QUANTUM MEMORY SYSTEMS AND QUANTUM REPEATER SYSTEMS COMPRISING DOPED POLYCRYSTALLINE CERAMIC OPTICAL

A quantum memory system includes a doped polycrystalline ceramic optical device, a magnetic field generation unit, and one or more pump lasers. The doped polycrystalline ceramic optical device 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 optical device, and the doped polycrystalline ceramic optical device is doped with a rare-earth element dopant distributed within a crystal lattice of the doped polycrystalline ceramic optical device, such that at least 50% of the rare-earth element dopant is doped into grains of the crystal lattice at locations apart from the grain boundaries of the crystal lattice.