Abstract
String breaking is a fundamental phenomenon in quantum chromodynamics (QCD) and other lattice gauge theories (LGTs) with charge confinement. Pairs of quarks carrying color charge are bound together by gluon strings, forming color-neutral particles such as mesons and baryons. As the quarks are pulled apart, the string tension increases until the system has enough energy to create a new quark-antiquark pair, breaking the string. This process is observed in high-energy heavy-ion collisions and plays a crucial role in the evolution of the early universe, yet its real-time dynamics remain challenging for numerical simulation. In this work, we report the experimental observation of string-breaking dynamics in a mixed-field Ising model using a programmable trapped-ion quantum simulator. The system simulates a string connecting two external static charges, with site-dependent magnetic-field control enabled by a dual array of tightly focused laser beams addressing individual ions. Using a Hamiltonian quench protocol, we observe the spatiotemporal evolution of the string as the string tension suddenly increased beyond the breaking threshold. Additionally, we investigate string breaking as a first-order quantum phase transition by ramping through the transition point. In this regime, the non-equilibrium string-breaking dynamics are characterized by bubble nucleation and scaling behavior consistent with a generalized Kibble-Zurek mechanism. Our work establishes the potential of analog quantum simulators for QCD and LGT simulations.