Programmable lithium niobate photonic chip for near-ideal path entanglement and frequency entanglement

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 modulation, to produce multiple near-ideal 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 hold a wide wavelength tuning range and high coupling efficiency from the chip. Our work paves the way for the development of programmable multi-functional quantum light sources and further promoting various quantum information tasks and enriching the architectures of on-chip quantum information processing.