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Weekend: Brain-bending science explained

Quantum crypto just around the corner, allegedly

Researchers at Toshiba have developed an LED (light emitting diode) capable of firing a single photon at a time, which could make sending encrypted messages truly secure.

Researchers believe the diode could be used for quantum cryptography, a secure form of optical communication. Quantum cryptography is far safer than normal encryption as its security is based on fundamental laws of quantum physics.

Current systems of quantum cryptography are not fail-safe because they emit more than one photon (particles of light) at a time, essentially allowing a hacker to break certain parts of a code without being detected.

"Single photons are rather like magic bullets of molecular biology, in that the laws of quantum mechanics result in the certain failure of any attempt to intercept the information," said Toshiba Research's professor Michael Pepper.

Photons can be polarised to different states; this polarisation can be used to define binary positions. Unlike common forms of encryption where with patience a hacker could probably work out a key, the basic tenet of quantum physics on which the system works means if those photons are intercepted the hacker will have no idea how to read them.

But, most importantly, his interception will alter the message and the recipient will know immediately that someone has snooped.

"A single photon source is a building block for a wide range of applications in quantum information technology, of which secure optical communications is the most immediate," said Dr Andrew Shields, who leads the research team at Toshiba's labs at the University of Cambridge. "In the future we may see that quantum effects enable new optical technologies, rather like the laser did a few decades ago."

In contrast to systems used now, quantum cryptography can be completely uncrackable. But there are problems with using single-photon technology.

"Using single photons is a very inefficient way to communicate, because the photons tend to be scattered out of the fibre, so we envisage using quantum cryptography only to form a shared cryptographic key," said Shields.

Dr Shield hopes these developments will create a future platform for quantum computing, but said he views this "as a longer-term application".

For more information on quantum cryptography, click here.


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