Nathalie de Leon

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ORAL HISTORIES
Nathalie de Leon

Credit: David Kelly Crow

Interviewed by
David Zierler
Interview date
Location
Video conference
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In footnotes or endnotes please cite AIP interviews like this:

Interview of Nathalie de Leon by David Zierler on April 16, 2021,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
www.aip.org/history-programs/niels-bohr-library/oral-histories/46999

For multiple citations, "AIP" is the preferred abbreviation for the location.

In this interview, David Zierler, Oral Historian for AIP, interviews Nathalie de Leon, Assistant Professor of Electrical Engineering at Princeton. de Leon describes being an “interloper in EE” because her degree is in chemical physics, and she surveys her research agenda and how it fits across a range of departments at Princeton. She describes her Filipino heritage and her upbringing in the Philippines and in California, and discusses her scientific interests and her admission to Stanford for her undergraduate study. de Leon describes her interests in laser spectroscopy and she compares the difficulties as a student woman of color in STEM against those as a faculty woman of color in STEM. She describes her graduate research at Harvard to work with Hongkun Park on a variety of projects, including nanowire devices, photoelectrochemistry, and plasmonics. de Leon discusses many exciting developments in NV centers, and she explains her decision to remain at Harvard for her postdoctoral research to do QED experiments with atoms. de Leon describes the opportunities that led to her faculty appointment at Princeton, and the process of getting her lab operational. She discusses advances in superconducting qubits and she describes the value of applying metrics to make STEM more inclusive. At the end of the interview, de Leon explains why her curiosity about applying material science to quantum technology permeates all her research, and she expresses optimism for the future, but unknown, possibilities of quantum computing.

Transcript

Zierler:

Okay, this is David Zierler, oral historian for the American Institute of Physics. It is April 16th, 2021. I’m delighted to be here with Professor Nathalie de Leon. Nathalie, it’s great to see you. Thank you for joining me.

de Leon:

Thank you. Yeah, thanks for reaching out.

Zierler:

Alright, so to start, would you please tell me your title and institutional affiliation?

de Leon:

I’m an assistant professor of electrical engineering at Princeton University.

Zierler:

How long have you been at Princeton?

de Leon:

Since the beginning of 2016, so I guess about five years.

Zierler:

Now, electrical engineering at Princeton, how much of that is what other departments might call applied physics? How much of it is computer science? How did these disciplines work administratively at Princeton?

de Leon:

Yeah, well, so, I’m kind of an interloper because I don’t have any degrees at all in electrical engineering (laughter). But we’re sort of in an unusual department in that I would have to hazard a guess about the exact number but probably around a third of the faculty also do not have degrees in electrical engineering, so it has a pretty strong tradition of applied physics. We also have a lot of strength in more traditional electrical engineering disciplines. But I think, you know, for historical reasons, it was sort of the home of applied physics at Princeton, and then because we have this core strength there, they’ve really built on that over the years.

Zierler:

And what would you call yourself, at the end of the day?

de Leon:

That’s kind of a funny question for me because, you know, my undergraduate degree was in chemistry. My PhD was in chemical physics, which was sort of shared between the chemistry and physics departments at Harvard. And then I did my postdoc in a group in physics, which was an atomic physics group. So, like, no interface with chemistry or even- basically, the interface with solid state systems was sort of starting up when I got there. It’s like pretty far over into physics land. So, I’m a little bit of everything. I think I’m disowned by all communities (laughter). If I’m talking to chemists, my chemistry knowledge is really woefully poor because I have not used chemistry terms really earnestly since I was about twenty. And then, you know, in physics, like physicists care a lot about purity of their discipline, so I don’t know if I really fully, fully count as a physicist either. My undergrad advisor sort of was a little bit similar. He was always like- he had one foot in chemistry, one foot in physics, and would always sort of chastise people for trying to categorize things too narrowly. So, maybe I’ve carried a little bit of that ethos on myself.

Zierler:

Nathalie, a question we’ve all been dealing with this past year plus in the pandemic, how has your science been affected one way or the other by isolation, remote work, not seeing your colleagues, not having access to the laboratory work that’s most important to you? How have you fared overall?

de Leon:

I guess I should maybe start by saying that we’ve been relatively fortunate in this regard. Princeton tried really hard to put in a testing- asymptomatic testing and contact-tracing protocol that seems to have worked really well for the community. So, we sort of reopened up for research operations towards the end of the summer, and life has been not normal but pretty close to normal, at least for the students and postdocs. They can go into lab. There are some density restrictions and things like that. In the very, very beginning when everybody was sent home and, we were really sort of trapped, I think there were a couple of small benefits like silver linings to being forced to sit and think about your data really carefully. So, like, our one really good story out of quarantine is that we had been taking this particular type of data for a really long time. Like, I mean, I think our data sets in my group extend all the way back to when I was a postdoc. So, we had many, many years of data, and there were a few times over the years that somebody would be fitting this data and would come back with just like a funny looking exponent. And I could say that just fundamentally doesn’t make sense from a series of simple arguments that I can make that are just like textbook results that I can look up, and we had sort of run roughshod over it. Like, there’s this poor undergrad who kept on bringing these data sets that I said were analyzed incorrectly. And then in quarantine, we started talking to colleagues at my old postdoc group, and it turned out that they had seen something that was sort of similarly puzzling. And basically, being forced to sit at home and not just plough forward with the next data set, but just sit and think carefully about this stuff, we came up with a pretty nice interpretation. It turned out that that was a real result we had just been ignoring. It’s sort of your classic what is this? There’s this, like, philosophy of science result where you show people playing cards, and then if you ask them like what suit it is, and then you just change the color of the cards, they get super confused. It’s kind of a similar thing. We were just like, no, this can’t be true for like several years. And then, finally, just being forced to like sit around and think for a while really helped. And we came up with sort of a nice picture of what was going on, and a nice new analytical result. And I think it’s the kind of thing that maybe my group would not have done in normal times, so it sort of shook a few things loose, just forcing us to change pace. And, honestly, the first couple of months when we got back into lab were among some of the most productive for my students. So, I think also just being forced to like sit and think carefully for a little while was really helpful, and hard to manufacture in other circumstances. That being said, it was just- it’s really a silver lining (laughter). It really was not a net positive, you know. It’s very painful to be separated from everyone. I think it’s hard to keep up the same level of creativity when you’re not having the same kinds of conversations and the same contact. For me, in particular, I’ve had to sort of re-find some kind of balance. Like, it turns out that it’s really easy to sit on Zoom all day, which is maybe not terrible for the nuts and bolts productivity of let’s get this paper out, or let’s finish this thing that we wanted to think about, but is really catastrophic for broad creative thinking. So, I think it’s the kind of thing that, you know-

Zierler:

Which is where the science happens in that space?

de Leon:

Yeah. Well, and certainly the science two years from now-

Zierler:

Yeah, yeah.

de Leon:

-all comes from that kind of thinking. So, it turns out I didn’t realize this, but maybe a big part of my process was, as much as I complained about it, getting in an Uber to Newark Airport, and sitting at the gate with nothing else to do but think for a little while, and maybe sitting on the airplane and, you know, not having access to email was actually really helpful (laughter). So, I’ve tried to find ways to carve out space that’s like that, even when I can only walk a couple miles from the house.

Zierler:

As important as it will be to get back in person with collaborators, of course, one of the big storylines in science this year is the value of remote data analysis, and computer simulations, for better or worse, de-coupling the physical need to be present in the laboratory. What are some aspects of pivoting in real time that even when there is that opportunity to go back physically in the lab on a regular basis, what are some of the takeaways that might be relevant for, and valuable for, your research going forward?

de Leon:

Yeah. Well, some of them are sort of prosaic. Like the density restrictions have forced us to think a little bit harder about what do you actually need to be in lab for, and what should you try to turn into more of a robot? And we’ve maybe invested a little bit more in automation than we would’ve otherwise. And you have to work really hard to make things stable enough that automation works well. So, I think the funny thing about experimental physics is, like, there’s a lot of engineering involved, right. You’re taking- you’re trying to coax some complex system into existence, and the degree to which engineering- it- to be better, it makes sense, depends a lot on sort of your own abilities, right (laughter). So, some people will, like, just white-knuckle their way through an experiment, and say, like, “Okay, I can just work super hard, and get the data set that I want, even if this thing is constantly falling apart like a house of cards because I can just be in lab twenty hours a day.” Yeah. Like one good example is, we currently have a solution for putting microwaves in our UHV chamber that requires being very talented at soldering (laughter). So, in some ways, it’s not a very robust solution, right, because now if we have to put a new thing in, someone has to train up to do that. But I totally see how the postdoc ended up in this position because I think that was also my-

Zierler:

(Laughter).

de Leon:

-my instinct when I was doing more nuts and bolts stuff in the lab was definitely, like, I’m just going to practice, and get really good at this. So, we’ve probably been forced to do a little bit more automation. I think also, maybe our lesson from this, like, sit and think about the data a little bit more carefully was that you can do a lot more with numerics than you would maybe anticipate. My impulse is always like let’s just make an attempt over the mountain, right. Like, I’m a very hypothesis-testing kind of driven experimentalist where what I want is the- I’m always optimizing over information per unit time. Like, what can we do to get more data that we can stare at? But then there’s always value to taking the data that you have, and maybe thinking a little harder about it.

