Recently, the Key Laboratory of Quantum Information of the Chinese Academy of Sciences led by Academician Guo Guangcan of the University of Science and Technology of China made a major breakthrough. The research team of Li Chuanfeng and Huang Yunfeng successfully prepared eight-photon entangled states, setting a new record for the number of preparations and operations of multiphoton entanglement in the world. The results were published online on November 22 in Nature Communications.
Quantum entangled states are the basis of various quantum information processes. Because photons have the advantages of strong anti-interference ability and fast propagation speed, the preparation and manipulation of multi-photon entangled states has always been the focus of research in the field of quantum information. At present, the non-linear process in crystals is commonly used in the world to generate multi-photon entangled states. Because this process is probabilistic, the difficulty of generating multi-photon entangled states will increase exponentially as the number of photons increases. Prior to this work, the world reported that up to six photon entangled states could be prepared.
The researchers improved the existing preparation methods of entangled light sources, using specially cut nonlinear crystals to prepare high-luminance two-photon entangled sources. The new method can compress the cone beam of the generated photon pair into a small circular spot, which greatly improves the collection efficiency. They used single-mode fiber collection technology to overcome the problem of optical path stability and improved the two-photon entanglement, and then used a polarizing beam splitter to realize three gate operations to cascade the two-photon entangled state into an eight-photon entangled state, and used independent research and development. The sixteen-channel conformance analyzer effectively overcomes the problem of detection and analysis of the eight-photon entangled state. Finally, the researchers verified the entanglement properties of the eight photons by using the entangled eyewitness technique, and further used the generated entangled states to complete the complexity experiment of the eight-party quantum communication. The experimental results surpassed the classical limit and showed the superiority of quantum entanglement.
This achievement means that the preparation and manipulation of multi-photon entanglement has reached an unprecedented eight-photon level. It will be used in quantum communication networks, entanglement-based quantum computing and other quantum information processes. It will also promote the characteristics and classification of quantum entanglement. And other basic physical problems.
The research was supported by the Ministry of Science and Technology and the National Natural Science Foundation of China.
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