April 29, 2022- 8:55 p.m.
Washington – Google announced it has a quantum computer that is 100 million times faster than any classical computer in its lab.
Every day, we produce 2.5 exabytes of data. That number is equivalent to the content on 5 million laptops.
In a giant technological step toward this end, Chinese scientists have established the world’s first integrated quantum communication network, combining over 700 optical fibers on the ground with two ground-to-satellite links to achieve quantum key distribution over a total distance of 4,600 kilometers for users across the country.
The team, led by Jianwei Pan, Yuao Chen, and Chengzhi Peng from the University of Science and Technology of China in Hefei, reported in Nature their latest advances toward the global, practical application of such a network for future communications.
The advantage of this “quantum key distribution” (QKD) is that quantum physics dictates that the very act of observing a particle irreparably changes it.
So any spies who tried to intercept the quantum key could be immediately detected by the changes in the particles.
So far, the most common QKD technology uses optical fibers for transmissions over several hundred kilometers, with high stability but considerable channel loss.
Materials in cables can absorb photons, which means they can typically travel for no more than a few tens of kilometers. In a classical network, repeaters at various points along a cable are used to amplify the signal to compensate for this.
QKD networks have come up with a similar solution, creating “trusted nodes” at various points. The Beijing-to-Shanghai network has 32 of them, for instance.
At these waystations, quantum keys are decrypted into bits and then re-encrypted in a fresh quantum state for their journey to the next node.
Another major QKD technology uses the free space between satellites and ground stations for thousand-kilometer-level transmissions.
In 2016, China launched the world’s first quantum communication satellite (QUESS, or Mozi/Micius) and achieved QKD with two ground stations 2,600km apart.
In 2017, a more than 2,000km-long optical-fiber network was completed for QKD between Beijing and Shanghai.
Using trusted relays, the ground-based fiber network and the satellite-to-ground links were integrated to serve more than 150 industrial users across China, including state and local banks, municipal power grids, and e-government websites.
In essence, the achievement indicates that quantum communication technology can be used for future large-scale practical applications.
Similarly, a global quantum communication network can be established if national quantum networks from different countries are combined, and if universities, institutions and companies come together to standardize related protocols.