Zierler:

Nathalie, given that, as you say, a third of the faculty, give or take, do not have degrees in electrical engineering, and given your unique research path, what might that say more broadly? Given that Princeton is obviously an institution that sets the tone more widely than just its immediate environs, what might that say about the future direction of electrical engineering, and what it means more broadly?

de Leon:

Yeah, I don’t feel very qualified to comment on the future of electrical engineering because, to be maximally honest, I don’t really know that much about the history of electrical engineering (laughter). Like, I’m not sure. To me, sometimes faculty meetings feel a little bit like I’m an anthropologist who has landed in some remote culture, you know and I just— I don’t really understand their fights, and I don’t understand where all of these, you know, tribal lines are drawn exactly. I do think that the kind of nice thing about engineering as distinct from, say, a natural sciences department is, you know, physics and chemistry have been essentially the same disciplines or, you know, you can draw boundaries around these disciplines all the way back to the eighteenth century. It’s like it’s an extremely long tradition. And engineering departments, you know, they come and go. Like, we- there are not really that many metallurgy departments anymore, right. So, these departments tend to be much more focused on what is useful right now for mankind? And I think that that just sort of naturally makes the boundaries a lot fuzzier. So, I think here I don’t really know very much about the trajectory of electrical engineering as a whole, but I think, locally, inside my subfield and, you know, my discipline narrowly, there’s sort of an interesting thing that’s happening where- so, you know, my group works on quantum technologies, quantum computing, quantum communication, quantum sensing. And this is a discipline, or this is an area of interest that has historically been almost one hundred percent inside of physics. Most of the groups who have worked on this over the last twenty or thirty years have really been solidly inside of physics departments. But I think now that we’re starting to build much more complex systems and starting to think of ways to really deploy technologies as opposed to just doing proof of principle demonstrations, there is now a more natural interface with a lot of other departments. Actually, I have a review article that just came out today in- or yesterday in Science, arguing that we need to attract a lot more material scientists and chemists into the field of quantum computing because this is definitely the time for them to make a really huge impact on the field. So, similarly, now that we’re starting to build more complicated systems, I can completely see a big role for people who think more about systems engineering or architecture. And, in that way, it’s kind of nice to have this interface with people who think about systems at a different level.

Zierler:

Let’s take it all the way back to the beginning. Let’s start first with your parents. Tell me a little bit about them and where they’re from.

de Leon:

So, my- well, I should start by saying I’m the only scientist in my entire family, extended family, everything. The funny thing about going home is, like, we spend so much time caring about this very particular kind of social group of people, and they just- they cannot understand anything that I’m saying, and do not- and it’s very nice. It’s very nice to escape academia-

Zierler:

So, you’re an anthropologist at home and in the faculty meetings?

de Leon:

(Laughter) Yeah, exactly. No. So, my parents both grew up in the Philippines. My dad is ethnically Chinese, so his dad was like a stowaway on a boat from China. He was part of this big Chinese diaspora around Southeast Asia when, you know, when the communists took over China. So, and I was born in the Philippines, and then my- so, this is a little convoluted but my mother’s father had been- he was a boat captain, a ship captain, you know, commercial seaman, who was stuck in San Francisco when Pearl Harbor was bombed. So, even though he was Filipino, because he was there, basically, the U.S. government told everyone who was kind of stuck, as long as they weren’t Japanese, that they could just stay for the duration of the war because they weren’t just going to let them sail off. And they said, “You can either just hang out here, or you can join. And if you join, then you can be a U.S. citizen.” So, that’s how he became American citizen. So, my grandfather was in the U.S. coastguard, went back home to the Philippines after the war, and met my grandmother, but still had the right to U.S. citizenship that entire time. So, after he raised a family, they all became adults and got married, they realized that they all, you know, should probably just emigrate to the U.S. because they had this right to do so. So, my parents had me, and then we all moved when I was like one. So, I grew up in California.

Zierler:

Where did your parents meet?

de Leon:

I think in college. They have some story about meeting at a party. I don’t think it’s a particularly interesting story (laughter).

Zierler:

Did you go- did you return to the Philippines as a kid? Did you retain that connection?

de Leon:

Yeah. Well, so, we have a lot of extended family there, and my grandmother on my dad’s side was still there, so we would go during the summers when I was a little kid. And for a two-year period when I was in high school, we actually lived in the Philippines. My dad had some business thing that he was trying to do, and so we moved when I was in, yeah, at the end of middle school. And we were supposed to stay there for longer, but then the big financial crisis in the mid-nineties happened, and it gets- there’s some dynamic in Southeast Asia because of this Chinese diaspora where it gets very dangerous for ethnic Chinese people when there are economic downturns. So, it was starting to get scary. There were kidnappings. And, like, in Indonesia, they were just going house to house, and kind of, you know, doing terrible things to the ethnic minorities. So, we decided that there was no point in staying if it was going to be unsafe, because we had a home in America (laughter). So why stick it out in a dangerous situation? I ended up moving back to California my junior year and finished out high school in the States.

Zierler:

Did your parents have professions that they could establish in the United States, or what were the circumstances of them coming here in terms of economic opportunity?

de Leon:

I think like a lot of immigrant stories, they didn’t have a profession. They just sort of came here and did what they could. So, my dad got a job at a bank, working for Bank of the Orient for several years. And then my mom was staying at home with the kids until the two of them decided to open a dry cleaners together when I was in elementary school. And that was what they had until my parents wanted to move back to the Philippines to open a business there. And then so my dad was sort of a little bit of a serial small business kind of entrepreneur.

Zierler:

And when they went back to the Philippines, was the idea to stay there permanently, or this was just a stint?

de Leon:

I think my dad had a particular business opportunity, so the idea was not to necessarily stay there permanently but longer than- they certainly were planning on doing it longer than two years. And it ended up only being- I think my dad was there for a total of six years in the end. So, he went a little bit ahead of us, and stayed for a little longer after we came back.

Zierler:

What were your feelings about going to the Philippines? Did you welcome that?

de Leon:

Oh, I was like miserable (laughter). It was a really I- sometimes, I’m glad that I didn’t like keep a diary or anything as a kid (laughter). What I remember about it is that I didn’t have a lot of friends when I was a kid, and then, by the end of middle school, I had this great group of friends, you know, and I felt like I had finally kind of figured things out a little bit socially. And then they were just taking me away from all of that. So, I think I actually had quite a bit of angst about the whole thing. You know, I was thirteen. I think all thirteen-year-olds are kind of miserable no matter what. It threw a big wrench in things. But I think I came back- I mean, not that you ever want to engineer situations like this. I do think I came back a little bit more resilient, just being taken totally out of context and then having to do it all over again, right, like have to shift all the way back to a different context. And it was very different going from- I don’t want to badmouth my high school that I went to because it was a very good high school, and I got a very good education there (laughter). But it was very not diverse, so I went from an international school in the Philippines that had, I don’t know, like dozens of nationalities and people who are not just ethnically diverse but just genuinely had grown up in a totally different country in completely different circumstances now going to this one high school, to a place that was like ninety percent white, very upper-class. The first thing that somebody asked me, I remember, my second day of school at this new high school was, when I said that I just moved from the Philippines, they asked, like, how I can speak English so well? (laughter) And it was just like kind of a big shock, you know.

Zierler:

And with no accent either (laughter).

de Leon:

And with no accent whatsoever (laughter). So, it took- that took a lot of adjustment as well. It was a great place to go to high school, and it was really like a wonderful public school, so I don’t have any complaints. But it was kind of a big culture shock a couple of times over moving and then moving back.

Zierler:

Nathalie, given you were in the Philippines during very formative years, what did that do in terms of affecting your understanding of your cultural heritage?

de Leon:

That is-

Zierler:

In other words, did you feel before that that you were just an American kid of Filipino parents? Did you feel a strong connection to your Filipino heritage before your family went back?

de Leon:

Yeah, I think- I know there’re a lot of people who have, like, very deep feelings about their heritage. I think for whatever reason, maybe just because the way my parents were trying to integrate into society as immigrants in the eighties, I never felt like it was a really integral, deep part of me as a person. Like, I think I saw it more as, like, it’s nice that I have this different food and, you know, that my- like, I enjoyed the fact that I could understand another language, and that my- I can’t speak it at all, but I can understand it and that my grandparents and cousins had a different perspective on life, and I always found that interesting. But I don’t think I spent- I don’t think I have any interesting answers basically. I don’t think I spend a ton of time really contemplating my heritage or ethnicity. I did gain a little bit more of an appreciation when I moved there for the fact that the Chinese experience was very different. I think I just saw it previously as, like, well, my parents grew up in the Philippines, and then we moved here. But the fact that my dad’s family as ethnic minorities had such a different experience of things was brought into much sharper relief when we actually moved there.

Zierler:

When did you get interested in science, especially given that no one in your family thought along those lines?

de Leon:

Yeah, I don’t actually know (laughter). So, I think I had a lot of different interests when I was a kid. Like, it wasn’t- I don’t think I was necessarily one of those kids that was, like, I’m going to be a scientist, you know, from like age five, which I know some of my colleagues are much more like. I had a lot of different things that I wanted to do. I think if there was one thread that was science-related, it would be that I did a lot of like, you know, tinkering with chemicals, which I think would just be illegal now. I think this is the kind of thing that, like, the FBI would come in and bust you for (laughter). But, even as early as middle school, you know, I had sort of figured out that you could mix together household chemicals, and make things explode, and make other things happen, and make things turn color, and things like that. And I had sort of increasingly ambitious projects going through high school. So, yeah, I remember as a chemistry major in college, people would ask the question like, “Did you get here through drugs or explosives?” (laughter) And then my answer was definitely explosives, so that was how I landed in chemistry. But, in parallel, I mean, you know, I was doing- I don’t know, Model UN, and speech and debate, and newspaper. Like, I had a lot of different activities. And, in some ways, I think I was always just hungry to do something and would kind of try to do it at as high a level as I could, and really like throw myself into it. And then in college, I got into research, and that was really what convinced me to stay in science, and I really liked it. I liked the fact that it was so open-ended, and that you could just kind of, you know, come up with pretty elaborate plans, and act on them. And then, you know, I think like all of the lateral thinking involved also really appealed to me, that like you could be really playful, like, find many, many different ways to solve the same problem. And sometimes the way to solve a problem was, like, hustling to get something weird done as opposed to just, you know, deliberately planning a very specific type of experiment (laughter). Like, you could kind of skin the cat in different ways.

