  Integrated quantum optics becomes a consequent tendency towards practical
quantum information processing. Here, we report the on-chip generation and
manipulation of photonic entanglement based on reconfigurable lithium niobate
waveguide circuits. By introducing periodically poled structure into the
waveguide interferometer, two individual photon-pair sources with controllable
phase-shift are produced and cascaded by a quantum interference, resulting in a
deterministically separated identical photon pair. The state is characterized
by 92.9% visibility Hong-Ou-Mandel interference. Continuous morphing from
two-photon separated state to bunched state is further demonstrated by on-chip
control of electro-optic phase-shift. The photon flux reaches ~1.4*10^7 pairs
nm-1 mW-1. Our work presents a scenario for on-chip engineering of different
photon sources and paves a way to the fully integrated quantum technologies.
