Programmable Lithium Niobate Photonic Chip for High‐Fidelity Path Entanglement and Frequency Entanglement

The quantum photonic chip is a powerful platform to prepare multi‐functional quantum light sources and actualize complex quantum information processing for its advantages of integration, stability, mass production, and reconfigurability. In this work, we design and fabricate a lithium niobate quantum photonic chip, consisting of tandem multi‐poling structures, Mach–Zehnder interferometers, and electro–optic modulators. By programming these components, we produce multiple wavelength–tunable high‐fidelity quantum light sources, including anti‐bunching, path, and frequency entangled photon pairs. The anti‐bunching photon pairs exhibit off‐chip Hong–Ou–Mandel interference visibilities above 99%. The fidelities of both frequency and path entanglement exceed 0.99. Meanwhile, all the quantum states maintain high coupling efficiency from the chip. Our work paves the way for the development of programmable multi‐functional quantum light sources and fiber‐based quantum sensing and quantum communication networks that are sensitive to the useful brightness and quality of quantum light sources.