Zierler:

So, this is to say when you got to Stanford as a freshman, you were open-ended. It wasn’t just specifically chemistry. You didn’t even know if it was science that you were going to pursue?

de Leon:

Yeah, that’s right. I think, you know, I think like one of my scholarships to Stanford was actually like a journalism-based thing. So, I was really- I was sort of all over the place. Stanford does have a little bit of a prevailing culture that the technical fields are more respected. So, like, I think everything that you need to know is in the terms that people use to refer to the different majors. So, you’re either a techie or a fuzzy. You sort of know that you don’t want to be a fuzzy- just like once they call it that (laughter). And so, there’s like sort of a clear social hierarchy, and I think if you’re on the fence, Stanford has a little bit of a way of pushing you towards more technical subjects. But I had this class- actually, okay, no, I remember what it is. I had this class that I took fall quarter. It was like the first quarter at Stanford, CHEM thirty-two, which I don’t think exists anymore, which was like the honor’s general chemistry course. And this class was just like- I don’t know if there’s a better metaphor- if there’s something that’s worse than drinking from a firehose, like trying to drink a whole swimming pool or something (laughter). But the swimming pool doesn’t give you the right rate. Anyway, I’m sure it was something- a geyser. Drinking from-

Zierler:

A geyser (laughter).

de Leon:

-geyser, there you go. But, basically, what they did was, they tried to talk about pretty modern topics that we were totally not prepared for, but then their goal was, here’s the topic. Now let me give you this extremely fast background information to get up to that topic. And it was one of the hardest classes I ever took, and it was very demanding. But we all came out of it like, you know, feeling like we had done something. And there- so there was this cohort that just got really into it because of this one hard class. So, it’s a little funny because, in some ways, you’re just so malleable. I was like an eighteen-year-old. Who knows what would’ve happened if I had taken a similar class in electrical engineering or a completely different discipline (laughter). But that sort of convinced me that it was a cool subject that was worth pursuing.

Zierler:

Nathalie, did you experience more broadly being, you know, in Stanford, Silicon Valley, the internet boom and bust, and the startup culture that permeated Palo Alto, as an undergraduate?

de Leon:

A tiny bit. I think it’s like a lot- I think it’s much more intense now than it was when I was there. So, I arrived right after the little dotcom bubble burst. So, it was maybe locally a depressed time for getting into, you know, startups and all of that stuff. At the same time, I think like- I think Mark Zuckerberg is one year behind me or something (laughter). So, clearly, there are a lot of people who, you know, jumped into the rising edge at the end. And, yeah, I mean, a very large fraction of my friends from undergrad are, like, VPs of these big tech companies. So, like a lot of them went and joined Google, Facebook, whatever, around the time that we were graduating, and after that, and kind of got into that path. It’s definitely a different way of seeing the world, I think, and its always kind of nice to have that interface. I don’t think- from what I’ve experienced, I don’t know if I would really necessarily flourish in that world (laughter).

Zierler:

Were there any particular professors who were formative in turning you on to research as an undergraduate?

de Leon:

My undergrad advisor, Dick Zare, he was the one who was teaching this gen chem class that I told you about, and then I went and took an intensive seminar that you could do before sophomore year called Sophomore College. There are many different classes inside of this format, and I did one of those courses with him, and then ended up joining his lab. And I was in his lab for the whole rest of undergrad, so sophomore through senior year.

Zierler:

Which was geared toward what? What did they do in this lab?

de Leon:

Dick is a laser spectroscopist, who ended up doing a lot of analytical chemistry. So, that was sort of what he was passionate about by the time I joined his lab. And he had an enormous group. So, when I was there, it was over forty people, so it was kind of this big, sprawling empire with a lot of different things going on from protein analysis to fundamental reaction dynamics to developing new analytical chemistry techniques. And what my project was, was we were doing laser-based mass spectrometry on meteoritic samples to try to learn about chemical reactions in space, basically. So, you know, the question was could you look at markers of complex organic synthesis if you did spatially resolved mass spec mapping? Which was a very cool project, particularly- I mean, it’s a little out there, right, like trying to do astrobiology. But it was really great for me as an undergrad because there was, you know, this complex bit of instrumentation. I was given kind of a lot of freedom for an undergrad. In retrospect, like, I do not allow undergrads to have that much freedom in my lab (laughter). So, it was really like sort of a magical set of circumstances that I had, like, a very supportive, you know, graduate student mentor that I was working with, and kind of this big instrument where you could do stuff on different pieces of it at a time. And, but, yeah, that was a really great undergrad experience.

Zierler:

How was the department in terms of diversity and inclusivity? As a woman, a woman of color, did you ever- were you ever made to feel not on the inside at all, or was that not really an issue for you?

de Leon:

So, I guess I would be lying if I said it was not an issue at all. Like, there were definitely a lot of things that happened. There were all these stories basically, right. The department was extremely undiverse. I think there was one female faculty. I’m not sure if I’m forgetting somebody, but I can only think of one right now in the department. And there were maybe only like two or three in physics too. So, like, just broadly, you know, these were- I mean, and things aren’t- honestly, things aren’t that different now. I think my department up until last year had only three female faculty members. So, it’s not a- you know, it’s not like everything has changed in the last twenty years magically or anything. And you would definitely hear stories. Like, there were a couple of incidents where faculty would make comments that really hurt people’s feelings that were really aimed at, you know, a general sentiment that maybe women aren’t good at science, as a group. And I remember sitting around and hearing these stories, and, you know, it definitely affects things. It affects whether or not you think that it’s going to be a good environment for you. But I- I don’t know how to put this.

Zierler:

Did you ever use that sentiment to positive effect, like you can prove them wrong kind of thing?

de Leon:

Yeah, I mean, I guess, I don’t know how to put this. I, for better or worse, a lot of the environments that people complain about as being not very inclusive or not very welcoming, I think I’ve almost always flourished in them. So, I don’t know if that sounds bad (laughter). But, like, basically, you know, labs where there are a bunch of people who sit around and brag, you know, about their technical prowess, you could sort of read as being unwelcoming. And I love- I do really well in those environments. So, I think I’ve always been, like, maybe a little competitive, and I kind of enjoy that amount of posturing or something like that. At least as a teenager and as a twenty-something-year-old, I really flourished in that sort of environment, and that’s certainly what I ended up in in grad school and postdoc. Like, it was definitely like those sorts of groups. I think I now can see how it is that there are people that really don’t do well in those environments, and there are ways to retain the good aspects, and pushing people to do really well, and just celebrating what people can do well without it being so much of a frat house is sort of the bad end of it, right (laughter).

Zierler:

An eating club, we should call it though. This is Princeton.

de Leon:

(Laughter) Yeah, exactly. But, yeah, I wouldn’t say that I necessarily had- I’m not going to claim that I had worse than average struggles, basically, as a result of it. But it was certainly something that I noted that would come up from time to time. I will say I think it’s worse that it’s faculty.

Zierler:

You mean your experience is worse as a faculty member?

de Leon:

Yeah, my experience of gender discrimination and sexism and things like that is probably a lot worse as a faculty. I’m not sure that I can exactly put my finger on it.

Zierler:

Well, maybe it’s just-

de Leon:

Like it-

Zierler:

-that that’s the source, and you’re not sheltered from it because you’re in it?

de Leon:

Yeah. Well, I think it’s a few things. So, one is that it’s much more obvious to me now how decisions get made, which you don’t see when you’re not on this side of like faculty hiring. And that process is horrifying (laughter). I don’t think that there’s anyone who would disagree with that statement. So, the fact that there is so much just explicit bias that creeps into the process is really shocking to me. I think the other thing is that I think female faculty have sort of these funny burdens that get put on them. One of them is just like logistical and administrative, which is that it’s not- you know, it’s all sort of well-intentioned. But, like, any committee, they’re going to want to fill out some card for diversity. And what that means is that, you know, if women are only ten percent of the faculty, but then they have to have representation on every single committee, then you’re suddenly oversubscribed, you know, or overburdened with committee service by a factor of five or something relative to your colleagues.

Zierler:

There might also be the additional factor of there’s a cultural expectation of not saying no so easily?

de Leon:

Yeah, I think there’s probably a little bit of that. But then I think the other burden that maybe I wasn’t totally prepared for that I see a lot more is that there’s just so much more scrutiny somehow, like. And I totally see how it happens, right. If I sit in a conference, and there’s only like three women and hundreds of men, then you’re just going to know who the other women are (laughter). Like, you just stick out more. I think you stick out more the same way that you would if you had purple hair. Everyone would remember that there was the one person at the conference with purple hair, right? But what that means is, you know, how many people’s records actually stand up to really, really close scrutiny? Like, there’s always something to be kind of a jerk about, and what I notice is just that people will be just incredibly critical of their female colleagues in a way that they won’t about their male colleagues. So, it’s something like- yeah, I don’t know how to say it better than that. It’s basically just like really intense scrutiny. So, it doesn’t mean that they’re necessarily always going to be really negative. Like, there’s also sort of a positive side of it, which is that maybe you get a little more attention for your results than you would otherwise. But it is- I went to this NSF workshop when I had just started, and there was a very famous female scientist who got up and made a point. And then there was a guy who just got up and like yelled at her. And it was just so shocking because you almost never hear adults raise their voice like that, especially in professional settings. And then- and I just thought, well, that’s really weird. They must have some like beef or something that I don’t understand. And then I saw it happen again to another woman at a conference, and then I saw it happen to a woman in a, like, broader faculty meeting. And then I started thinking like-

Zierler:

This is pattern recognition here.

de Leon:

Yes, maybe there is something here, you know, that people- so, I don’t really know exactly what that is, but it does seem like you’re just sort of more of a lightning rod for stuff, or something like that.

