Prof. Dr. Marko Žnidarič Awarded Prestigious ERC Advanced Grant

The project addresses one of the fundamental questions of modern physics — how a simple description eventually emerges from the enormous complexity of quantum systems. Prof. Dr. Marko Žnidarič describes the content of the project as follows: "The project deals with systems composed of many quantum particles. The difficulty in studying them is that they become extremely complex very quickly: the more particles there are, the less tractable they become — and this grows exponentially with the number of particles and also with the observation time. In practice, it is therefore only possible to describe relatively small systems exactly. If such a system is left to itself, it usually loses its complexity over time and becomes simpler. Therefore, there is no longer any need to track every detail - for instance, exact position of every atom, but only a few general quantities, such as temperature. The central question of the project is therefore: how can we understand and explain this transition from large to small complexity?"

Prof. Dr. Žnidarič then explains how the project approaches this research question: "The research direction of the ERC project Effective non-unitarity in many-body systems tackles this problem differently from previous work. Instead of a fully exact (unitary) description, the project focuses only on the quantities that really matter. The emphasis thereby shifts from theoretical elegance to practical relevance, leading to a non-unitary description. The idea is essentially some 40 years old, yet only recent results from our research group indicate how it might actually be carried out — and, in the process, reveal appealing connections with areas of mathematics that are less familiar in physics," and adds: "If successful, the project can be expected to yield a new method for studying such systems and a fresh perspective on questions such as how to quantify chaos in quantum systems with many particles. This is also important for the development of future quantum computers."

The head of the laboratory in which Prof. Dr. Žnidarič works, Prof. Dr. Tomaž Prosen, the recipient of two ERC projects, commented on the significance of the project as follows: "Marko Žnidarič's ERC project touches on the very foundations of statistical physics — a question that has preoccupied us ever since the pioneering work of Ludwig Boltzmann: how can we understand the irreversible macroscopic behaviour of extended natural systems whose microscopic dynamics is fully reversible (time-reversible)? For example, how can quantum dynamics, in which no information is either discarded or created, account for relaxation to equilibrium - a phenomenon that never reverses of its own accord? In his work, Žnidarič has for many years been developing innovative methodological approaches. Many of these have entered the arsenal of standard methods in this vibrant research field, which in recent years has been gaining in relevance, not least because of its close connection with emerging quantum technologies. I am extremely pleased that the ERC recognized the breakthrough potential of his proposal and selected it for funding in what is probably the most selective Advanced Grant call for established researchers to date."

An important achievement for the researcher, the faculty, and the university

In this year's call, the ERC awarded 319 Advanced Grants with a total value of 838 million euros, intended for leading scientists across Europe. The call is considered one of the most competitive to date: it received a record 3,329 proposals - 31% more than the previous year - with 9.6% of proposals selected for funding. 

This is the 25th ERC project awarded to the University of Ljubljana. The UL FMF is the University's most successful member institution in securing ERC funding and the only faculty in Slovenia to have received eleven ERC grants, including seven as host institution. This remarkable achievement places the University of Ljubljana and UL FMF among the most successful research institutions in the region and reflects both the excellence of their research and the high-quality environment the Faculty provides for researchers and their teams.

About the ERC

The European Research Council (ERC) was established in 2007 by the European Union as the leading European institution for funding frontier, pioneering research across all scientific fields. In its selection it follows a single criterion — scientific excellence — regardless of the nationality or age of the researchers. It offers four core schemes: the Starting Grant (to begin an independent research career), the Consolidator Grant (to consolidate it), the Advanced Grant (for established researchers), and the Synergy Grant (for collaborative research). The ERC budget is part of the Horizon Europe programme.