Recent advances in mechanical strain engineering of low-dimensional semiconductors and their applications in high-performance quantum emitters

In the past decades, low-dimensional semiconductors received intensive research interest. By introducing intentionally size-confined nanostructures or crystal imperfections, low-dimensional semiconductors have been broadly exploited as zero-dimensional quantum dots (QDs) for high-performance quantum emitters. The QD-based nonclassical light sources allow not only the deterministic generation of single photons but also entangled-photon pairs. However, the randomness in strain, shape and composition in semiconductors results in unpredictable transition energies for different QDs. This complication impedes the generation of single and entangled photons with well-defined energies, which fundamentally limits the success probability of scalable quantum information technologies. Strain engineering, a unique and powerful method to reshape the electronic states of semiconductors, has advanced the development of all-solid-state low-dimensional semiconductor based single and entangled-photon sources. In this review, the recent progress of employing mechanical strain field to control the electronic states and optical properties of low-dimensional semiconductors is reviewed. A comprehensive summary of diverse strain engineered devices for engineering the exciton binding energy, the coherent coupling of electronic states, the optical properties of low-dimensional semiconductors including single and entangled photons are provided. In addition, prospects and challenges of deploying the strain-engineering technique for future scalable quantum networks and photonic quantum circuits are discussed.