Zierler:

Let’s go back to a happier more naïve time perhaps when you were thinking about graduate school, perhaps not thinking about these issues that you’re thinking about now so much, but just academically, intellectually, what kind of advice did you get about programs to apply to, or people to work with? And obviously why not just go for a PhD straight in chemistry?

de Leon:

Yeah, so, to be honest, Dick just sat me down, and said, “Here’s where I think you should apply” (laughter). And then once I got into those schools, he said, “Here is who I think you should meet with.” And that was more or less kind of my approach. I think a few of the faculty, I had been to their talks, and I was like sort of interested in them. But he kind of said, “You know, what you’re doing is picking a group, not a school, so just ignore all of this other stuff, and you should do something that you’re really interested in. But, most importantly, you should do something that’s really hard and”-

Zierler:

And the focus was chemical physics, no matter where you went?

de Leon:

Well, it was- or physical chemistry. So, I applied, you know, basically to a broad—I mean, this was also true when I applied for faculty positions. I was basically applying across like four or five different departments, so I’ve always been maybe a little bit broad.

Zierler:

Another nomenclature question, of course, because, as you put it, it does sound a little interchangeable, what did you understand or what was Dick’s perspective on the difference between physical chemistry and chemical physics? DE LEON: So, I actually don’t know (laughter). I have no idea. Like, I’m sure people have their proprietary definitions. Functionally, what it meant at Harvard was that I had to take essentially all of my coursework in physics. So, it was just sort of a different degree program.

Zierler:

It sounds like it was more weighted- it was a physics program with a heavy emphasis on chemistry, and not vice versa.

de Leon:

Yeah, I’m not- I think it’s pretty fifty-fifty in terms of, like, the people. It’s a very tiny, it’s like two or three people a year so, I’m not even sure how to take statistics. But it had some nice, like, salary bump too something like, you know, it was just all of these stupid little second-order considerations (laughter). I think to first order, what Dick told me that- I- which is what I tell my students now, my undergrad advisees who are applying, it’s you’re really picking a group. So, you know, go to a place where there are two or three groups that you would be really excited to work with. But everything else, courses, how quals are structured, all of that stuff is really secondary. It’s very different from going to undergrad, where there’s like a whole menu of ways that you can live your life or whatever (laughter). Here, you’re just, you know, embedding yourself in a single research group for over half a decade of your life. So, that’s the first-order consideration.

Zierler:

Growing up in California, going to Stanford, what were your impressions of a very different east-coast elite institution such as Harvard?

de Leon:

Yeah, I think- I guess again, you know, my parents were immigrants, and, you know, we didn’t have like a lot of ideas I guess, about the distinction- the fine distinctions between these places. I think if I had, you know, if you had asked me when I was applying to undergrad, I would’ve been able to produce some list of the top schools. But I was pretty agnostic. Like, I think I would’ve been perfectly happy. I didn’t see it as, like, I need something that’s a perfect personality match or anything like that. Stanford loomed large because it was local, so, you know, there’s always a little bit of geographic bias, and I ended up applying there early so then I just didn’t have to make a decision (laughter). So, it was just done after that first round. When I was going to grad school, I could see some pretty clear cultural differences. You know, it was- I think maybe that it took me by surprise that there were such big differences among institutions in terms of like values. I think if you had asked me when I was twenty, I would’ve thought all of these places are basically the same, you know, to within the architecture being different or something like that. But then maybe my digestion of all of this by the end of grad school is that you could kind of learn a lot about a place by asking like what’s the value that people trying to talk about the most in terms of praising other people. So, at Stanford, it was impact. People were always talking about impact (laughter). That, like, that guy had a lot of impact on his field, or this person had a lot of impact on this space. And at Harvard, I think- I hope I don’t offend people with this but it’s really- people talk about how important people are. So, it’s a slightly- it’s slightly different (laughter). It’s not orthogonal, but it’s definitely different. At Princeton, I think, people are all-

Zierler:

If the emphasis is on individual and not groups, perhaps, might be the way of looking at it?

de Leon:

Yeah, or maybe the emphasis is on kind of summing over an individual’s accomplishments as opposed to- and, you know, and thinking about their influence over other- over the rest of their field, over their colleagues. Whereas at Stanford, I think it’s much more focused on, like, the specific actions. Like, this action had an impact on this, or this result had an impact on this big thing. And at Princeton, it’s all about depth. That’s what people talk about. He’s a very deep researcher, is what you hear. So, it’s, again, it’s- none of these things are necessarily good or bad. But it’s a very different sort of cultural bent. And that doesn’t mean every person who’s valued at Princeton is a very deep researcher, right. But it’s just you can see how just the way people discuss it means that they really value it.

Zierler:

Did Dick have specific ideas about who you should work with at Harvard, or you sort of developed that on your own?

de Leon:

Well, Hongkun was his grad student, so I sort of stayed inside the family in some ways. No, I think he tried to be a little hands-off about, you know, you got to go find your own path (laughter). So, he was encouraging, but then not telling me to work for this person. Don’t work for this person.

Zierler:

What was Hongkun’s research at the time you connected?

de Leon:

Yeah, so, it changed a lot from that time to now. So, at the time, what I had started working on was- sorry, it’s been a while since I talked about this stuff (laughter). The field is called single-molecule transistors, so basically, as a postdoc, Hongkun had figured out how to make these very small gaps in metal electrodes where you can then deposit molecules and trap a single one in one of these junctions, and then you can probe them using electrical transport. So, you just sweep voltage, and look at current, and then you can probe the—what’s happening in the molecule and do some form of spectroscopy. And that was a fairly large effort in his group. He was doing things like that, and then also wiring up chemically derived nanowires, and studying their transport. So, it was like a low temperature, low dimensional transport group. And I got there just as he had gotten tenure, and I think he used the opportunity of getting tenure to start going in completely different directions (laughter). So, he had just started or he was just getting a big, like, bio kind of nano-bio interface sort of project going. So, I ended up being like the last person in his lab that had a cold dilution refrigerator (laughter). And the thing is, like, that all ended I think in like my second or third year of my PhD. So, the- for about a year or two, I was really in the desert, searching for a topic to work on.

Zierler:

So, this did not feed into your thesis research ultimately?

de Leon:

Well, my thesis ended up being sort of cobbled together (laughter). It was three or four totally disparate topics just smooshed together into a not very well-crafted story. I have definitely not opened my thesis since I wrote it (laughter). I did a lot of random things. I worked on some, like, nanowire devices, and I was doing like photoelectrochemistry. I worked on a lot of stuff that just like didn’t work and didn’t go anywhere, and in the end, kind of landed in plasmonics and nanophotonics. So, that was how I started talking to Misha Lukin’s group because we were- I was making these plasmonic resonators, and one of the applications is to couple them to quantum emitters. So, we were putting nanodiamonds with NV centers on them, and I was doing that in collaboration with Misha’s group, and then I ended up staying there for a postdoc. So, somehow after all of this, I landed in nanophotonics, but I, in some sense, I don’t have any formal training in nanophotonics because, like, Hongkun’s group didn’t really do nanophotonics at the time. We had like one postdoc that he had hired from a real photonics group, and I learned a lot from that guy. But then- but otherwise, you know, most of what I know comes from a reading group that I started with a couple of other people in Misha’s group. We were like, “We should probably understand this photonics stuff if we’re going to do this research” (laughter). And then we all just got together and read through John Joannopoulos’s Photonic Crystals book over a few-month period. So, we’d just get together at lunch and, you know, discuss some chapter.

Zierler:

Overall, was Hongkun’s group purely in a basic science mode, or were there discussions about applications or even patents?

de Leon:

I don’t think there were very many patents while I was there. So, it was mostly, I guess, if that’s the taxonomy, then I’d say mostly basic science. I think when I joined the group, what he would’ve said was that they were a nanoscience group. So, I think probably there are not so many groups that would label themselves that way now. But, at the time, like, you know, there was a fairly robust community of people who were just looking at anything that you could place in nanometer dimensions, and then see how its behavior changes. So, it was pretty broad. There were material scientists, physicists, chemists, engineers. The postdocs all kind of came from different departments in terms of their training, so it was a really nice environment for, you know, learning how to do things with a broad set of techniques.

Zierler:

Now, Lukin is somebody that you would’ve just interacted with because, by definition, chemical physics is interdisciplinary, or was there some particular interest that you had that guided you to Lukin?

de Leon:

No, so, the interface there was this last project that I worked on in my PhD, so it was this plasmonic resonator stuff. So, yeah, basically Misha and Hongkun were collaborating on plasmonics, and then my project ended up going over to Misha’s group, you know, to kind of do the last stages. And then it just made sense to continue, so I was working on trying to make nanophotonic cavities to couple to NV centers to do cavity QED measurements. In parallel, there was this whole set of ideas for trying to couple nanophotonic devices to cold atoms like trapped in vacuum. So, I ended up sort of doing the nanophotonics on that project and having an interface with those guys. And then towards the end of my postdoc, I guess I sort of came into randomly the trajectory that I seem to have accidentally stumbled into as a professor, which is that it was just very clear that the thing that was holding us back was that people didn’t have any control over the material system at all. So, you could make whatever devices you wanted to around an NV center, but the NV center was not very happy when you did that. And, like, how do you understand what it is that you did to the surface that made it so unhappy? So, I went down a little bit of a rabbit hole that really nobody cared about (laughter). Like, people just would totally turn off their brains when I was talking their ears off about all of these different types of spectroscopy. It ended up being kind of this weird problem that I just kept on working on through the beginning of my faculty position, and it opened up into a lot of other related problems.

Zierler:

Did you have any questions about through lines, the stapled-together thesis, what might have connected the various things that you worked on?

de Leon:

No, I think, you know, it’s not that uncommon basically for people to staple together a few papers and try to make a thesis out of it (laughter). I think my whole defense was about the stuff that I worked on towards the end, so that was all kind of at least one continuous story. And then there’s lots of people who have random chapters in their thesis about previous things that they did.

