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What is the size and shape of single optical photon?


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4 hours ago, Duda Jarek said:

You write "Different experiments give different results", so I ask for elaboration, but instead of giving any example you write further "You should be able to evaluate some basic QM experiments." - which ones?

For someone who posts as prolifically as you do about QM, to plead ignorance of QM is quite something.

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My limited, chemist's understanding of QM is that you can't really speak of an "objective" EM field configuration for a single photon. If you could, it seems to me it would be a classical object rathe

From those lectures on quantum mechanics that I looked at on YouTube, it follows that the photon has no shape or trajectory. A photon has only two points, where it was born and where it was absorbed.

A number of interesting facts/data came to mind when I saw this question. [1] Scientific theories are models we use based on known data...[2] The dual nature of light/photons...[3] the fact that light

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8 hours ago, Duda Jarek said:

From one side, can we directly measure processes inside a star? Rather not, but does it prevent us from searching for models of what actually happens there? Also rather not: we can build self-consistent models based on general knowledge, and tune details of what we don't know to get agreement with measurements of indirect consequences.

Science is about models that align with observational and experimental data. While we obviously can never measure "directly" what is happening inside a star, we are able to apply other validated scientific models [such as light] to gauge what is happening inside a star...we call that process  spectroscopy. in other words, simply applying the principal of spectroscopics, based on electromagnetic radiation/light and the observational data we see.

Not sure why you keep mentioning "creationism" and comparing it with science...with science of course, we have evidence to proceed with, despite in some situations of maybe not knowing why. Keep in mind science is a discipline in continued progress and is not weighed down by myth and such. If a new hypothesis describes in a better manner, the light/photons and the wave/particle duality currently described by theory, and it ticks all the boxes and more, it will be accepted after of course running the gauntlet of professional critical review.

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Physics is much more than clicks of detectors - we have also lasers e.g. with attosecond-scale pulses, resonators ...

... or delays also in atomic processes, like observed ~21 attosecod delay in photoemission ( https://science.sciencemag.org/content/328/5986/1658 ) - EM radiation, being mainly response to electron dynamics, propagates ~6nm during this time.

 

So what exactly happens during such 21as of production of EM field of single optical photon?

This is "what happens in the center of star" type of question - we might be never able to directly measure its details, but should have self-consistent models of what actually happens there - based on general knowledge e.g. of electromagnetism, verified by indirect consequences.

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18 hours ago, Duda Jarek said:

This is "what happens in the center of star" type of question - we might be never able to directly measure its details, but should have self-consistent models of what actually happens there - based on general knowledge e.g. of electromagnetism, verified by indirect consequences.

Again, we call that process  spectroscopy. in other words, simply applying the principal of known and proven  spectroscopics, based on electromagnetic radiation/light and the observational data we see.

The following may be relevent also..............

https://phys.org/news/2021-05-capturing-photon-harnessing-quantum-noise.html

MAY 7, 2021

Capturing a single photon of light: Harnessing quantum's 'noise problem'

Scientists at Raytheon BBN Technologies have developed a new way to detect a single photon, or particle of light—a development with big applications for sensors, communications and exponentially more powerful quantum computer processors.

The team has published its work, which centers on the use of a component called a Josephson junction, in the academic journal Science. The discovery builds on the same team's previous research into a microwave radiation detector 100,000 times more sensitive than existing systems.

more at link................

 

the paper:

https://science.sciencemag.org/content/372/6540/409

Abstract:

Josephson junctions are superconducting devices used as high-sensitivity magnetometers and voltage amplifiers as well as the basis of high-performance cryogenic computers and superconducting quantum computers. Although device performance can be degraded by the generation of quasiparticles formed from broken Cooper pairs, this phenomenon also opens opportunities to sensitively detect electromagnetic radiation. We demonstrate single near-infrared photon detection by coupling photons to the localized surface plasmons of a graphene-based Josephson junction. Using the photon-induced switching statistics of the current-biased device, we reveal the critical role of quasiparticles generated by the absorbed photon in the detection mechanism. The photon sensitivity will enable a high-speed, low-power optical interconnect for future superconducting computing architectures.

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some interesting answers here also.................

https://www.quora.com/What-is-the-size-and-shape-of-a-single-optical-photon

Q: What is the size and shape of a single optical photon?

