Non-classical states of light play a fundamental role in quantum technology. From photonic quantum computers and simulators to quantum communication and sensing, quantum states of light enable performing tasks that may outperform their best classical counterparts. Semiconductor quantum dots embedded in photonic nanostructures offer the most advanced classes of quantum light sources. Importantly, the underlying physical processes determining device performance are today fully understood, and dedicated engineering projects are currently advancing these sources toward real-world quantum technology applications. We review the performance of deterministic single-photon sources based on quantum dots in photonic crystal waveguides, the approach with the highest performance specs since it intrinsically combines suppression of leaky modes and Purcell enhancement to the slow-light waveguide mode. Furthermore, we present prototype data from sources that are commercially available today and have performance metrics approaching the ideal.
Loredo et al. (2026) studied this question.