  Dynamical spin-structure factor (DSF) contains fingerprint information of
collective excitations in interacting quantum spin systems. In solid state
experiments, DSF can be measured through neutron scatterings. However, it is in
general challenging to compute the spectral properties accurately via many-body
simulations. Currently, quantum simulation and computation constitute a
thriving research field, which are believed to provide a very promising
platform for simulating quantum many-body systems. In this work, we establish a
link between the many-body dynamics and quantum simulations by studying the
non-equilibrium DSF (nDSF) measured on direct product states, which are
accessible in contemporary quantum simulators with Rydberg atoms,
superconducting qubits, etc. Based on the many-body calculations of transverse
field Ising chains, we find the nDSF can be used to sensitively probe the
multi-spinon continua associated with the two-spinon creation and the
spinon-antispinon process, etc. Moreover, we further demonstrate that the
low-energy spinons can be confined -- forming spinon bound states -- under a
finite longitudinal field. Our results pave the way of quantum simulation and
manipulation of fractional excitations in highly-entangled quantum many-body
systems.
