Such an apparatus has many potential uses. Because the passing atoms can monitor the number of photons in a cavity without perturbing it, one can witness the natural death of photons in real time. If a photon disappears in the cavity walls, that disappearance would register immediately in the atomic interference pattern. Such experiments should provide more tests of quantum theory and may open the way to a new generation of sensors in the optical and microwave domains.

3 Comments

1. 1. billsmith 11:03 PM 10/9/12

   "spontaneous emission of a photon by an excited atom is in a sense induced by vacuum fluctuations."
   
   "Induced"? I knew about vacuum fluctuations as an explanation for the Casmir effect, but I'd not heard this theory. While the beginning of this article is written in a tone of "old news" (which is always the best kind of science to deeply reflect on), I wonder if this theory is still new enough to be controversial.
   
   I'm especially curious about the "in a sense" part. Can someone here explain that to me? Such complications are frequently omitted and/or horribly abused by pseudo-scientific types who fail to realize that quantum physicists (when deprived of their wave functions) often resort to loose metaphors. I'd like to know where this metaphor breaks down.
   
   
   ---
   I'm impressed by the technical feat of a grad student putting a beryllium ion 80 nanometers away from itself (on the order of a thousand times its stationary diameter and ten times the wave packet's width).
   http://www.nist.gov/pml/div688/grp10/upload/bkthesis.pdf
   
   And likewise impressed by the measurement of decoherence over time.
   http://phd.fisica.unimi.it/assets/docs/PC_and_Seminars/0910/SlideHaroche.pdf
   
   Perhaps those quantum optics x-ray lasers could one day be used for fusion ignition?
   http://www.nature.com/nature/journal/v481/n7382/full/nature10721.html
   
   By the way, why weren't Rydberg atoms defined until halfway through the article? If I'd not already known, I would have been a bit confused. And some of the superscripts are missing; for example, 10 to the 23 was rendered as 1023.

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2. 2. europamoon100 11:39 AM 10/13/12

   "And some of the superscripts are missing; for example, 10 to the 23 was rendered as 1023."
   
   I agree: Presenting numbers without their proper superscripts and subscripts is dumb, and it should never be allowed to happen under any circumstances. Yes, it was allowed to happen out of human carelessness, and nobody or nothing else can be blamed.
   If there is any difficulty in typesetting and presentation, then the people of Scientific American should use 10^23, which is generally understood for exponentiation.
   There is also "ten to the 23rd power" - just use Plain English. Never allow it to be presented as a four-digit number.
   
   

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3. 3. europamoon100 11:54 AM 10/13/12

   "Atoms and photons in small cavities behave completely unlike those in free space."
   
   "completely unlike" ?? Very questionable.
   If even one similiarity can be found, then that is a false statement. I am sure that some similarities can be found.
   For a quick example of one, the rest mass of a photon is zero, no matter what.
   As for the atoms, their electrons continue to "orbit" the nuclei of the atoms and the energy levels of those electrons continue to take on discrete levels according to the rules of quantum mechanics.
   The nuclei of the atoms continue to behave completely the same, whether the atoms are in cavities, in free space, or in condensed matter.
   
   You remind me of the TV commercials that advertize the products as "perfect" or "ideal". Well, no - No commercial product is perfect or ideal. We don't even have ideal gases here, nor ideal simple machines such as levers.

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