New Concepts and Computational Methods To Tackle Quantum Nature of Matter

In January 2017, the Simons Foundation announced the creation of the Center for Computational Quantum Physics (CCQ), the third computational center within the foundation’s Flatiron Institute. The CCQ will develop the concepts, algorithms and computational tools needed to understand large interacting quantum systems, capture the quantum dynamics of electrons and ions in chemically realistic environments and make the results available to the scientific community.

Formal operations will begin in September 2017, and at full strength, CCQ will comprise up to 60 scientific and support personnel, including junior and senior staff scientists, as well as sabbatical and summer visitors.

The center is directed by Antoine Georges, who holds the chair in condensed matter physics at the Collège de France and is also professor of physics at École Polytechnique and at the University of Geneva. Andy Millis, professor of physics at Columbia University and associate director of physics at the Simons Foundation, is CCQ co-director. I sat down with Antoine and Andy to talk about the goals of CCQ and what they hope it will accomplish. An edited version of the interview follows.

Why start a computational center for quantum physics?
Antoine: I view CCQ as a place for computer-aided theoretical quantum physics. The possibility of investigating the quantum mechanics of many-electron systems and doing material science based on first principles of quantum mechanics is an enormous scientific challenge. We feel that having a center whose mission is to develop the very basic science that is needed is very timely because there has been progress in this field.

Andy: Developments over the last 20 years have opened up new computational horizons. Taking proper advantage of those advances requires research infrastructure at a scale which is just not feasible for individual university faculty.

What makes CCQ unique?
 Antoine: There are two things, perhaps three. One, its agenda will be targeted at fundamental issues. So we are not aiming to do large-scale materials screening computations or materials design. The agenda of CCQ will be pushing the frontier of basic theoretical methods to the next level. And there are not so many places that can support this in a sustainable way in the long term.

The second is that CCQ will bring together, in a single place, scientists who have a diversity of expertise. We’ll have people who come from quantum many-body physics and quantum chemistry and people who are into algorithms and the development of software libraries.

The third thing is that CCQ will benefit from interactions within the whole Flatiron Institute. Having a single place where many scientists who share an interest in computational science and computational methods in different fields — astrophysics, applied math, biology and so on — I’m sure there will be some very good things coming out of it.

What are some of the problems CCQ will tackle?
Antoine: We want to push the basic methods for the quantum many-body problem. There are various routes to do that, various types of algorithms. They will need to be pushed one step further.

In terms of physics and chemistry, we want to target several challenges. One is electron correlations in various kinds of solid-state materials. Understanding a whole range of electronic properties may lead to new materials with unique functionalities that do not exist naturally.

Nonequilibrium dynamics in quantum systems is another fundamental direction we want to push. It would help us understand, for instance, electron transfer in molecules during photosynthesis or light-induced superconductivity.

Another field I want to mention is the coupling of materials to the light field of quantum cavities. This is a fast developing interface between materials science and quantum optics.

And importantly, we want to see the vigorous development of open-source software libraries that could be taken to the next level within CCQ and made available to the international community.

From a materials science perspective, what do you hope CCQ will accomplish?
Andy: Back when I was starting as a summer student at Bell Labs, one of the scientists there, Kumar Patel, summarized materials science in three words: heat, beat and hope. The creation of new materials today isn’t exactly trial and error, but we would like to take the field to a new level of rational design.

The ambitious goal that I would like to see reached in my lifetime is a turnkey system: specify what you want a material to do, and we can do the calculation to design such a material — we can determine what combination of elements you should put together and in what structure. The ultimate goal is to reach a point where you can rationally design what you want, such as a drug that binds to a particular receptor, or a material that is a good battery.

Considering that CCQ will take a computational approach, what role does experimentation play?
Andy: To get to the point of, say, rational materials design, you have to be sure that: a) you understand all the science that goes into the behaviors; and b) your theories and methods and algorithms and codes actually work and do what you think they’re doing. For both of those things, detailed comparison to experiment is essential. What really gives you confidence that a theory is good is when it predicts something that wasn’t known before.

Experiments also keep surprising you. As time goes on experiments get better and better: they can measure more things at higher precision. And you keep finding things that are surprising and outside current theory. So a continuing interchange with experimentalists is going to be enormously valuable.

Antoine: CCQ and the Flatiron Institute in general don’t have experimental labs; we have theories and computational scientists. So it will be very important for CCQ in particular to reach out to the experimental community, broadly defined — from chemists and materials scientists to experimentalists exploring materials with a large variety of probes.

How will you accomplish CCQ’s mission?
Antoine: We want to build CCQ as a focal point for the international community and attract the best scientists. We’ll have regular staff positions, faculty jobs and short- and long-term visitors, including sabbatical visitors and summer visitors. We plan to organize a range of seminars, workshops and other meetings. In the slightly longer term, we may want to sponsor some postdocs to work in experimental labs in connection with some theoretical issues raised at CCQ.

Andy, how did you zero in on Antoine to be CCQ’s director?
 Andy: Basically, it goes back to selecting the themes for the different units of the Flatiron Institute. The foundation has a process, and the science teams on the grants-making side of the foundation contributed to it by brainstorming with everybody we knew about general subject areas. Once a potentially interesting topic was identified, we would organize a half-day meeting, where we would bring six to eight people who were interested in the topic. They would present and discuss their ideas for the most important science and how it relates to what an institute might do. And from some of these discussions, compelling visions for Flatiron centers emerged.

For instance, we had an astrophysics meeting, and before it was even over, it was obvious this was the field that needed a computational center, and that David Spergel was the right person to lead it. The Center for Computational Astrophysics was formally announced in the fall of 2015, only a few months after the meeting.

The Center for Computational Quantum Physics came about in a broadly similar way. We had some background because within the foundation we were already running the Simons Collaboration on the Many Electron Problem, which covers one part of the intellectual ground of this new center.

We knew Antoine because he is a member of the collaboration. Indeed in our meetings to set up the collaboration, we had already noticed that Antoine is a person with a broad and compelling intellectual vision, a strong track record of scientific results, and a demonstrated ability to bring people together and assemble teams that can move forward to a common goal. Our panel meeting reinforced this impression, and we were delighted when Antoine decided to come and lead this exciting endeavor.