  Multiphoton entanglement plays a critical role in quantum information
processing, and greatly improves our fundamental understanding of the quantum
world. Despite tremendous efforts in either bulk media or fiber-based devices,
nonlinear interactions in integrated circuits show great promise as an
excellent platform for photon pair generation with its high brightness,
stability and scalability \cite{Caspani2017}. Here, we demonstrate the
generation of bi- and multiphoton polarization entangled qubits in a single
silicon nanowire waveguide, and these qubits directly compatible with the dense
wavelength division multiplexing in telecommunication system. Multiphoton
interference and quantum state tomography were used to characterize the quality
of the entangled states. Four-photon entanglement states among two frequency
channels were ascertained with a fidelity of $0.78\pm0.02$. Our work realizes
the integrated multiphoton source in a relatively simple pattern and paves a
way for the revolution of multiphoton quantum science.