Zierler:

Did you give much thought to leaving Harvard for a postdoc elsewhere, or were you on a trajectory with momentum where it simply just made the most sense for you to stay where you were?

de Leon:

Yeah, I- actually, I really wanted to go back to California (laughter). That was sort of my original goal. I had promised my car when we moved out to Boston, and I put Massachusetts plates on him, that he would have California plates again. I think now he’s going to die in New Jersey, which is so sad (laughter). But, yeah, so I think sort of the choice that I had when I was looking at postdocs was either to kind of stay in the field that I was in, or make a big, drastic shift. And it looked like there was a really big opportunity to make a very drastic shift if I stayed in Misha’s group.

Zierler:

And you welcomed this? This was a good opportunity for you?

de Leon:

Yeah, I thought so, it was a unique opportunity. I was like the first person to do fab in Misha’s group, so I sort of taught his group how to do- how to go to the clean room, basically (laughter). So, it was-

Zierler:

Fab is an acronym?

de Leon:

No, fabrication.

Zierler:

Fabrication?

de Leon:

Yeah, fabrication. So, you know, it was sort of this really interesting opportunity where he was interested in going in a new direction. I happened to have the skill set to go in that direction. And then sort of in return, I could learn about sort of the world from their perspective and, you know, learn about atomic physics and quantum optics. So, it was sort of a really unique opportunity. In parallel, I met my now husband, so, and he was still finishing his PhD. So, I sort of had to stay close by in Cambridge and-

Zierler:

You accepted the two-body problem, right then and there.

de Leon:

Yeah, exactly.

Zierler:

What did you work on for your postdoc? What was that big opportunity?

de Leon:

Yeah, so, what I was trying to do was- so, there’s this, you know, long history of people doing what are called cavity QED experiments with atoms. So, they do things like- like Jeff Kimble’s group, for example, at Caltech had, you know, these beautiful experiments where they’d take like a neutral atom, drop it through a really high finesse cavity, and then you could see a really strong interaction between, you know, a single photon traveling through this cavity, and your atom. So, there were a lot of people who were interested in doing similar experiments in the solid state, and there were a number of experiments from Jelena Vuckovic’s group at Stanford looking at these things called quantum dots- epitaxial quantum dots, and they were making photonic crystals around them, and then also doing these cavity QED experiments. So, those were really beautiful experiments, but the challenge with sort of doing anything kind of beyond proof of principle cavity QED is that the spin coherence times of those quantum dots are extremely short, and in a fundamental way where you can’t just, you know, do some engineering to make them better. So, the promise here was that if you take these color centers in diamond, which have very long spin coherence times, and nice coherent optical transitions, that you could do completely new things. So, the idea was to sort of put them in photonic crystals, get this very strong atom photon interaction, and then use that to do things like, say, quantum networks where you distribute entanglement across many different NV centers that are in separate cavities, and then use this entanglement as a resource for communication. So, that was sort of the promise, and people had done a lot of the pieces. So, in Misha’s group, they had already demonstrated spin photon entanglement, and people had done a lot of spectroscopy on these NV centers. So, the real challenge was that there was no way at the time to make photonic crystals out of diamond. And so normally the way that you’d make a photonic crystal is you have some heterostructure where you have a device layer that you care about, and it’s sitting on top of something that you can get rid of. But, for diamond, there is no such thing as these heterostructures. You have to sort of only grow diamond on top of other diamond. So, it’s sort of a funny problem, but you just have too much diamond (laughter). And it’s like what do you do with this bulk crystal? So, we came up with this method for kind of machining the diamond, basically, etching it in a way that you could carve out something that was suspended, and made photonic crystals that way. And then the problem that we ran into, which I kind of alluded to earlier, was that you did this thing, and then now all these beautiful properties in the NV center that you had to begin with would just get worse and worse and worse. And, so, there’s now, I guess, like, ten years later, a fairly large graveyard of other people who have tried to do the exact same experiment and failed in various ways. And it’s- it looks like it’s just a very hard problem. The NV center has this enormous permanent dipole moment in the excited state that couples to electric field. So, even if you have problems at the part-per-billion level, you just see this enormous sort of diffusion of your optical line, so it sort of kills your ability to do any of this stuff.

Zierler:

What are you seeing now that wasn’t possible to be seen before?

de Leon:

Well, so, what that took me to as a professor was trying to just find alternative material systems. I think there were sort of two directions that I ended up pulling off of this- off of my little tombstone in this graveyard (laughter). The first was, well, maybe you should just make a system that isn’t so sensitive, right? Like, maybe you can find a way to engineer a system that’s fundamentally insensitive to these processes, and design something ab initio. And then the second track was can we just fix these problems, right? Like, can we understand what’s going on at the surface, or what’s going on when we do this fabrication, to try to improve things overall? And I ended up spending, you know, the first few years working on exactly those two problems. Most color centers in diamond that people have been looking at are- they’re sort of manna from heaven. It’s like somebody pulls a diamond out of the ground that happens to have this color center, and then you just study it for like a decade and try to figure out everything that you can about it. Or somebody has a reactor where they accidentally contaminate their diamond because the plasma hits the wrong window at some time, and then it turns out that, like, that’s a really excellent sample. But that’s a terrible basis for trying to discover new things, right, because it’s all just serendipity. So, what we did was we came up with, you know, first, let’s write down some design principles for these defects, and then let’s just intentionally introduce them by ion implantation, and then just find ways to deal with ion implantation damage. So, once you’ve done that, it’s very general. You can just put the whole periodic table into the diamond and, you know, study what you get. And basically, right out of the gate, we discovered a new color center that was fundamentally insensitive to its environment, both from a perspective of these optical problems that NV centers have, and the spin coherence time was actually quite long. So, that was kind of, you know, one big track of research in my group.

Zierler:

You’re very generous with your use of the “we.” So, first of all, at Harvard, who is the “we”? Who are your key collaborators?

de Leon:

Yeah, so, at Harvard, oh, gosh, it’s- well, it’s a long list because Misha tends to be- his style is that he, you know, gets a lot of people interested in a problem, and then tries to stick different expertise together.

Zierler:

And is Misha fully engaged in this, or is there a whole broad portfolio that he’s involved in?

de Leon:

So, his group now is gigantic, so I’m not sure how things work now with quite so many people. But when I was there, there were only thirteen experimentalists. It’s a unique arrangement because he is a theorist by training, but then he has this huge group that’s, you know, half experimentalist and half theorist. So, on the experiment side, in some ways, it’s- you know, you have a lot of freedom to decide what you’re going to do, and how you’re going to do it, because Misha’s never going to come in and tell you how to align a laser or, like, what exact, like, pulse generator to buy or anything like- that’s not really like the space that he lives in (laughter). It’s a really special place because he is enormously creative and can come up with completely new directions. But then you have quite a bit of freedom as the experimentalist to kind of choose your own directions within that broad direction. But, yeah, I just did-

Zierler:

What was the value of having theorists and experimentalist together in one group, which is a- it’s a pretty unique arrangement?

de Leon:

Yeah, no, it’s enormously valuable, and very unique, and it’s a really special place. So, I think- how do I put this? I think the thing that’s really amazing about that group is that it’s not only that you have theorists and experimentalists under one roof, but it’s also that you’re doing both at a high level. So, like, it’s not unheard of for experimental groups to have a house theorist that helps them analyze their data, right. But then, generally, those theorists are not necessarily working at the forefront of theory.

Zierler:

Sure.

de Leon:

They’re more just sort of applying theoretical techniques to data analysis. But in Misha’s group, there really are like theorists who are doing, like, theory PhDs and theory postdocs. And I think what that does is it both sort of keeps the experimentalists on their toes to really justify what they’re doing at a fairly high level, and I think it also grounds the theorists, right, because then they spend more time thinking about what’s possible in experiment, and then that allows them to, instead of thinking about everything in completely abstract terms, to really write down concrete proposals for, look, if you guys could figure out how to do X, Y, and Z where X, Y, and Z sound hard but not impossible, then look at this incredible frontier that you could push into. And I think having that really close interface is really something special.

Zierler:

Just generally this just sounds like an idealized version of how theorists and experimentalists should always interact (laughter). But it’s unique to your group.

de Leon:

Yeah. Yeah, no, I think, no, it’s a- it is really a great place, and I think-

Zierler:

Nathalie, what might exemplify that point, like a real advance in the group, in Misha’s group, where you have this close collaboration of real theorists and experimentalists doing really cutting-edge stuff where the collaboration moves the needle forward in a way that it might not otherwise have?

de Leon:

Yeah, I feel like not super well-qualified to comment on what’s going on now. But I think almost having-

Zierler:

No, I mean when you were a postdoc, just your recollection of those interactions.

de Leon:

My experiment was maybe not very interesting to theorists because what we were trying to do is solve this really hardnosed technical problem and do this really hard experiment. But, for example, like, you know, right next door, the theorists had had these proposals for how to use Rydberg interactions to do particular things for a very long time, and they were refining these proposals, and there’s always somebody thinking about it. And then a lot of those experiments sort of came to fruition around the time that I was there, and the fact that the theorists had laid out this roadmap already, and had been thinking so carefully about it meant that it was very easy for the experimentalists to come and just like clean up, right? Like, they just knew how their first three papers were going to be written, and when they uncovered surprises, it was clear how to think about those surprises, and, you know, what directions to move in once they had those surprises. So, just seeing that process was really interesting.

Zierler:

What were some of the key funders of Misha’s lab? Was it mostly NSF?

de Leon:

No, I think it’s everyone. I think he basically has every pot of money (laughter). It was a lot of DOD and NSF, I think, and maybe these days a little more Department of Energy.

Zierler:

Nearly five years, is that a standard amount of time for a postdoc in your field?

de Leon:

Is that how long I was there? It was 2011 to- oh, yeah. Yeah, I guess I would’ve scored it as four, but it’s because I ended up spending another half-year there after I got my job.

Zierler:

Because you got to Princeton in, like, mid-year essentially, January.

de Leon:

Yeah, in January, that’s right. Yeah, I ended up staying longer because my husband had just started his postdoc, and he wanted to finish a couple of papers.

