Hackers, take notice: Ultrasecure quantum video chats are now possible across the globe.

In a demonstration of the world’s first intercontinental quantum link, scientists held a long-distance videoconference on September 29 between Austria and China. To secure the communication, a Chinese satellite distributed a quantum key, a secret string of numbers used to encrypt the video transmission so that no one could eavesdrop on the conversation. In the call, chemist Chunli Bai, president of the Chinese Academy of Sciences in Beijing, spoke with quantum physicist Anton Zeilinger, president of the Austrian Academy of Sciences in Vienna.

“It’s a huge achievement,” says quantum physicist Thomas Jennewein of the University of Waterloo in Canada, who was not involved with the project. “It’s a major step to show that this approach could be viable.”

Using a technique known as quantum key distribution, scientists share secret strings of numbers while ensuring that no eavesdroppers can intercept the code undetected. Those quantum keys are then used to encrypt information sent via traditional internet connections. Decoding the transmission requires the same key used for encryption, foiling would-be snoops.

NO EAVESDROPPING During a videoconference made secure with quantum mechanics, physicist Anton Zeilinger holds up a model of the quantum-communications satellite Micius. © ÖAW

China’s Micius satellite, which launched in 2016, uses lasers to beam photons, or light particles, to ground stations on Earth. Micius sent a series of photons encoding a string of 0s and 1s to a ground station near Beijing. The satellite stored information about the sequence until it reached a station near Vienna, where Micius beamed down another string of photons. Then the satellite combined the two sets of numbers and relayed additional information to the stations to allow them to create matching keys.

Previously, scientists have used Micius to distribute quantum keys between the satellite and the ground, teleport the properties of photons from the ground into space (SN Online: 7/7/17) and produce photons with their properties linked, or entangled, despite being separated by 1,200 kilometers (SN: 8/5/17, p. 14). The video chat marks the first time researchers were able to exchange quantum keys between two different continents.

Although the chat was not completely secure from hacking, it was about a million times as secure as what’s possible with standard, or classical types of encryption, says Rupert Ursin, a physicist at the Institute for Quantum Optics and Quantum Information in Vienna and a member of the Austrian team. The Chinese and Austrian teams also exchanged images using theoretically uncrackable methods.

In the future, scientists envision widespread quantum networks allowing secure communication worldwide. “We are facing, now, a new era of having a global quantum internet ready to be deployed,” Ursin says.