The creation of an "entanglement gun" brings the prospect of a light-based quantum computer a step closer. The ability of entangled photons to spin in two different senses will allow quantum computers to encode a 0 and a 1 simultaneously, allowing even a small quantum computer to outperform the fastest supercomputer for some tasks.
A team from Toshiba Research Europe in Cambridge, UK, and the University of Cambridge made the entanglement gun from a "quantum dot", formed by a patch of indium arsenide semiconductor no more than 10 nanometres across. When an 80-megahertz alternating current passed through the quantum dot it trapped two negatively charged electrons and two positive "holes". On each cycle of the current, the electrons and holes combined to eject a pair of entangled photons.
We created a train of entangled photons "spat out as if from a gun", says Mark Stephenson of Toshiba. "And we did it with an electric current, which is easy to manipulate."
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