21 September 2022

Exploring new worlds

Physicist and MCQST Spokesperson Immanuel Bloch has been named Clarivate Citation Laureate for his pioneering research in the field of quantum simulation. The award honours researchers whose work has been cited an exceedingly large number of times and is considered pioneering for a new area of research. On this occasion, LMU editor, Hubert Filser talked with Immanuel Bloch about his motivation for research, his many achievements throughout the years, as well as current projects. Discover below the insightful interview.

When Immanuel Bloch led Angela Merkel and Markus Söder through the laboratories at the Max Planck Institute of Quantum Optics in Munich last year, it soon became apparent that the physicist was comfortable in this distinguished company. For a basic researcher, such encounters tend to be rare. Yet Bloch was just as confident then as he is in the summer of 2022, as he chats with representatives of Google Quantum AI in Santa Barbara, full of curiosity about their ambitious projects. Before that, he had spent a month as guest professor at Stanford University and taken part in discussions about quantum simulations. Currently, he is participating in a workshop at the Kavli Institute for Theoretical Physics in Santa Barbara.

It is a busy schedule for the summer break. “It’s not so bad,” he says and shrugs his shoulders. He is sitting in an office at the Kavli institute as we speak via Zoom. “It’s not like I do it every year. It’s nice to meet up with so many colleagues and make new contacts, and it’s good to meet people outside one’s own group.” This is something he missed during the lockdowns of the last two years. “I’m soaking everything in,” he says. “I’ve got so many new ideas; I need to organize them and write them down.”

Professor of Physics at the age of just 31

Bloch, 49 years old, answers my questions with speed and precision. I soon realize that I am listening to a physicist who thinks fast and acts fast – including in his research career. Currently head of nine research groups, both at LMU and at the Max Planck Institute for Quantum Optics (MPQ) in Garching, where he is director, Bloch was always keen to progress quickly as a researcher. At 24 years old, he completed his undergraduate studies in physics; at 27 he got his PhD; and at 31 he became a Professor of Physics. Now he has been named Clarivate Citation Laureate – another important accolade to go alongside his Leibniz Prize and his Körber Prize. The Citation Laureate is awarded by analytics company Clarivate to researchers whom it considers to be candidates for the Nobel Prize by virtue of their frequent citation in high-ranking scientific publications. Around a sixth of nominees have subsequently gone on to win the highest award in the scientific world.

When asked about this, Bloch laughs. “Statistics are one thing. Prizes come or not, as the case may be, and there are so many great scientists deserving recognition.” All the same, he is very pleased about the Citation Laureate award for him and his research group, “because it relates to my most important work,” says Bloch. “We’ve clearly created something of lasting value, and that’s gratifying. That being said, prizes were never the motivating force for my research. I always wanted to do what interested me and to discover new things in physics.”

© J. Greune / LMU

Basis for a quantum computer

Immanuel Bloch is a quantum physicist, specialized in quantum simulation and one of the founders of this field. Put simply, quantum simulation is about gaining a better understanding of e.g. solid-state materials, especially phenomena such as magnetism and superconductivity. “The behavior of these systems is very complicated – and even more difficult to calculate,” explains Bloch. “This is where our new model systems help, which are based on so-called ultracold atoms.” The physicists load the atoms into crystals of laser light, so called optical lattices, and manipulate and observe them. These optical lattices simulate the regular structures of a material. There is much interest in this field of investigation, and not only because the principle could serve as a possible basis for a special computational form in quantum computing.

“The developments of the past twenty years have been truly amazing,” says Bloch. He talks excitedly about the possibilities of quantum simulation, which even Google has come to recognize. The day before, Google Quantum AI scientists had spontaneously invited him to visit their headquarters. “The Google researchers see one of the most promising applications precisely in the areas we are pursuing,” he says. “They have even been inspired by some of our experiments, and that does make me proud. Google is often held up as a paragon when it comes to practical applications. All I can say is that Google is interested in very similar scientific questions as we are. This is something we really should make clear to our politicians.”

“I just followed my enthusiasm”

Quantum physics fascinated him as a student, he tells me, particularly the new research coming out at the time about Bose-Einstein condensates. When physicists speak about quantum physics, they are apt to lurch without warning into such exotic subjects as Bose-Einstein condensation, a phenomenon predicted by Albert Einstein and Satyendra Nath Bose in 1925, whereby all particles of a system are in the same quantum state. It was realized in a very pure form only in 1995, when Bloch was a physics undergrad. The experiment involved cooling millions of atoms in a condensate down to extremely low temperatures, such that they became practically motionless. “I could feel it back then, that a breakthrough had been achieved,” explains Bloch. “You could see matter waves for the first time; millions of particles behaving like a coherent wave. Quantum mechanics on a macroscope scale!”