A:That's completely ill-defined. A photon is a unit of energy in a mode of the electromagnetic field. The mode itself is defined by boundary conditions. For example, a mode can be defined by the mirrors in a laser cavity. It's tempting to treat the photon as some sort of ping-pong ball bouncing back and forth between the mirrors, but the principle of superposition means that the photon is travelling in both directions, to form a standing wave. However, it is the mode shape that is important for working with single photons, as once you know the mode, you can align all your optics to ensure the photons go where you want them. For example, if you want to overlap two photons, it is their mode shapes that must be overlapped. This can be tested in a two photon interference experiment called Hong-Ou-Mandel interference. So mode shapes can be reasonably well defined, and that's as much as we can say about the shape of a photon.

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While there are still needed theoretical models e.g. of single photon, this ~decade old attosecond chronoscopy brings hope to finally verify them experimentally - gathered: https://scholar.google.pl/scholar?cites=15193546925951882986&as_sdt=2005&sciodt=0,5&hl=en
E.g. 2020 "Probing molecular environment through photoemission delays" https://www.nature.com/articles/s41567-020-0887-8

Quote

Attosecond chronoscopy has revealed small but measurable delays in photoionization, characterized by the ejection of an electron on absorption of a single photon. Ionization-delay measurements in atomic targets provide a wealth of information about the  timing  of  the  photoelectric  effect,  resonances,  electron  correlations  and  transport.

 

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On 4/30/2021 at 1:25 AM, Duda Jarek said:

Optical photon is produced e.g. during deexcitation of atom, carrying energy, momentum and angular momentum difference.
So how is this energy distributed in space - what is the shape and size of single photon?

Looking for literature, I have found started by Geoffrey Hunter, here is one of articles: "Einstein’s Photon Concept Quantified by the Bohr Model of the Photon" https://arxiv.org/pdf/quant-ph/0506231.pdf

Most importantly, he claims that such single optical photon has shape similar to elongated ellipsoid of length being wavelength λ, and diameter λ/π (?), providing reasonably looking arguments:

Is it the proper answer?

Are there other reasonable answers, experimental arguments?

 

 

The photon is treated as a point-like particle in Particle Physics as all elementary particles are treated. They have no structure, shape and size. At wikipedia's photon page (Photon - Wikipedia) can be found in the "Wave–particle duality and uncertainty principles" section the following: 

"However, experiments confirm that the photon is not a short pulse of electromagnetic radiation; it does not spread out as it propagates, nor does it divide when it encounters a beam splitter.[62] Rather, the photon seems to be a point-like particle since it is absorbed or emitted as a whole by arbitrarily small systems, including systems much smaller than its wavelength, such as an atomic nucleus (≈10−15 m across) or even the point-like electron."

This way, the works trying to find shape and size of photons you have mentioned would go in the direction of the development of a new theory in Physics and that's why I got interested in this thread. I think that is the right direction of development in particle Physics, to give structures to the particles, but this is not treated in current Physics. By the way, I'm one working in this direction but finding hard troubles to present my point of view in good Physics' environments like this Forum. It always end in the Speculations' or even Trash sub-forums...

P:S: Wish good luck for you in your research.

Edited by martillo
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15 minutes ago, martillo said:

"A single photon passing through a double-slit experiment lands on the screen with a probability distribution given by its interference pattern determined by Maxwell's equations.[61]  However, experiments confirm that the photon is not a short pulse of electromagnetic radiation; it does not spread out as it propagates, nor does it divide when it encounters a beam splitter.[62]

from https://en.wikipedia.org/wiki/Photon - [62] is Saleh, B.E.A. & Teich, M.C. (2007). Fundamentals of Photonics. Wiley. ISBN 978-0-471-35832-9.

Could anybody elaborate on this not being a short pulse of electromagnetic radiation?

So what happens during these observed delays e.g. of photoemission?

 

If it is about interference like Mach-Zehnder, there is both EM wave governed by Maxwell equations, and quantum amplitude governed e.g. by Schrodinger -  "pilot" wave for psi=sqrt(rho) exp(-iS/hbar) Madelung substitution( https://en.wikipedia.org/wiki/Pilot_wave_theory#Mathematical_formulation_for_a_single_particle ).
For let say Mach-Zehnder interference, there is no doubts that "pilot" wave of quantum amplitudes propagates through both trajectories.

However, the question is about corpuscular part of wave-particle duality, does it also propagate through both trajectories, or maybe only through one like in this diagram (from http://redshift.vif.com/JournalFiles/V16NO2PDF/V16N2CRO.pdf ) :

1619754157368-png.282262

In case of interference of electron, it is elementary charge - cannot split in two, in experiments it is always nearly point-like charge ... also, scenarios with electron going through lower or upper arm differ by electric field around such setting influencing surrounding atoms - they are very different.
For single photons, there are e.g. these experiments measuring averaged trajectories of interfering photons: https://science.sciencemag.org/content/332/6034/1170.full

The-trajectories-from-Fig-3-plotted-on-t

There are also experiments being able to use both wave and particle part of duality simultaneously, e.g. https://en.wikipedia.org/wiki/Afshar_experiment

So while quantum amplitude of single photon: the wave part of wave-particle duality seems to form e.g. plane waves, the corpuscular part seems to travel through a concrete trajectory (e.g. from the screen to our eyes).

