  Harmonic oscillators count among the most fundamental quantum systems with
important applications in molecular physics, nanoparticle trapping, and quantum
information processing. Their equidistant energy level spacing is often a
desired feature, but at the same time a challenge if the goal is to
deterministically populate specific eigenstates. Here, we show how interference
in the transition amplitudes in a bichromatic laser field can suppress the
sequential climbing of harmonic oscillator states (Kapitza-Dirac blockade) and
achieve selective excitation of energy eigenstates, Schr\"{o}dinger cats and
other non-Gaussian states. This technique can transform the harmonic oscillator
into a coherent two-level system or be used to build a large-momentum-transfer
beam splitter for matter-waves. To illustrate the universality of the concept,
we discuss feasible experiments that cover many orders of magnitude in mass,
from single electrons over large molecules to dielectric nanoparticles.
