Is photon-photon annihilation possible in an optical fiber?

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Discussion Overview

The discussion revolves around the possibility of photon-photon annihilation occurring within an optical fiber, particularly in the context of a reported experiment involving the interaction of photons. Participants explore the implications of photon interactions, the role of entanglement, and the nature of absorption processes in different mediums.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants reference a report claiming that two photons can annihilate each other when a third photon is introduced, questioning the validity of this claim and its implications for conservation of energy.
  • Others argue that photon-photon interactions in vacuum are unlikely, but possible, and mention the concept of a photon-photon collider, noting the rarity of such interactions.
  • It is suggested that in matter, photons can simply be absorbed, leading to their apparent disappearance, which may not relate to annihilation in a vacuum.
  • Some participants emphasize that the reported annihilation is likely an artifact of the optical fiber environment, rather than a true interaction between photons.
  • There is a discussion about the relevance of entanglement to the absorption process, with some asserting that it does not affect the fundamental nature of photon interactions.
  • Concerns are raised about the terminology used in the report, particularly the word "obliterated," and whether it accurately describes the process observed in the experiment.

Areas of Agreement / Disagreement

Participants express differing views on whether the reported photon-photon annihilation is a valid phenomenon or simply a result of absorption processes in the optical fiber. There is no consensus on the interpretation of the experimental results or the implications for photon interactions.

Contextual Notes

Participants note that the behavior of light in matter differs significantly from that in vacuum, and the specific conditions of the experiment may limit the applicability of conclusions drawn from it. The discussion highlights the complexity of photon interactions and the potential for misinterpretation of experimental outcomes.

Larry Pendarvis
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Consider this report:

http://www.physics-astronomy.com/2015/01/quantum-teleportation-of-subatomic.html
"Then, the researchers shot a third particle of light at the photon traveling down the cable. When the two collided, they obliterated each other. Though both photons vanished, the quantum information from the collision appeared in the crystal that held the second entangled photon."
There have been several reports of this result, all claiming photon-photon annihilation.
Is that possible? I am not asking if it is rare, I am asking if it is at all possible. The two photons that annihilated each other were not in this case even entangled.
If it is possible (however rare) for a neutrino and an antineutrino to annihilate giving a photon pair, then the time reversal would be photon-photon annihilation... but I'd guess you would have to get the phase just right. In which case you would not need the MEV energy of an electron-positron pair, but only the rest-mass energy of twice the neutrino, meaning that very-long-wavelength photons would work.

Is this result some kind of artifact of being in an optical fiber? The researchers do not seem to have any concern for conservation of energy; they do not mention what products of the annihilation there might be, the photons simply vanish, in their view.
 
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Photon-photon interactions in vacuum are unlikely, but possible. There are concepts of a photon-photon collider (e.g. http://www.nature.com/nphoton/journal/v8/n6/full/nphoton.2014.95.html), but it would be expensive and the scientific use is probably not so great.
Electron/positron pairs would be the most interesting result (starting at 1 MeV center of mass energy), the reaction to neutrinos (starting somewhere below 1 eV) would be extremely rare and impossible to observe.

In matter, light behaves different, and two photons can go missing simply by absorption in the material, for example. This has nothing to do with the vacuum process.
 
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mfb said:
Photon-photon interactions in vacuum are unlikely, but possible. There are concepts of a photon-photon collider (e.g. http://www.nature.com/nphoton/journal/v8/n6/full/nphoton.2014.95.html), but it would be expensive and the scientific use is probably not so great.
Electron/positron pairs would be the most interesting result (starting at 1 MeV center of mass energy), the reaction to neutrinos (starting somewhere below 1 eV) would be extremely rare and impossible to observe.

In matter, light behaves different, and two photons can go missing simply by absorption in the material, for example. This has nothing to do with the vacuum process.
But this report stated clearly that the disappearance was the result of annihilation; the third photon was what annihilated the other one. This was essential to the claimed teleportation. What is more, the experiment seems to have been able to do this on a regular basis, so it can't be rare at all.
 
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Larry Pendarvis said:
But this report stated clearly that the disappearance was the result of annihilation
No I don't think so.
There is also two-photon microscopy where two photons get absorbed ("vanish") together.

The entanglement of one of the photon does not change anything. Yes the third photon gets the state from a different photon - so what. Interesting for entanglement, but irrelevant for the absorption process.

And again, this has nothing to do with photon-photon interactions in a vacuum.
 
mfb said:
No I don't think so.
There is also two-photon microscopy where two photons get absorbed ("vanish") together.

The entanglement of one of the photon does not change anything. Yes the third photon gets the state from a different photon - so what. Interesting for entanglement, but irrelevant for the absorption process.
I am pretty sure that the report did make that claim. The photon would not have "vanished" without that third photon, otherwise why did they bother? And the word that was used was Obliterated, which I can't find a definition for.
So what was going on there was simply some kind of double-absorption that would not occur unless they fired that third photon, is that what you are saying? And the same experiment in a vacuum could not possibly have that result.
 
Larry Pendarvis said:
The photon would not have "vanished" without that third photon, otherwise why did they bother?
It would have, but then there would be nothing interesting to study.

Larry Pendarvis said:
And the same experiment in a vacuum could not possibly have that result.
Yes. The material is absolutely necessary for the experiment they did.
 
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mfb said:
It would have, but then there would be nothing interesting to study.

Yes. The material is absolutely necessary for the experiment they did.
Usually one does one's best to reduce absorption in an optical fiber. Here they rely on it.
 

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