Metamorphic materials for quantum computing

Quantum information and computing are at the forefront of computer science, but their implementation relies on significant developments in materials science. In particular, suitable, lattice-matched substrates for two promising approaches-electrostatically defined quantum dots in Si/SiGe heterostructures, and superconducting circuits containing Josephson junctions-do not exist. Instead, these approaches rely on metamorphic substrates. In this article, we focus on the general structure and requirements of SiGe quantum dot heterostructures, the demands they impose on the underlying substrate, and the impact that properties of the metamorphic substrate have on device performance. Superconductor Josephson junction materials are briefly discussed in a similar fashion, and opportunities for future developments in both systems are described.