This was exactly what he was looking for: “I just followed my enthusiasm,” he says. This led him to Stanford after his graduation. When his professor there, Mark Kasevich, was moving from Stanford to Yale, he wanted to take Bloch with him. But Bloch wanted to live in Europe – and this remained the case in later years, when he turned down various offers to work in the United States. Visiting subsequent Nobel Prize winner Theodor Hänsch in Munich in 1998 was a decisive moment. “He picked me up in Munich and drove me out to Garching to show me around,” recalls Bloch. “He spent an extraordinary amount of time in striving to win me over. That was impressive. And it turned out of course to be a good decision.” The manner in which Hänsch does science was very appealing to Bloch, the freedom, the trust he gives to his staff to pursue their research independently.

Trust, enthusiasm, intuition: key values even in austere world of physics

Even in the intellectually austere world of basic physics, it would seem that human qualities such as trust, enthusiasm, intuition, and an instinct for new paths are essential. In Munich, Bloch built the first experiment. He was “looking for the place where the new field could meet modern solid-state physics.” That is to say, he wanted not only to have millions of particles all behaving the same as in the Bose-Einstein condensate, but something that is more complex to describe and in which the interactions between the particles play a special role. These interactions give rise to more complex and new organizational principles in matter, which play a fundamental part in modern solid-state physics in domains such as magnetism and superconductivity. “We wanted to implement ideas from quantum physicists like Ignacio Cirac and Peter Zoller,” says Bloch. (As an aside, Bloch is currently working with Cirac in the MCQST (Munich Center for Quantum Science and Technology) cluster of excellence and at MPQ.)

© J. Greune / MPQ

Absolute control over atoms

Doing this required the development of completely new apparatuses. The researchers had to design a laser setup that beamed in light from all directions; they had to learn how to cool atoms in one area of the lab bench and then transport them to the laser lattice. Everything needed to be precisely coordinated. The goal was to obtain absolute control over the atoms so as to simulate specific states of matter and switch back and forth between two different states: a so-called Mott insulator and a superfluid.

For months, Bloch worked away on the experiment with his colleagues Markus Greiner, Tilman Esslinger and Olaf Mandel at the LMU labs in Schellingstraße. He tried things out, programmed apparatuses, and adjusted equipment down to the micrometer. Doggedly, he implemented an idea he had in his head, an experiment without a model, without a blueprint. “The desire to try something new, which nobody had done before – that was my motivation,” says Bloch.

Success came three years later, in the summer of 2001, after many a night taking measurements till dawn. “To actually observe this transition was one of those rare moments of utter joy,” recalls Bloch.

Experimental dawn of quantum simulation

To this day, the experiment is considered the experimental dawn of quantum simulation. It was the first time that a solid-state system was modeled with a quantum system. The original idea was formulated by Nobel Prize winner Richard Feynman in 1982, and almost 20 years later Bloch was one of the first to realize it in practice. A new field of research was born that is now also actively pursued in other platforms such as trapped ions, photons or superconducting circuits. Subsequently, the ultracold atom technology was further refined such that it became possible, for example, to photograph individual atoms in such lattices. Quantum gas microscopy is the name of this field, and here too Bloch is one of the pioneers. “Eight years later, we were able to see the phase transition from our 2001 experiment in the microscopic image and observe the behavior of the atoms quite directly atom by atom, simultaneously with the team of Markus Greiner at Harvard,” says Bloch.

Bloch has now been investigating ultracold atoms, which he traps in crystals of light, for over twenty years. The variety of systems and phenomena they describe has increased, and the technology has become increasingly precise in pursuit of ever better control. When talking to him, I can really sense how important this control is to him as a physicist. One needs to be persistent, says Bloch, constantly questioning oneself and refining the technology.

For laypeople, the benches with the lasers, fiber optics, lenses, reflection mirrors, and vacuum chambers look like a bewildering tangle of equipment. It often takes years to build up an experiment like this. It means employing forward-looking apparatus design. “We want of course to remain competitive years down the road,” says Bloch. “On the one hand, we have to integrate new things that other research groups have not mastered. But on the other hand, we cannot be too risky in our approach. After all, it is supposed to work in the end.”

