The Department of Physics is delighted to welcome Professor Stefan Rotter (Vienna University of Technology) as a Colloquium Speaker for the academic year 2025/26. Please join us to listen to Professor Rotter's seminar.
A reception will be held directly after the seminar in 8 West 3.15, where tea and coffee will be provided.
The seminar is open to anyone from the university, students are encouraged to attend.
Title
Fisher Information in Optics
Abstract
In this colloquium, I will discuss how the concept of Fisher information provides a unifying framework for understanding the fundamental limits of optical measurements. When we infer properties of an object from scattered light, Fisher information quantifies how much can, in principle, be learned from the measurement, independently of any specific reconstruction algorithm. I will show how this viewpoint leads to practical strategies for improving optical experiments, including the use of wavefront shaping to actively maximise the information carried by scattered light [1].
A particularly striking recent result is that Fisher information can be treated as a physical quantity that flows through space: its density and flux obey a continuity equation that closely mirrors the Poynting theorem for electromagnetic energy [2]. This analogy provides new physical intuition for how information is redistributed in complex and disordered optical systems. In the final part of the talk, I will briefly outline how these ideas extend beyond wave physics and how analogous notions of Fisher-information flow can be defined in artificial neural networks, offering a bridge between optical measurement theory and modern machine-learning methods [3,4].
References:
[1] D. Bouchet, S. Rotter, and A. P. Mosk, Maximum information states for coherent scattering measurements, Nature Physics 17, 564 (2021).
[2] J. Hüpfl et al., Continuity equation for the flow of Fisher information in wave scattering, Nature Physics 20, 1294 (2024).
[3] I. Starshynov et al., Model-free estimation of the Cramér–Rao bound for deep learning microscopy in complex media, Nature Photonics 19, 593 (2025).
[4] M. Weimar et al., Fisher information flow in artificial neural networks, Physical Review X 15, 031072 (2025).
Biography
Stefan Rotter is Professor and Head of the Institute for Theoretical Physics at Vienna University of Technology (TU Wien) in Austria. After studying in Vienna and Lausanne, he held a postdoctoral position at Yale University. Since founding his research group in 2011, he has focused on non-Hermitian physics, theoretical quantum optics, and the propagation of classical and quantum waves in complex media. His group collaborates closely with experimental teams, with two joint publications being named among Physics World’s Top 10 Breakthroughs of 2022. Stefan has co-authored several widely cited review articles on wave phenomena, was selected as an outstanding referee by the APS, and has served as a guest professor at the Institut Langevin and at ENS in Paris.