a billiard ball, perfectly spherical, with a charge 1 at the center, and that’s it. And someone with mania or bipolar disorder, you give them lithium, two or three weeks later, it tempers it out. I’ve taken lithium on and off, partly to explore whether it works for me or how it feels. And then I discovered this experiment performed in 1986 on rats, where they were feeding different lithium isotopes, the two lithium isotopes, to rats, and they were observing very different behavior, which is still a very mind-blowing experiment, and it may not have been right. But I basically started trying to learn as much as I could about lithium, as much as I could about neuroscience. I tried to learn some biology.

You know, I’m not a biologist, but I was learning what I needed, I felt. And it was lonely. Intellectually, it was lonely, because I didn’t want to work on these problems with any junior people, like postdocs or students, because I thought that would be maybe the kiss of death. And I had no idea whether it was going anywhere. Even now, I’m not sure. But I didn’t want to drag down any junior people. So, as I joke, my collaborators were Wikipedia and Google. [laughs] The world’s knowledge is at your fingertips, of course.

Zierler:

But I’m thinking in terms of potential collaborators. I mean, you could be working with anybody, ranging from neuroscientists to computer engineers.

Fisher:

Yes. We’re now working with biochemists and enzymologists and biologists who explore mitochondria. With soft condensed matter physicists, chemical engineers, who are looking at small calcium phosphate molecules. We’re also working with people doing nuclear magnetic resonance, because we’re trying to measure the nuclear spin of the phosphorus atom, the putative holder of the quantum information. And now, on the theoretical side, we’ve started playing around a little bit with toy models. There’s a very talented grad student that now has been working with me for three years, and I got him interested in these toy models, because I thought they were maybe interesting in and of themselves — toy models for quantum processing. Conceivably quantum processing with so-called Posner molecules in the mitochondria, but we don’t know. And in thinking about that, we stumbled into a rather nice class of problems which physicists and quantum computing people find interesting. So, I’m quite excited about that, actually, as well.

Zierler:

Matthew, it’s a relatively new field for you, but in this short time that you’ve been involved with it, relatively speaking: what are some of the dead ends that you’ve come upon rather quickly? And what are some of the avenues of pursuit that you didn’t even consider at the beginning that were only possible because of what you’ve done so far?

Fisher:

We came across one dead end. In our story of the quantum brain, the quantum information is stored in nuclear spins. In order for the quantum mechanics to influence biochemical reactions or the biochemistry, you need to find a mechanism for chemical reaction rates to depend on the nuclear spin states. The quantum mechanics has to somehow influence the chemical reaction rates. I’ve conjectured a way that this might manifest itself, involving small symmetric molecules. Our experiments revealed that molecules with only two-fold symmetry do not affect chemical reaction rates. But the jury is still out for three-fold symmetric molecules.

Zierler:

And that’s because there is such a thing as quantum biology. I mean, there’s concepts that make quantum biology a little more well developed.

Fisher:

Yes, but it’s very disparate. Quantum biology consists of three or four very surprising phenomena where people have argued — and it’s probably true — that some quantum mechanics is playing a role. In olfaction, maybe, in magneto-navigation for birds, in photosynthesis. But quantum biology is not yet any sort of coherent field.

One of the things that made it hard for me to get into this quantum brain project was Roger Penrose’s book, The Emperor’s New Mind, arguing that for conscious awareness you need quantum mechanics to be operational. But the necessary biology was not developed in a convincing way, at least to me. In fact virtually every physicist that’s looked at Roger Penrose’s book says: oh, he’s — kind of crazy. And so now I’m trying to do the crazy. [laughs]

Zierler:

But unfortunately, probably, that reaction has set the field back, where perhaps more people might have been involved.

Fisher:

It’s possible. Certainly, it made it a little bit harder for me to get traction. But the thing about creativity is you have to initially not care what other people think about what you’re doing, because if you’re taking judgment from other people— “Oh, Matthew, I don’t think that’s right” — well then, you can’t be creative.

Zierler:

To what extent do we need true quantum computing in order to have any of these ideas bear out experimentally?

Fisher:

This is not really a joke, but one of the criticisms I’ve had is that: Matthew, I don’t think biology and evolution is smart enough to develop a quantum brain. So you can ask generally: has evolution been smart enough to evolve a quantum computer? Life evolved two to three billion years ago, through organisms in the ocean, then the invertebrates, the vertebrates, the mammals, and, finally humans, Google engineers — they’re now building the quantum computer. Evolution continues. Our scientific endeavors have become part of evolution. And if we’re successful at building a quantum computer, we would have seen that evolution did indeed find a path to evolve a quantum computer. So in some sense, if we can build a quantum computer, that’s like a proof of principle. [laughs]

But the quantum computers would be very different than what I believe might be going on in the brain. Laboratory quantum computers are very controlled. The experimentalist is making measurements. They tune this knob, they turn that knob, and they couple these together, and they’re controlling it, but not touching it too much. Yet, if there’s quantum processing going on inside mitochondria, as we have proposed, there’s a lot of stochasticity. There’s a lot of noise. So, one has to somehow have quantum mechanics being relevant in a wet, squishy environment, and that’s really quite different than what one has in a quantum computer.

