Year: 2026
Type: article
Abstract: Bethe strings are bound states of constituent particles in a variety of interacting many-body one-dimensional (1D) integrable quantum models relevant to magnetism, nanophysics, cold atoms and beyond. They are the quantum analogue to bright solitons. As emergent fundamental excitations, they are predicted to collectively reshape observable equilibrium and dynamical properties. Small individual Bethe strings have recently been observed in quantum magnets and superconducting qubits. However, creating states featuring intermixtures of many, including large, strings remains an outstanding experimental challenge. Here, using nearly integrable ultracold Bose gases, we realize such intermixtures of Bethe strings out of equilibrium, by dynamically tuning interactions from repulsive to attractive. We measure the average binding energy of the strings, revealing the presence of bound states of more than six particles. We find further evidence for them in the momentum distribution and in Tan's contact, connected to the correlated density. Our data quantitatively agree with predictions from generalized hydrodynamics (GHD). Manipulating intermixtures of Bethe strings opens new avenues for understanding quantum coherence, nonlinear dynamics and thermalization in strongly-interacting 1D systems.
Source: Nature Communications
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $6,990
Awards: G1768993395, Dynamics of Probed, Pulsed, Quenched and Driven Integrable Quantum Systems, exp. quantum physics, quantum gases, low-dimensional quantum systems, ultracold molecules, Atoms, Light, and Molecules, G4710139657, Correlated Molecular Quantum Gases in Optical Lattices, G5062013453, G5302217128, Quantum Science Austria, G8590477180, EXC 2111: Munich Center for Quantum Science and Technology (MCQST)
OpenAlex ID: W7204623795