Waveguide excitation and spin pumping of chirally coupled quantum dots

On-chip excitation of single quantum emitters is a key requirement for developing scalable quantum photonic technologies. Here, we report a remote excitation protocol on an integrated semiconductor chip, in which a single quantum dot (QD) is driven in-plane via a photonic-crystal waveguide through a p-shell optical transition. The chirality of the waveguide mode is exploited to achieve both directional absorption and directional emission, resulting in a substantial enhancement in directional contrast, as measured for the Zeeman components of the waveguide-coupled QD. This remote excitation scheme enables near-unity directionality (≥ 0.95) across∼56% of the waveguide area, with significant overlap with the Purcell-enhanced region, where the electric field intensity profile is near its peak. In contrast, conventional out-of-plane local excitation yields only ∼25% overlap. This enhancement increases the likelihood of locating Purcell-enhanced QDs in regions that support high directionality, allowing the experimental demonstration of a six-fold enhancement in the decay rate of a QD with directionality of 90 ± 3%. The remote p-shell excitation protocol thus establishes a benchmark for waveguide quantum optics by combining Purcell enhancement with high directionality. This approach enables efficient on-chip spin initialization and control in solid-state quantum technologies operating in high-β-factor regimes, with implications for scalable quantum networks and integrated devices.