Zierler:

How did the opportunity at Princeton come together for you?

de Leon:

I don’t think there is any, like, interesting story (laughter). I went and applied in the regular cycle, just as everyone does, ended up interviewing at, you know, something like ten places, had some number of offers, had to talk to all those places, sort out the two-body problem. That’s basically it.

Zierler:

Did you give much thought to what it might mean to join an electrical engineering department, which was new territory for you?

de Leon:

Well, so, I had applied quite broadly because I am sort of- I’m very in-between disciplines already and have kind of a broad set of research interests. So, like, I interviewed at chemistry, physics, applied physics, and electrical engineering departments, and then linear combinations of those things at various schools. So, no, I mean when you’re applying for jobs, you just want a job (laughter). I don’t think there was a lot of deep thought about going into one department over another. I think it was important to me that I find like a good group of colleagues, and a reasonable spiritual home, and it was clear that there were at least enough people who were doing applied physics here that I wouldn’t be a total fish out of water.

Zierler:

What kind of support did you get from Princeton in terms of any ideas you had about setting up your own lab?

de Leon:

What do you mean by that?

Zierler:

Like, did you get a startup package? Was there the sense that you could come here, and you had well-formed ideas of what you wanted to do, and you would get the support to do it?

de Leon:

Yeah, I mean, so, there’s a lot of things that are now fairly standard and routine in terms of recruiting assistant faculty. I think all of these places, you know, they have the resources to do so, and they want to see their assistant faculty succeed. Like, their aim is not to bring you here for like a Hunger Games style, you know, like let’s just see who survives kind of thing, so-

Zierler:

Which is a change. This is not how it used to be, of course.

de Leon:

Yes. Yeah, my understanding is that it was not like this in- as recently as, like, the late nineties.

Zierler:

Sure.

de Leon:

So, it’s a pretty recent change. Yeah, no, I mean, I had a startup package, and some lab space, and, you know, some ways to get started before getting my own grants. And I’d say, you know, overall, they’re quite supportive of assistant faculty. I think that’s relatively common at a lot of schools now.

Zierler:

So, the opportunity to build from scratch obviously gives you lots of leeway to think about the research questions that are most important to you? So, on that note, did you see this as a place essentially to continue what you were doing at Harvard, or what might there be new opportunities to take on new research that you weren’t doing previously?

de Leon:

Yeah. So, I guess- I’m not sure. On some level, when you start as an assistant professor, it’s scary and stressful enough that you just sort of take your two or three best ideas and try to run with them. Maybe other people have a very different experience of this and are able to do long-range strategy in a way that I wasn’t.

Zierler:

Well, just to go back to Hongkun’s point when he got tenure, all of a sudden, all kinds of new projects started cropping up. Maybe there’s a-

de Leon:

Yes, no, no, I-

Zierler:

-an inherent conservatism there?

de Leon:

No, no, that’s right. There’s a difference. There’s definitely a difference when you get tenure because then (laughter)- because now it’s a very different, like, set of considerations. But I think when you’re starting from an empty lab and no grants, then the goal is to just not wash out and, you know, be as productive as possible. So, I’m sure that there are other people who are better at this who have been writing their own Nobel Prize citations since they were twenty-five and managed to strategically work their way to that citation (laughter). But I think in my case, you know, I had small ideas. I had this one project that I had kind of started as a postdoc in Misha’s group that I knew nobody cared about, people didn’t want to hear about at all, but now that I had the freedom to work on it because nobody could tell me what to do, I was just going to do it. So, the idea there was just I think I’m on to something, so I’m just going to do it. There was no grand vision. It was just I’m going to understand diamond surfaces, and I think I have like programmatically a good idea for how to understand it, and just sort of burrowed myself into this hole.

Zierler:

So-

de Leon:

And then separately, I had one maybe minorly clever idea about making a new color center, and we just went and did it, and I think, you know, got a little bit lucky basically that it worked the first time.

Zierler:

So, what are some of the advances five, six years out working on these problems that you took with you from graduate school? Where’s the lab now? What are some of the accomplishments? DE LEON: This new color center is very exciting, and it’s the only color center that anyone has found that has good optical properties and these long spin coherence times. So, what we’re trying to do is now deploy them in quantum networks, so we have a lot of activity going on to create a spin photon interface. We recently reported optically detected magnetic resonance. We’re trying to integrate them into nanophotonic devices. And then kind of separately, we have this whole pipeline for trying to discover other defects. So, you know, a lot of that pipeline was just figuring out how to do spectroscopy in this sort of weird regime where we were trying to get really high sensitivity. And we have this joke plot in the lab where we can show that our sensitivity changed by six orders of magnitude over the time that we were trying. And what I like to say is that first five orders of magnitude was stop doing stupid things (laughter). But that last order of magnitude was definitely trying to do some clever things. And I think this is the only path that anyone has to really doing this stuff systematically. I bet if you had asked people five or six years ago, like, is there any possibility of systematically discovering new systems, and making them better, they would’ve said, like, “No, that material stuff is too hard.” So, I think we have managed to plot our way to something that is programmatically unique, and likely to yield a lot of really interesting stuff. And then on the surfaces stuff, I- you know, kind of the main big accomplishment there was that we were able to learn enough about diamond surfaces that we could improve the coherence time of really shallow NV centers by about an order of magnitude. The reason that that’s really important is if you want to use an NV center for sensing, then both your sensitivity and your resolution are going to depend on how close you can get to this other thing. So, if you’re close to this other thing, and you’re also close to a surface, and the surface is really lousy, then you just end up getting a lot of noise from that surface. So, what we did was we figured out how to do direct spectroscopy of the surface to beat down all of these sources of noise. So, now we sort of routinely make these substrates that have kind of world-record shallow NV centers, and we’re now just deploying them as sensors. So, we’re spinning out a large number of experiments now where we’re just taking advantage of our kind of position in this space.

Zierler:

Nathalie, given that you’re doing things that are not happening anywhere else, what- who else values this work? In what ways is this research valuable to people that you might not necessarily be closely collaborating with but they’re really appreciating what it is that you’re accomplishing?

de Leon:

Yeah. Well, so, there’s- okay, nobody cares about the surface stuff, or did when I started (laughter). But there is an enormous community of people working on color centers in diamond. So, this is, like, immediately interesting. It’s now- I shouldn’t make it sound like this is totally unappreciated. I mean, dozens of groups around the world who are trying to do exactly this, where you take an NV center, put it next to something else, and sense it. So, the stuff that we’ve done is sort of immediately applicable to everything that they’re doing, and, you know, it’s sort of a big enabling tool or enabling something- advance, I guess. It’s not really a tool. Separately, I think the other lesson that I learned was that this systematic material spectroscopy is something that almost nobody in my field does, broadly speaking. So, there are all these other quantum platforms, trapped ions, superconducting qubits, semiconductor quantum dots, and they’re all dealing with the exact same set of problems, which is that they have really poor control over surfaces and interfaces in the constituent material systems. And almost all of them do the exact same thing that the NV center community did before we started our work, which is like you just do something, and then you measure your qubit, and then you do something else, and you measure your qubit again. And, you know, this is a lot like middle school science fair kind of stuff where you, like, you have a plant, and you pour Coca-Cola on the plant, and the plant died (laughter). Like, it’s just not very sophisticated (laughter). And it’s clear that if you could actually measure properties of the plant, and do things quantitatively, you would actually learn something. So, what we started doing was just trying to correlate direct material spectroscopy and analysis with these qubit measurements, and discover its sort of like what are the actual microscopic sources of noise. In the course of working on the diamond surface stuff, I discovered that this was like a very broadly applicable technique. We then started working on superconducting qubits a couple of years ago. So, I’ve kind of branched out into completely different physical systems as a result. And the kind of exciting thing that happened there is there was this, like, stagnation in improvements in superconducting qubits for the last almost decade. Like, the last time somebody set a record for the lifetime of a planar qubit was 2012, and it’s been stuck around one hundred microseconds since then. And that’s despite enormous investment. IBM has hundreds of scientists working on this problem. Google has this massive superconducting qubit effort, and there are all of these academic groups. And I think what happened was just people got very clever about microwave design, and then were just like the material stuff is too hard. I’m not even going to try. And what we did was, in collaboration with Bob Cava, who’s a solid-state chemist, and Andrew Houck’s group, who works on these superconducting qubits, we just said, “Okay, let’s just take a look at these materials and see if there’s anything that we can learn and systematically improve.” And, again, sort of right out the gate, we just replaced the superconductor that Andrew’s group with another superconductor that has better oxides because that just seems like a really likely source of problems, and immediately sort of broke this record by about a factor of three. So, that was just like the first thing we tried. So, it just seems like now there’s this entire orchard of low-hanging fruit where if you just do a little bit of systematics on the materials to understand what you’re looking at, that there’s a lot of possibility for just qualitative improvements in these things.

Zierler:

It sounds like possible breakthroughs on many fronts in the future, hopefully.

de Leon:

Hopefully, yeah (laughter).

Zierler:

As you put it, Nathalie, you know, coming up, you were in large sprawling groups at Harvard. Have you adopted that same approach for your group? Do you like it on the large size, or do you like things more small?

de Leon:

I can’t imagine ever having a group of like forty people. That just seems- it’s like a different sort of enterprise. Like, I’m still very involved, and I think we don’t have like a lot of data analysis notebooks that I haven’t at least opened and run myself (laughter). So, that’s-I don’t know if that makes me really hands-on. I definitely- I know what’s going on in all my experiments, and do a lot of like deep troubleshooting, and it’s hard to scale that to ten to twelve experiments or, you know, more than that. My group right now is around ten people. Maybe it’ll drift up to fifteen. But I don’t think it’s ever going to be gigantic. In terms of disciplines, I think I am a little bit sprawling though. Like, I have postdocs that come from EE, from physics, from many different disciplines inside physics, material science, from chemistry. So, I did learn something about, you know, the benefits of that kind of environment. And I would say that we tend to not- I don’t know if “sprawling” is exactly the right word, and I also don’t know if “interdisciplinary” is exactly the right word. But I think we do- I have figured out that we have a slightly different approach to science from a lot of experimental physics groups. So, most physics groups, they kind of have a set of capabilities that they see themselves as specializing in, right. So, it’s like I know how to do this kind of measurement in this kind of apparatus, and then they’ll make relatively small excursions from that. But their goal is to do the most beautiful physics that they can, given the constraints of their apparatus, and then try to make improvements in their apparatus to access the next kind of bit of beautiful physics. I think we tend to take more of a perspective of, like, here is some problem, like a medium to long-term problem. What would it take to really solve that for real? The answer might not be physics, right (laughter). The answer could be something com, the answer could be chemistry. The answer could be a lot of other things. And, so, I think what that requires is that you find collaborators, you know, to work on various parts of these problems. We sort of expand into a large number of other techniques. I’m not a surface scientist by training at all, but we went and built a surface spectroscopy tool in my lab for being able to do a lot of the stuff. And it wasn’t because I was particularly enamored with surface science. I didn’t want to become a surface scientist. But it was just the thing that we had to do to solve the problem that we were staring at.

