Cambridge reports 'entangled' LED

LONDON — Scientists at Toshiba Research Europe Ltd. and the Cavendish Laboratory of the University of Cambridge have developed a novel light source which they are calling the Entangled Light Emitting Diode.

The device is similar to a semiconductor LED but contains a nanometer-scale quantum dot that produces the engtangled photons which could be used in quantum computing and highly secure optical networking.

Entangled photon pairs have the essential attribute that their properties are inter-related. Although measuring either photon in the pair produces a random result, these two seemingly random results are always the same for the two photons of an entangled pair. This means that measuring one photon appears to alter the property of its entangled twin, even if it is hundreds of kilometres away. This peculiar feature of quantum theory was referred to by Albert Einstein as "spooky action at a distance."

"Although entangled light has been produced previously by shining an intense laser beam on crystals, the new simple device is the first voltage-powered source," said Andrew Shields, who directs the work at Toshiba Research Europe (Cambridge, England). "The discovery is significant because it will allow electrical addressing of many entangled light emitters on a single chip, opening the path to ultra-powerful semiconductor processors based on quantum computation."

The work done in Cambridge offers a route to allow compact, cheap entangled emitters to be produced, enabling new applications that exploit the quantum properties of light.

"For successful operation it was essential to optimize the thickness of the semiconductor material surrounding the quantum dot to control the supply of current to the dot. In addition the properties of the dot itself had to be carefully tailored to produce entangled emission," said Mark Stevenson, senior research scientist on the project.

The team has written a paper which was published in Nature on Thursday (June 3).