Nanofabrication boosts quantum dot photon efficiency past 80%

III-V quantum dots now generate photons with collection efficiencies exceeding 80%, a major advance in extracting light while maintaining quantum coherence. The achievement follows forty years of development since the first epitaxial semiconductor quantum dots, nanostructures measuring just 20 nanometers in scale. These artificial atoms trap electrons and holes, behaving as two-level quantum systems capable of emitting single photons on demand. Advances in nanofabrication and cavity quantum electrodynamics have yielded devices where performances now rival those achieved with natural atoms and ions. Transmission electron microscopy reveals the scale of individual InGaAs quantum dots embedded in GaAs to be approximately 20 nanometers, demonstrating the incredibly small dimensions of these structures critical for advanced photonics. This leap in efficiency addresses a major challenge in quantum photonics: effectively extracting light while maintaining the delicate quantum coherence necessary for reliable operation. The enhanced photon extraction stems from the development of quantum dot-photon interfaces that exploit the Purcell effect, a phenomenon that amplifies and directs spontaneous emission into a specific optical mode. Over the past two decades, progress in semiconductor nanofabrication and cavity quantum electrodynamics has transformed these theoretical concepts into practical, highly efficient integrated devices. This progress has established quantum dots as a leading…