DFG Research Unit FOR 5522
Welcome to FOR 5522!
Our team from seven Germany-based research institutions and international research partners investigates nonequilibrium dynamics of closed quantum systems with ultra-cold atoms and state-of-the-art theory.
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International Conference:
Quantum thermalization in closed systems: From theory to
experiments
In May 2025, our RU will run an international conference covering timely topics from the Quantum thermalization of closed quantum systems. Please visit the webpage for list of lecturers, topics & application.
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FOR 5522 PhD School on Nonergodic Quantum Dynamics
Markus Heyl (Universität Augsburg)
Introduction to nonergodic quantum matter
FOR 5522 selects three Start-Up Fellows
Collaboration Meeting on Quantum Chaos & Ergodicity
Rishabh Jha explains SYK physics.
Quantum Gas Laboratory Tübingen
Research highlight:
Probing quantum many-body dynamics using subsystem Loschmidt echos
The Loschmidt echo generally contains key information about a quantum system, relevant across various scientific fields including quantum chaos, quantum many-body physics, or high-energy physics. However, it is typically exponentially small in system size, posing an outstanding challenge for experiments. Here, we experimentally investigate the subsystem Loschmidt echo, a quasi-local observable that captures key features of the Loschmidt echo while being readily accessible experimentally. Utilizing quantum gas microscopy, we study its short- and long-time dynamics. Performing these measurements in the ergodic regime and in the presence of emergent kinetic constraints, we provide direct experimental evidence for ergodicity breaking due to fragmentation of the Hilbert space. Our results establish the subsystem Loschmidt echo as a novel and powerful tool that allows paradigmatic studies of both non-equilibrium dynamics and equilibrium thermodynamics of quantum many-body systems, applicable to a broad range of quantum simulation and computing platforms.
Group: I. Bloch, M. Aidelsburger (LMU Munich)
Research highlight:
Observation of Hilbert-space fragmentation and fractonic excitations in
two-dimensional Hubbard systems
The relaxation behaviour of isolated quantum systems taken out of equilibrium is among the most intriguing questions in many-body physics. Quantum systems out of equilibrium typically relax to thermal equilibrium states by scrambling local information and building up entanglement entropy. However, kinetic constraints in the Hamiltonian can lead to a breakdown of this fundamental paradigm due to a fragmentation of the underlying Hilbert space into dynamically decoupled subsectors in which thermalisation can be strongly suppressed. Here, we experimentally observe Hilbert space fragmentation (HSF) in a two-dimensional tilted Bose-Hubbard model. Our results mark the first observation of HSF beyond one dimension, as well as the concomitant direct observation of fractons, and pave the way for in-depth studies of microscopic transport phenomena in constrained systems.
Joint Experiment-Theory collaboration (Bloch, Moessner, Pollmann, Zeiher groups)