ERC Grant For Thorsten Schumm

Manipulating atomic nuclei with lasers: Thorsten Schumm has founded a new field of research that long seemed almost impossible – and has now been awarded an ERC Advanced Grant for this work.

How do we study atoms and molecules? Very often, by shining a laser beam on them. If the wavelength of the laser light is exactly right, atoms or molecules can absorb it; other wavelengths have no effect. Countless quantum experiments are based on this principle. It has made important measuring instruments possible.

For atomic nuclei, this long seemed impossible. The wavelength of laser beams is much too large to be absorbed by typical atomic nuclei. But in 2024, Thorsten Schumm and his team were able to show that certain atomic nuclei of the element thorium can indeed be manipulated with lasers – opening up an entirely new field of research. Schumm has now been awarded an ERC Advanced Grant by the European Research Council. With this funding, he aims to significantly expand the possibilities of this new technique.

Quantum optics with atomic nuclei
Researchers around the world had been searching for the long-predicted thorium laser transition, but it was Schumm’s team that achieved the breakthrough in 2024: “The first excitation of an atomic nucleus with a laser was a crucial step. But for us, this is really just the beginning,” says Thorsten Schumm. “We now know that the principle works. But we have many ideas for how to improve it significantly, so that we can build high-precision measuring instruments that surpass everything known so far.”

Crucial to this success were thorium-containing crystals that had been produced at TU Wien over many years of work. They are irradiated with laser light of the right wavelength; some of the thorium atomic nuclei then absorb a photon and switch to a state of higher energy. “At present, however, we excite only a very small fraction of the thorium nuclei in this way,” says Thorsten Schumm. “About one atomic nucleus in ten thousand. That is measurable, but still too little for many practical applications.”

The goal: Maximum control over the atomic nucleus
The major goal of the new project is to reach a regime of strong excitation: a large fraction of the atomic nuclei should be excited at the same time. “We want to achieve truly reliable coherent control over atomic nuclei,” says Thorsten Schumm. “That would mean that we could carry out quantum experiments with atomic nuclei that have, in similar form, been performed for decades with atoms and molecules. It would open up an enormous range of possible measurements.”

A key advantage of atomic nuclei over atoms or molecules is that they are much less susceptible to disturbances. “The electron shell of an atom, for example, reacts very sensitively to external electromagnetic fields,” explains Thorsten Schumm. “If you want to carry out precision measurements, you have to shield it carefully from external fields. When using atomic nuclei, this problem disappears. In principle, this makes much more precise measurements possible with atomic nuclei – from special high-performance sensors and quantum information storage systems to novel nuclear clocks.”

Familiar ideas in unknown territory
“Quantum optics has been an extremely fruitful field of research for decades,” says Thorsten Schumm. “We are now taking this field into a new dimension: We are moving from atoms and molecules, which are a few angstroms or nanometres in size, to atomic nuclei, which are ten thousand times smaller. The basic principle remains the same – but we are transferring it into a completely different area of physics: from atomic and molecular physics to nuclear physics.”

The research project is called “COCONUT” (Coherent Control of a Nuclear Transition), has received more than 3.5 million euros in funding, and will run for five years.