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1 hour ago, Duda Jarek said:

from https://en.wikipedia.org/wiki/Photon - [62] is Saleh, B.E.A. & Teich, M.C. (2007). Fundamentals of Photonics. Wiley. ISBN 978-0-471-35832-9.

Could anybody elaborate on this not being a short pulse of electromagnetic radiation?

So what happens during these observed delays e.g. of photoemission?

 

If it is about interference like Mach-Zehnder, there is both EM wave governed by Maxwell equations, and quantum amplitude governed e.g. by Schrodinger -  "pilot" wave for psi=sqrt(rho) exp(-iS/hbar) Madelung substitution( https://en.wikipedia.org/wiki/Pilot_wave_theory#Mathematical_formulation_for_a_single_particle ).
For let say Mach-Zehnder interference, there is no doubts that "pilot" wave of quantum amplitudes propagates through both trajectories.

However, the question is about corpuscular part of wave-particle duality, does it also propagate through both trajectories, or maybe only through one like in this diagram (from http://redshift.vif.com/JournalFiles/V16NO2PDF/V16N2CRO.pdf ) :

1619754157368-png.282262

In case of interference of electron, it is elementary charge - cannot split in two, in experiments it is always nearly point-like charge ... also, scenarios with electron going through lower or upper arm differ by electric field around such setting influencing surrounding atoms - they are very different.
For single photons, there are e.g. these experiments measuring averaged trajectories of interfering photons: https://science.sciencemag.org/content/332/6034/1170.full

The-trajectories-from-Fig-3-plotted-on-t

There are also experiments being able to use both wave and particle part of duality simultaneously, e.g. https://en.wikipedia.org/wiki/Afshar_experiment

So while quantum amplitude of single photon: the wave part of wave-particle duality seems to form e.g. plane waves, the corpuscular part seems to travel through a concrete trajectory (e.g. from the screen to our eyes).

I'm still analyzing the experiments you mention but I must point out that much care must be taken in considering if they are about beams of light composed of, let me say, short "trains" of electrons or individual single photons. They are two very different things. Seems you are talking about single photons while the experiments mention beams of light. Am I wrong?

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They mostly use ultrashort pulse laser or electron wavepackets, plus techniques like frequency comb to get these amazing time resolutions.

I don't think we can assume that they use single e.g. photon source (?), however, they use single photon atomic transitions - to be able to assume that only one was absorbed.

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I think there's a confusion in the interpretation of the results in the experiments you mention. I interpret the patterns in the receivers of the experiments as obtained by a progressive distribution of the places where the sucessive photons arrive. I mean that the graphs are not the amplitude of a "pilot wave" of a single photon but the distribution of the density on the places where many photons arrive.

You say for the colored tridimensional graph: "there are e.g. these experiments measuring averaged trajectories of interfering photons:" and the heigh in the graph is said to represent the "probability density" of photons. For me this apply for many photons arriving, not single ones.

 

 

 

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Oh, so you refer not to attosecond chronoscopy, but to "Observing the Average Trajectories of Single Photons in a Two-Slit Interferometer" https://science.sciencemag.org/content/332/6034/1170.full - it is for single photons.

On the left you have source of single photons from one of two slits. In the center you have calcite (birefringent crystal) which encodes which-way information in photon polarization. On the right you have measurement of both position and polarization. This is weak measurement: weak enough not to destroy interference, but allowing to obtain averaged trajectories from statistics.

Experimental-setup-for-measuring-the-ave

They write these trajectories agree with dBB:

Quote

Single-particle trajectories measured in this fashion reproduce those predicted by the Bohm–de Broglie interpretation of quantum mechanics (8), although the reconstruction is in no way dependent on a choice of interpretation.

 

Edited by Duda Jarek
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I still don't get it or you are not getting my point now.

In those experiments even if there were single photons travelling at a run they collect progresive data of many runs. The resultant graph is made with the data of all the runs collected corresponding to many photons, not just one. The graph would be the distribution of the arriving data of many photons, not the amplitude of some property of just one. I mean, the graph corresponds to the statistics of the behavior of many photons not the structure of just one. The graph could give some clue about the structure of the photon but it is not a "photograph" of it.

