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posted by Fnord666 on Tuesday October 03 2017, @08:47PM   Printer-friendly
from the yes-and-no dept.

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."

I can't wait to use this!


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  • (Score: 1, Informative) by Anonymous Coward on Wednesday October 04 2017, @08:42AM (1 child)

    by Anonymous Coward on Wednesday October 04 2017, @08:42AM (#576950)

    I'm not sure how or if you can get around the possibility that the satellite could transmit photons it has already measured

    On the if: Yes, definitely. That's the whole point of quantum key distribution.

    On the how: There are basically two different methods. Method 1 is that you rely on the inability of measuring an unknown quantum state without changing it. So if someone tries to find out the state, he'll necessarily change it, and that change will be detectable.

    Method 2 uses entangled photons, and basically the key is generated non-locally at both end points. Here the key is never actually transmitted, and monogamy of entanglement ensures that no third party can be also entangled with the sender's half of the entangled pair, as that would break entanglement between sender and receiver. Entanglement (actually non-locality, which for noisy states is a stricter condition) can be tested by verifying that the Bell inequality is violated.

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  • (Score: 2) by wonkey_monkey on Wednesday October 04 2017, @08:00PM

    by wonkey_monkey (279) on Wednesday October 04 2017, @08:00PM (#577148) Homepage

    On the if: Yes, definitely. That's the whole point of quantum key distribution.

    I think I see it... the satellite could pre-set the spins of the photons it sends out, but only along one axis. If the ground stations happen to both use the other axis, the spins won't be correlated and they'll realise this when they come to construct their key.

    Is that right?

    --
    systemd is Roko's Basilisk