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Date:

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Thursday, 23 Oct. 2025

Video-Recording for any system with MP4-support

- Video.mp4 (ca. 400 Mb)

15:15 – 16:20

Manne Siegbahn Memorial Lecture 2024:

"Universal Matter-Wave Interferometry"

Speaker: Prof. Marcus Arndt

(University of Vienna)

Abstract:

Quantum mechanics is celebrating its centenary, commemorating de Broglie’s matter

wave hypothesis, Heisenberg’s matrix mechanics, Schrödinger's wave equation and

many other fundamental achievements. Confirmed by countless experiments, quantum

theory has since become the foundation of a vast range of technologies. Yet, we still

struggle to grasp the meaning of the quantum wave function, the interpretation of its

formalism and its implications for the nature of reality. This talk will illustrate the

conundrum by exploring how quantum superpositions and extended wave functions of

massive objects can be prepared in states that appear forbidden from the perspective

of our macroscopic everyday world.

I will discuss the experimental conditions, realizations, and applications of matter-wave

interferometry which we have extended across diverse material classes and ever-increasing

mass scales: from C60 molecules to vitamins and polypeptides, molecular clusters, and

metal nanoparticles containing thousands of atoms in a single delocalized body. In all cases,

we confirm that quantum superpositions can be realized, in stark contradiction to a

classical world view that assumes massive bodies traveling along well-defined trajectories.

Our experiments have grown from ‘Schrödinger kittens’ to mesoscopic cats and I will

highlight the next steps on this journey.

Pushing quantum superpositions to even larger masses and complexity demands substantial

advances in quantum state preparation. I will present our recent progress in cooling

optically trapped dielectric nanorotors, with masses in the gigadalton range. Preparing these

systems in their quantum ground state of vibration now enables unprecedented control over

their rotational quantum states and spatial alignment, paving the way for new matter-wave

experiments in rotational phase space.

While our primary aim is to explore the boundary between quantum and classical phenomena,

the tools and methods developed for matter-wave interference also open new avenues for

quantum sensing. They allow us to probe tiny forces and torques, with applications in physical

chemistry, biomolecular physics, and materials science.

About the Speaker:

Markus Arndt is Professor of Quantum Nanophysics at the University of Vienna.

His group explores the foundations and applications of matter-wave interference with

mesoscopic objects such as tailored molecules, clusters and biomolecules and mesoscopic

nanoparticles to understand the interface between quantum science and classical observations

as well as to develop new tools for quantum assisted sensing on biologically relevant

nanomaterials.

More information at https://www.quantumnano.at/