Chinese University of Science and Technology made new progress in cooperative research on integrated quantum entangled light source

[ Instrument R&D of Instrumentation Network ] Guo Guangcan, a member of the Chinese Academy of Sciences and a professor at the University of Science and Technology of China, Ren Xifeng and others collaborated with the Zhu Xining team of Nanjing University and the Hong Kong Polytechnic University, East China Normal University and other units to achieve breakthroughs in the research of high-dimensional, multi-photon quantum entangled light sources . On June 26, the research results were published in Science.

With the development of optical quantum information technology, the existing quantum light source preparation solutions are faced with the problems of complex optical system, low integration, weak stability, etc. in terms of improving the entanglement dimension and the number of entangled photons, which can no longer satisfy quantum computing and quantum communication. , Quantum measurement and other fields, restrict the development of optical quantum information toward large-scale integration. Recently, the study of "superstructured surfaces" has provided a brand new path for the development of quantum light sources and photon information technology.

The researchers introduced the metamorphic surface technology, combining the metamorphic lens with the nonlinear optical crystal to form a brand-new metasurface quantum light source system. They prepared a 10X10 metamorphic lens array. The array evenly divided the pump laser into 10X10 parts. In the BBO crystal, the spontaneous parametric down-conversion process occurred, which could prepare 100-dimensional path entanglement and multiphotons. Increasing the number of lens arrays can further increase the dimension of entangled photons.

The fidelity of the entangled states of the two-dimensional, three-dimensional and four-dimensional paths formed by the experiment reached 98.4%, 96.6% and 95.0% respectively. Not only that, meta lenses have flexible light field control capabilities, which can be integrated to control the phase, polarization, and amplitude of the light field. Through the phase design of the meta-lens, the research team carried out a precise phase encoding of the prepared quantum entangled state, and proved it well through experiments. In terms of multiphotons, the researchers used the 415 nm femtosecond laser as the pump source to measure the coincidence curve of 4 and 6 photons prepared by the system, and showed the results of the 4-photon Hong-Ou-Mandel interference. The high interference contrast proves that the generated multiphoton quantum light source has very good properties.

This work has achieved high-dimensional, integrated two-photon and multi-photon entangled light sources by introducing super-structured surface technology, which breaks through the technical bottleneck of existing quantum light sources and the limitations of information coding dimensions, and is expected to be applied to high-dimensional quantum communication and quantum The fields of computing and quantum storage are of great significance to the development of quantum information technology with higher information capacity and higher security.

This work was supported by the Ministry of Science and Technology, the National Natural Science Foundation of China, the Chinese Academy of Sciences, Anhui Province and the University of Science and Technology of China.