Electronic excitations are crucial in many fields of science and engineering. Time-resolved spectroscopy is widely used to detect dynamics of excited particles (electrons) and quasiparticles (e.g., excitons or plasmons). In the scheme of “femtochemistry” established since decades, one excitation is placed into the system by a pump pulse and its evolution observed by a time-delayed probe pulse. However, this does not resolve correlations between multiple excitations making it impossible to understand important quantum phenomena. We shall develop and apply new experimental methods to determine multi-particle correlations, based on isolating higher (than fourth) orders of perturbation theory systematically. We will separate these contributions without requiring a-priori models. With tailored femtosecond laser pulse sequences, we circumvent the stochastic nature of light–matter interaction even though we use only classical light and retrieve information from specific orders of a perturbative expansion, hitherto only accessible theoretically. We also consider that many materials are heterogeneous. Thus, we isolate multi-particle correlations in space by combining high nonlinear orders with fluorescence microscopy and photoemission electron microscopy. This enables us to avoid ensemble averaging and obtain information for specific domains down to the single-molecule limit. Our methods will be applied to determine exciton diffusion in organic materials, chiral excitonic couplings, plexciton–plexciton interactions, quantum coherence in multi-exciton generation, phonon–phonon couplings in quantum dots, and the role of dark states in correlated materials. We expect IMPACTS to change how complex systems are studied with ultrafast spectroscopy. Overcoming limitations of single-particle models, we seek a holistic picture of correlated dynamics, impacting our understanding and application of solar energy conversion, transport in functional materials, and quantum technologies.

Exciting findings from animal electrophysiological research in the last years suggest that an increased rate of body movements results in an enhanced response of neurons within the visual system despite the absence of visual changes. It is unclear why such modulation occurs in areas which process visual input. In humans, little is known about the influence of body movements on sensory brain areas mainly due to the technical challenges of measuring brain responses during pronounced muscle activity. However, psychophysical studies in humans show that also percept and perceptual demands are connected to the rate of movements. These two lines of evidence suggest a general link between rhythmic body movements and perceptual processes. The main aim of the proposed research is to decode the relationship between body movements and percept and to identify the underlying mechanism. To this end human non-invasive recordings from electro- and magnetoencephalography (EEG, MEG) as well as invasive human and animal multi-electrode recordings collected during movement execution will be analyzed. Directly relating perceptual processes and their underlying neuronal oscillations to rhythmic body movements offers an approach circumventing some of the methodological problems. This research could uncover a new mechanism of how our system modulates perceptual processes through body movements. The proof of such a mechanism would constitute a ground-breaking step in understanding perception during natural behavior. We need to keep in mind that in the awake state our body is constantly in motion. However, up to now, the vast majority of studies which investigate sensory brain responses are conducted under strict movement suppression. Besides facilitating exciting new insights, this research can strengthen the assumption that the knowledge we have gathered about artificial situations generalizes to our natural behavior.