  Here we present the quantum storage of three-dimensional
orbital-angular-momentum photonic entanglement in a rare-earth-ion-doped
crystal. The properties of the entanglement and the storage process are
confirmed by the violation of the Bell-type inequality generalized to three
dimensions after storage ($S=2.152\pm0.033$). The fidelity of the memory
process is $0.993\pm0.002$, as determined through complete quantum process
tomography in three dimensions. An assessment of the visibility of the stored
weak coherent pulses in higher-dimensional spaces, demonstrates that the memory
is highly reliable for 51 spatial modes. These results pave the way towards the
construction of high-dimensional and multiplexed quantum repeaters based on
solid-state devices. The multimode capacity of rare-earth-based optical
processor goes beyond the temporal and the spectral degree of freedom, which
might provide a useful tool for photonic information processing.
