Bright entangled photon pair generation from a quantum dot in a weak nanowire cavity

A quantum dot (QD) embedded on-axis in a tapered photonic nanowire waveguide on a gold mirror is a promising platform for generating on-demand entangled photon pairs. Site-selected InP nanowires can be grown with high-quality InAsP QDs emitting from 870 nm to 1550 nm. However, the nanowire quantum dots (NWQDs) cannot be grown directly on gold, and therefore the photon pair extraction efficiency was measured to be ~6% on the substrate since the QD emits in both directions of the waveguide. We developed a pick-and-place transfer technique, to deterministically move NWQDs onto a gold mirror without degradation of the optical characteristics of the QD. We observe a 2.5-fold enhancement in brightness and a 1.58x decrease in the lifetime due to a weak Purcell enhancement. This corresponds to an increase of the pair extraction efficiency to ~49% on gold. Combining this with a previous result showing near-unity entanglement fidelity from the same NWQD platform, we aim to overcome the fundamental limit of probabilistic entangled photon pair sources to develop a truly deterministic entangled photon pair source.