Switchable pinning landscapes for flux quanta using arrays of ``magnetic vortices''*

We constructed a superconducting/ferromagnetic hybrid system in which the \textit{ordering} of the pinning potential landscape for flux quanta can be manipulated. Flux pinning is induced by an array of magnetic nanodots in the ``magnetic vortex'' state, and controlled by the magnetic history. This allows switching \textit{on} and \textit{off} the collective pinning of the flux-lattice. In addition, we observed field-induced superconductivity that originates from the annihilation of flux quanta induced by the stray fields from the ``magnetic vortices.''