Fig. 2. Hybrid quantum photonic integration approaches.

(a) Wafer bonding approach to combine different materials. (b) Wafer bonding of a GaAs nanobeam with QDs to silicon nitride waveguides: single photons from the QD are adiabatically coupled to the silicon nitride waveguide[20]. (c) Bonding of a silicon on insulator waveguide wafer with III-V dies[54]. (d) Transfer printing approach for hybrid integration. (e) Transfer printing of a quantum-dot-cavity to a silicon waveguide [32]. (f) Transfer printing of 2D material (WSe₂) to a SiN waveguide: single photons emitted from the monolayer are coupled to a silicon-based photonic circuit[57]. (g) Pick-and-place technique using a nanomanipulator. (h) Pick-and-place integration of a InP nanowire QD to a silicon nitride waveguide fabricated on a piezoelectric crystal for strain tuning of the quantum source and the circuit[24], (i) Hybrid integration of InAs/InP QDs to silicon photonic waveguide using pick-and-place technique[26].