VU Scientists Unlock Quantum Mysteries That Could Lead to Future Technology Development
Dr Arnoldas Deltuva, a scientist from the Institute of Theoretical Physics and Astronomy at Vilnius University (VU) Faculty of Physics and master’s student Darius Likandrovas, in collaboration with an international team of colleagues, have advanced our understanding of the interactions between the particles that make up atomic nuclei – protons and neutrons. Their innovative study was published in “Physical Review C” under the prestigious Editor’s Suggestion category.
Typically, atomic nuclei possess not only a ground state – the lowest energy configuration – but also excited states, which have higher energies and exist only shortly before decaying. This enables scientists to probe the structure and interactions of the nucleus. “We investigated the helium-4 nucleus, also known as the alpha particle. This nucleus is remarkable in that it has no bound excited states, even though its ground state exhibits an exceptionally large nucleon separation energy. We sought to understand why this is the case and what conditions govern the underlying processes, both in nature and in laboratory experiments. By theoretically modelling nuclear properties and comparing the results with experimental data, we revealed how universality connects the behaviour of the helium-4 nucleus with that of cold atoms and molecules – despite nuclear systems having energies a trillion times greater,” explains Dr A. Deltuva, adding that solving such quantum physics problems could lead to unexpected applications in future technology development.
“Simplified models that allow us to isolate and examine a selected physical effect in more detail are also important for understanding the essence of physical processes,” says young researcher D. Likandrovas. In his bachelor’s thesis, he explored how an increasing Coulomb interaction in a two-particle system transforms a bound state into a virtual or resonant one, thereby simulating the parametric evolution of the excited state of helium-4.
VU theoretical physicist Dr A. Deltuva emphasises that performing such calculations requires not only expertise in physics but also strong skills in mathematics and programming. “The foundations for this line of research were laid about fifteen years ago. Currently, only a few research groups worldwide, including our team in Lithuania and colleagues in Belgium, Italy, and France, are capable of performing four-nucleon reaction calculations using a rigorous quantum framework. For this study, we joined forces with each group carrying out benchmark calculations using their own method,” he explains. Dr Rimantas Lazauskas, an alumnus of the VU Faculty of Physics, who is continuing his scientific career at the University of Strasbourg in France, also contributed to this research.
Supercomputers are often used to perform calculations of nuclear processes, as accurate quantum mechanical modelling of nuclear reactions is an extremely large-scale task. “A system of integral equations with many variables can be discretised and converted into an algebraic one, but if all its coefficients were written into a matrix, it would require up to a billion terabytes of data. We need to look for “smarter” solution methods,” says Dr A. Deltuva.
This time, VU scientists performed large-scale computer calculations using the resources and software of the Institute of Theoretical Physics and Astronomy. Their programs are the result of decades of work, paving the way for understanding the interactions and properties of the microscopic world, which is important for technological progress. Examples include the modelling of light nucleus fusion reactions, which are relevant to thermonuclear fusion, and simulations applied to the engineering of cold atom systems. To solve some of the tasks, scientists are developing neural network methods, working together with their colleague Dr Darius Jurčiukonis, on a project funded by the Research Council of Lithuania, “Research in nuclear and particle physics using machine learning” (No. S-CERN-24-2).
In the near future, the scientists plan to study even more exotic systems containing strange particles known as hyperons, as part of the recently approved project “Theoretical Modelling of Hypernuclear Reactions,” funded by the Research Council of Lithuania.