China succeeds in 'unhackable' quantum test undersea

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Chinese scientists successfully tested quantum communication under the surface of the sea, marking a global breakthrough in such technology.

The experiment was conducted by Jin Xianmin, and his team from Shanghai Jiao Tong University. In their experiment, the team was able to conduct communication secured by quantum mechanics between two underwater points several hundred meters apart, Jin told reporters on Monday, adding that the team was also able to securely communicate with satellites and aircraft from a point several meters under the sea.

Quantum communication is ultra-secure as a quantum photon can neither be separated nor duplicated. Accordingly, it is impossible to wiretap, intercept or crack information it transmits.

Jin Xianmin working in his lab. /Xinhua Photo

Once operationalized, such technology is expected to come in handy in the field of military, finance, and public information safety, according to Jin.

To carry out the experiment, the team collected samples of saltwater from six sites in the Yellow Sea, which they placed in containers, to see whether variations in the water affect their results, Jin said.

A beam of light was then shot through a crystal, which split it into pairs of photons, which are connected at the sub-atomic or quantum level.

This means that the performance of the pair of particles is now linked, theoretically over any distance, allowing data to be transmitted between the two.

Quantum particles in pairs /VCG Photo

Jin said that although the floating matter and salt in the sea can result in the loss of photons, the research team found a window which can enable the photons to travel and hence preserve enough photons to securely communicate.

"Such windows can be spotted by commercial photon detectors," said Jin.

He noted that if the seawater, which covers more than 70 percent of the Earth, cannot be covered, the global quantum communication will remain incomplete.

"The quantum communication is highly secured and is free from interruptions, so solving the problem of underwater quantum communication is a good news for the Navy," Li Jie, a Beijing-based naval expert, told reporters on Monday.

Ground stations transmit and receive quantum signals with satellites, but now information can be communicated underwater. /Xinhua Photo

However, according to Jin, the experiment is just the first step toward underwater quantum communication, and there is still a long way to go before a quantum communication network can be built incorporating both the sea and sky.

China has made several breakthroughs in the field of quantum communication in recent years.

Before Jin, a team from the University of Science and Technology of China led by Pan Jianwei, an academician with the Chinese Academy of Sciences, announced in July that they overcame the sunlight noise and demonstrated free-space quantum key distribution over 53 kilometers during the day.

China is striving to set up the first-ever global quantum communication network by around 2030, through linking a satellite constellation consisting of dozens of quantum satellites and ground-based quantum communication networks, according to Xinhua News Agency.

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Source(s): Global Times