If we think of laser light as a stream of light particles, the so-called photons, then they are completely
Such isolated photons, for example, arebasic requirement for a quantum network. Until now, single quantum emitters, such as a single atom or a single molecule, generally acted as sources of such streams of individual photons. If a quantum emitter is excited by laser light and fluorescence, it will always emit exactly one photon for each quantum jump. For this type of source, it is still a challenge to efficiently “feed” the emitted photons into the fiberglass to send as many of them as possible to the receiver.
Physicists from Germany, Denmark and Austria succeededcreate a kind of "turnstile" for light in glass fibers that allows light particles to pass through only one at a time. The proposal for the experiment came from theoretical physicists Dr. Sahand Mahmoudian and Professor Clemens Hammerer from Leibniz University Hannover and colleagues from the University of Copenhagen. The experiment was carried out with the help of the research group of Professor Dr. Arno Rauschenbeutel at the Humboldt University of Berlin. For this purpose, the scientists used a powerful atom-light interface, in which atoms are trapped next to an optical nanofiber and associated with light guided in the nanofiber.
These special glass fibers are one hundred timesthinner than a human hair, and atoms are held at a distance of 0.2 micrometers from the surface of the fiberglass. At the same time, they are cooled by laser light to temperatures of a few millionths of a degree above absolute zero. This system allowed researchers to precisely control the number of atoms along the laser beam. Then, during the experiment, the researchers analyzed how often the photons leave the fiber individually or in pairs.
When about 150 atoms were captured aboutnanofibers, it turned out that the transmitted light consisted almost only of isolated photons. Thus, all atoms together acted on photons like a turnstile regulating the flow of people. Surprisingly, the effect was the opposite when the number of atoms was increased: then the atoms passed photons, preferably in pairs.
This discovery opens up a whole new waycreating bright single-photon sources with built-in fiber. At the same time, the principle of operation demonstrated by the researchers can be applied to a wide range of the electromagnetic spectrum (from microwaves to X-rays). This opens up the possibility of generating single photons in spectral ranges for which there are no sources yet. Researchers have already applied for a patent for this technology.
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