Compact entanglement sources for portable quantum information platforms

We discuss two novel entanglement sources utilizing spontaneous parametric downconversion in periodically poled waveguides. Using quasi-phase matched KTP crystals, we have demonstrated a post-selection-based polarization-entangled degenerate source at 810 nm, as well as a post-selection-free non-degenerate collinear source producing entangled photons at 810 nm and 1550 nm. The sources exhibit high brightness and state quality - with the non-degenerate source achieving fidelities and purities up to 99% - with clear paths for further improvement. Furthermore, they are compact, stable, and need little alignment when set, critical for practical quantum communication and network applications. Lastly, their small size, weight, and power (SWaP) makes them an attractive option for mobile platforms, e.g., with drones or satellites.