Perspectives of low temperature physics: From defect engineering strategies to quantum technologies (Brief Review)

For the past forty years, there has been substantial research effort focused on the properties and optimization of high-temperature superconducting materials. Various defect engineering strategies have been employed to increase their critical temperature Tc, including the optimization of compositions via the introduction of substitutional doping, as well as external parameters such as pressure. Intensive investigation in superconducting materials, apart from producing technological applications, has also led to advances in fusion materials and, more recently, materials for quantum computing applications. Research in doped semiconductor materials has now progressed from nanoelectronic applications to the exciting era of quantum applications. In this review, we briefly discuss recent characteristic paradigms of quantum bits (qubits) and then turn to bound excitons at lower temperatures. In particular, we discuss the criteria to form qubits in diamond, focusing on the nitrogen-vacancy centers. We move on to examine excitons, their advantages, formation, and potential manipulation via strain. The discussion is linked with related research in techniques in high-temperature superconductor materials.