The creation of an 鈥渆ntanglement gun鈥� brings the prospect of a light-based quantum computer a step closer. The ability of 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 in Cambridge, UK, and the University of Cambridge made the entanglement gun from a 鈥渜uantum dot鈥�, 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 鈥渉oles鈥�. 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 鈥渟pat out as if from a gun鈥�, says Mark Stephenson of Toshiba. 鈥淎nd we did it with an electric current, which is easy to manipulate.鈥�
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Unreliable conversion
Entangled photons have previously been made using a crystal to split laser light into photon pairs. The trouble with such 鈥減arametric down conversion鈥� is its unpredictable nature. 鈥淪ometimes you get two pairs of photons, sometimes one, sometimes zero,鈥� says Stephenson. 鈥淭hat鈥檚 not exactly reliable if you want an error-free quantum computer.鈥�
The work is an important development says of the University of Basel in Switzerland. 鈥淥ther sources of entangled photon pairs are all optically rather than electrically driven, and they don鈥檛 always give you what you want. The really neat thing about the new semiconductor device is that you can get the entangled photons when you want them, simply by applying a voltage pulse to the device.鈥�
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