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Interview of Ana Maria Rey by David Zierler on April 6, 2021,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
For multiple citations, "AIP" is the preferred abbreviation for the location.
Interview with Ana Maria Rey, Professor Adjoint at the University of Colorado at Boulder, and a fellow at NIST and JILA. Rey describes the nature of this tri-appointment, and she discusses some of the difficulties in keeping up her research during the pandemic. She recounts her childhood in Colombia and her early education in an all-girls school and her undergraduate education at the University of Los Andes in physics and the opportunities leading to her acceptance to the University of Maryland for graduate school. Rey describes joining Charles Clark’s group that was focused on modeling ultra-cold atoms, and she explains her initial work at NIST. She explains her decision to take an initial postdoctoral position at NIST before joining ITAMP at Harvard, where she focused on developing improved models to study the behavior of atoms trapped in crystals of light. Rey describes the opportunities that led to her appointments in Colorado, and her subsequent interests in metrology, the quantum advantage, and trapping molecules. She explains how it felt to be named a MacArthur Fellow and why it is important for her to interact with experimentalists in the quest to build better atomic clocks. Rey explains her efforts to create dark matter detectors and how she hopes that her work on quantum matter will help bring about quantum computers. She provides her perspective on how to advance diversity and inclusivity in the field, and she delineates her research interests as they pertain to basic science and applications. At the end of the interview, Rey conveys optimism that her research will make advances to the broader understanding of the quantum world.
This is David Zierler, oral historian for the American Institute of Physics. It is April 6, 2021. I am so happy to be here with Professor Ana Maria Rey. Ana Maria, it’s great to see you. Thank you so much for joining me.
Oh, good morning, David. It’s a pleasure for me to join you today.
Okay. So, to start, would you please tell me your titles and institutional affiliations? And I put an “s” on both, because I know you have more than one.
Yes. Well, great. So, I am a Professor Adjoint at the University of Colorado at Boulder and belong to the Physics department. And I am a NIST employee: National Institute of Standards and Technology. I am actually a NIST fellow, and I’m also a JILA Fellow. JILA is a joint Institute between the University of Colorado (CU) and NIST. It used to be called Joint Institute of Laboratory Astrophysics. Not anymore. I mean, JILA now is just JILA. So, JILA is an institution that has people from the university and people from NIST. JILA has an important atomic, molecular, and optical physics program. So yes, I’m part of it.
There’s so much more to further understand with your affiliations. So, the first question there is: are you primarily a federal employee, and the University of Colorado contributes to one salary, or do you get separate salaries?
No. My full salary comes from NIST. I am a government employee. But we have the advantage that we have our offices inside the CU campus, not the NIST campus. So really, we belong to what is called the quantum physics division which is located at JILA. And it’s great to have the opportunity to be a government employee but actually have our offices in the CU campus, because there are less restrictions that we have to satisfy. For example, we can use Skype. We can use Dropbox. These are all the federal regulations that are very restrictive for people that work in the actual NIST campus. The other great advantage of being in the CU campus, is that it allows us to have interactions with the physics students and have the possibility to also be connected to the faculty in the physics department. In fact, I have an adjoint professor position at the university. Because of that I have to teach classes in the physics department. I don’t receive any salary from CU, but I have the opportunity to have students, train them, and also to apply for grants through the university. These would not be possible if we were only NIST employees.
And your affiliation in the department—as an associate professor—so, let’s say—
No, no, no. I’m an adjoint professor.
An adjoint professor. So, let’s say you move to a new institution. Let’s say you move to Berkeley or something like that. Does a new position open up in the physics department that didn’t already exist?
No, nothing directly coming from the University. But NIST could hire someone else.
I mean, the university is not giving me any salary.
I see. I see.
It would be an open position at NIST that could allow the person to actually have connections with the Physics department.
Now, when you came out to Boulder, did you have this adjoint appointment from the beginning?
No. Well, my position is a NIST position. JILA people have, as I said, components from NIST and the university. So, the position that I was hired in was a NIST position. But actually, to become a NIST employee, you have to be a US citizen, but I was not. So, what I did is that I came mostly with a university research professorship, but I was always paid by NIST. In other worlds my official position initially, in order to back up my government position, was through the university. Initially, the requirement to receive my actual NIST position was to hold a green card. This rule changed, and then it happened that in order to get my official NIST position, I actually needed to be a US citizen, so it took a little bit longer. Basically, since I arrived to the university around 2009 until 2017. In 2017 I became aa US citizen and almost immediately after that a NIST fellow.
Where do you interact with graduate students? In the department, or at NIST?
In the department. Yeah. I’m never at the NIST campus. My office is at the CU campus. We are in a building that is the JILA building. It has now two towers, or one big tower and one a small tower. And yes, my office is between them. The offices of my students and other members of JILA, and the JILA fellows working on AMO theory are all close by.
Ana Maria, a question we’re all dealing with right now, particularly for you, who is so reliant on laboratory work and analysis: how has the past year and the pandemic gone for you?
Yeah. Well, I have the advantage that I’m a theorist. So, I don’t have a lab. And my group needs just computers, paper, and pencil. And so, it has been challenging in the sense that interactions with my students over Zoom sometimes is exhausting. You are sitting from 8 a.m. to 5 p.m. through meetings all day. But we are, perhaps, among the people that have been less affected, because we don’t need to be physically in our office. In principle I can do my work at my office or at home, as long as I have the possibility to chat with my students. So, we have met over Zoom for more than a year. My students are desperate though. They really want to have interactions, because the way that productivity happens, and the way that ideas come, is mainly by informal discussions, that they don’t necessarily happen at home — they happen very naturally if all of them are in the same office, asking questions between themselves, not necessarily at their own homes, separately sitting at a desk. But that’s okay. I mean, I think more challenging has been the fact that kids have been home, and then being a mother and a teacher has not been easy — well, now it is better given that, since last week, my son is going to school four days per week. But before, it was very challenging to deal with school and work.
And what does the scene look like in Boulder? Is the plan for mostly back in person by September?
