Ángela Capel Cuevas | Meet the MCQSTians: they are curious about science and passionate about their research, have diverse careers paths, work in inter-disciplinary teams, and are at the forefront of the second quantum revolution. In this series, we regularly feature members of the MCQST community.

“Never believe that you are not good enough. Do not let anyone tell you that.”

Ángela Capel Cuevasis an MCQST Distinguished Postdoc who joined the group of Michael Wolf and Robert König at the Department of Mathematics at TU Munich in 2020. We invited Ángela to share why she’s excited about her work, how she became interested in quantum information theory, and what motivated her to move to Germany and work in Munich.

Can you briefly explain your research project?

My research focuses mainly on the study of quantum dissipative evolutions for quantum many-body systems, a field that arises in the interplay between quantum information theory and quantum many-body systems. More specifically, I am interested in the velocity of convergence of thermal dissipative evolutions to their equilibriums and their study via quantum functional inequalities.

In the last years, I have focused on an approach to obtain estimates for the speed of thermalization of such systems by obtaining results of positivity of modified logarithmic Sobolev inequalities (MLSIs), a particular case of quantum functional inequalities. The positivity of a MLSI for thermal evolutions implies in particular that there is a rapid decoherence of the system. This property is of interest because it has been recently used as a viable method for the preparation and control of relevant phases of matter, as well as to estimate the run-time of algorithms based on the efficient preparation of a Gibbs state, for instance.

In my Ph.D. thesis, I developed a strategy to prove positivity of MLSIs for certain dynamics that is based on results of quasi-factorization of the relative entropy. This strategy has proven to be notoriously useful, as we have produced several non-trivial results in this direction in the past few years, until recently obtaining the first examples of positivity of MLSI for quantum lattice spin systems independently of the system size.

Currently, I am mainly interested in the relation between dynamical properties of a thermal evolution and static properties regarding the decay of correlations on its fixed point, a Gibbs state. In my last result, jointly with some collaborators from TUM and other institutions, we have shown that any 1D quantum system modelled by a Davies generator with commuting interactions thermalizes rapidly (in the regime mentioned above), taking a big step in a long-standing open problem. In this result, we have used our most recent techniques on decay of correlations on Gibbs states and on some quantum functional inequalities.

© C. Hohmann / MCQST

Most of my work is devoted to research, and my research is mainly theoretical. Therefore, I don’t have a lab where I perform experiments, nor do I have to realize difficult numerical computations or simulations. For my research, I need very simple tools: paper and pen to write down some computations, a computer to access the literature and write papers, and a blackboard to discuss ongoing projects with my collaborators.

I could say that I spend around 90% of my time working in front of a computer. Before COVID-19, the situation was slightly different, since on-site collaborations were much easier and usually more productive. Now, all the in-person discussions have transformed into video calls, of which I am used to having several per day. Some time ago, I also spent time once in a while to travel to conferences where I could present my results, or to do research stays or pay short visits to important centers of investigation, where I was fortunate enough to establish collaborations with researchers of great relevance to my work, most of which are still active collaborations.

What keeps you excited and makes you want to start work in the morning?

What excites me the most about our job is the possibility of solving a long-standing problem by tackling it with original ideas and tools, and from a different perspective from those that have been used before. The number of researchers devoted to quantum information theory is so large, and the investment in it is so vast (compared to some other research fields) that new relevant results appear every day. The possibility of waking up every day to discover these new results, to learn the new techniques, and to read about new important problems, knowing that I am closer to solving a problem of relevance and contributing to the community, is what excites me the most in the morning.

"What excites me the most about our job is the possibility of solving a long-standing problem by tackling it with original ideas and tools, and from a different perspective from those that have been used before. "

What inspired you to become a quantum scientist? Did you always know you wanted to be a scientist?

