  For simulating laser-plasma interactions, we developed a parallel,
multi-dimensional, fully relativistically particle-in-cell (PIC) code, named
YUNIC. The core algorithm is introduced, including field solver, particle
pusher, field interpolation, and current interpolation. In addition to the
classical electromagnetic interaction in plasmas, nonlinear Compton scattering
and nonlinear Breit-Wheeler pair production are also implemented based on
Monte-Carlo methods to study quantum electrodynamics (QED) processes. We
benchmark YUNIC against theories and other PIC codes through several typical
cases. YUNIC can be applied in varieties of physical scenes, from relativistic
laser-plasma interactions to astrophysical plasmas and strong-field QED
physics.
