We fabricate an inversely-designed nanophotonic quantum dot polarization de-multiplexer and observe the coupling of single embedded InAs quantum dot to two orthogonal output waveguides.

Single solid-state quantum emitters offer consid-erable potential for the implementation of sources of single indistinguishable photons, which are central to many photonic quantum information systems. Nanophotonic geometry optimiza-tion with multiple performance metrics is imperative to convert a bare quantum emitter into a single-photon source that approaches the necessary levels of purity, indistinguishability, and brightness for quantum photonics. We present an inverse design methodology that simultaneously targets two important figures-of-merit for high -performance quantum light sources: the Purcell radiative rate enhancement and the coupling efficiency into a desired light collection channel. We explicitly address geometry-dependent power emission, a critical but often overlooked aspect of gradient-based optimization of quantum emitter single-photon sources. We illustrate the efficacy of our method through the design of a single-photon source based on a quantum emitter in a GaAs nanophotonic structure that provides a Purcell factor Fp = 21 with a 94% waveguide coupling efficiency, while respecting a geometric constraint to minimize emitter decoherence caused by etched sidewalls. Our results indicate that multiobjective inverse design can yield competitive performance with more favorable trade-offs than conventional approaches based on a pre-established waveguide or cavity geometries.

Epitaxial quantum dots can emit polarization-entangled photon pairs. If orthogonal polarizations are coupled to independent paths, then the photons will be path-entangled. Through inverse design with adjoint method optimization, we design a quantum dot polarization demultiplexer, a nanophotonic geometry that efficiently couples orthogonally polarized transition dipole moments of a single quantum dot to two independent waveguides. We predict 95% coupling efficiency, cross talk less than 0.1%, and Purcell radiative rate enhancement factors over 11.5 for both dipoles, with sensitivity to dipole misalignment and orientation comparable to that of conventional nanophotonic geometries. We anticipate our design will be valuable for the implementation of triggered, high-rate sources of path-entangled photon-pairs on chip.

We use inverse design to develop an optimized nanophotonic geometry for efficient, Purcell-enhanced, waveguide-coupled, path-entangled photon pair sources based on single embedded quantum dots.

We demonstrate a new, multi-objective inverse design strategy for single-photon sources based on single quantum emitters, and show that it can produce comparable performance, with more favorable trade-offs, than conventional design based on pre-existing nanophotonic geometries.