  Quantum optimal control, a toolbox for devising and implementing the shapes
of external fields that accomplish given tasks in the operation of a quantum
device in the best way possible, has evolved into one of the cornerstones for
enabling quantum technologies. The last few years have seen a rapid evolution
and expansion of the field. We review here recent progress in our understanding
of the controllability of open quantum systems and in the development and
application of quantum control techniques to quantum technologies. We also
address key challenges and sketch a roadmap for future developments.
