The Quantum Information Key Laboratory of the Chinese Academy of Sciences, led by Guo Guangcan, a member of the Chinese Academy of Sciences and a professor at the Chinese University of Science and Technology, has for the first time successfully developed a silicon-based conductive film quantum integrated chip. Recently, the research team of Ren Feng of the laboratory made new progress in the research of quantum integrated optical chips. They cooperated with Dadao Zhan, a professor at the State Key Laboratory of Modern Optical Instruments of Zhejiang University, and used silicon nano-waveguide intrinsic mode for the first time on silicon photonic integrated chips. As a new dimension of quantum information coding, the coherent transitions between single photon states and quantum entanglement states in polarization, path, waveguide mode, and other degrees of freedom are realized. The interference visibility is more than 90%, which is the photon on the integrated quantum optics chip. The manipulation and conversion of degrees of freedom provide important experimental evidence. The related results were published in Nature Communications on June 20 [Nature Communications 7, Article Number 11985 (2016)]. The first author of the dissertation was Feng Lantian, a doctoral student of the University of Science and Technology of China, Zhang Zhiming, a postdoctoral doctor, and Zhang Ming, a doctoral student of Zhejiang University. Compared with free-space optics and fiber optics, integrated optics devices and systems have many advantages such as small size, scalability, low power consumption, and high stability, and thus have received extensive attention in the fields of classical optics and quantum information. In the past research on integrated quantum optical chips, people usually used polarization degrees of freedom or path degrees of freedom, that is, using different polarization or different paths to achieve quantum information encoding. Among them, polarization coding can only realize the two-dimensional quantum information process, and can not achieve high-dimensional coding. Therefore, there are obvious shortages in information capacity and security. Although path coding can realize high-dimensional quantum information process, it is in order to prevent different path information between The crosstalk between the paths is usually large, which greatly restricts the integration and enhancement of the quantum optical chip. Ren Xifeng's research group and collaborators proposed for the first time the use of the multimode waveguide's eigenmode as a new degree of freedom for encoding quantum information. Using a multimode waveguide supporting multiple waveguide modes is expected to achieve high-dimensional encoding of quantum information. For example, for a SOI waveguide with a width of about 2.4 microns, 8 guided modes can be supported, corresponding to 8-dimensional photon information encoding. In particular, these modes are orthogonal to each other, effectively avoiding the problem of information crosstalk. At the same time, multiple degrees of freedom of photons can also be used in the quantum information process to significantly increase the information capacity. The researchers successfully implemented any coherent conversion between polarization, path, and waveguide mode freedom using the new silicon substrate mode converter and mode multiplexer. The single-photon and two-photon interference visibility was over 90%. The possibility of manipulating multiple degrees of freedom at the same time in an integrated quantum-optic chip lays an important foundation for realizing the high-dimensional quantum information process in integrated quantum optical chips. The study was funded by the National Natural Science Foundation of China, the Chinese Academy of Sciences, the Ministry of Science and Technology, the Ministry of Education, and China University of Science and Technology and Zhejiang University. ZHEJIANG HESHUO TECHNOLOGY CO.,LTD , https://www.hosuocn.com