Record! Mozi realizes quantum state transmission at 1200 km surface

Academician Pan Jianwei of the University of Science and Technology of China and his colleagues Peng Chengzhi, Chen Yuao, Yin Juan, etc. used the “Mozi” quantum science experimental satellite to realize the long-range transmission of quantum states between two ground stations 1200 kilometers apart on the earth for the first time, taking an important step towards building a global quantum information processing and quantum communication network. The results were published online in The Physical Review Letters.

Thousand kilometers of quantum state transmission .png

1,000-kilometer quantum state transmission courtesy of the University of Science and Technology of China

In 2012, Pan Jianwei’s team realized quantum teleportation in 100-kilometer free space for the first time in the world. After 10 years, the team successfully achieved a breakthrough and refreshed the new record of quantum state transmission at 1200 kilometers of surface.

Long-distance quantum state transmission can usually be achieved by using quantum teleportation, which is one of the important ways to build a quantum communication network and a necessary element to achieve a variety of quantum information processing tasks. With the aid of long-distance quantum entanglement distribution, quantum states can be measured and then reconstructed to complete long-distance transmission, and the transmission distance can theoretically be infinite.

However, in the implementation, the distance and quality of the quantum entanglement distribution will be affected by factors such as channel loss and decoherence. How to continuously break through the limitation of transmission distance has always been one of the important research goals in this field.

Using the spaceborne entanglement source to first distribute entanglement to distant places, and then preparing and reconstructing the quantum state, is one of the most likely paths to achieve long-distance quantum state transmission. However, due to the influence of atmospheric turbulence, it is very difficult to achieve quantum interference-based quantum state measurements after photons propagate in atmospheric channels.

In previous experiments, the preparation party of the quantum state transmission is the owner of the quantum entanglement source, and it is impossible to provide entanglement by a third party to achieve the quantum state transmission of the first distribution and then the transfer state. With the successful launch of the “Mozi” quantum science experiment satellite, Pan Jianwei’s team first realized the entanglement distribution of two stations of thousands of kilometers, and the “Mozi” platform provided valuable entanglement distribution resources for quantum communication experiments.

In order to overcome the problem of quantum light interference after long-distance turbulent atmospheric transmission, the experimental team used optical integration bonding technology to achieve an ultra-high stability optical interferometer, which can be stable for a long time without active closed loop. Combined with the quantum teleportation scheme based on the two-photon path-polarization hybrid entangled state, the transmission verification of the remote quantum state was completed between Lijiang Station and Delingha Ground Station in Yunnan Province. Six typical quantum states were verified in the experiment, and the transmission fidelity exceeded the classical limit.

The reviewers believe that “this experiment is more challenging than previous experiments, overcomes major technical challenges, and has important implications for future applications of quantum communication.” (Source: China Science Daily Wang Min)

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