Zierler:

Perhaps to logically play this out, in terms of the criticism that perhaps this is a zany idea, right — could you turn back and say: well, if it’s not quantum processing, what else might be happening in the brain? In other words, is there a more logical explanation that we have to say: this makes a lot more sense than what you’re proposing?

Fisher:

We don’t understand what consciousness is. I think we can all agree that we ourselves have it when we’re awake — not too depressed, or alert enough. [laughs] Consciously functioning. But what is it? I mean, the neuroscientists have no clue. How do anesthetics work? An anesthesiologist turns consciousness off and on. This is mind blowing to me. We don’t know what’s controlling it. But one thing that does control it is drugs. Some drugs modulate the tenor of the conscious state, as does lithium. And so one would like to understand how lithium works. Even if it’s not quantum, what is it doing? And we have no idea. I believe that consciousness while magical is not mystical. It’s something that should, in principle, be understandable within the scientific method.

Zierler:

Meaning, Matthew, that this research is not leading you any closer to any metaphysical ideas about there being a soul that we might not ever be able to understand?

Fisher:

No. I think when we die, that’s it. This might seem like a bit of chutzpah, since we don’t understand conscious awareness, but still I am a skeptic.

Zierler:

What I’m really asking is, this line of inquiry — certainly you weren’t there before, but this line of inquiry has not made you any more amenable to the notion that these things are actually real?

Fisher:

Oh, you mean like the soul, and things like that?

Zierler:

Correct. Right.

Fisher:

Not at all. Our exploration of whether quantum mechanics is operational in the brain is a scientific endeavor. When people ask me, but what are the chances that it is? I think, maybe one in a hundred? One in a thousand? It’s a one-off event, but my answer depends on my mood a lot. [laughs] When I’m in an optimistic mood, I think maybe it’s one in 10. Right?

Zierler:

[laughs] Right.

Fisher:

But when my mood is a little more dour, I’m thinking it’s all nonsense. But if we could rule out quantum mechanics in the brain, that would be pretty important. Because I think we’re following the only real path that evolution could have found to evolve quantum processing in the brain. And did evolution follow that path? Probably not. If we can really show that it couldn’t, because the biochemical ingredients are not there to function properly — then I would be prepared to say that we’re just robots. We’re classical robots, it’s a bit sobering. But we’re still amazing, I guess — the brain.

Zierler:

This is to say that if we do not have true quantum processing, in the way that a machine or a robot does not have free will, we don’t have free will, either. Is that the idea?

Fisher:

Exactly. If we don’t have quantum processing, we are no different than our silicon computers, although our architecture is of course very different. I can ask you - do you think at some point, maybe 10, 20, 30, 40 years down the road — our classical computers will be so complex that they will wake up, and become consciously aware?

Zierler:

I mean, not only that, but we don’t even have to think at that point of classical computers as necessarily being separate from our own physical reality. There might be a level of integration that further muddies the distinctions.

Fisher:

Perhaps. Imagine that Google, maybe 30 years from now, can build a multipurpose quantum computer, and you take one of these self-driving cars with their video cameras and silicon computers on board, and you put this big quantum computer on the top of the car. And the quantum computer decides where it’s going to drive. [laughs]

Zierler:

[laughs] Make things easier in one sense. There’s no doubt about that.

Fisher:

Yes.

Zierler:

Matthew, what have been some of the most promising experimental tests that you can run that might tell us one way or another whether these ideas have legs to them?

Fisher:

There’s a number of necessary, but surely not sufficient, experiments that need to be performed. And so far, the ones that are absolutely necessary, came out OK. But there’s a particular enzymology experiment, exploring, in effect, whether nuclear spins can modulate chemical reaction rates. If not, that would be pretty bad for the whole enterprise. The early round of experiments showed an intriguing effect, but it needs to be done much, much more carefully.

Zierler:

Matthew, I certainly wouldn’t want to ask you to compare yourself to Niels Bohr, but I can’t help but think about the debates that he had with Albert Einstein, and to look at some of the people who are sort of naysayers of your ideas, and if you ever sort of draw any sustenance from Niels Bohr, in terms of his sense of adventure and understanding about how the universe might be operating in ways that are very hard to believe, essentially?

Fisher:

Maybe. But with the discovery of quantum mechanics it was in our face, experimentally.

Zierler:

But that took a process to demonstrate that we might be in the middle of now, with regard to what you’re doing.