Yes. The university is committed to do almost everything in person in the fall. I think most of the people at JILA will also go back to their office after they’re fully vaccinated. So, I expect that the majority of the JILA fellows will be back by May. Schools hopefully will be in person all five days so I think it will be less challenging.
Ana Maria, as a theorist, as a scientist, what are you most looking forward to getting back to after the pandemic?
Well, I mean, just interactions with my group, with other faculty, really. Holding group meetings in person makes a big difference. Yeah, so basically going back and interacting with colleagues, have meetings that are not in a Zoom box. I think humans are social creatures. We need eye contact. We need socialization and that part is missing now. My group collaborates very closely with experimentalists, and although we keep having group meetings with them, it's also very different. Before we used to have a group of 50 sitting in the same room, brainstorming ideas. Basically, social interactions are key for research, so we need them back.
Ana Maria, on a personal level, Latin America has been hit very hard by the coronavirus. How has Colombia done, and how has your family and friends back in Colombia—how have they fared over this past year?
Yeah. I mean, because underdeveloped countries don’t have enough resources for people to not work, I mean, even though the government, many times, is trying to do the best that it can to prevent the spreading of the virus by lock downs that forbid people go outside it has not worked out well. People need to work, and so for many people the situation has been very bad. I mean, the intensive care units have been full for months. The pandemic in Colombia has been something like a rollercoaster, going up, down, up, down. The first wave was so bad that the country closed all airports. I mean, I could not visit my parents I didn’t want to fly, but even if I wanted to, I could not because international flights could not go into Colombia. During this year the level of poverty, unemployment, has grown significantly. But the country is doing its best given the situation. I mean, the government has tried to prevent the spreading of the virus as much as it can. There has been really formal lockouts, very strict, so my parents have been in their apartment without the possibility to go out. It’s different here in Boulder, that even though there was a lockdown, you could go and walk for one hour with a mask. Even walking out was not okay in Colombia. During Christmastime, the situation was really complicated. It improved, and now they’re in their third wave. But since three months ago the government is trying very carefully to provide vaccinations to all their people. So, my parents, for example, they just got vaccinated. They got the Chinese vaccine. That’s what the country could afford. Let’s see how the situation evolves. Economically, Covid has hit Colombia very hard, unfortunately. And we will see what happens and how much time it takes the country to recover.
Well, let’s talk about happier times. Let’s go back to the beginning of your life. And first, let’s start with your parents. Tell me about them and where they’re from.
Yeah. Well, they’re both from Colombia, and my father was born in a very small town in Colombia. It’s called El Guamo. And my mother was born in Bogotá. My mom, she’s an economist, and my dad, he’s a lawyer. So, they had the privilege to both have a college degree. For my dad the schools that he could attend in El Guamo were not very good quality, so he moved to Bogotá, at a very early stage of his life and joined El Seminario, an institution that was controlled by the Catholic Church, where in principle, they train priests. So, since he was 7 years old, he was sent to Bogotá to this place. And he learned Latin there, and he prepared for college. He loved math but his parents convinced him that he had to do something that gave him a good salary to support his family. So, he became a lawyer. My mom, she liked math, and she pursued an degree in economics, and they both met at the university. And yeah, I mean, they have been very successful in the sense that they have worked very hard. My mom worked most of the time at universities. I mean, she was in the economics, or in the business administration departments at different universities. My dad was instead a lawyer, but he landed in a lottery that actually was supported by the Ministry of Health because the people in Colombia like to bet a lot, so lotteries make a lot of money. Because of that lotteries help support the health system in Colombia. My dad was the manager of a lottery, and he worked there most of his working life. And then he retired. Yes, they were very good role models of life. I have two more siblings, and we are a very solid family. In Colombia, the concept of a family is very important, so yes, I think my family roots have been fundamental to what I am now.
Ana Maria, where did you grow up? What neighborhood?
I grew up in Bogotá, in a small neighborhood in the north part of the city. It is a good neighborhood. My home was a penthouse. In Colombia, unfortunately, there exists a very strong differentiation of classes. I belonged to the middle upper class in Colombia.
Was the church a big part of your upbringing, of your family’s heritage?
Well, a little bit, yes. I mean, in the sense that my school was a Catholic school. As I mentioned, my father was educated by the church but, he stopped to believe in Catholicism very early. My mom is more religious. They sent all the kids to Catholic schools. So yes, I grew up in a Catholic environment. But I did not necessarily believe in god. And well, just after I finished the school, I went to the university, where we were not enforced to actually go to Mass or keep our Catholic traditions.
Your school was an all-girls’ school, or was it co-ed?
All-girls’ school. A very old-fashioned, conservative, all-girls’ school. Yes. We had uniforms, and yes, very traditional, very conservative.
Ana Maria, when did you start to get interested in science?
Very early, I think. My dad said that when I was 3 or 4 years old, I was thinking that I wanted to become a nuclear physicist. I don’t know. I don’t remember that. But he was telling me that he knew I was going to do something related to science. And since very early in my career, I liked the idea of using math to describe how the world behaves. So, in fifth grade in school, I loved math, and then in seventh grade, I had a fantastic teacher that introduced me to physics. He gave me extra books to read. He knew that I’d enjoy them since in Colombia at that time it was not that easy to get textbooks that were in English. I mean, they were very expensive, so he gave me some extra books that he had. In Colombia, there is only 11 years of school. I was in 11th grade when I needed to decide what to do. Well, physics was definitely what I wanted to do. But to my parents, it was a concern. For them I could not do physics because in Colombia, physics is something that is not well paid. So, if I wanted to become someone and to raise a family, I needed to have a profession that could give me the salary to do it. They were very strongly opposed for me to become a physicist.
Ana Maria, of course, you didn’t have anything to compare it to, but I wonder as a young girl, as a young woman, interested in science, if there was any advantage to go to an all-girls’ school.
