Researchers at the University of Cambridge have developed a novel technique for generating single photons, by moving single electrons in a specially designed light-emitting diode.
This technique, reported in the journal Nature Communications, could help the development of the emerging fields of quantum communication and quantum computation.
Up to now, single-photon sources have been made in research labs from self-assembled quantum dots in semiconductors, or structural defects in diamonds. The formation of these dots and defects is a random process, so it is hard to predict the location and the photon energy (or wavelength) of these single-photon sources. This randomness may pose a challenge in integrating a source into a large quantum network.
The researchers showed that they were able to generate a single photon in a different, controlled, way, without the need for a quantum dot or a defect, by moving only one electron at a time to recombine with a hole.
They made a device near the surface of Gallium Arsenide (GaAs) by using only industry-compatible fabrication processes. This device consists of a region of electrons close to a region of holes, and a narrow channel in between.
In order to transport only one electron at a time, they launch a sound wave along the surface. In GaAs such a surface acoustic wave also creates an accompanying electrical potential wave, in which each potential minimum carries just one electron.