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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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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.
Joint Experiment-Theory collaboration (Aidelsburger, Bloch, Heyl groups)
Research highlight:
Emergence of constrained dynamics from a Fock-space perspective: Novel
insights
Recently, three teams from our research unit arrived at novel insights on
the emergence of constrained dynamics from a Fock-space perspective. In
two efforts, a mechanism for the formation of dynamically isolated groups
of Fock-space nodes was discovered by utilizing known concepts from the
theory of localized single-particle excitations in frustrated lattices.
This has led to the notion of Fock-space cages [1,2]. For the formation of
Fock-space cages, the relevant aspect is the connectivity of nodes in
Fock-space. In a third direction [3], the competition of off-diagonal
terms and digonal terms in the chosen Fock space basis was also accounted
for. To that end, centrality measures from graph theory were generalized
to Hamiltonians. For the paradigmatic quantum East model, a clear
connection between non-ergodic dynamics and these generalized graph
measures could be established.
[1] Jonay, Pollmann, arXiv: 2504.20987
[2] Ben Ami, Heyl, Moessner, arXiv:2504.13086
[3] Menzler, Bañuls, Heidrich-Meisner, arXiv:2504.03458