Observation of Domain Wall Confinement and Dynamics in a Quantum Simulator*

Confinement is a ubiquitous mechanism in nature, whereby particles feel an attractive force that increases without bound as they separate. A prominent example is color confinement in particle physics, in which baryons and mesons are produced by quark confinement. Analogously, confinement can also occur in low-energy quantum many-body systems when elementary excitations are confined into bound quasiparticles [1]. Here, we report the first observation of magnetic domain wall confinement in interacting spin chains with a trapped-ion quantum simulator [2]. By measuring how correlations spread, we show that confinement can dramatically suppress information propagation and thermalization in such many-body systems. We determine the excitation energy of domain wall bound states from non-equilibrium quench dynamics. Furthermore, we study the number of domain wall excitations created for different quench parameters, in a regime that is difficult to model with classical computers. This work demonstrates the capability of quantum simulators for investigating exotic high-energy physics phenomena, such as quark collision and string breaking. [1] F. Liu, et al., Phys. Rev. Lett. 122, 150601 (2019). [2] W. L. Tan, P. Becker, et al., arXiv: 1912.11117 (2019).