Several types of metamaterials are being studied. Nanowires can use quantum dots as the unit cells or artificial atoms of the structure, arranged as periodic nanostructures. This material demonstrates a negative index of refraction and effective magnetism and is simple to build. The radiated wavelength of interest is much larger than the constituent diameter. Another type uses periodically arranged cold atom cells, accomplished with ultra-cold gasses. A photonic bandgap can be demonstrated with this structure, along with tunability and control as a quantum system. Quantum metamaterial prototypes based on superconducting devices with and without Josephson junctions are being actively investigated. Recently a superconducting quantum metamaterial prototype based on flux qubits was realized.