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SYQT: Symposium Quantum Thermalization

SYQT 1: Quantum Thermalization

SYQT 1.4: Invited Talk

Wednesday, September 10, 2025, 12:15–12:45, ZHG104

Observation of Hilbert-space fragmentation and fractonic excitations in tilted Hubbard models — •Johannes Zeiher — Ludwig-Maximilians-Universität München — Max-Planck-Institut für Quantenoptik

Neutral atoms trapped in optical lattices are a versatile platform to study many-body physics in and out of equilibrium. The relaxation behavior of isolated quantum systems taken out of equilibrium is among the most intriguing problems in many-body physics. Quantum systems out of equilibrium typically relax to thermal equilibrium states by scrambling local information and building up entanglement entropy. In this talk, I will present our recent experiments on probing an exception to this expected thermalization behavior in two-dimensional tilted Hubbard models with strong kinetic constraints. Combining local initial-state control with site-resolved measurements in our quantum-gas microscope, we find a strong dependence of the relaxation dynamics on the specific initial state - a hallmark of the shattering of the underlying Hilbert space in disconnected fragments. Leveraging the control over individual atoms, we furthermore inject mobile excitations into an otherwise immobile state and track their dynamics. We find subdimensional dynamics, which is a feature characteristic of fractonic excitations. Our results pave the way for in-depth studies of microscopic transport phenomena in constrained systems.

Keywords: Neutral atoms in optical lattices; Quantum simulation; Thermalization in closed quantum systems