  Recently, intensely driven laser-matter interactions have been used to
connect the fields of strong laser field physics with quantum optics by
generating non-classical states of light. Here, we make a further key step and
show the potential of strong laser fields for generating controllable
high-photon-number coherent-state superpositions. This has been achieved by
using two of the most prominent strong-laser induced processes: high-harmonic
generation and above-threshold ionization. We show how the obtained
coherent-state superpositions change from an optical Schr\"odinger "cat" state
to a "kitten" state by changing the atomic density in the laser-atom
interaction region, and we demonstrate the generation of a 9-photon shifted
optical "cat" state which, to our knowledge, is the highest photon number
optical "cat" state experimentally reported. Our findings anticipate the
development of new methods that naturally lead to the creation of
high-photon-number controllable coherent-state superpositions, advancing
investigations in quantum technology.
