China launched a 2,000-kilometer quantum fiber link connecting Beijing and Shanghai on Friday, allowing unhackable communication between the cities.

This is the world's longest and most sophisticated quantum link, and it will serve as the backbone connecting quantum networks in four cities: Beijing, Shanghai, Jinan in Shandong province and Hefei in Anhui province, said Pan Jianwei, China's leading quantum physicist.

During the link's launch in Beijing, Bai Chunli, the president of the Chinese Academy of Sciences, made video phone calls using the quantum link with scientists and government officials in Jinan, Hefei and Shanghai, congratulating them for their hard work.