Chinese researchers have completed a practical demonstration of quantum key distribution, showing that it’s possible to encrypt and send data between two locations in a highly secure way.
The announcement proves that the fiber-satellite quantum communications network that China has spent more than 10 years building can generate and distribute cryptographic keys for real-world purposes. These keys should render communications impenetrable to hackers—at least in principle.
“It’s a spectacular demonstration,” says Charles Clark, a fellow with the Joint Quantum Institute at the University of Maryland. “It’s the first time that there’s been long-distance communication using quantum key encryption in something like a videoconferencing application.”
In the demonstration on Friday, a team from the Chinese Academy of Sciences led by physicist Jian-Wei Pan generated a secure key from a quantum satellite called Micius that launched in August 2016. The satellite has special equipment onboard to produce photons suspended in superposition, single particles of light whose peculiar properties can be used to generate a random sequence of bits.
That string of bits then serves as a sort of secret code with which two parties can encrypt and decrypt messages, through a scheme known as one-time pad. The main security advantage of such a system is that the principles of quantum mechanics make it impossible for outsiders to read a message without altering it. “The quantum communication itself offers a way for unconditional secure key exchange,” Pan says.
Quantum encryption has long been an alluring theoretical possibility, but executing key distribution on an international scale has required substantial investment. China has built five ground stations to communicate with Micius. These connect to a 2,000-kilometer fiber optic backbone between Beijing and Shanghai (completed in 2016). Together they form the world’s first space-ground quantum network.