A doped polycrystalline ceramic optical device including quantum memory system and quantum repeater

A quantum memory system includes a doped polycrystalline ceramic, a magnetic field generation unit, and one or more pump lasers. The doped polycrystalline ceramic is positioned within a magnetic field of the magnetic field generation unit when the magnetic field generation unit generates the magnetic field, the one or more pump lasers are optically coupled to the doped polycrystalline ceramic, and the doped polycrystalline ceramic is doped with a rare-earth element dopant that is uniformly distributed within a crystal lattice of the doped polycrystalline ceramic.