From growth to integration: Quantum dot devices for quantum photonics

Semiconductor quantum dots represent one of the most promising classes of deterministic single-photon sources for emerging quantum technologies. These nanostructures offer several key advantages, including extremely low multi-photon emission probabilities, high photon fluxes, and the potential for large-scale production using well-established semiconductor fabrication techniques. Their operation has been thoroughly demonstrated in the visible and near-infrared spectral regions, and considerable effort is now focused on adapting these devices to emit within the telecommunication wavelength bands. Achieving this compatibility is an essential milestone toward realizing fiberintegrated quantum communication networks. This review provides an overview of various methods for the growth of quantum dots, alongside strategies implemented at the device level to improve their optical performance across a range of emission wavelengths. A particular emphasis is placed on work conducted by the Chair of Technische Physik at the University of W€urzburg, but we do present our work in the broader context of other approaches. We examine major advancements in epitaxial growth techniques on indium phosphide (InP) substrates, as well as innovations in mechanical strain tuning using piezoelectric elements, and photonic integration via micropillar cavities and circular Bragg grating structures. Furthermore, we discuss recent progress in enhancing photon indistinguishability within the telecom C-band using advanced excitation schemes and cavity quantum electrodynamics, including efforts in deterministic cavity positioning. Collectively, these developments underscore the strong potential of quantum dot-based devices as foundational components for scalable, high-performance quantum photonic systems.