Well, I can say that my school was fantastic, in the sense that it put a lot of emphasis in science and math. The principal of the school was a woman who was among the first ones to obtain a college degree in biology in Colombia. She was aware of the importance of math and science. For example, she sacrificed arts and physics education classes for math or science lectures. For her science and math were the priority. I’m very grateful since she promoted my interest in science. In one particular class she taught us—she had all the girls in the class, we were like 30 girls per classroom sitting on the stairs—and then she started asking us about math problems we needed to solve fast. She wanted us to be very quick through solving problems and things. That class, called test, started since we were in kindergarten. So no, definitely for me, school nurtured me and facilitated my interest in science and math.
And as you say, if your parents were concerned about job prospects, just that your father got that same advice from his parents, and he ended up as a lawyer. I wonder, on the social and political side of things, to the extent that Colombia is a conservative society, were you ever made to feel—in school, outside of school, in your family—that science was not an appropriate profession for a girl, a young woman, to pursue?
Yes. My parents were really concerned about my future. Unfortunately, education can be very expensive in Colombia since good universities are private so, you have to pay. There are only a few public universities. When I was planning to apply to college, they said: “Since we are responsible for your future we cannot afford to pay a degree in physics for you. If we do that, we are going to waste our money, and you’re not going to be successful. If you go to college and like science and math you have to pursue an engineering degree. We will not pay for a physics degree.” I didn’t have any other choice so when I applied to college, I applied to the engineering program. But in Colombia, like here, we have an exam that we take when we go to high school, and this exam is very important for being accepted in college. And I got a very, very high score in that exam. So after I applied to the electrical engineering program, and they accepted me. Nevertheless, I got a call from the college of art and science saying that actually, they had a fellowship for students that obtained top scores in that exam. This fellowship would allow me to study physics for free. So, as soon as I heard from them I switched my application, and I started in physics degree. My parents were not very happy, but they changed their mind. After I finished my degree in physics, I wanted to pursue a PhD program. In Colombia, it was not possible, so I had to go abroad. And well, I did. When that happened my parents realized that it was possible to do a successful career outside Colombia which was not part of their options initially. And actually, when my sister was thinking about what career she wanted to pursue my mother herself brought my sister to the physics department at the university. So, they did change their minds, and that’s good. When I started my physics degree, there were, at the most, eight people in my class. I think this number has increased significantly in the recent years. Interestingly, when I was there, the number of female and male in physics were very similar kind of 50/50, or 40/60 at the most. Unfortunately, I believe the number of women has decreased. I don’t know why.
Ana Maria, what was your favorite kind of physics as an undergraduate?
Well, for me, interestingly, the more challenging a subject initially is for me, then I start to like it more. When I started my college degree, I had a fantastic teacher in thermodynamics and in statistical mechanics. She was very strict, and she had a very nice way to teach. She wanted us to gain intuition. But it happens that when I took my first exam with her, I got a very poor grade. So, after that I started to prepare myself more and understand what she was trying to teach us. Thanks to her I learned very well statistical mechanics and, quantum mechanics. In fact, quantum mechanics, for me, has been always a fascination. It is the part of physics I enjoy the most.
Did you know that you wanted to pursue theory for graduate school, even as an undergraduate?
Well, in Colombia, the point is, experiments are really limited. So, the majority of the people are trained as a theorist. I mean, the experiments that we had there at that time were very, very rustic. For testing the doppler effect, we have to bring our own radio. Tight it to a rope and start moving it around making circles in the air. We had to determine the change in frequency. Given the way I was trained I wanted to be a theorist. And it doesn’t mean that most of my classmates ended up doing theory. There were a few that ended up doing experiments. Others that had also a bit more connection with engineering, they also ended up doing experimental physics. But the majority of my classmates, of course, became theorists as myself.
Ana Maria, as you got the advice to travel abroad for graduate school, did you ever consider programs in Argentina or Brazil?
No. My parents could not afford paying for me a PhD degree abroad. That is OK because in the US for pursuing a PhD you do not need to pay it yourself. You just apply for an RA or a TA. Even Europe was complicated, so I think the default was trying to apply for a university in the US where, really, you do not need to worry about funding. Also, the US has been always at the frontier in quantum science. Argentina and Chile are in a bit in better conditions than Colombia for sure, but never at the level of the US. So, if there was a place that really you knew that you could be successful, it was the US.
And what advice did you get in the US? How did you know what schools to apply to, what professors to work for?
Yes. We had a classmate who applied the year before to US universities, and he got admitted at the University of Maryland. He liked it a lot. So, the University of Maryland was the place where we knew there was the possibility to be accepted. Of course, you can imagine the universities in Colombia are not necessarily very well recognized in the US. So, I applied to the University of Maryland at College Park. The applications were expensive, so you could not afford to apply to many places. I was told that maybe I could have a chance at Cornell—my parents had a friend who did his PhD there, so I applied to Cornell too. The University of Texas was at the same level than University of Maryland, College Park, so I did apply to University of Texas, too. And well, I was accepted by these two—by University of Maryland and University of Texas. I decided to go to Maryland because my husband at that time was accepted there too and because I got a fellowship from the University of Maryland. I got married the day before going to the US. My parents are very conservative, so I had to be married if I wanted to go abroad with someone.
Ana Maria, how was your English by the time you arrived in College Park?
Well, I have always had a very strong accent. My school was not bilingual. We did learn English a little bit, but our classes were always in Spanish. We learned the verbs and the conjugation and all of that, but after finishing high school, my level of English was not that good. During my college degree, our textbooks were in English, so I could practice while I studied physics. But my pronunciation was not the best. So, my parents sent me for two months to Canada, to Vancouver, very close to Seattle. I lived with a family there for two months before applying to the different universities in the US. The plan was to prepare myself and lean English at the level required for a PhD program. I know people could understand me. I could understand them. But of course, my accent was and has been very strong. The two months in Canada were actually very useful.
[laugh] Relative to your other students, Ana Maria, when you started taking classes, how well prepared did you feel coming from Bogotá, relative to your American classmates?
Extremely well trained. The University of Los Andes, where I did my college degree had a very high level. So actually, the textbooks that we used during my undergraduate program were the textbooks that universities here use for the graduate program. So basically, I had done the majority of the problems that were assigned here. So, I just had to go to my prior notes and look at what I had done before in Los Andes. I had solved the majority of the problems so, it was easy. That’s good, because of course, you are trying to adapt to a new place, new friends. The fact that I didn’t need to worry too much about my courses, because I already knew most of the concepts, was good.