May be someone more knowledgeable could help us more in this...

 

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The "observing average trajectory" experiment is only against "photon is huge because of going all trajectories in interference" type of claims - no, only its wave part of duality, "pilot wave" travels all the trajectories.

The particle part of duality, the corpuscle, seems to travel single trajectory - especially for charged indivisible electron, but it seems also true for (tough to split) photon - the question is about size of this part.

 

Attosecond chronoscopy seems very useful to test such models of photons as wavepacket also of EM field.

But generally I still miss concrete experimental arguments to estimate this size.

Edited by Duda Jarek
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3 hours ago, Duda Jarek said:

The "observing average trajectory" experiment is only against "photon is huge because of going all trajectories in interference" type of claims - no, only its wave part of duality, "pilot wave" travels all the trajectories.

Well, seems here is a case where different interpretations can be given to a same experiment. All what I can say is that my point of view can give an interpretation without a "pilot wave" guiding it but assuming the presence of many photons in the phenomenon. 

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You need e.g. interference in Mach-Zehnder for single photon. Here is the only article with such claim I have seen: https://arxiv.org/pdf/1709.10344

But personally I believe we need also the wave part of wave-particles duality - to get also other QM-like phenomena e.g. orbit quantization, Casimir effect - see their gathered hydrodynamical analogs: https://www.dropbox.com/s/kxvvhj0cnl1iqxr/Couder.pdf

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5 hours ago, Duda Jarek said:

You need e.g. interference in Mach-Zehnder for single photon. Here is the only article with such claim I have seen: https://arxiv.org/pdf/1709.10344

Several experiments assume the emission of single photons or electrons. Something very difficult to guarantee in practice. I mean, how to distinguish between short trains of particles emitted in spite of single ones? Not so easy...

 

Edited by martillo
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8 minutes ago, martillo said:

Several double-slit like experiments assume the emission of single photons. Something very difficult to guarantee in practice. I mean, how to distinguish between short trains of photons emitted in spite of single ones? Not so easy...

No, not really. The experiment I recall (IIRC the first to claim single-photon) attenuated the light well past the point where you’d expect multiple photons, and multiple photons would have the possibility of multiple detections if they diffracted into different orders, so this could be checked. Plus the possibility of using a detection method that would have an amplitude proportional to the photon number. So care is required in setting up the experiment but not something I’d call “very difficult”

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37 minutes ago, swansont said:

No, not really. The experiment I recall (IIRC the first to claim single-photon) attenuated the light well past the point where you’d expect multiple photons, and multiple photons would have the possibility of multiple detections if they diffracted into different orders, so this could be checked. Plus the possibility of using a detection method that would have an amplitude proportional to the photon number. So care is required in setting up the experiment but not something I’d call “very difficult”

I don't find that attenuating the source until single events like sparkings do really guarantee the emission of single photons or electrons. That was what has been done in the past, I know, but I disagree.

 

38 minutes ago, Duda Jarek said:

Single photon sources are used for decades ( https://en.wikipedia.org/wiki/Single-photon_source ), or just imagine single deexciting atom.

In the link you provided of wikipedia it is said:

"a true single-photon source was not created in isolation until 1974. This was achieved by utilising a cascade transition within mercury atoms." and "Another single-photon source came in 1977 which utilised the fluorescence from an attenuated beam of sodium atoms."

Consider that for instance Young's double slit experiment was performed in 1801 assuming the emission of single photons. Mach–Zehnder experiment in 1892.

The question now is how many experiments currently considered have taken this into account...

Edited by martillo
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13 minutes ago, martillo said:

The question now is how many experiments currently considered have taken this care into account...

If they're done correctly... 

All of them...

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24 minutes ago, martillo said:

I don't find that attenuating the source until single events like sparkings do really guarantee the emission of single photons or electrons. That was what has been done in the past, I know, but I disagree.

Why? Is this based on any physics?

The detection rate was such that the expected photon occupancy would have been significantly less than 1

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18 minutes ago, dimreepr said:

Please, explain...

 

 

18 minutes ago, swansont said:

Why? Is this based on any physics?

The detection rate was such that the expected photon occupancy would have been significantly less than 1

Heated filaments have been used as source of particles, photons or electrons, and the heating was attenuated until single events are observed in the experiments but this does not guarantee that a unique atom of the filament has emitted a particle. It is possible that multiple atoms of the filaments emit single particles each but in total many particles could have been emitted quite at the same time producing at the end a group of particles travelling together.

Edited by martillo
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