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Article  Physicists prove double-slit experiment can be recreated in time, not just space

#1
C C Offline
https://thedebrief.org/physicists-prove-...-in-space/

EXCERPTS: . . . In Thomas Young’s day, the double-slit experiment involved a relatively simple setup, which included a thin, opaque sheet with two thin perforations oriented side by side, through which light shone onto a detector located behind the sheet. As light enters the slits, it splits into two waves that produce the characteristic interference, either enhancing or canceling each other out and producing a series of bands on the detector, varying in strength based on the amount of light that struck different areas.

Of particular interest to researchers, firing single particles toward the slits still produced the interference pattern, seeming to suggest that the light particle could split into two and travel through both slits at once.

Unlike the “classic” version of the experiment, the Imperial researchers employed their “time slits” to alter the frequency of light passing through indium-tin-oxide, a metamaterial that is also frequently used in smartphone screens. This allowed its color to be changed, rather than just its direction like in Young’s original version, resulting in a similar interference pattern through the manipulation of light coloration.

In the Imperial team’s experiment, the indium-tin-oxide’s reflectance was altered at ultrafast timescales with the use of lasers, which researchers used as the “slits” for the light passing through it, resulting in changes of reflectivity over periods of just a few femtoseconds.

[...] the Imperial team believes the fine control of light through such metamaterial surfaces under conditions similar to those employed in their experiment could have a range of technological applications... (MORE - missing details)

PAPER: https://www.nature.com/articles/s41567-023-01993-w
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#3
Kornee Offline
I would question the fundamentalness of the reported time diffraction experiment. Unlike the traditional double slit diffraction, where single photons pass through the slits unaltered except for slight transverse momentum shifts, here nonlinearities are an inherent feature. Altering characteristic frequency implies photon creation and destruction is necessarily involved. Hence we are not dealing with interference involving the same photon from start to finish.
One could argue the significance is then no more than that involving the interference between two dipole antennas, one having FM modulation of output.
Quantum optics is a tricky topic and one can expect some controversy will develop over this latest claim.
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#4
confused2 Offline
(Apr 5, 2023 02:24 AM)Kornee Wrote: I would question the fundamentalness of the reported time diffraction experiment. Unlike the traditional double slit diffraction, where single photons pass through the slits unaltered except for slight transverse momentum shifts, here nonlinearities are an inherent feature. Altering characteristic frequency implies photon creation and destruction is necessarily involved. Hence we are not dealing with interference involving the same photon from start to finish.
One could argue the significance is then no more than that involving the interference between two dipole antennas, one having FM modulation of output.
Quantum optics is a tricky topic and one can expect some controversy will develop over this latest claim.
Interesting points.
As far as I know photons only interfere with themselves except in very rare circumstances and I don't think this is one of those rare circumstances - which I think rules out your "not the same photon" objection. Is interference between two dipole antennas an example of 'not the same photon' interference? I will need to think about that .. any thoughts meanwhile?
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#5
Kornee Offline
(Apr 5, 2023 12:31 PM)confused2 Wrote: Interesting points.
As far as I know photons only interfere with themselves except in very rare circumstances and I don't think this is one of those rare circumstances - which I think rules out your "not the same photon" objection. Is interference between two dipole antennas an example of 'not the same photon' interference? I will need to think about that .. any thoughts meanwhile?
Dirac set the ideological position back in the 1920s - "photons only ever interfere with themselves, never with other photons". His argument iirc centered on the claim that to do otherwise would violate conservation of energy. Just how that followed I never quite figured out. At any rate he was wrong but many physicists still subscribe to it as generally valid but that photon-photon interference does occur under special circumstances.

To me it's blatantly obvious that for case of two or more independently powered (or passive i.e. parasitic) antennas, interference is a long known fact. With no violation of conservation of energy reported or present in the classical theory. There are some strange consequences of personal reputation setting the tone in physics as elsewhere.
PS: This article may help: https://physics.stackexchange.com/questi...ith-itself

PPS: From above article, i learned something new re historical precedent: It was Poincare not Dirac who first put forward photons only self-interfering:

"Dirac in his book on QM describes interference of a photon with itself but his statement was not original. I read a H. Poincaré article (1912) where he concludes that if we accept quantum nature of the light, then each quantum (photon) interferes with itself, not with other photons. Poincaré arrived at this conclusion by considering a very low intensity beam (flux of one by one quanta). But I am not sure whether it was pronounced for the first time or he wrote what was a "quantum folklore" of that time."

And another article i just dredged up: https://aapt.scitation.org/doi/abs/10.11...alCode=ajp
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#6
confused2 Offline
We could cite standing waves an example of interference

[Image: Size-of-microwave-cavity-resonator-and-b...cavity.png]
[Image: Size-of-microwave-cavity-resonator-and-b...cavity.png]


https://www.researchgate.net/publication...cavity.png
The feature of double slit interference is that it isn't two waves meeting at a point and passing on .. there's just nothing there in the dark fringes. How the experiment in the OP fits in I don't yet know.

For interfering EM (I think.. nearly 50 years since I last looked at this ) you get a maximum in the B field where the E fields cancel .. so you can draw total cancellation in either field but not both at the same time.
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#7
Kornee Offline
For EM standing waves yes E & B field nodes and antinodes are orthogonal in space and time, but For propagating wave(s), far-field interference from relatively closely spaced different sources yields reinforcement or cancellation the same in space and time for both E & B fields. Which is more the analog for double slit interference.
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#8
confused2 Offline
Kornee Wrote:..closely spaced different sources yields reinforcement or cancellation the same in space and time for both E & B fields.
Yes, 180 degree phase shift does cancel but they come back .. which I don't think the DSE photons do .. or do they? - cancel that .. I think they do the same thing with the same geometry .. they pretty much have to.
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#9
Kornee Offline
(Apr 5, 2023 05:00 PM)confused2 Wrote: Yes, 180 degree phase shift does cancel but they come back .. which I don't think the DSE photons do .. or do they? - cancel that .. I think they do the same thing with the same geometry .. they pretty much have to.
Yep. The break between classical & quantum is as we know build up of an interference pattern when only single particles pass through either slit (or both in some povs) at any given time.
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#10
Syne Offline
In the double-slit experiment, you never see interference banding from single photons. Every photon hits the detector once. It's only after many photons are detected that the results show. So the original experiment never showed interference involving the same, single photon. It's only after running many photons through the slits that the pattern starts to emerge. So there has always been an element of time necessary.

If the same photon can pass through different slits at a distance, it's pretty trivial that it can pass through at slightly different times.
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