© J. Greune / MPQ

Inspiring a love of research in others

Clearly, Bloch is also able to motivate his doctoral students to embark on such adventures, accepting years without publications in the confidence of making new discoveries. One reason for this lies in his ability to inspire other people to be passionate about research. In our discussion, he comes up with some unusual descriptions for his experiments, such as when he describes the task of controlling the unruly atoms of a gas in the following terms: “It’s like an orchestra in which everybody is playing a different note and there is total chaos.” The low temperatures of the ultracold gas tame its atoms “such that everybody plays a single note, a well-tempered note.” Here we have an image of the physicist as conductor. Bloch says that intuition is very important in experimental physics, and intuition often operates through such pictures. “We don’t use formulae all that much when discussing things,” says Bloch. “A pictorial and intuitive understanding of a phenomenon is very important – we use this when explaining our work.”

It is no wonder, then, that he has won awards for good teaching and has been invited to lecture in the likes of Cambridge, Yale, and Stanford. “Teaching for me is a wonderful experience – I love passing on my knowledge,” says Bloch. “Inspiring young people to become excited about a field of research is a beautiful thing. You always have to reflect on what you’re saying while explaining complex subjects; the discussions are hugely important; I often get questions that I had never even thought of myself.” Sometimes his research hits road bumps, and at these times he draws a lot of energy from the lectures with his students. In addition, he gets to know future doctoral candidates. 20 of his researchers have since become professors, and 45 have successfully defended their doctoral thesis. “Perhaps the greatest achievement in the life of a researcher is ultimately seeing how many people one has educated that have managed to obtain interesting positions in science and industry.”

A sense for practical applications

Moreover, Bloch is not only interested in basic research. Bloch’s team pursues various avenues, and he attaches a lot of importance to technical developments such as his research into a type of microwave freezer for molecules, which was recently published in the leading scientific journal Nature. Here, Bloch and his team developed a new method for cooling gases of polar molecules down to almost absolute zero. The particular characteristics of molecules compared to simple atoms make them especially interesting for quantum simulation. Here again he describes the ups and downs of research. Success arrives sometimes only after years of trying, says Bloch. This is what makes long-term funding so valuable, such as that available through the Munich Center for Quantum Science and Technology (MCQST) cluster of excellence, where Bloch is one of the spokespersons. “We can pursue such topics over multiple years without having to demonstrate a success every year.”

In general, there is a real spirit of optimism and excitement in the realm of quantum research. Whether all hopes will be fulfilled, only time will tell. Bloch also mentions the hype surrounding quantum computers. The practical applications could end up coming in fields that are just not on our radar at the moment. “We’re trying not to get caught up in the hype,” says Bloch. “We also point out problems; after all, we’re not a private company that needs to promote its results.” At the same time, Bloch is aware that the high expectations are attracting funding. With a budget of a billion euros, the EU’s Quantum Technologies Flagship is one example. In Bavaria, too, we now have Munich Quantum Valley as an overarching network with 380 million euros in state and federal funding. Politics has sidled up to research, so to speak. Munich Quantum Valley was set up with the aim of bringing research projects to industrial application and especially of expediting the founding of start-ups. “Without this funding, we’d quickly fall behind the Chinese and the Americans,” says Bloch. “It’s good to accumulate experience in this area as well.”

Accordingly, Bloch is providing free advice to the first start-up to emerge from Munich Quantum Valley. “planqc” has set itself the goal of developing a highly scalable quantum computer that operates at room temperature. The technology will be based on atoms trapped in optical lattices. “It’s a good thing when ideas from basic research can be marketed,” says Bloch. At the same time, he is keenly aware that basic researchers like himself have arrived in a world where politicians are suddenly paying close attention and where corporations like Google, IBM, and Microsoft are jumping in. “The terrain has changed a lot,” says Bloch. “We must keep our ship on course and continue to do the things we believe in.”

Short bio

Born in 1972, Immanuel Bloch began his undergraduate studies in physics at 18 years old. He obtained his doctorate in 2000 under Theodor Hänsch. In 2003 he moved to Mainz, where he took up a professorship at the age of 31. In 2009 he returned to Munich and simultaneously took on the roles of Director of the Max Planck Institute for Quantum Optics and Chair of Experimental Physics – Quantum Optics at LMU. Since then, he has also become spokesperson of the MCQST cluster in Munich and is involved in Munich Quantum Valley

Source: LMU website