Complex Quantum Systems
We consider complexity and associated phenomena emerging in quantum matter: from low-dimensional (topological) materials to quantum gases, from classical to quantum, from integrability to many-body quantum chaos, from few to many particles.
Our group with guests (Yuriko Baba, Prof. Caio Lewenkopf, Prof. Steven Tomsovic)
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2025: News and Events
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Poster prize for Lukas Beringer at CAPS and CQA Winter School on Ultracold Quantum Many-body Systems (February 20, 2025)?
The prize was awarded to Lukas Beringer for his presentation of the poster entitled "Controlling Many-Body Quantum Chaos: Bose-Hubbard Systems" during the "CAPS and CQA Winter School on Ultracold Quantum Many-body Systems" held in the Centro de Ciencias de Benasque (Spain) from February 16th to February 22nd 2025.
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Young Colloquium der Regensburger Physik: Ein Podium über Klima und Kommunikation (January 1, 2025)?
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Statistical analysis of complex many-body states reveals hidden structure
Statistical mechanics is largely based on the assumption of ergodicity, which is reflected in a quasi-random behavior of corresponding many-particle quantum states. Such a behavior is already mimicked by a single quantum particle in a complex geometry with a wave function resembling a random spatial landscape. Nearly half a century ago, however, silent spatial correlations had been explored by Michael Berry upon superimposing random plane waves. Here we show that corresponding structures also exist in the huge dimensional (Fock) space of quantum fields describing quantum mechanical many-body systems. We show how corresponding correlations in many-body space can be unveiled -- with possible implications for the statistical physics of cold atoms.
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2024: News and Events
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Prof. Dr. Wolfgang Ketterle (December 16, 2024)?
2001 Nobel Laureate Wolfgang Ketterle (MIT) visited our group and the department giving a great colloquium talk?
copyright: Julia Dragan
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Symposium of the DPG (October 21 - 23, 2024)?
"Die Zukunft unseres Klimas: Komplexe Herausforderungen von der Physik bis in die Gesellschaft"
(The future of our climate: complex changes from physics to society) at Magnus-Haus Berlin
more information can be found here (in German)
Scientific organizers:
K. Richter, St. Falk, A. L?schel, F. Neumann, V. Wirth, K.F. Ziegahn
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Quantum simulation and computation at the edge of chaos
organized by K. Richter and J.D. Urbina at the
XLIV Dynamics Days Europe
Bremen, July 29 -? August 2, 2024
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German-Taiwanese Quantum Materials Day (July 19, 2024)
This event brings together colleagues from both countries working in condensed matter physics, low-dimensional materials, and correlated states of matter. Geared primarily towards young researchers, this symposium offers a unique opportunity to connect, share knowledge, and build international relations.
Program can be found here.
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Taiwanese-German WE-Heraeus-Seminar (July 14 - 18, 2024)?
From Fundamentals to the Future: Advancing Functionalities of Two‐Dimensional Quantum Materials
at Evangelische Akademie Tutzing
Scientific organizers:
K. Richter, A. Knothe, (Universit?t Regensburg), M.-H. Liu, T.-M. Chen (National Cheng Kung University, Taiwan
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Klaus Richter DPG president for the term 2024-2026 April 1, 2024)?
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2023: News and Events
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Meeting at UR (December 6-8, 2023)?
???
The program can be found here.
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Quantum survivors in a chaotic sea?
Non-equilibrium quantum states formed from many particles are extremely fragile and usually do not survive for long, but "decay" rapidly: they thermalize due to chaos. In a recent publication we show that, intriguingly, there exist such survivors in ultracold atomic gases that, despite chaotic dynamics, perform hundreds of stable oscillations as a unique signature of stability and quantum coherence. The observation of such "many-body scars" opens up far-reaching implications for the occurrence and preparation of stable macroscopic quantum states.
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International Presidential Visiting Scholar Fellowship 2023 for Prof. Ming-Hao Liu
The executive board of the University of Regensburg awards Ming-Hao Liu (National Cheng Kung University in Tainan, Taiwan) this fellowship for the year 2023. It comprises financial support for a research stay in our group during July, where he will work on Electron Optics in Graphene and on research topics related to SFB 1277. Furthermore, he will give a lecture on Electronic transport in a nutshell: from free electron gas to graphene.
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Controlling Quantum Chaos: Optimal Coherent Targeting
Chaotic dynamics has the propensity to be the villain of quantum device control as it leads rapidly to scrambling of quantum information and entropy production, certainly a fundamental hindrance to controlling quantum evolution. We could show that chaos,?conversely, can be harnessed to control and efficiently?guide the evolution of a?complex?quantum system toward?desired states of matter, i.e. targeting. ?In effect, is it possible to mimic a quantum Maxwell demon to some extent.
The work has been published in Physical Review Letters.
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2022: News and Events
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Professor of the year 2022 (November 16, 2022)
Klaus Richter has been awarded the title "professor des Jahres" by the UNICUm Foundation.
(picture @UNICUM)
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Klaus Richter designated DPG president (November 11, 2022)
The Vorstandsrat of the German Physical Society (DPG) has elected Klaus Richter as next DPG president fpr the term 2024-2026.
(picture @DPG)
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Semiclassical Roots of Universality in Many-Body Quantum Chaos (November 11, 2022)
Our Topical Review has been published in Journal of Physics A.
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