  This paper describes an approach to construct temporally shaped control
pulses that drive a quantum system towards desired properties. A
parametrization in terms of periodic functions with pre-defined frequencies
permits to realize a smooth, typically simple shape of the pulses; their
optimization can be performed based on a variational analysis with Floquet
theory. As we show with selected specific examples, this approach permits to
control the dynamics of interacting spins, such that gate operations and
entanglement dynamics can be implemented with very high accuracy.
