String-breaking dynamics in a quantum simulator

In quantum field theory, spontaneous particle formation can occur when the potential energy between two elementary particles increases with their separation, as if they were confined by a string. When the separation exceeds a critical value, new particle pairs can form and the string breaks. Simulating this process ab initio requires solving quantum many-body dynamics of the strong force, a task for which quantum simulators may outperform classical computational methods. Here we probe the spatiotemporally resolved dynamics of string breaking in a (1 + 1)-dimensional  lattice gauge theory using a programmable trapped-ion quantum simulator. We emulate the effects of external static charges and strings, using site-dependent control of effective magnetic fields through an array of focused laser beams addressing individual ions. We show that isolated charges spread freely in the absence of string tension but exhibit localized coherent oscillations as the tension increases. We further observe the breaking dynamics of a string initially stretched between two static charges following an abrupt increase of the string tension. We find that charge pairs appear near the string edges and subsequently spread out into the bulk, revealing a mechanism for dynamical string breaking distinct from the conventional Schwinger mechanism.