Dominik Bucher, MCQST member, has received the prestigious Starting Grant from the European Research Council (ERC) this year. Science journalist Hubert Filser has interviewed Dominik on his fascination with science, passion for chemistry, and working on pioneering interdisciplinary work .

Two worlds entangled: quantum technology and (bio)chemistry

When Dominik Bucher flew back to Germany, he had four diamonds in his luggage. Not traditional diamonds destined to be worn as jewelry, yet ones so valuable that the researcher stowed them in his hand luggage when returning from the US. They were a farewell gift from Ron Walsworth of Harvard University, his American mentor. The physicist gave him the diamonds last year on loan for his research in Munich. “We declared them to customs as scientific carbon samples,” states Bucher. “They are worth a thousand euros each.”

Accordingly, his employees in the Garching laboratory have carefully fixed the light gray shimmering diamond chips to their experiment, the idea being not to lose a single one. For scientists, diamonds are of particular interest if they have small defects at their surface consisting of imperfections in the lattice structure, meaning that the crystal structure contains a nitrogen atom instead of a carbon atom. These can be used as high-precision quantum sensors to measure smallest temperature changes or changes to an electric or magnetic field. To do so, researchers use the spin state of the defects, which can be visually stimulated and influenced from the outside using microwaves. Such prepared defects in diamond are extremely sensitive to the magnetic properties of molecules near their surface.

An ambitious project

“It is a high-precision instrument,” says Bucher. “In this department, we are one of the first chemistry groups in the world to use these diamond quantum sensors,” he continues. That is precisely why Bucher has now received the prestigious Starting Grant from the European Research Council (ERC), which he will also implement as part of the “Munich Center for Quantum Science and Technology” (MCQST), the Munich-based cluster of excellence. In his “SingleCellQNMR” ERC project, Bucher wants to develop novel sensors, which will be used to investigate the metabolism of individual cells, which is of interest for cancer research, among other things. “It is a pretty ambitious project,” he says.

At first, everything in the laboratory seems rather improvised, not as if this were a highly precise cutting-edge technology. There is an open box on the floor that contains a new magnetic coil delivered that day. “We like to tinker around here,” Bucher says, handing out a pair of protective laser goggles before pulling back one of the experiments’ black curtains. A green laser irradiates the affixed diamonds from below, stimulating the nitrogen defects in diamond. Bucher has already set up three experiments within a small space here at the Chair of Physical Chemistry at the Technical University of Munich in Garching. They are separated from each other via several transparent strips, similar to those found at the entrance of cold storage rooms. “At the beginning, it was meant to protect the optics from dust,” he says. “Now the strips are also a Covid-19 protection measure.”

The new ERC experiment is currently being developed next door in a second laboratory. The team of researchers refer to it, jokingly, as the “graveyard” due to the many odds and ends around from old experiments: vacuum tubes, an ancient color laser, outdated measuring devices. All equipment that had been set aside as it might once again serve a purpose but which had been standing around unused for years before Bucher and his groups took over the rooms. Bucher laughs at such things. “My goal is to develop a new generation of techniques for chemistry and biology,” says the chemist. “In that respect, this place suits me well.”

© C. Hohmann / MCQST

“I am a cross-border worker” – working at the absolute threshold

Standing in such a laboratory, it is easy to underestimate his pioneering interdisciplinary work. From the outside, it is not clear at first glance the kind of high precision the researchers here want to achieve. After all, the lasers for stimulating the quantum sensors in the diamonds are not specially designed and the electromagnets used do not seem unusual at first. But the readings up on the screen show that high-precision magnets are used here. The values of their magnetic fields are stable down to the sixth decimal place. “That is not enough because the accuracy of our measurement signals depends on that,” says Bucher. “We work in the absolute threshold range, but achieving this precision with tricks is what makes it fun. What we do here is always associated with new ideas and inspiration.” You just have to be creative, thinking unconventionally, and try things out. He often tinkers with solutions for weeks.

The chemist has long had this desire to experiment. “For me, science is also the joy of trying things out,” he says. Bucher recounts that he has been crazy about chemistry since he was a teenager experimenting with chemicals in his parents’ garden shed in Munich, where he grew up, “just for fun and just for me.” Initially with substances from the Kosmos chemical set, later with chemicals such as perchlorates he ordered from dubious Internet dealers and used for pyrotechnic experiments. “At some point, the police rang,” says Bucher. “I was saved by the fact that I was on the verge of starting to study chemistry at the Technical University of Munich.”

“I want to merge different fields.”

However, Dominik Bucher is more than just a scientist who enjoys experimenting. He says that his postdoctoral time at Harvard with Ron Walsworth was especially tough. After studying chemistry at the Technical University of Munich and then completing his doctorate in biophysics at LMU, Bucher went to Harvard as a postdoctoral researcher. There, the plan was to study quantum technology and, above all, extremely sensitive quantum sensors for chemistry and biological science – and develop a completely new, extremely sensitive NMR (Nuclear Magnetic Resonance) technology for microscopic volumes. “I had no knowledge of NMR; we wanted to measure chemical information with our quantum sensors, but the spectral resolution was too poor, the measured lines were just too wide,” says Bucher.

“A successful researcher needs to be tenacious and resistant to frustration.”

Even though, after a year and a half, he finally made the theoretical breakthrough and found a way to increase the resolution, he initially failed with the technology. The magnets did not provide stable fields. “That is when I learned that in order to be a successful researcher, you need to be tenacious and tolerant to frustration,” says Bucher. “I do not give up.” What is important is the ability to solve problems, not lose faith in one’s own creativity. There were months where he spent seven days a week, often twelve hours a day, in the lab.

When Bucher describes his years at Harvard, he seems like a lone fighter who has set himself great goals and yet continues undeterred by the challenges. Now, he seems to have found his place in the niche between diverse fields of science. “I sit between all the fronts,” he says. “I use new physical methods to deal with chemical issues. This is new territory.” But at the same time, he is driven by his conviction: “I believe that we can make new discoveries at the threshold between different fields of science. For example, the new quantum sensors could offer completely new analysis possibilities in chemistry and biology, which is also the goal of the ERC Starting Grant.

However, he also knows that his approach to certain issues at the interface between different sciences is exactly the right one. “I want to merge different fields,” says Bucher. “That would not be possible if I were only familiar with a single field.” In biochemistry, there are open questions that can only be answered using methods from physics. Conversely, he also knows what limits the method. “Here, I can adapt the chemical system or find model systems to make the measurements possible,” says Bucher. That is how he operates, also with the new ERC grant, in which he applies a novel method from quantum physics to biological and chemical issues.

Nevertheless, he also admits that, with all the ideas and issues that concern him, he would probably be overwhelmed quickly on his own. “My employees are the experts in their disciplines; I often know less than them,” says Bucher. Bucher now employs eight researchers in various projects, and his team will continue to grow with the ERC project, which provided him with more than 2.1 million euros. Here, too, the physical chemist relies on teamwork to link up with other disciplines. He employs experts in various subjects, physicists and chemists, laser and optics specialists, biologists who work with cell cultures, engineers for the sophisticated microwave electronics or the stability of the magnets used. Bucher emphasizes the importance of interdisciplinary work. “Our integration into the MCQST cluster is ideal in this regard; I want to establish quantum technology in chemistry,” says Bucher. “Although I am a rarity in the cluster, coming from a chemistry background, I can work specifically with colleagues from physical subject areas and tackle exciting issues with them. That is extremely valuable to me.” Probably even more valuable than his diamonds.

Related read: Two ERC Starting Grants awarded to MCQST members