Last updated June 18, 2018 at 10:29 am
China has completed an important milestone towards building a global quantum-encrypted communication network.
An illustration of the Chinese satellite Micius. Credit: Jian-Wei Pan
A link from the quantum-enabled satellite Micius allowed scientists in China and Austria to exchange quantum encrypted data for images and a video stream.
The breakthrough last month is the first step toward a secure “quantum internet”.
The exchange proves that Micius is capable of providing intercontinental quantum-secured communications.
A secret key was created between the two countries distributed from Micius through a satellite-to-ground secure link.
Public key cryptography that can’t be hacked
That allowed scientists in the two countries to share images and a 75-minute video conference between Beijing and Vienna, with absolute security.
Whereas traditional public key cryptography can be hacked, quantum key technology makes eavesdropping virtually impossible.
The satellite is a part of the Quantum Experiments at Space Scale (QUESS) project – the nickname “Micius” was the name of an ancient Chinese philosopher.
It was launched into orbit in August 2016 – the first satellite in history to have the ability to process quantum particles. It has previously relayed a quantum signal between cities, a precursor to this experiment.
Spooky action at a distance
While quantum cryptography uses a string of 1’s and 0’s in the same way as digital cryptography, its bits, or qubits as they are known, are represented as quantum states — in this case of entangled photons.
This entanglement, once described by Albert Einstein as “spooky action at a distance”, means that the characteristics such as position, momentum, spin, and polarisation of each individual quantum particle in a pair or a group of particles, are highly correlated, no matter how far apart they may be.
In this case, the satellite created pairs of entangled photons and beamed one half of each pair down to each country’s base station.
How to distribute keys without interception
By another law of quantum mechanics, any attempt to observe the quantum state changes that state. That makes it impossible to intercept and read the transmitted qubits.
The problem, as with all encryption, is how to distribute keys without interception and this experiment would appear to have solved this issue.
The capability demonstrated by the experiment “is sufficient for the very early stages of a quantum internet, similar to the state of cell phones in the 1970s”, the research leader Jian-Wei Pan of the University of Science and Technology of China (USTC) in Hefei was quoted as saying.
He said that the network could be used for encrypted voice calls and emails transmitting sensitive financial or diplomatic information.
A report of the experiment was published on 19 January in the journal Physical Review Letters.
