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posted by chromas on Wednesday September 05 2018, @08:21PM   Printer-friendly
from the oooh-shiny! dept.

Superradiance: Quantum Effect Detected in Tiny Diamonds:

"Superradiance" is the phenomenon of one atom giving off energy in the form of light and causing a large number of other atoms in its immediate vicinity to emit energy as well at the same time. This creates a short, intense flash of light.

Up until now, this phenomenon could only be studied with free atoms (and with the use of special symmetries). Now, at TU Wien (Vienna), it was measured in a solid-state system. The team used nitrogen atoms, built into tiny diamonds that can be coupled with microwave radiation. The results have now been published in the journal Nature Physics.

[...] "When the atom absorbs energy, it is shifted into a so-called excited state. When it returns to a lower energy state, the energy is released again in the form of a photon. This usually happens randomly, at completely unpredictable points in time," says Johannes Majer[...]. However, if several atoms are located close to each other, an interesting quantum effect can occur: one of the atoms emits a photon (spontaneously and randomly), thereby affecting all other excited atoms in its neighborhood. Many of them release their excess energy at the same moment, producing an intense flash of quantum light. This phenomenon is called "superradiance."

"Unfortunately, this effect cannot be directly observed with ordinary atoms," says Andreas Angerer, first author of the study. "Super radiance is only possible if you place all the atoms in an area that is significantly smaller than the wavelength of the photons." So you would have to focus the atoms to less than 100 nanometers -- and then, the interactions between the atoms would be so strong that the effect would no longer be possible.

One solution to this problem is using a quantum system that Majer and his team have been researching for years: tiny defects built into diamonds. While ordinary diamonds consist of a regular grid of carbon atoms, lattice defects have been deliberately incorporated into the diamonds in Majer's lab. At certain points, instead of a carbon atom, there is a nitrogen atom, and the adjacent point in the diamond lattice is unoccupied.

[...] Just like ordinary atoms, these diamond defects can also be switched into an excited state -- but this is achieved with photons in the microwave range, with a very large wavelength. "Our system has the decisive advantage that we can work with electromagnetic radiation that has a wavelength of several centimeters -- so it is no problem to concentrate the individual defect sites within the radius of one wavelength," explains Andreas Angerer.


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  • (Score: 5, Interesting) by Spamalope on Thursday September 06 2018, @12:57AM

    by Spamalope (5233) on Thursday September 06 2018, @12:57AM (#731058) Homepage

    If I'm following correctly, they're getting excited atoms to emit together.
    It wasn't clear to me what the mechanism is. They didn't seem to imply it was a chain reaction, though some of the wording was unclear.
    I think they meant either that the trick they're using got the atoms to share the same frame for the purposes of emission such that the probability collapses for each at the same time. Apparently this is a form of entanglement.
    I think quantum light is only in the sense that they're playing with individual quanta of light. aka single energy state emission.

    I'd love to see a Feynman type clear explanation of this.

    For example, does this relate to lasing? Or have applications in that direction?

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