Nanophotonics provides a promising approach to advance quantum technology by replicating fundamental building blocks of nanoscale quantum optic systems in large numbers with high reproducibility on monolithic chips. While photonic integrated circuit components and single-photon detectors offer attractive performance on silicon chips, the large-scale integration of individually accessible quantum emitters has remained a challenge. Here, we demonstrate simultaneous optical access to several integrated solid-state spin systems with Purcell-enhanced coupling of single photons with high modal purity from lithographically positioned nitrogen vacancy centers into photonic integrated circuits. Photonic crystal cavities embedded in networks of tantalum pentoxide-on-insulator waveguides provide efficient interfaces to quantum emitters that allow us to optically detect magnetic resonances (ODMR) as desired in quantum sensing. Nanophotonic networks that provide configurable optical interfaces to nanoscale quantum emitters via many independent channels will allow for novel functionality in photonic quantum information processors and quantum sensing schemes.

Photonic integrated circuits that are manufactured with mature semiconductor technology hold great promise for realizing scalable quantum technology. Efficient interfaces between quantum emitters and nanophotonic devices are crucial building blocks for such implementations on silicon chips. These interfaces can be realized as nanobeam optical cavities with high quality factors and wavelength‐scale mode volumes, thus providing enhanced coupling between nano‐scale quantum emitters and nanophotonic circuits. Realizing such resonant structures is particularly challenging for the visible wavelength range, where many of the currently considered quantum emitters operate, and if compatibility with modern semiconductor nanofabrication processes is desired. Here, it is shown that photonic crystal nanobeam cavities for the visible spectrum can be designed and fabricated directly on‐substrate with high quality factors and small mode volumes. Designs are compared based on deterministic and mode‐matching methods and the latter is found advantageous for on‐substrate realizations. The results pave the way for integrating quantum emitters with nanophotonic circuits for applications in quantum technology.

The prime example of a two-dimensional photonic crystal featuring Dirac cones is based on the honeycomb lattice. Colloidal self-assembly can produce a two-dimensional colloidal structure over a large area but is limited to hexagonal-close-packed structures. Therefore, it has been challenging to fabricate honeycomb monolayers by colloidal self-assembly. Here, we fabricate a dielectric honeycomb lattice in a large area by template-assisted self-assembly and analyze its photonic structure. Although the Dirac point occurring at the K point is not accessible by light in free space, a part of the upper Dirac cone above the light line is verified by a Fourier analysis of the back-focal-plane image. Because the template-assisted self-assembly enables additional geometrical perturbations in the honeycomb lattice, various lattices can be fabricated. This additional degree of freedom may provide an alternative way of fabricating photonic topological insulators.

A quantum emitter placed in a nanophotonic structure can result in non-reciprocal phenomena like chiral light excitation. Here, we present a theoretical model to couple circularly polarized emitters described by the density matrix formalism to the electromagnetic fields within a finite-difference time-domain (FDTD) simulation. In particular, we discuss how to implement complex electric fields in the simulation to make use of the rotating wave approximation. By applying our model to a quantum emitter in a dielectric waveguide and an optical circulator, we show how the excitation of the quantum system depends on its position and polarization. In turn, the backcoupling can result in strongly asymmetric light excitation. Our framework and results will help better understand spatio-temporal dynamics of light field in nanophotonic structures containing quantum emitters.