Since I was a child, I have always wanted to be a scientist. My interest in physics and mathematics started from a very early age. Both of my parents studying engineering; my brother, mathematics; my sister, chemistry; and my mom being a high school chemistry and physics teacher for nearly 30 years, have a lot to do with my passion for science. Moreover, when I was 11, I started participating in math competitions, a habit that I kept until I finished high school (and which I complemented with some physics and chemistry competitions). At the age of 14, I was selected for a program to support mathematical talent in children by receiving biweekly classes of extracurricular mathematics at the university. This made me definitely decide that I wanted to study mathematics.

My interest in quantum science, however, appeared much later. My whole childhood, I had claimed that I wanted to be a scientist, in general, and an astrophysicist, in particular. For that, I decided that I wanted to study mathematics and physics, and then specialize in astrophysics. I started with my bachelor’s in mathematics; in the second year, I started a bachelor’s in physics, and combined them until I finished the first one. Then, I realized I loved research and I had a big interest in every branch of mathematics, but particularly in functional analysis and differential geometry. Moreover, I was passionate about the idea of applying my knowledge of mathematics, acquired during the previous five years, to the study of problems arising from physics. Combining all these interests, I was fortunate enough to find David Pérez-García’s group at Universidad Complutense de Madrid, where I was able to write a thesis in mathematics applied to quantum information theory.

What drew you to Munich?

I decided to come to Munich as a postdoc for a number of reasons. First of all, when I was finishing my Ph.D. and started looking for opportunities, the idea of joining the Chair of Mathematical Physics at TUM was one of my favorites, since I already had some ongoing collaborations with members of the group and some of the most important experts in the world from my field were already here. Michael Wolf had been a strong collaborator of my former Ph.D. supervisor for many years and the connections between the two groups had been really fruitful in the past. Additionally, the opportunities presented by MCQST, the numerous academic activities related to quantum science that are frequently organized in Munich, as well as the possibility to interact with all those world-class scientists that carry out their research in our universities and research centers, made me finally choose Munich to continue my research career. And, thanks to MCQST, I had the funds to actually do it.

Moreover, the city and the region were very attractive for me and I felt I could really enjoy spending some time in Munich and visiting its surroundings. Unfortunately, the situation changed drastically because of coronavirus, but I have still been able to partially get to know the Bavarian culture firsthand.

"The particular effort that Germany is making in this matter, by creating positions such as the MCQST Distinguished Postdoc, is something that I strongly appreciate."

What are the biggest challenges that you’ve faced, and how have you overcome them?

The biggest challenges I have faced in the last years have to do with a lack of self-esteem and frequent doubts about my potential for success in a research career. I would probably say I suffered from “impostor syndrome” for years.

Since the middle of my bachelor degree and until I finished my first master degree, I encountered several situations in which I was partially discriminated against for either being a woman or for studying the same program as my boyfriend. In the first case, while I was competing against a male partner for an “honorable mention” in a specific course during my bachelor studies, the professor of the course told me that, in case we finished the term with tied grades, my male partner would get the honor, since “he was a man and, thus, he could have a profitable research career.” Related to the second case, during my master studies, in a course in which we had to hand in exercises that we were allowed to do in groups. However, the professor told me he was unsure how to grade me, since I had done the exercises jointly with my boyfriend, and he “could not properly evaluate if we both had contributed to the solutions, or just my boyfriend.” And these are just some examples.

These kinds of situations made me believe for years that I was not good enough to pursue a research career, and even less to be able to one day interact with world-class scientists. It took me years of meeting people and hearing their stories to realize that I was not the only one in such a situation, and that the problem was not on my side, but on society’s. Nevertheless, I am fortunate enough to say that, during my Ph.D., the situation changed drastically for the better for me, and nowadays I feel more than welcome in every group or society I belong to, and with any researcher I talk with. The particular effort that Germany is making in this matter, by creating positions such as the MCQST Distinguished Postdoc, is something that I strongly appreciate.

© C. Hohmann / MCQST

"I also learned that it is essential to provide the younger members of our community with some space to present their work and speak their minds, which can completely determine the career of junior researchers."

What was your most memorable moment or proudest achievement?