What was the intellectual process for you, in terms of determining a topic for your thesis research? In other words, did you have specific ideas on what you wanted to work on, and you found graduate advisors to help you with that? Or, did you develop the relationship with your graduate advisors and developed with them what would become your thesis research?
Yes. So, what I did in Colombia for my thesis as an undergraduate student was on general relativity. I studied the propagation of light close to a black hole. I liked this idea a lot and enjoyed learning general relativity. But my advisor in Colombia, a very practical person said to me: “I authorize you to work on general relativity as an undergrad because it’s great to learn. But if you go abroad and do pursue a PhD program, you have to switch onto a field that is more practical, where there are experiments, instead of abstract math. It has to be on a direction where you have the capability to collaborate with an experiment, and model it.” When I applied to the University of Maryland at College Park, I wanted to apply what I learned about curved spaces and nontrivial geometries, to something more useful. So, I just wrote in my application that I wanted to do nonlinear optics. A professor at Maryland doing plasma physics got interested in my profile and offered me an RA position. This was not very common. And of course, that was going to be not easy because I had never worked in plasma physics but I accepted and gave it a try. I said “I will try, and if I like it, great. If not, maybe I can switch then to do something else.” I arrived to Maryland, and I started to work on plasma physics, but I didn’t like it. It was a lot of numerical work. I was just interested in more analytic problems. I did not enjoy sitting and trying to program a code on nonlinear differential equations. So, I talked to my advisor there, and he said: “Well, maybe you should try to something else.” In fact, during the first year of the university, we heard talks in different fields, and one of these talks was given by Bill Phillips. He was the Nobel Prize winner because of his work on trapping and cooling atoms I heard his talk, and I liked it a lot.
What was it about it that you liked? What was compelling to you?
Well, Bill is a fantastic speaker. During that talk he explained all the challenges and then told us about the satisfaction he felt when he succeeded to trap and cool atoms. I was interested in nonlinear equations and it happens that the equation that ruled the behavior of ultra-cold atoms at that time was highly nonlinear, so it’s very similar to what I was trying to model when I was studying how light propagates through curved space. So, it caught my interest because what Bill was talking about was overlapping with the topic that I was thinking before. Second, the possibility to actually control atoms and manipulate them with light sounded amazing for me. My plasma physics advisor knew someone working in cold plasmas that actually had connections with Bill. So he said: “Well, why don’t you go and visit NIST and see what they have?” And well after Bill’s talk and given the encouragement of my advisor at the time, I went to NIST. There I met Charles Clark, an atomic physics theorist. He was modeling ultra-cold atoms, I asked him if-- can I join his group and he said yes. So basically after my first year at the university, I started to work at NIST in ultra-cold atoms. And this has been the topic of my research since then.
Charles Clark and Theodore Kirkpatrick—were they co-advisors, or one was the primary advisor?
So, the problem is that Charles was a NIST person, so he could not formally advise someone working at the university. I mean, he had some type of a joint appointment, but not official. So, Ted Kirkpatrick was my formal advisor at the university. He was a very nice person, but I think I talked to him like, four times, five times at the most. He was just the person who signed all the documents. And I mean, yes, I started working in ultra-cold atoms, Bose-Einstein condensates, and I think he was one of the professors in the physics department who had the best connection with this topic. He was doing condensed matter, not exactly cold atoms but I just contacted him and Ted accepted to serve as my advisor.
And so, obviously it was from Charles that you gained an early appreciation for the science that you could do at NIST.
Yes. Charles was fantastic. Very supportive. But he just was part of a bigger network. And what I loved what was the network, the possibility to go around the corner and talk to an experimentalist. For example, Bill was part of the network. Bill Phillips has always been an inspiration for me. The way he thinks about science is amazing. At that time, Charles was extremely busy. He was the chief of the electron optical divisions at NIST. So, he had a lot of responsibilities that were not necessarily physics related, but more administrative work. So, even though I did discuss the papers that I wrote with Charles, he was not going to tell me what to do. I always got ideas of what to do more from discussions with experimentalists.
And physically, would you spend a lot of your time in Gaithersburg?
Well, that was interesting. Yes, but I did have to take classes at the University of Maryland, in College Park. So, I needed to get a car. Getting a car was a life changing game when I was at NIST. The first month was terrible, because going from Maryland to NIST without a car, it can take more than three hours. It was terrible. I had to take a bus, and then another bus, and then wait for one hour for the NIST bus to pick me up at the station. When I got a car, my life became much easier. I worked four days at NIST, and one day at the university. My interactions with my classmates at Maryland were almost zero, because I just was there for the periods when I was taking the actual classes, no interactions after that.
What were some of the central conclusions of your thesis research? REY: When I got interested in ultra-cold atoms, the field was at the stage where they can model the behavior of the atoms by solving one differential equation that is nonlinear. This equation, called the Gross-Pitaevskii (GP) equation. It was the equation that people used to solve the behavior of trapped atoms, and it worked amazingly well. So, anything seen by the experiments could be predicted in theory by solving this equation. But when I started my PhD, the experiments were able to go one step ahead by, instead of trapping the atoms as a bulk, they were able to trap the atoms in optical lattices. Optical lattices or a crystal of light are periodic potentials for atoms made by light. Imagine in an egg cartoon. Experiments were able to trap atoms, one or two atoms in at individual lattice sites. Because of the stronger confinement and more relevant role of interactions GP stopped working. So, we were not able to use the usual semiclassical tools to model the behavior of atoms. Instead experiments were entering a regime where actually, quantum effects started to show up prominently. So, what I did in my PhD was to develop new tools that actually could model the behavior in these different types of conditions. So interestingly, at that time the atomic physics community didn’t know the methodologies. What I did was to go and talk with cosmologists at the university. He told me that actually he developed techniques that can model the early universe, and that he could teach me how to adapt these methods that were developed for particles moving very fast, to the regime we were dealing with in the lab: nonrelativistic, very slow atoms. So basically, what I did was to borrow methods developed in cosmology and adapt them to actually reproduce the cold atom behavior not captured by the GP equation. So, that basically was one of the most important contributions of my thesis work. They were complicated methods. Later, I learned that these methods were overkilling, and there are simpler ways to actually model these problems. But I didn’t know that at that time. So, at the least, it was one of the first methods that showed that you still can model the behavior of atoms, in these more complicated conditions.
