  Realistic modeling of qubit systems including noise and constraints imposed
by control hardware is required for performance prediction and control
optimization of quantum processors. We introduce qopt, a software framework for
simulating qubit dynamics and robust quantum optimal control considering common
experimental situations. To this end, we model open and closed qubit systems
with a focus on the simulation of realistic noise characteristics and
experimental constraints. Specifically, the influence of noise can be
calculated using Monte Carlo methods, effective master equations or with the
efficient filter function formalism, which enables the investigation and
mitigation of auto-correlated noise. In addition, limitations of control
electronics including finite bandwidth effects as well as nonlinear transfer
functions and drive-dependent noise can be considered. The calculation of
gradients based on analytic results is implemented to facilitate the efficient
optimization of control pulses. The software easily interfaces with QuTip, is
published under an open source license, well-tested and features a detailed
documentation.
