Quench dynamics of long-range spin systems from Keldysh diagrammatics

• Applicant: Dr. Björn Sbierski
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas ; Theoretical Condensed Matter Physics
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 465199066

The recent surge of experimental achievements in analog quantum simulation challenges theorists to describe time evolution in quantum many-body systems. Starting from a simple product state, the dynamics of the wavefunction is dictated by the designed and well characterized Hamiltonian and the associated Schrödinger equation. We consider quantum spins on two and three dimensional lattices as paradigmatic examples of strongly interacting quantum systems. These models can be realized in arrays of interacting Rydberg atoms, for example. We propose to circumvent the unfeasible full solution for the wavefunction dynamics by focusing only on measurable observables as one- and two-point functions. Building on our previous work in the equilibrium case, we plan to describe the time evolution of these observables via high-order perturbation theory in the interaction. Crucially, the expansion coefficients are functions of time which will be calculated exactly to high orders such that resummation techniques can be brought to bear. Benchmarks against established techniques like tensor- and neural networks will be crucial. Finally, we plan an extension to spin models with long-range interactions.

• DFG Programme: Research Units
• Subproject of: FOR 5413: Long-range interacting Quantum Spin systems out of equilibrium: Experiment, Theory and Mathematics