Rudolph Clausius was born on 02.01.1822 and served as Professor of Physics at the University of Bonn from 1869 till his death in 1888. He is one of the most eminent scientists of the 19^th century, his legacy includes the mechanical theory of heat, the invention of the entropy and much more with relevance to numerous fields of science.

The University of Bonn has commemorated his legacy with a series of lectures during the winter term 2021/22. For more information, including a lecture by Dieter Meschede, klick the image.

Dieter Meschede holds a seminar at the Institute of Physical and Theoretical Chemistry of the University of Bonn, giving an overview of the research activities of the group. The seminar can be viewed at this link.

Knowing how fast a quantum process can be reveals the ultimate limits to information processing. The brachistochrone problem for two-level quantum systems—the fastest path connecting two quantum states—has been long known. These solutions, however, are generally not applicable to larger quantum systems. In Phys. Rev. X 11, 011035 (2021), we experimentally demonstrate a shortest-duration quantum process that fundamentally cannot be reduced to two-level dynamics.

We carry out fast coherent transport of an atomic wave packet over a distance 15 times its size using an optical conveyor belt. Our measurements of the transport fidelity sharply resolve the transition from a quantum-controllable to a quantum-noncontrollable process as the time is shortened, thus revealing the existence of a minimum duration—a quantum speed limit. Based on a geometric approach to quantum state dynamics, we provide a close lower bound on the minimum process duration beyond the two-level-system paradigm.

These results shed light upon a fundamental speed limit of quantum state dynamics. Identifying quantum processes of the shortest duration is important in quantum sensing and quantum computing.