Did Charles Clark actually sit on your thesis committee?
Yes. Yes. Charles was really, really supportive. He was busy, and that’s good, in the sense that he gave me the freedom to do whatever I wanted to do. I mean, as long as my work had connections with experimentalists at NIST Charles was happy with what I was doing. He read all the papers very carefully. We called the review process “paper torture.” We sat for hours correcting all typos and trying to write the paper the best way possible. Charles always supported me in any development that I had during my PhD.
Did you have your postdoc all set up at NIST, even before you defended?
[laugh] My PhD thesis was recognized as one of the best theses in atomic molecular and optical physics in 2004 by what is called the DAMOP division, which is part of the American Physical Society. Charles nominated me for this award, and actually, I won the award—I was the first woman to win this type of award. This opened a lot of windows for me. I got an offer to do a postdoctoral fellowship at ITAMP, Institute of Theoretical Atomic Molecular Physics. This is a very recognized Institute at Harvard. At the time, I also had the two-body problem. I had to wait for my husband to finish his PhD. But not for very long. He finished six months after me. Charles offered me a postdoctoral position at NIST for one year, while I was waiting for him.
Now, your initial postdoc at NIST—did you take that as an opportunity to improve and refine your thesis research, or did you take on new projects at that point?
I didn’t continue necessarily doing exactly what I was doing in my thesis, but very related work.
What were your impressions of ITAMP at Harvard when you first got there? Did it seem like an impressive place? Was there good stuff going on?
Well, ITAMP was a very nice place. ITAMP was not exactly at the Harvard campus. ITAMP was at the CFA, Center for Laboratory Astrophysics. ITAMP was a very nice place, very welcoming, very nice. But the core of the research actually was done in the physics department at Harvard. So, I tried to find an office also there. They were like a 20-minute walk distance away. I really wanted to collaborate with the people at the physics department, so I needed to have an office there. The physics department was not as friendly as I expected, though. There was a lot of competition. At NIST, even the Nobel Prize [winner] —had the door completely open. If you wanted to talk to him, you just walk into his office, maybe you knock to indicate that you were there but that was it. You didn’t need to make an appointment. When I went to Harvard, for me it was interesting to see that many of the doors were closed, and you really needed to make an appointment to talk to the professors, and maybe this appointment never materialized. [laugh] I sent an email trying to make an appointment, and it was never answered in many cases. I was not used to that. Everything was very friendly when I was at NIST in Maryland. Then, I went to Harvard, and it was always a hassle to connect with the professors there. It took me like one year to penetrate this barrier. After I managed to let people know me, then things changed again. After you are within the circle people had more time for you, and you can talk with them in a nicer way. But it was tough. They were hard times. But I learned a lot from them.
What were some of the main research achievements you had during your years at Harvard?
I learned how to better model the behavior of atoms trapped in crystals of light. When I arrived to Harvard, the person who did one of the most well cited experiments in optical lattice was arriving as a faculty member. So, I had the possibility to interact with him very closely and tried to understand better what could be the exciting physics that could come from this type of experiment. Can I model them not only to see something interesting, but also something useful that can advance quantum science? When I did my PhD, we were using what is called bosonic atoms that come in one flavor. When I was at Harvard, I started to understand what happens if we have not only one flavor, but two flavors. Two flavors can become the basis of an atomic clocks. During my last year there, when I already knew that I was going to come to JILA, the place that has the best clock in the world, was the time when the idea of combining many-body physics with precision measurement materialized. So, for example, atomic clocks are so precise that they allow us to measure very small energy scales. But they’re impacted by the complexity of a many-body system. If I use the clock to understand the complexity of the underlying many-body system, then I not only gain understanding of the many-body system, but I can then use this understanding to build an even better clock. So, this is where everything is started, this idea of a marriage between many-body physics and precision metrology.
Ana Maria, did you interact with Lene Hau at all during your time at Harvard?
No. I interacted with Mikhail Lukin who was part of the Center for Ultracold Atoms (CUA). Unfortunately, Lene was not part of it. Because I had all these issues trying to connect with people at Harvard, I did my best to connect to people that were in the Center for Ultracold Atoms, not people outside the center. When I was doing my PhD at NIST, one of the postdocs in Charles’ group was Zac Dutton. He was one of the students that did the theory for the slow light experiments that she was doing. So, I mean, she was very well in my radar, but because I wanted a stronger connection with the CUA, then I didn’t do too much effort to meet her.
How well were you managing the two-body problem as your postdoc at Harvard was coming to an end, and you were thinking about your next opportunity?
Yes. This was interesting. At that time, because we didn’t know what was going to happen, we did manage to have an offer from Colombia. So, this was our backup plan.
Columbia University, not Colombia the country?
Colombia my country.
So, La Universidad de los Andes, where I did my undergraduate program offered us faculty positions to me and my husband at that time. So, we had a backup plan. It made the job finding process a little bit less stressful since I was able to push a little bit when I received an offer in the US. I said: “Okay, I need to solve my two-body problem. Otherwise, I’ll just go back to Colombia,” where we would have the two-body problem solved.
Because you could both have faculty appointments in Colombia.
Yes, exactly. Exactly.
That must have been attractive to you, just to be back closer to your family also.
It was, but—
But not professionally.
Not professionally. It was just a backup plan. I mean, we knew that we would have a position there, but we would not be able to do the most exciting research necessarily, because the resources in Colombia are not as good as in the US. It worked very nicely at JILA. They were really, really supportive. They had a lot of people having a two-body problem, and they knew how important—especially for female faculty—it is to make sure that we can solve it. And I’m so fortunate that they really solved it. I mean, they contacted the applied math department, and they found a position for him there. So, that was great. It made everything much easier.
