Comparison, optimization, and application of various spontaneous parametric downconversion sources of polarization-entangled photon pairs

As benchtop quantum information protocols become increasingly more advanced and the distances over which these experiments are performed become significantly longer, integrated optics provide a small, robust, and practical alternative to traditional bulk optics. Waveguide technology makes it possible to create bright entangled-photon sources that can be used on platforms where weight and stability requirements are limiting factors, e.g., on aerial or even space-based mobile platforms, which could allow reconfigurable long-distance transfer of photonic qubits. Specifically, for our goals, we are working on the characterization and optimization of both highly nondegenerate and degenerate Spontaneous Parametric Down-Conversion waveguide sources of collinear polarization-entangled photon pairs using various entanglement methods determined by the relevant application. Our ultimate goal is to create polarization-entangled photon pairs that are also spectrally unentangled, a necessary condition for efficient multiphoton protocols, e.g., for quantum repeaters. Additionally, highly nondegenerate polarization-entangled photon pairs can be manipulated to create frequency-entangled pairs for ultra-high-timing-resolution interference-based quantum metrology on the attosecond-level. This metrology scheme would enable new technologies for both biomedical and defense applications