  We report on the experimental observation of period multiplication in
parametrically driven tunable superconducting resonators. We modulate the
magnetic flux through a superconducting quantum interference device, attached
to a quarter-wavelength resonator, with frequencies $n\omega$ close to
multiples, $n=2,\,3,\,4,\,5$, of the resonator fundamental mode and observe
intense output radiation at $\omega$. The output field manifests $n$-fold
degeneracy with respect to the phase, the $n$ states are phase shifted by
$2\pi/n$ with respect to each other. Our demonstration verifies the theoretical
prediction by Guo et al. in PRL 111, 205303 (2013), and paves the way for
engineering complex macroscopic quantum cat states with microwave photons.
