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Quantum Confidential

  • Posted 11.03.11
  • NOVA

If you were a spy, how could you ensure that an encrypted message got safely to your allies? Send it using entangled particles! Here, watch how a technique called quantum cryptography could save a state secret from falling into enemy hands.

Launch Video Running Time: 02:16



Posted: November 3, 2011

Text:Top Secret: Quantum Cryptography

Quantum entanglement is a strange connection between two tiny particles.

If you observe or measure one of the entangled particles, the other one appears to change.

This occurs even when the two are separated by vast distances.

Scientists have begun to use this spooky principle to hide secret information.

It's called quantum cryptography.

Narrator: Imagine you are a spy entrusted with getting the nation’s most sensitive secrets into the hands of an ally.

How can you create a secure code to disguise your messages, so that even the most powerful quantum computer could not break it?

The trick is to use particles, like photons, to carry the key to your code securely from one person to another, before any important messages are sent.

Here’s how:
Normally, if a code’s key gets intercepted, no one’s the wiser until it’s too late, and somebody else is already using it to read your secret messages. But if the code key is made of two sets of entangled particles, your secrets could be safe. Measuring or observing either set of particles will disturb them, so if someone intercepts your code key and tries to read it, the particles will change.

Thanks to quantum entanglement, once the code key’s been looked at, the legitimate sender now knows the code’s been compromised and can make a new one before any real secrets are shared.



Edited by
Steve Audette
Production help from
Anna Rothschild
Original footage
© WGBH Educational Foundation 2011

Image Credits

(main image: spy in alley)
© WGBH Educational Foundation 2011
(matrix data shine)
© circotasu/Pond5

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