Metamaterials in superconducting and cryogenic quantum technologies

Fault-tolerant superconducting quantum processors are limited by decoherence, limited connectivity, and the wiring burden at cryogenic temperatures. This review surveys superconducting “metamaterials”: circuits built from many repeating, deeply subwavelength building blocks (unit cells) that tailor dispersion, impedance, and bandgaps. By shaping the electromagnetic (and sometimes acoustic) environment of a qubit, these networks can suppress or enhance radiative decay and frequency shifts (Purcell and Lamb effects) and provide compact multimode structures for multiplexed control and photon-mediated coupling. We emphasize the practical trade-offs—added dielectric participation, fabrication disorder, and leakage through spurious chip/package modes—and the measurements needed to quantify them. The review summarizes design and tuning approaches (including Josephson/Superconducting Quantum Interference Device implementations), materials and fabrication limits, and mode-resolved benchmarks, and it highlights emerging directions such as topological lattices and engineered reservoirs while clearly separating demonstrations from proposals.