Now, your appointment initially-- when you got to Boulder, was it with JILA only?
Well, it was always through NIST. Yes. My salary has always come from NIST. I am part of the quantum physics division which is a key part of JILA. So yes, JILA was always the central piece. At that time, what happened is that because I was not a US citizen nor had a green card, the only option for hiring me was through the university. So, the university had to open a position. It was a research professor position not tenure track. Basically a temporary position. Later, they changed the rules, and I had to become a US citizen before I could become a NIST employee.
Ana Maria, what was your research at this point? What were the kinds of things you were working on as you made this transition?
Yes. Well, NIST is the National Institute of Standards and Technology. Of course, metrology is at the heart of it. So when I joined JILA, one of the most exciting ideas was the possibility to collaborate with Jun Ye. He had the best atomic clock in the world. And so, the research that I envisioned was trying to explore many-body physics with his clock. So what has been, and what still is, the main core of my research is to try to see how we can use ultracold atoms or molecules or ions—I mean, systems that we can control in the lab with light to explore quantum mechanics. At the moment, one important application of quantum mechanics is metrology. We believe, not yet demonstrated, that metrology or better clocks, better interferometers would strongly benefit from quantum mechanics. This is what people call quantum advantage. If I have a system that is just classical — will have less sensitivity if I make my system strongly quantum. So, what we are trying to do is to try to understand how we fully control quantum systems and make them fully quantum, and then use them for something useful. We are also thinking how we can emulate the behavior of other systems, like solid-state crystals. This is the idea of quantum simulation: I have a fully controllable system. I have another system that shows exotic properties, but it’s so complex that I will never be able to model. But if I can have a clean system that shares very similar properties, but it is clean, and I can modify it. Then if I can see the phenomena that I expected to see in this more complicated system in my clean system, then I might be able then to tweak my fully controllable system and reach conditions that are much better. This is the idea behind quantum simulation—we use a fully controllable system to imitate and surpass the capabilities of a real material or a real system. The holy grail but what still at the very beginning, is the idea to try to build a quantum computer: computers made with quantum matter that can process information at a much faster rate than what we can in current computers.
Ana Maria, this raises almost a philosophical question, which is: if the simulators-- if the computer simulations are somehow better than what you can achieve in “real life,” doesn’t that get beyond the purpose of science and understanding the natural world?
Yes, but it can be very nice. For example, we could make materials that superconduct at room temperature or high-temperature superconductors. The ones that exist in nature superconduct at about 77 degrees Kelvin. So, it still is very cold. This is the temperature at which liquid nitrogen operate. So, it’s not room temperature yet. But if you have this simulator — understand what is the key properties of superconductivity, then we could learn how to design artificial materials that actually can superconduct at room temperature. We could still take advantage of what nature offers, but actually redesign better technologies that could be beneficial in many ways. I mean, it’s not that the real materials are not useful, but we can learn how they work and then tweak them to make them better.
Ana Maria, as you got comfortable at NIST in Boulder, in what ways was it different, and in what ways was it similar to NIST Gaithersburg?
Yes. So actually, it was very similar in terms of friendly atmosphere, great people, strong collaboration between experiment and theory, perhaps with the advantage that there are more people doing quantum physics or ultracold physics at JILA than at Maryland. When I was at NIST Gaithersburg, I was part of Charles’ group that was the electron optics division, not the physics division. The physics division was in another building which was very close but not as close as it is at JILA, where you really just go downstairs and find the experiments. So similar, but even better. That’s why I love JILA. It’s really the place where people believe that success is nothing individual. Success is a group concept.
As a professor-- as an assistant research professor when you first got there, what opportunities did you have to interact with undergraduates and serve as a mentor to them?
Actually, my connection to undergraduates has been a little bit limited. I interact more with graduate students. Training undergraduates takes effort, and so the topics that we do require a little bit of knowledge, if you really want to progress a bit. It is easier to start working with people that already have the minimal background to tackle the problems we want to solve. I have worked with undergraduates but in a very selective way. So, once I worked not even with an undergraduate but a high-school student that was joining the advanced quantum class for undergraduates. And one professor at JILA told me: “He is a genius. For sure you want to talk to him.” And this student, this high-school student, was really a genius. So, I had the possibility to talk to him, and he was better than my graduate students. Such an amazing person. The other was one undergraduate that I hired because he was from Colombia, and he wanted to do an internship in the US. So, I sponsored his internship here at JILA, and I worked with him. My graduate students helped me, but he was very productive. But yeah, I work mostly with graduate students and postdocs.
And what are some of the things that your most successful graduate students have been focused on? What are their interests? What have they been doing in the past 10 or so years?
Oh, well I have been very impressed with the level of graduate students that we have here in Boulder. Basically, what they are doing is trying to understand the complex behavior of a many-body system for applications in metrology and in quantum simulations. What is the biggest things that we have done? For example, we can use systems of trapped ions and make them interact and control interactions in such a way that they can measure frequencies very precise. We have shown how we can control quantum mechanical systems and use them to understand how information is apparently lost in a black hole. I mean, this is very interesting the idea that that quantum systems, in some degree, can emulate the behavior of black holes. This is something that we demonstrated in the lab. By changing the properties of the lasers, we can make a system go backwards in time. We have learned how to control molecules. Molecules are more complicated than atoms, but still, we have been able to understand their properties and control them, and hopefully maybe use them for simulation of magnetism in solids. In summary, what we have done is trying to either use atomic systems for applications in metrology to make connections to the physics of solid-state materials, and high-energy systems like black holes. Quantum simulation is one of the most interesting projects that is happening in my group.
Ana Maria, since you arrived at Boulder, what have been some of the most important technological and computational advances as a theorist that have been relevant for the kinds of things you’re interested in?
