Scientists Firstly Realize All-photonic Quantum Repeater----Chinese Academy of Sciences

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Scientists Firstly Realize All-photonic Quantum Repeater

Jul 12, 2019

Quantum repeaters, as the important components of a scalable quantum internet, enable the distribution of quantum states over long distances. The standard paradigm for a quantum repeater consists of three basic technologies, i.e., entanglement swapping, entanglement purification, and quantum memory. However, the limited performance of current quantum memories remains a major obstacle in realizing practical quantum repeaters.

Recently, the research team led by Prof. PAN Jianwei, Prof. CHEN Yuao and Prof. XU Feihu from University of Science and Technology of China of Chinese Academy of Sciences has demonstrated the all-photonic quantum repeater which eliminates the need for matter quantum memories, offering a new approach to construct the long-distance optical quantum internet. The study was published in Nature Photonics.

Scientists conducted the experiment which adopted a GHZ state and a passive scheme to realize the selective Bell measurement in the repeater nodes. By manipulating a 12-photon interferometer, they implemented a 2×2 parallel all-photonic quantum repeater, and observed an 89% enhancement of entanglement-generation rate over standard parallel entanglement swapping.

These results provided a new approach to design quantum repeaters with efficient single-photon sources and photonic graph states, and suggested that the all-photonic scheme represents an alternative path towards realizing practical quantum repeaters.

In the future, the research team will be devoted to combining the all-photonic scheme with the matter-memory-based scheme. These two schemes are important parallel research directions towards achieving a practical quantum repeater. By doing so, the repeater graph state (RGS) can relax the requirement of long coherent time of quantum memory, while a quantum memory can reduce the requirement of large size for the RGS.

The successful demonstration of all-photonic quantum repeater suggests that the quantum memory is no longer a necessary condition for building a quantum repeater, which opens up a new way for the research on long-distance quantum communications and networks.