Scientists find wider angle on quantum crypto

A Scottish-American collaboration could give quantum cryptography a bandwidth boost, according to Glasgow University.

Quantum cryptography works because it is possible to entangle particles, or permanently pair them up so that whatever you do to one, the other instantly exhibits the same properties, The entanglement works no matter how far apart the particles are. It is ideally suited to cryptography because any attempt to interfere with a message effectively destroys it.

According to work published in the journal Science, the researchers in Glasgow, Strathclyde and Rochester (USA) have found that as well as a particle's spin – referred to as either up or down – entanglement applies to the orbital angular momentum too.

Professor Miles Padgett, Professor of Physics at the University of Glasgow, said: "God does play dice. It has been difficult to show this is the case with angle because angles are problematic: no-one can agree on how to measure them. If I say an angle is 10 degrees, you might say its 350 degrees. It depends on your starting point.

"The fact that an angle can take many different values means that each particle of light, a photon, can be encoded to carry the whole alphabet, potentially increasing the data rate of quantum cryptography – the only guaranteed form of secure communication.”