I told you that I spent a lot of effort during my PhD trying to not use a simple nonlinear mean field equation to model the behavior of atoms in optical lattices. At that time in collaboration with cosmologists we developed field theoretical techniques that were able to go beyond and account for more complicated quantum behaviors. These methods however were difficult to implement. You had to integrate over all the past history of the system. One of the biggest developments we accomplished when I came to JILA was to find alternative ways to model quantum behaviors without the additional overhead that the field theory methods required. Not only the methods we developed were much simpler to implement but moreover worked better. For example, is that in many cases you can model the behavior of a quantum system just by adding some noise in the initial conditions and then solve the simple same nonlinear equations that people were solving before. If you are able to actually properly account for this noise, you surprisingly can solve for the behavior of complex systems in a way that you never thought you were able to simulate before. This has been one of the biggest discoveries that now is allowing us to model the behavior of experiments. The problem [laugh] in quantum mechanics is that the number of states you need to keep track grows exponentially with system size since particles can be in many states at the same time. Even for twenty particles the number of states accessible to the system becomes intractable. Imagine for realistic experimental systems made of thousand particles. In this case the number of states cannot be stored even in the most powerful supercomputer—it doesn’t have enough memory to store all this information and try to solve the behavior. So, you have to do approximations. And what we have learned is that there are specific approximations that work fantastically, and things that you thought were impossible to solve we can now. The experiment has been able to check that our predictions are correct. That indeed, these very, very, very complicated systems behave in a way that we were predicting.
Ana Maria, what did it feel like when you were named a MacArthur Fellow?
Oh, yes. That was amazing. I could not believe it. I received a call from the MacArthur Foundation. They were saying: “Well, surprise. Actually, you have been elected a MacArthur Fellow. Congratulations!! But you will need to keep it secret for some time while we do the video, do all the preparation for the announcement of the prize.” But. So, yeah, it was a call out of the blue. It was amazing.
Besides being a great honor, did you find that it was useful at all to you? Did it introduce you to new people? Did it open research possibilities that may not have been available to you before?
Oh, it was a very important step in my career. I received a lot more invitations, so had the possibility to travel more, to disseminate my research, to establish new connections. I also appreciate the opportunity to be part of MacArthur meetings and meet fantastic people. I mean the possibility to understand how people can be doing history or art, and they can be as creative as a person doing science. So yes, it made a huge impact in my scientific career and my personal way of seeing life.
Just to bring our conversation up to the present, what have been some of the major research projects you’ve been involved in, in the past few years?
One of the parts that I enjoy very, very, very much is to have a strong collaboration with experiments. The capability of doing theory in a way that is going to be able to be tested by an experiment, and moreover, that you can make the experiment measure things that actually result in what you predicted or not. In the latter we have to modify our theory and account for what is happening in the experiment until our theory fits. So, during my last few years, my main effort has been to collaborate with various experiments at JILA and to push them towards becoming better quantum simulators or to explore quantum mechanics in a way that was not possible before. I can say, our theory has helped to improve atomic clocks. These are the most precise sensors you have ever imagined. Atomic clocks used to be limited by collisions. If you have a good sensor, you want to put more particles, because it gives you a higher signal-to-noise. If you have more particles to measure, you expect that you are going to have more signal, and this is always useful, but that used not, unfortunately, to be the case, because if you start to put more atoms in the clock, they collide, and collisions disrupt their clock precision. So one of the biggest developments that we have done in collaboration with Jun Ye’s Sr clock is to model the collisions in the clock. By doing that we discovered a way to make them not relevant allowing clocks to become much more precise. In other words, because we understood the collisions, we were able to remove them. So, this marriage between many body physics and metrology has been one important development. Also, we have been able to use trapped ions for quantum simulations. We are very interested in learning how we can control hundreds of ions and actually use their properties to emulate from the behavior of a black hole to the behavior of electrons in a metal. We have been able to control ultracold molecules. JILA has been the premier institution to control atoms and molecules. Molecules are really hard to cool down and manipulate. Nevertheless, JILA has been always the leader institution on cooling and trapping molecules since 2008. My research has been focused on guiding the experiments on how we can use molecules for engineering quantum materials. I finally tried to understand the behavior of atoms loaded in what is called “optical cavities.” In many cases, when you talk about interactions for atoms it requires atoms to bump into each other. But by building the systems in a cavity, we can make an atom interact with another atom, even if it is very far away by the exchange of cavity photons.
Ana Maria, because your research really ranges from the atomic level all the way to black holes, I’d like to ask: in what ways have related disciplines in physics—cosmologists, astrophysics, molecular physics—in what ways have your colleagues in these fields benefitted from your research? And conversely, in what ways have these fields been relevant for your research?
I think it’s not only my research, but it’s interesting that in the last few years, there has been a synergy between different fields in science. So before, like 10 years ago, 20 years ago, an atomic physicist and someone working in general relativity didn’t have anything to interact with. Quantum entanglement has emerged as the key concept that gave connecting tissue between atomic physics, condensed matter, high energy, general relativity, and chemistry.
Quantum information and entanglement are the bridging elements between all these different fields. By understanding the dynamics of entanglement, we can establish connections between cold atoms and a black hole. My group has helped to tighten these connections. So, for example, we went to a conference where there were high energy theories saying: “Please, if someone figures out how can I reverse time and measure these type of correlations, we could build a simulator of quantum gravity.” So what I thought was: “Okay, we need an atomic system that can go backwards in time. How can I do that in a lab?” And we did figure it out a way. The trick was just to formulate the problem in a different way. And yes, we demonstrated that we could actually measure these correlations in an experiment without very fancy tools. I mean, I’m not an expert in quantum gravity at all. But if someone asks me: “How can I do this in current cold atom experiments?” I have the capability to come up with a way. So, for example, in a recent publication we explained how cold atoms can behave as a superconductor and feature dynamics that in real materials would require ultrafast pulses, or very complicated setups to see. Whereas in a cold atom lab, we can just turn two knobs and actually change see this exciting physics.
Ana Maria, in what ways do you see your research contributing to some of the ongoing mysteries in cosmology? Things like understanding how gravity interacts with the other forces, or searching for dark energy, or searching for dark matter.
