Many technologies that are based on quantum physics rely on the existence of identical light particles. An important step towards applications such as tap-proof communications and the quantum internet has been taken by a team of researchers.
It is possible to make use of quantum effects in a variety of ways. It is very difficult to produce such particles. They need to have the same wavelength and shape as well.
A team of researchers led by Richard Warburton at the University of Basel, in collaboration with colleagues at the University of Bochum, have succeeded in creating the same photon from different sources.
A single photon from a quantum dot.
The physicists used quantum dots in their experiments. The electrons are trapped in the quantum dots and can only take on certain levels of energy. The light is used to make a transition. A single photon can be created with the help of a laser pulse.
In recent years, other researchers have created the same photon with different quantum dots. They had to use optical filters to pick and choose those that were most similar. Only a small amount of usable photons remained.
The more ambitious approach was chosen by Warburton and his partners. The quantum dots were made from the pure Gallium Arsenide produced by the specialists in Bochum. It is possible to keep the natural variations between quantum dots to a minimum. Two quantum dots were exposed to electric fields. The fields adjusted the energy levels of the quantum dots so that they had the same wavelength of light.
It's almost identical.
The researchers used a half-silvered mirror to show the difference between the two particles. Light particles were either reflected as a pair or passed through the mirror as a pair. They were able to conclude that the photons were the same. Twins were formed even though they were not related.
An important building block of quantum computers was realized by the researchers. There are gates that can be used to implement quantum computers.
The yield of identical photons is around one percent. He was a part of the experiment. We already know how to increase that yield in the future. The twin- photon method could be used in different quantum technologies.
More information: Liang Zhai et al, Quantum interference of identical photons from remote GaAs quantum dots, Nature Nanotechnology (2022). DOI: 10.1038/s41565-022-01131-2 Journal information: Nature Nanotechnology
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