  Tailored light-matter interactions in the strong coupling regime enable the
manipulation and control of quantum systems with up to unit efficiency, with
applications ranging from quantum information to photochemistry. While strong
light-matter interactions are readily induced at the valence electron level
using long-wavelength radiation, comparable phenomena have been only recently
observed with short wavelengths, accessing highly-excited multi-electron and
inner-shell electron states. However, the quantum control of strong-field
processes at short wavelengths has not been possible, so far, due to the lack
of pulse shaping technologies in the extreme ultraviolet (XUV) and X-ray
domain. Here, exploiting pulse shaping of the seeded free-electron laser (FEL)
FERMI, we demonstrate the strong-field quantum control of ultrafast Rabi
dynamics in helium atoms with high fidelity. Our approach unravels the
strong-field induced bound-continuum coupling of the electronic states in
helium and enables substantial suppression of the ionization rate, with
prospective applications in many XUV and X-ray experiments. Leveraging recent
advances in intense few-femtosecond to attosecond XUV to X-ray light sources,
our results open an avenue to the efficient manipulation and selective control
of core electron processes and electron correlation phenomena in real time
