Chinese team makes password quantum leap

It's another kind of "quantum supremacy" – a Chinese team of scientists has successfully established a satellite-based quantum network that can send passwords 1120 kilometers away.

It’s another kind of “quantum supremacy” — a Chinese team of scientists has successfully established a satellite-based quantum network that can send passwords 1,120 kilometers away.

The distance is about 10 times farther than the old optic fiber-based quantum tech could cover. This formidable leap is seen as a new step forward toward the practical application of quantum communication.

The team’s research has been peer reviewed and published on the website of renown research journal Nature.

 Quantum Key Distribution is a secure way to allow the exchange of encrypted messages between remote users.

In previous studies, scientists demonstrated QKD in a laboratory over optical fiber and between a satellite and ground station.

But QKD between two users on the ground requires trusted relays, or quantum repeaters, to avoid signal loss and extend the distance, which poses security risks.

In the satellite-ground QKD test, for instance, a quantum key was generated and distributed by China’s quantum satellite from Quantum Experiments at Space Scale.

The satellite, nicknamed Micius, had all the quantum key’s information. If Micius is hacked, there is a risk of information leakage.

The team, led by quantum communication expert Pan Jianwei, used Micius to send a pair of photons ­— the basic unit of all lights — to ground stations — Delingha in Qinghai Province and Nanshan in the Xinjiang Uygur Autonomous Region.

A secured quantum link between the two ground stations was established with no trusted relays and the Micius satellite had no information about the secure key.

Due to a physical phenomenon called “quantum entanglement,” the pair will always act the same way no matter how far apart they are, making them a perfect storage for passwords.

What’s more, the password will change itself when it gets intercepted, making it hacker-proof on a theoretical level.

Pan said the study increases the secure distance of QKD without trusted relays on the ground tenfold and ensures secure communication, even when the satellite is compromised.

“If you saw one of the photons, the entanglements will be broken,” Pan said.

“And you will realize that the password is no longer safe. So, even if the satellite was built by people you don’t trust, it’s still safe.”

According to the paper published in Nature, the speed of the quantum network is extremely slow compared with broadband ethernet or 4G — it’s only 0.12 bits per second.

With that said, the albeit underwhelming speed is more than enough for governments to transmit top secrets.

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