Fisher:

Schrödinger wrote this book, What Is Life? which was before the discovery of DNA, and he talked about aperiodic crystals as maybe containing the genetic information. So there’s lots of brilliant scientists to take inspiration from, and from the quantum physicists that developed the subject initially. They were surely pretty open-minded.

Zierler:

[laughs] Matthew, for the last part of our talk, I’d like to ask sort of a few broadly retrospective questions, and then we’ll look to the future, in terms of where your interests are headed. My first question is, to what extent — I mean, the timing works out, but intellectually, when you received the Buckley Award, was that — did the timing work out so that you felt like the contributions you had to make in the more traditional setting of condensed matter — was that a sort of bookend, intellectually and academically, that might have allowed you to branch out into these different areas of physics?

Fisher:

I may not have thought about it in that way at the time, but I think there’s some truth to that. It’s pretty gratifying to be honored by one’s colleagues for work that one has been lucky enough to do. And maybe the prize did serve as a bookend for my quantum condensed matter physics career.

Zierler:

Yeah. And so, on that note, what are some of the points of connection, or the narrative through-lines, that you brought from your previous work into this, and where is this for you, intellectually as a scholar, sort of brand-new territory and has really nothing to do with what you came into it with?

Fisher:

Well, studying quantum mechanics for some 40 years was necessary, even to get off the ground. And the maturity that one develops over the years was necessary as well.

Zierler:

Yeah.

Fisher:

…I brought in an understanding of the richness of quantum mechanics, and that we don’t understand it fully — really, an appreciation of that. And that harks back to Tony Leggett, my thesis advisor.

Zierler:

And in terms of the new things, the things where it really — your knowledge of quantum mechanics only gets you so far — what was the sort of blank-slate kind of stuff that you really had to learn as a beginner, or think about as a novice to the field?

Fisher:

I had to learn basic biology. I barely remembered ATP from high school biology. And I had the big biology books, and would be reading through them, and neuroscience books. There was certainly a lot new to learn.

Zierler:

And to come back to the question of your interest or not in basic science versus real-life applications…

Fisher:

Okay.

Zierler:

…I mean, I don’t have to tell you, it’s extraordinarily exciting to think about any number of treatments, or understanding of the mind, that might come as a result of that. I understand these things are very far afield, but to allow your imagination to run wild, how might lives improve long-term as a result of the things you’re doing now?

Fisher:

Well, if quantum mechanics is operational in the brain, and we can really get our hands on it, then it’s at least plausible that it’s got something to do with the conscious state. I think one might hope, or dream, that there might be new drugs, new treatments, for mood disorders. And that’s a passion. There have been very few new drugs for depression — in fact, hardly any — in the past 10 or 15 years. So, this quantum brain research would then be the closest way that I could make a difference in people’s lives, in the best-case scenario.

Zierler:

Matthew, looking forward, for my last question: because there is such a sense of adventure into the unknown, with this work that you’re doing now, and because there is the potential for such fundamental advance and discovery in any number of paths of inquiry — how will you know, if and when, you hit upon something? What are the feedback mechanisms that over the course of your life in science, you have the intellectual maturity, you have the know-how, you have the perspective, to realize, “I’m onto something here. This is something real”?

Fisher:

Well, I think it’s going to be results of experiments. The Posner molecule, this small calcium phosphate nanocluster, must be inside mitochondria. The experiments that we’ve done so far suggest that the Posner molecule is in the test tube. And there are other experiments. What worries me a bit is that after three more years of experiments, we still won’t know whether quantum mechanics is operational in the brain. The experiments are hard. The results will be ambiguous. And that would be, in some sense, the worst-case scenario, but it may be the scenario that we’re dealing with. The best-case scenario is that we find really promising results. So, I don’t know what my future holds, three years from now.

Zierler:

Are there open loops, I should say, from your previous research that you might want to return to at some point?

Fisher:

Well, what I’ve been trying to do is learn some quantum information theory. And with Covid, I have sat down to read some of the books. But it’s a challenging field for me. It’s hard to get a physical picture for quantum information sciences. So, looking forward, as far as my theoretical thinking quantum information sciences and their implications for small quantum computers is something that I find fascinating, and that I will try to contribute to if I can.

Zierler:

Well, it’s certainly something to stay tuned for. It’s quite exciting.

Fisher:

Indeed. So, tell me a bit about yourself.

Zierler:

Okay. Well, first let me say, I’m going to cut the recording there, but I’d like to say on record first, I’m so happy that we were able to do this, and it’s been quite extraordinary hearing your story and how the personal aspect really does inform the science. So, it’s a tremendously important lesson, and it’s one that infuses all of the work that I do, so I’m just so happy we were able to do this. So, thank you so much.

Fisher:

Well, thank you. I appreciate that. It’s kind of you.