The paths of photons are random, but coordinated

Dec 20, 2012
David García works in the laboratory for quantum photonics at the Niels Bohr Institute. He experiments with nanophotonic structures in order to control the emission and propagation of photons. The research shows that photons can ‘sense’ each other and coordinate their way through a complex material.

(Phys.org)—Researchers at the Niels Bohr Institute have demonstrated that photons (light particles) emitted from light sources embedded in a complex and disordered structure are able to mutually coordinate their paths through the medium. This is a consequence of the photons' wave properties, which give rise to the interaction between different possible routes. The results are published in the scientific journal, Physical Review Letters.

The real world is complex and messy. The research field of photonics, which explores and exploits light, is no exception, and in, for example, biological systems the statistical disorder is unavoidable.

Drunken people and photons

"We work with nanophotonic structures in order to control the emission and of . We have discovered in the meantime, that inevitable in the structures lead to random scattering. As a consequence, the transport of photons follow a random path – like a drunken man staggering through the city's labyrinthine streets after an evening in the pub," explains David García, postdoc in at the Niels Bohr Institute at the University of Copenhagen.

The illustration shows how the scattering of photons occurs in a complex photonic medium. Two photons are emitted from a light source in the centre and move through a labyrinth to illustrate complex scattering. The photons take different paths through the medium, but they are interdependent in the sense that that the chance of observing a photon at one outlet is increased if a photon is observed at the other outlet.

If we continue with this analogy, then it is not certain that just because one drunken man comes home safely, then a whole crowd of drunken people spreading out from the pub will also find their way through the city's winding streets. There is no relationship between the different random travellers.

But there is when you are talking about photons. They can 'sense' each other and coordinate their travel through a material, according to new research.

"We have inserted a very small light source in a nanophotonic structure, which contains disorder in the form of a random collection of light diffusing holes. The light source is a so-called quantum dot, which is a specially designed nanoscopic light source that can emit photons. The photons are scattered in all directions and are thrown back and forth. But photons are not just , they are also waves, and waves interact with each other. This creates a link between the photons and we can now demonstrate in our experiments that the photons' path through the material is not independent from the other photons," explains David García.

Spectroscopy of complex materials

The illustration shows how the scattering of photons occurs in a complex photonic medium. Two photons are emitted from a in the centre and move through a labyrinth to illustrate complex scattering. The photons take different paths through the medium, but they are interdependent in the sense that that the chance of observing a photon at one outlet is increased if a photon is observed at the other outlet.

By analysing the path of the photons through the medium valuable insight is potentially gained about microscopic complex structures.

"The method could be a new way to measure the spatial properties of complex disordered materials, like biological tissue, and since the light sources are very small, you will be able to place them without destroying the material and you have the potential for very high spatial resolution," explains David García.

Explore further: Biology meets geometry: Describing geometry of common cellular structure

More information: prl.aps.org/abstract/PRL/v109/i25/e253902

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User comments : 6

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Lurker2358
1 / 5 (4) Dec 20, 2012
Case 1:
A, Photons are sent and only 1 Photon is observed.
B, Photons are sent and 2 Photons are observed.
C, Photons are sent and no photons are observed.

Case 2:
A, No Photons are sent and no photons are observed.
B, No photons are sent and no photons are observed.

There is an "observer effect" or confirmation bias.

When you see no photon you don't know what happened, did they send no photons at all, or did both photons fail to escape?

When you see A photon and then check for the other, it appears to be more correlated than it actually is, because it's actually impossible to have photons when they aren't sent.

If you observed one escaping photon, then it means both were sent. You obviously have a higher chance of observing the second photon when photons were sent, than you would if no photons were sent at all.

this is how stupid these experiments actually are.

It is simple classical mutual cause correlation.
VendicarD
5 / 5 (3) Dec 20, 2012
Incoherent.
Ducklet
1 / 5 (2) Dec 20, 2012
I'm curious whether there's always by necessity an _increase_ in escapes, or whether this is a function of how the material (potential paths) aligns with the interference. I.e., whether in some materials, or the same material with a different orientation, photons might be _less_ likely to escape if you fire off more than one. Also, maybe odd vs even photons matters?
RealityCheck
1 / 5 (3) Dec 20, 2012
Hi Lurker2358.
Case 1:
A, Photons are sent and only 1 Photon is observed.
B, Photons are sent and 2 Photons are observed.
C, Photons are sent and no photons are observed.

Case 2:
A, No Photons are sent and no photons are observed.
B, No photons are sent and no photons are observed.
...
...


I suspect that they meant to say a 'particular' outlet is correlated with another 'particular' outlet. That is, when a photon is observed to exit at one outlet (there are MANY outlets), then the other photon exits from a persistently 'correlated' outlet rather other different/random outlets. The info is not clear as to whether this connectedness of outlet PAIRS is a 'certainty' or a 'very high probability' or observed 'more often than not'. But it's particular pairings of outlets that I took away from reading that item. Have an enjoyable and safe holiday season, Lurker, everyone. Cheers....but not too much, hey!
Husky
not rated yet Dec 26, 2012
i see a link with the article about superconducting bismuth lattice layers forming different lanes that allow closely neighboured currentflows to sense eachother and sync up, just substitute photon wavefunction with electron wavefunction
MaxwellsDemon
not rated yet Dec 27, 2012
I can see how parallel waves could interact...but waves propagating in opposite directions?...that's just weird. It's nice to see that quantum physics still hasn't become scrutable.

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