Quantum Cryptography: Secure Light Streams

Researchers at Cambridge, England-based Toshiba Research Europe have developed a new type of light-emitting diode (LED) that fires photons in a single, steady stream. The technology could eventually lead to the mainstream adoption of quantum cryptography, a secure form of optical communications that’s virtually impervious to hacker attacks.

Many data security experts view quantum encryption as the Holy Grail because nature guarantees its effectiveness. Under the peculiar laws of quantum mechanics, the very act of intercepting a stream of photons barreling down a fiber-optic cable changes the information it is carrying?including encryption data. “The bits themselves are encoded on some property of the photon, such as its polarization or phase,” says Andrew Shields, Quantum information group leader.

The only way the system could possibly be defeated would be for a hacker to measure a photon stream and then transmit identically encoded photons down the line to the intended recipient, says Shields. Fortunately, however, single photons have the curious property that the encoded state carried by the single photons cannot be copied faithfully. “If a hacker tries to copy the encoded photons, he would introduce errors that can be detected by the sender and intended recipient,” says Shields.

Attempts at using lasers to fire timed single photon streams have failed to work except under strict laboratory conditions. Toshiba, on the other hand, promises that its new LED will work just about anywhere, can be built using standard semiconductor manufacturing techniques and is compatible with existing optical fiber cables.

Quantum encryption’s first users will be organizations that require continuous ironclad security, such as banks. But Shields says he believes that Toshiba’s relatively simple and inexpensive technology will eventually filter down to smaller organizations and perhaps even consumers looking to safeguard their credit card information. “We know what the challenges are and how to solve them, but it will take a few years,” he says.