Zierler:

I’ll ask two structural questions that might get you to pigeon-hole where you fit in academically, given that your research agenda is maybe not interdisciplinary, but it’s certainly diverse. I mean, that would be probably a very fair way of describing all of the different projects that you’re in. So, on the teaching side, what are the classes that you’re maybe expected to teach, or what are the classes that you enjoy teaching the most, or you feel the most qualified to teach?

de Leon:

Yeah. Well, so, I mean, we have a large number of applied physics courses in our department, so all of those are sort of inside my wheelhouse. I guess the classes that I have been teaching for the last few years are- I teach this device physics course for undergrads, and that one, they do- there’s like a lab component where they make their own transistors and diodes and things like that, so they actually go into the nano fab and, you know, and fabricate things themselves. And it has a whole sort of device physics lecture sort of traditional course component on top of it. And then my graduate seminar is on quantum material spectroscopy, so the idea there is to try to go through, you know, all of these different spectroscopy tools. So, I guess that makes me a spectroscopist. I don’t know. That’s a little funny to say (laughter).

Zierler:

It goes all the way back to undergrad though, in some ways.

de Leon:

Yeah, exactly (laughter). Deep inside, I’m really just a spectroscopist. And then I’m actually- I’m starting a new course in a couple of years- is it really in a couple of years? In a year, two new courses. So, I’m going to teach a quantum- start a new quantum lab course next spring where we actually have demonstrations of quantum information processing through a bunch of modules, and the students have to come in and really- they’re hard labs. So, it’s supposed to be an advanced lab course. And then I’m teaching a new course next year on quantum devices.

Zierler:

The other question, the other structural question is, what are the most important journals for you to publish in, and conferences to present at?

de Leon:

Yeah. So, I think I do probably mostly- well, other than the answer that, like, you want to publish in Nature and Science, I think I do mostly publish in physics journals, so a lot of my papers are in the Physical Review family.

Zierler:

More than chemistry journals or engineering journals? That’s where I was going with that. That’s -

de Leon:

Yeah, yeah, exactly. I think I- is this true? I might not have a single paper- well, I certainly don’t have a single paper from my independent career in a chemistry journal. I think that’s true. And I actually don’t know what counts as an engineering journal. I guess like the IEEE journals are- so, that- maybe that answers your question if I don’t even know (laughter)- ZIERLER: There you go (laughter). And what about conferences? Is the APS, is that most important for you?

de Leon:

Yeah, so, conferences, we don’t have like a natural home conference the way other groups do. So, it- we tend to be a little bit distributed across, yeah, APS March meeting, and APS DAMOP, which is the atomic physics conference, and then MRS. But I think if there was like an actual home, it’s a small conference to call a home, but it would be like the Quantum Science Gordon Conference is kind of like the most natural community for a lot of the work that I do.

Zierler:

To come back to the issue, we talked about the diversity issue as an undergraduate, and you already mentioned that you have a very different perspective now that you’re a faculty member. Specifically, this past year shut down STEM, things like that, it’s been a moment of reckoning, inward thought in the STEM community. From your perspective, where have you seen tokenism, sloganeering, really, you know, surface kind of discussions, and where have you seen actual meaningful commitment to things getting better and things changing?

de Leon:

Yeah, so, I do have to say I think there are a lot of encouraging changes that have happened since George Floyd-

Zierler:

Yeah.

de Leon:

-since all of the protests last year. It’s kind of easy to overweight changes and think that everything is going to get better. So, you know, a lot remains to be seen. But I think that was a big enough scale reckoning that it seems like it was just the jolt that people needed to try to reform a lot of things. So, actually, inside our department, we had a very large number of meetings. We normally don’t have faculty meetings over the summer, but we decided to have a large number of extra meetings in August to discuss how we could reform different parts of different aspects of the department in response, basically to address structural racism. Actually, even just the fact that people are willing to say the word “structural racism” now is just stunning to me. I think-

Zierler:

Meaning that it’s embedded in the system? It’s not just individuals saying dumb things?

de Leon:

Well, that and just using the word “racism.” I think, you know, just a couple- just two years ago, I think a lot of these conversations would’ve been wrapped in- how do I put this? Wrapped in sort of a lot of feelgood euphemisms about diversity, right, where the implication is that there’s nothing bad going on (laughter).

Zierler:

Yeah.

de Leon:

There’s nothing that we’re trying to address or redress. The thing that we’re trying to do is just like- it’s all good, right. There is-

Zierler:

Yeah.

de Leon:

We would like it if things were more diverse, and maybe there are some accidents for why we’re not as diverse as we could be, so then we should try to enhance- it was all about enhancing diversity.

Zierler:

Yeah. But you’re saying now-

de Leon:

And I think-

Zierler:

-there’s significant appreciation that harm occurs, and it needs to be addressed?

de Leon:

Yes, exactly. And I think two years ago if you had brought up in any meeting something about addressing systemic racism, or just used the word “racism,” I think a lot of people would’ve cringed-

Zierler:

Yeah.

de Leon:

-right and reacted in a way that put a chill on the meeting so that it would be hard to make progress. It was a lot about, like, managing people’s feelings and expectations about this stuff, and making sure that they didn’t feel like they were being accused of anything. And, yeah, something about- if you say, like, let’s all figure out how to enhance diversity, you’re all on the same team, and it’s all very feelgood (laughter). But if you say there is systemic racism, now, you’re all on the same team, but it’s the bad team (laughter). Let’s see what have we all done to contribute to this really bad system, and how can we fix it? So, even just that shift I think has been a really meaningful shift in how we talk about these things. And in the department, we completely changed how we do hiring. We completely changed how we do admissions. We made sort of a commitment to actually measuring what we do, and keeping good records because one of the places that systemic bias can lurk is if you don’t just write down why is it that we ruled out this person or- and, you know, and not this person, then it’s easy for a single individual’s bias to really, you know, infect the whole process, or it’s easier for everyone to kind of overlook someone for subtle reasons that are hard to track down. So, I’m very encouraged. I think, actually, our incoming class and the- this sounds very trite. But, basically, what we did was we stripped as much identifying information as we could and forced everyone to make arguments on the basis of substantive pieces of their application. So, instead of saying, like, “I could really see this guy being successful,” like very amorphous comments, you had to justify what you were saying based on things that you could find in the application. We ended up magically after that with the most diverse incoming class that we’ve ever had, and the largest number of underrepresented minorities.

Zierler:

This scenario you just described, by the way, I don’t know if you ever saw the movie Moneyball, but that’s exactly how the general manager of the Oakland “A”s, Billy Beane, “Don’t tell me, guy. I can see this guy succeeding in baseball. I don’t care what he looks like. What are the metrics? What are the metrics”-

de Leon:

Yeah.

Zierler:

- “that are going to show me this person is built for success?” That’s a remarkable parallel there. And for you personally, I mean, are you comfortable? Are you active in that space? Are you out in front of these issues, or you prefer to sort of more be who you are, look what you look like, and lead by example from that?

de Leon:

Yeah, I’ve been very active. So, I was very much in the middle of this process. It was basically me and two other faculty members that were leading the charge on this reform of our admissions and faculty hiring. So, yeah, I’ve been very, very vocal. And I think, you know, another role that maybe I wasn’t totally anticipating when I started my faculty position was the extent to which people would sort of seek me out for mentorship. And, you know, I think it just- it’s hard if you’re a young person to figure out who’s a good ally, and who isn’t. So, demographic markers are the easiest thing to cue off on. So, I actually- I have a large number of people who sort of reach out cold, and say, like, “Hey, here’s this thing that I’m dealing with.” So, I think it’s just made me a lot more acutely aware of just the issues people are dealing with, and how they perceive- yeah, basically just the difficulties that they face in this environment.

