First successfully developed recently, USTC silicon membrane quantum integrated chip. Ren Xifeng team has important progress in study of quantum integrated optical chips, they and state key laboratory of modern optics, photoelectric college, zhejiang university professor put the zinc cooperation, for the first time in silicon photonic integrated chip using silicon nanometer optical waveguide intrinsic mode as the new dimension of quantum information coding, has realized the single photon states and quantum entanglement in the polarization, paths, waveguide mode coherence between the different degrees of freedom such as conversion, its interference visibility all more than 90%, for integrated optical chip quantum photon multiple degrees of freedom of manipulation and transformation provides important experimental basis.

Silicon-based guide mode quantum integrated optical chip exactly is what? What significance? With these questions, the observer net interviewed USTC Ren Xifeng professor, professor ren unriddling for everyone, please.

Observer network: what is quantum optical chips?

Ren Xifeng: quantum optical chips refers to the integrated optical chip (unlike traditional chip, light instead of electrons for computing and storage) in quantum signal transmission and operation. Compared with the free space optics, fiber optics, the integration of optical devices and system has smaller size, extensible, low power consumption, high stability, a lot of advantage. So in the field of classical optics and quantum information has received widespread attention.

Observer network: quantum optical chips can be used in what areas? Quantum computer can be used for?

Ren Xifeng: quantum optical chips can be applied to quantum computation, quantum simulation, quantum communication and quantum metrology, and other fields. Due to the limitation of the quantum entanglement source, the research of quantum optical chips at present is mainly a handful of quantum bit transmission and operation, if the future in single photon quantum progress smoothly, quantum optical chips may be used to implement distributed quantum computer.

Observer, you put forward adopting multimode waveguide intrinsic mode as a new degree of freedom of coding quantum information relative to what the practice of innovation in the past?

Ren Xifeng: in quantum optics chip former research, people usually use the polarization degree of freedom, freedom or path is using different polarization or different paths to realize quantum information coding. Among them, the polarization encoding can only achieve two-dimensional quantum information process, cannot achieve higher dimensional coding, so obvious deficiencies in information capacity and security; Although path coding can achieve high dimensional quantum information process, but in order to prevent crosstalk between different path information, its path spacing generally larger, greatly restricted the quantum optical chips has promoted the integration and function extension.

For the first time, we put forward using eigen mode of multimode waveguides as coding new degree of freedom of quantum information. Use a support multiple mode of multimode waveguide is expected to achieve high dimensional quantum information coding. , for example, width is about 2.4 micron SOI optical waveguide, can support the eight guide mode, corresponding to the eight photonic information coding. Orthogonal to each other between these patterns, in particular, effectively avoid the problem of information crosstalk. At the same time, also can be in the process of quantum information at the same time using multiple degrees of freedom of photons, which significantly increased information capacity.

Observers, can attain "the polarization, arbitrary coherence between the degrees of freedom of path and the waveguide mode conversion, single photon and two photon interference visibility are more than 90%" mean? Can achieve the result of what?

Ren Xifeng: can "polarization, arbitrary coherence between the degrees of freedom of the path and the waveguide mode conversion, single photon and two photon interference visibility are more than 90%", means that we in the integration of quantum optical chips can manipulate multiple degrees of freedom at the same time, in the preparation of multiple degrees of freedom at the same time entangled quantum entangled state, further enhance the security of information capacity and information transmission, to realize the integration of quantum optical chips in high-dimensional laid the important foundation of quantum information process.

Observer, you are to develop silicon-based guide mode in the process of the quantum of the integrated optical chip what is the biggest difficulty and challenge, how to overcome the difficulties?

Ren Xifeng: because we have adopted a new degree of freedom, therefore from the experiment scheme design, to sample processing, testing are others didn't do it, we need to from the beginning, all this is the main difficulties we face. Based on the basis of deep research in the field of quantum information our laboratory, and collaborators in the aspect of silicon-based optical chips processing rich experience and perfect processing conditions, we one by one to solve the various problems encountered in the experiment, such as the coupling efficiency, the phase drift, dynamic control, etc.

Observer, quantum optical chips in the future may have what use?

Ren Xifeng: as stated earlier, although quantum optics research in the field of quantum information occupies the important position, but with the constant improvement of the light path complexity, platform optical stability, scalability, etc have already can't satisfy the need of further research, development encountered bottleneck. And quantum optical chips has small size, extensible, low power consumption, high stability, a lot of advantage. So in the field of classical optics and quantum information is received widespread attention, in the quantum computation, quantum communication, quantum simulation and measurement are has potential application value.

Observer, USTC technological achievements a lot recently, China university of science and technology of jian-wei pan and his colleagues zhang qiang, lilly, etc, and the Chinese academy of sciences Shanghai institute of microsystem and information technology, and the United States at the Massachusetts institute of technology researchers, using linear optical system, implemented in 20 kilometers of fiber optic lines Quantum fingerprint identification (Quantum Fingerprinting).

Can you say something about your opinion of the fingerprint identification technology?

Ren Xifeng: quantum fingerprint identification I am not very familiar with, so this problem may pan team more comprehensive and profound understanding.

Observer, a few days ago, Shanghai jiaotong university scientific research team in the lab successfully captured the Mayo rana fermion, Mayo rana fermion is said to be promising in the field of quantum computer, what do you think about it? Can quantum optical chips used in quantum computer?

Ren Xifeng: Mayo rana fermion indeed has important use in the field of quantum computer, actually another team is also in our laboratory is engaged in the related experimental study.

Quantum optical chips at present as a result of the limitation of quantum entanglement light source on the photon number, the main also focused on some original rational validation aspects of quantum scheme. However, with the progress of the quantum single photon sources, the future study of quantum optical chips will inevitably reflects the advantage in terms of a quantum computer.

Observer, for China's achievements in quantum information technology in recent years, how do you evaluate? Nature to launch the special Chinese scientists recently, what do you think?

Ren Xifeng: China in quantum information technology has made a series of international cutting-edge research results, in the fields of quantum information research maintained the highest standard of research in the international, especially in recent years, countries in this area increasing investment, believe that the Chinese studies in the field of quantum information continue to walk in the forefront of the various countries in the world.