There was a moment during my Ph.D. studies in which I finally got the confidence that I had been missing for years. I was doing a research stay of 3 and a half months at Institut Henri Poincaré, in Paris, during a thematic program in “Analysis in Quantum Information Theory”, where I met many important researchers from the field. Each day, a new person would present their most recent research for 10 minutes so that everyone would get to know them better. And, of course, they started with the younger people.

The day it was my turn, I presented the first result of my thesis, and the only one I had in quantum information theory so far: an extension of the property of superadditivity for the relative entropy for general states. I was providing a version with a result that did not match the one in arXiv, since we had just improved it, but had not modified our public file yet. Someone from the audience spotted that: he told me that he knew that result, but with a different multiplicative constant, from which he even recalled the explicit form. It turns out he was a researcher who had written many papers that I had already read, and who I already admired in some sense. He had not only read my result, but actually remembered it and wanted to discuss it!

That day I realized that my research could actually be interesting for the community and that I could really have a research career. Moreover, I started believing that, someday, I could even discuss my results with those “big name” researchers. I also learned that it is essential to provide the younger members of our community with some space to present their work and speak their minds, which can completely determine the career of junior researchers.

Outside of science, what do you enjoy doing most?

My biggest hobby is traveling. Visiting as many places as possible in every single continent is one of my biggest ambitions. That is one of the side reasons why I love to work as a researcher: it allows you to travel anywhere on the earth, get to know exotic places, and interact with people from different cultures. In particular, during my Ph.D. studies, I was fortunate enough to spend several months in France, Taiwan, and the United States.

Aside from that, and taking into account the current difficulty of traveling anywhere, I enjoy doing many other things in my free time, such as reading detective novels or listening to musicals. In particular, I’ve recently become a big fan of puzzles of every possible size, which I like to do in one sitting, when they have 500 pieces, or enjoy them more slowly, when they are composed of 2,000 pieces, for instance. My most recent acquisition is an 18,000-piece puzzle with 4 different images of Neuschwanstein castle in the 4 different seasons of a year. I will probably start with it as soon as I finish a 42,000-piece puzzle with more than 200 monuments from all around the world.

If you weren't a scientist, what do you think you would be doing now?

It is difficult to picture myself in a job completely separated from science, as this has been my devotion since I was a child. However, if I had to choose something completely apart from science, I guess I would have opened a travel agency. Besides being a huge fan of traveling, I enjoy the preparation for my trips even more. I love designing itineraries and optimizing the activities to be done per day, as well as the budget to spend. I have even helped some members of my family and friends in this matter in the past few years.

What advice would you give to someone at the beginning of their science career?

My first piece of advice would be: “Never believe that you are not good enough. Do not let anyone tell you that.” Sometimes, people tend to think that they actually know you and your capacities better than yourself and they are in a position to judge you and negatively influence you with their comments. It can be a matter of implicit bias, in the case you belong to a minority because of your race, gender, sexual orientation, beliefs, etc. Someone might also think you are not good enough because you did not pursue what they see as the optimal path in research, such as having a Ph.D. and postdoc fellowships from some of the commonly considered best universities in the world. Each person follows their own path, and doing it in a different way does not mean that it is worse. If someone wants to do research, no one should forbid them to have the opportunity to do it.

And my second piece of advice is: “Enjoy what you do.” A research career can be extremely consuming. The rate of mental health issues in academia is extremely high and, unfortunately, I have seen first-hand, in some really close friends, the amount of stress that can be caused by not being able to solve a problem for some time, feeling that everyone else improves faster than you, or a poor relationship with a supervisor or with some collaborators that have different priorities. There are many approaches to fight against all these problems and many organizations one can reach out to for help. However, a researcher has to enjoy what they do on a daily basis, since our job is highly specialized. If we think it doesn’t matter that we’re having a bad time (during the Ph.D., for instance), because the situation might improve later, then it might already be too late for the researcher to be excited about their job ever again.

Find out more about our Distinguished Postdoc Fellowship and Ángela's research.