  We present the first version of the QEngine, an open-source C++ library for
simulating and controlling ultracold quantum systems using optimal control
theory (OCT). The most notable systems presented here are Bose-Einstein
condensates, many-body systems described by Bose-Hubbard type models, and two
interacting particles. These systems can all be realized experimentally using
ultracold atoms in various trapping geometries including optical lattices. In
addition we provide a number of optimal control algorithms including the
recently introduced GROUP method. The QEngine library has a strong focus on
accessibility and performance. We provide several examples of how to prepare
simulations of the physical systems and apply optimal control.