Zierler:

And just to bring our discussion up to the present on the science side, what are the things you’re working on right now?

de Leon:

Yeah. So, this- the superconducting qubit stuff is sort of like the big thing that is ramping up in my group right now. Part of it is because we have this big leadership role in this national quantum initiative DOE Center, C2QA: the Co-design Center for Quantum Advantage. So, it’s largely Princeton, Yale, Brookhaven, and IBM are kind of the center of mass of the whole thing. And that’s a super exciting opportunity for me because I’m jumping into a completely new field, you know. It’s like a parallel community, right. There are very few people who kind of switch between these platforms. And the really amazing thing about this center is that, you know, I have a lot of dumb ideas, but I get to run my dumb ideas by like Robert Schoelkopf and Andrew Houck and Michel Devoret, right. And then they can lead me in the right direction. And Andrew and I have a really exciting kind of experiment that we’re working on now to try to improve on this tantalum result that we had earlier this year or last year where we’re doing systematics, and it really looks like we can pull things out of the data. The way that I kind of see it is, like, we’re sort of putting the cultures of our respective groups together to try to do something new. So, you know, my training is at least partly in like atomic physics and metrology, and we’re always asking the question, like, how can you do these measurements as fast as possible with as high sensitivity and, for example, multiplexing them? And, also, as an atomic physicist, I think we should be able to understand all the data. I should be able to take a very large parameter sweep right down my model and fit it. And if I can’t fit it, it means I don’t understand all of the physics. And I think, you know, on the condensed matter side, those groups tend to have a slightly different perspective because usually in condensed matter, you don’t understand everything. So, it’s more like you’re trying to tease out some particular feature of the data. But if there’s a lot of stuff you don’t understand, maybe you just kind of ignore it. It’s not a big deal. So, here, with these measurements, I’m trying to enforce this discipline that, like, let’s try to understand everything. And through that process, we’ve been able to actually make some meaningful progress on the material side. Like, we can just see parameters, and we can see these things change when we do things, and it’s all very convincing in kind of a nice way. So, that’s the thing that’s, like, coming around the bend right now that’s very exciting. And then the other kind of- well, we have a lot of stuff that’s going on. So, we continue to work on those quantum networks and quantum sensing stuff. I have a few projects that I’m spinning up on the quantum sensing side that are kind of exciting, but maybe are too half-baked to talk about. We do have kind of a cool- I guess from the perspective of like interdisciplinary diverse research- a very neat collaboration with an organic chemistry group. Nothing makes me feel less like a chemist than the fact that I have a project in my group called the chemistry project (laughter). But we have a chemistry project (laughter). And the idea is that, so diamond surface chemistry is really difficult because diamond is very inert. Diamonds are forever. And the lattice constant is really small. So, like, kind of the normal stuff that you would try to do just doesn’t really work because it’s just very sterically hindered. So, normally, what people do is crazy stuff. Like, you stick it in a plasma where you’ve made this ionized gas, and are sort of etching the diamond but doing this horrible stuff to it. Or people do things like put diamond in essentially a bomb of hydrofluoric acid, and then ignite that bomb and then you could get fluorine terminated diamond. And what we discovered was- I was talking to Rob Knowles, who is a synthetic organic chemist at Princeton. And he pointed out to me that there is this whole new class of catalysts that people have been using on diamondoids, which are these small molecules that are like the subunit of a diamond lattice, and that this field had just been totally busted open in the last ten or fifteen years. And he was, like, that kind of looks like a diamond. It doesn’t seem like this should be that hard. And I was like, okay, I mean, lots of people have tried to do wet chemistry on diamonds and have failed. And Rob was like, “I bet we could do it in a year” (laughter). So I was like, “Okay, you’re very confident, so let’s try it.” And the thing that made this really challenging is that, normally, organic chemists when they are doing reaction discovery, they have all of these tools for doing small molecule spectroscopy, right? You can do your thing, run it through a column, do gas chromatography and mass spec, and NMR, and then really definitively know what bonds did you make, and in what orientation, and all of that stuff. But if you have a surface, you can’t do any of those things because you just have this single monolayer of atoms, and then knowing whether or not you’ve actually done your chemistry or not is quite difficult. So, my group’s role in this was both to prepare surfaces that were good enough to even try some of this reaction discovery, and then to develop a whole- oh, god, I am a spectroscopist (laughter)- a whole spectroscopy pipeline for figuring out whether or not you had a good hit on this surface chemistry, and then working in close collaboration. So, you know, we’d hand them a surface, they would try with one of these new sort of catalysts and some new chemistry, and then we would go screen it, and then we could find hits, and then find ways to verify it using synchrotron techniques. So, really excitingly, we have- we totally have reactions that work, which is very shocking to me. And Rob was right, it did take about a year. And then kind of the latest breakthrough is that it looks like we now really understand the mechanism of these things. So, I think, you know, I hope this is really going to take off in the next few months because it seems like there’s now a lot of things that we can try. And the short- or the medium-term goal, I should say, is if you really have this gentle kind of wet functionalization that works at the surface of diamond, then now you can meaningfully imagine putting things like proteins on the surface, right. So, if we can really functionalize it under conditions that expand the scope of groups that you can put on, then, you know, you have your little NV center sitting a few nanometers from the surface, and then I can take a protein, plonk it on the surface, put a bunch of stuff—a bunch of other stuff on the surface that keeps that protein happy, and then use my NV center to probe what’s going on in this protein.

Zierler:

Nathalie, for the last part of our talk, I’ll ask a broadly retrospective question, and then we’ll end looking to the future. So, I can tell already that you don’t have a grand prepackaged narrative that helps you make sense of all that you’ve done. Your research style and personality perhaps is not geared toward that. So, I’d ask the question like this. What are you most curious about in the research world that you operate in that would connect all of the different collaborations, all of the different experiments that you’ve been involved in? What is that curiosity that might help make sense of connecting all of these things together for you?

de Leon:

Yeah. So, I guess, if you’re asking for a prepackaged narrative, I think that there’s-

Zierler:

I’m not. I specifically said there isn’t one. But—

de Leon:

Well, what I’m-

Zierler:

-just what you’re most curious about.

de Leon:

Yeah. No, well, what I was going to say, I think if you asked somebody else in my field to characterize what I do, what they would probably tell you is something along the lines of material science for quantum technologies. I think that’s probably how a lot of outsiders would define my contributions. And it’s not that I’m resistant to that characterization, but I’m also like not really a material scientist (laughter). Like, I think it’s another one of these things where like, I can’t really claim to be a chemist. I guess I can sort of a little bit claim to be a physicist. But I definitely can’t claim to be a material scientist. Like, I don’t really have any formal training in any of these fields. But, in terms of what I’m most curious about, I think what I like is just rigorous hypothesis testing. Is that too stupid? Isn’t that what like- I think that’s what like all scientists are supposed to do (laughter). But, like, I guess- okay, there- I can see that there are many different styles of physics, right. Like, there are people who really like showing the beauty of physics, right. Like, they say, like, “Look, I have this target Hamiltonian, and then I have built this very elegant system where we can show that we understand everything.” And then here’s something that’s like a little bit surprising about it, you know, and it’s mostly- it’s almost like aesthetically motivated, like you’re trying to show like the beauty of that part of physics. And then there are other people who are really tool builders, right. Like, they really- what really excites them when they go into the lab is like how am I going to build this thing, and then make it better? And then they go through many, many iterations of, like, making that tool better and better. And I think I am somehow like not either of those things (laughter). So, I tend to be motivated by, here’s a problem that people have not solved. No, maybe that’s not right. You know, I think, okay, when my students bring me an array of problems, and they’re like, “I’m thinking about this, or I have this puzzling thing,” I think it’s pretty clear that I spend the most time thinking about things where we have a shot at learning a new thing about nature. Like, you know, that there’s a thing, there’s a phenomenon that we don’t understand, and now maybe we can try to understand it. And it does seem like inasmuch as, like, curiosity is really measured by, like, where do you spend all of your time, maybe that still makes me a spectroscopist (laughter). For example, we do have this big instrument that we’ve been building over several years, and I have really enjoyed that project. But I don’t think that I’m going to go spend the next five years building a better version of that instrument. Or when it’s, like, we have this technical problem to solve, to try to make this thing work, I will spend a lot of time on it, but I will spend much more time on a data set that someone sends me that’s like this peak is not supposed to be here, and I don’t understand it. And then I can come up with a lot of ways to test whether or not our understanding of it is right.

Zierler:

Last question, looking to the future, all of the buzzwords are there: superconducting qubits; quantum hardware; quantum information processing. They’re all there in your research agenda. Where does all of this fit into the broader effort to create true quantum computing, and to what extent might you push back on having your research subsumed in that larger and in some ways poorly defined effort?

de Leon:

Yeah. So, I mean, I think it’s clear that there are a lot of super exciting opportunities right now in taking sort of what we know about quantum mechanics and quantum information, and then trying to implement them in physical systems, and do something completely new. So, we’re sort of entering this whole realm of both kind of a new phase of quantum science, and maybe the really, truly new thing is quantum technologies, like really trying to build these things into meaningful technologies. And I think that’s really exciting. I think the reason that I wouldn’t want to be characterized as like completely subsumed in that is that it could be that that’s exciting right now, and then fifteen, twenty years from now, like, it becomes the domain of, you know, Intel or something, right. So, I think- you know, or if I discover that there is some way that I have a real shot at making a fundamental contribution to neuroscience, that’s really trite (laughter). I think a lot of physicists think that they can do neuroscience (laughter). Let’s say geoscience, you know, and I think if I had a shot at measuring something meaningful about the world around me that had nothing to do with quantum, then I would totally do that thing, right. So, I see this as, like, can you come up with new methods and, you know, new experiments to actually learn stuff about what’s going on? And, in the meantime, I have a set of really interesting applications for a lot of those things. But, like, you know, the ultimate goal of a lot of this NV center stuff is to actually build it into a biophysics platform.

Zierler:

Yeah.

de Leon:

I think if I could really be doing biophysics in- five years might be ambitious, but let’s say ten, then, you know, I will have thought that this whole enterprise was a big success.

Zierler:

So, that’s to say, Nathalie, that if some of your research is effective in creating true quantum computing, whatever that’s going to look like, whenever that happens, you’ll be happy to hear it. But that’s not necessarily how you’re self-defining the trajectory of your research?

de Leon:

Yeah, exactly. I mean, I think quantum computing is a really, really interesting application, and it, you know, it’s clearly a really interesting problem that’s very complicated, and I think that there’s a particular, you know, angle that I have on it that might- that has a shot at making some big contributions. But that’s sort of different from saying, like, every day, I wake up and say, like, oh, I really want to do Shor’s algorithm (laughter). I really need to factor this giant number, right. I imagine that the people who made like the first code-breaking computers they really wanted to break those codes, so they were really motivated to really build that computer. So, I think it’s clear that, you know, my interests in this are a little bit different.

Zierler:

Nathalie, it’s been so fun spending this time with you. I really want to thank you for doing an interview with me.

de Leon:

Yeah, thank you for emailing and reaching out. It was a lot of fun.