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Quantum cryptography takes flight

Successful reading of photon beam sent from airplane may one day lead to encrypted satellite communications

6:03pm, April 1, 2013
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Quantum cryptography has entered the friendly skies. A precise beam of photons sent from an airplane allowed researchers on the ground to create a nearly unbreakable encryption key to protect information. The experiment, reported March 31 in Nature Photonics, is an important step toward creating a secure global communication network based on beaming photons to and from satellites.

“It is a technical tour de force,” says Seth Lloyd, a mechanical engineer at MIT who was not involved in the study.

The idea of exploiting quantum mechanics to secure communication lines is not new: Since the 1980s, scientists have created encryption keys with sets of photons whose individual spins are known only to the sender and receiver. If a third party eavesdrops on the conversation, the photon spins change, alerting the communicating parties to stop exchanging information.

The impediment to any quantum communication, however, is establishing a robust connection that allows sender and receiver to detect and manipulate photons one by one. That’s hard enough to accomplish between stationary points (SN: 6/30/12, p. 10), but physicist Sebastian Nauerth of Ludwig Maximilians University of Munich and his team beamed the photons from an airplane flying at nearly 300 kilometers per hour.

The researchers installed a laser at the bottom of the plane that sent a narrow beam of photons to a ground station 20 kilometers away. The signal was strong enough and the tracking precise enough that a sender on the plane and a receiver on the ground would be able to establish a quantum encryption key, the researchers report. Such a key could one day be used to decode messages sent from anywhere in the world and relayed via satellite.


S. Nauerth et al. Air-to-ground quantum communication. Nature Photonics. Published online March 31, 2013. [Go to]
Further Reading

A. Witze. Quantum teleportation leaps forward. Science News. Vol. 181, June 30, 2012, p. 10. [Go to]

D. Castelvecchi. Welcome to the quantum internet. Science News. Vol. 174, August 16, 2008, p. 24. [Go to]

T. Siegfried, L. Sanders. Quantum weirdness. Science News. Vol. 178, November 20, 2010, p. 20. [Go to]

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