Long-Distance Quantum Message May Advance Code Making, Code Breaking

March 14, 2007

An experiment on the Canary Islands, off the coast of Africa, has smashed a record for sending messages encrypted using the quirks of quantum physics.

The researchers transmitted particles of light, or photons, 90 miles (144 kilometers) while keeping intact a strange invisible tie between the particles known as entanglement.

The demonstration shows that it would be possible to build a network of satellites that could beam ultra-secure messages between themselves and to Earth, researchers say.

Because of the unique and complex properties of entanglement, there is virtually no chance such messages could ever be successfully intercepted and decoded.

And the techniques used in the experiment could also be useful in creating quantum computers, which could exploit quantum physics to solve in seconds problems that would take today's machines years of work.

Quantum Message

In the experiment, a light beam carried a message from the island of La Palma to Tenerife, where a receiver was able to spot individual photons (see of map of the Canary Islands).

The transmission was ten times farther than anyone has been able to send entangled photons through the air before.

It's even farther than previous records for sending these signals through fiber-optic cables, like those used as telephone wires. (Related: "Physicists Teleport Quantum Bits Over Long Distance" [January 29, 2003].)

The work was published in the journal Physical Review Letters in January and presented at a meeting of the American Physical Society last week.

Unbreakable Code

When two particles become entangled, manipulating one instantly affects the other, no matter how far apart they are.

Continued on Next Page >>


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