Novel Devices ♦ news digest
Since the spin-orbit coupling is different in each lane, a transition also affects the strength of the spin-hall effect. By varying the electric field, the scientists can distribute the electron spins on the different lanes, thus varying the efficiency of their spin-charge converter.
By taking into account the valleys in the conduction band, Sinova and his colleagues open up new ways to find and engineer highly efficient materials for spintronics. Especially, since current semiconductor growth technologies are capable of engineering the energy levels of the valleys and the strength of spin- orbit coupling, e.g. by substituting Ga or As with other materials like Aluminum.
‘Electric control of the spin Hall effect by intervalley transitions’ by N. Okamoto et al appears in Nature Materials, 2014; DOI: 10.1038/nmat4059
lab at the Niels Bohr Institute.
Photons and electrons behave very differently at the quantum level. Electrons are so-called fermions and can easily flow individually, while photons are bosons that prefer to clump together. But because information for quantum communication based on photonics lies in the individual photon, it is necessary to be able to send them one at a time.
“So you need to emit the photons from a fermionic system and we do this by creating an extremely strong interaction between light and matter,” explains Peter Lodahl, Professor and head of the research group Quantum Photonics at the Niels Bohr Institute at the University of Copenhagen.
Quantum dots used to make a single-photon cannon
Researchers report control of photons with a 98.4 percent success rate
One of the most promising technologies for future quantum circuits are photonic circuits based on light (photons). Making such circuits, however, requires finding a way to create a stream of single photons and control their direction.
Now Scientists at the Niels Bohr Institute have succeeded in doing this - a breakthrough they published last month in Physical Review Letters.
“What we then do is shine laser light on the quantum dot, where there are atoms with electrons in orbit around the nucleus. The laser light excites the electrons, which then jump from one orbit to another and thereby emit one photon at a time. Normally, light is scattered in all directions, but we have designed the photonic chip so that all of the photons are sent through only one channel,” explains Søren Stobbe, Associate Professor of the Quantum Photonic research group at the Niels Bohr Institute.
Above: Postdoc Immo Söllner and PhD-student Marta Arcari have been the driving force in the work with the experiment here at the quantum photonics
Peter Lodahl and Søren Stobbe explain that it not only works, but also that it is extremely effective.
Issue VI 2014
www.compoundsemiconductor.net 139
The researchers have developed a kind of single- photon cannon integrated on an optical chip. The optical chip consists of an extremely small photonic crystal that is 10 microns wide and 160 nanometers thick. Embedded in the centre of the chip is a quantum dot light source (illustrated below with the yellow symbol).
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