Yeah. So, for example, with the trapped ion group at NIST, we think that we can make their system a sensor for dark matter. I mean we need to improve the signal to noise. But what we are proposing is that instead of using very large experiments, that require billions of investment and huge high-energy colliders, we can instead build tabletop experiments that could, for example, detect dark matter. We just have a paper submitted to Science where we showed that in principle, our ions can detect electric fields in a way that is better than any other system. Our system is still not at the level of detecting dark matter, but it might in the future. And for quantum gravity, we’re working with cavity systems, and we hope to be able to formulate a model that resembles the behavior of a black hole. How much we learn about quantum gravity with that is still to be seen, but at least we think that we can build the necessary ingredients to see in what extent a system in the lab can behave as a black hole. Yeah. At the core is the idea of quantum simulation that we can make a system behave like other completely different systems and show the same type of physics.
Ana Maria, you’ve explained why quantum computing will be so important for your research, but I wonder, before we get there, how your research might contribute to actually creating quantum computers.
So far atomic clocks have operated more like timekeepers. But these systems can have coherence times that are really, really long. So, one of the directions that we are exploring is up to what extent we can use these systems as the building blocks to make them a quantum computer. So, we are trying to understand how we can correlate the atoms in the clock and actually use these systems for processing quantum information. These are not the fastest systems, but they have very long coherence times a fundamental condition for a quantum computer. We are exploring this direction. We are also exploring quantum computing opportunities with 2D planar arrays of trapped ions. Molecules might be an alternative too. But even if we don’t make a quantum computer, at least we can investigate ways that we can harness and control these systems and use them for something relevant for quantum technologies.
Ana Maria, a much different question—not on the technical side, but on the political and social side—as you well know, over the past year, physics and STEM in general have undergone lots of discussions about diversity and inclusivity in the field. As a woman, as a Latin American woman, what is your position on these issues? Do you feel important? Is it important for you to be out in front in things like diversity and inclusivity, or do you prefer not to take a more central role and just do your work and lead by example?
I like the idea of promoting diversity and inclusivity. I think this is important, although sometimes I feel that the way to go is not forcing institutions to have more women in science now, but instead training new generations of women and foster their interest in science. So, I am a bit opposed to the idea that when we run a search, then by force we have to interview a few women candidates. The issue is that if the women applicants are not at the level we want, but nevertheless we are forced to interview them to check a box and report that we are promoting diversity no one wins. I think what needs to be done is to train new generations of women and underrepresented minorities very early in their academic years to like science and STEM. Doing that we will train a new generation of qualified people who can do a great job, and then compete at the same level as qualified males in the pool. So basically we need to go into the foundations and understand how we can make a difference. So, I think it’s really an important problem to solve, but it has to be done starting from the beginning instead of forcing something artificially. If you bring someone that is not prepared, the person will not feel capable to finish the job and you will disrupt their scientific career instead. You have just brought them to the wrong environment. That is why I participate so often in giving talks to high school students to try to promote science at early stages. It’s definitely a complicated problem.
Absolutely. It’s a complicated issue that deserves complicated answers, for sure. Ana Maria, for the last part of our talk, I’d like to ask you a broadly retrospective question about your career so far, and then we’ll end looking to the future.
And so, looking back on your career so far, it’s clear that you operate quite comfortably at the nexus of theory, that you work closely with your colleagues in the world of experimentation, and that you’re interested both in basic science and in applications—applications of that discovery. So I’d like to ask: where in your research are you most motivated by the basic science, just understanding how nature works? And where in your research are you specifically motivated by finding particular applications, even applications that could have real societal value?
Yeah. For me, fundamental science has been always at the core of my research. However, I am interested in physics not pure math, i.e. concepts that at some point can be tested by an experiment. So, for me, understanding the quantum world is fascinating. Now, of course I am interested in applications too, why is my work useful? If you are going to write a grant, you need to tell the program manager why she/he’s going to benefit from my work, and what it’s going to bring to society. But honestly JILA is a curiosity driven place. We want to understand how the world works. We do things that are fundamental now but very likely useful for the future. For example, we develop clocks with incredible precision, but it doesn’t mean that these clocks are going to be useful for GPS in the short-term future. We leave others to actually understand how something that is done in a laboratory can be translated out of the lab and used for an application like navigation. Of course, applications like quantum simulation and quantum computation or quantum metrology are important for us, but we see them as more long-term plans. I don’t know. I mean, hopefully that answers the question. So, that I’m interested in applications but understanding the fundamental properties of nature is the most beautiful part of science.
Ana Maria, looking to the future, there’s so much exciting research that you can contribute to, and of course, the challenge is the limitations of time: time in a day, time in a semester, time in a year, time to devote to your graduate students. What are the things that are most exciting to you in the world of discovery and basic science, that will give you the confidence to say, “These are the choices that I’m making. This is the research that I’m going to work on. This is the research that I’m not going to work on.”? How do you think you’ll make those choices on an ongoing basis, and what are you most optimistic about in terms of what those choices and what that research ultimately will yield in the rest of your career?
It’s interesting, because I don’t know exactly what I’m going to be doing in 10 years, but I know that it’s going to be interesting. I’m interested to model the complex behavior of quantum matter for different types of goals. The goals evolve in ways you didn’t envision before. So, I’m always going to be interested in trying to exploit the complexity of the quantum world and be surprised by it. I collaborate with many, many, many groups around the world, and enjoy guiding them into new directions: this year with some group in France, next year with some group in Germany or someone in Toronto. Theory will always be beyond the experiments. I think what I have done always in my career has been driven by understanding complex behavior of many-body systems, and this will continue to be the pattern. It is not clear how my research is going to fit in quantum gravity, in quantum information, in condensed matter, but I’m excited to continue exploring and see what comes out from it. So, what we are exploring now was unforeseen five years before. We didn’t think that experiments would have the capability to actually control an individual atom. So before, everything was in a bulk, but now, experiments are able to actually do it. What is going to be their next capability it is not clear. But hopefully, my research will push experiments and will lead to a better understanding of the quantum world.
So, you can’t predict, but you are confident that whatever you do, it will be exciting.
Yes. Yes, exactly. Yes.
Ana Maria, it’s been such a pleasure spending this time with you and interviewing you and hearing about your life and your science. So, I want to thank you so much for doing this.
Thank you, David. Thank you so much.