Constant beam, both slits analyzed double-slit experiment?

[Kurt Mueller]

TL;DR

Has an experiment been attempted wherein all photons in a beam are interacted with?

I keep seeing that it's assumed that photons interfere with each other, and there are other points of proof for this like destructive interference, etc., but I've never seen an experiment in which a constant beam is used but both slits are analyzed or the energy required for measurement is attempted to be applied to all photons passing through both slits.

Thank you.

 

[PeroK]

Summary:: Has an experiment been attempted wherein all photons in a beam are interacted with?

I keep seeing that it's assumed that photons interfere with each other, and there are other points of proof for this like destructive interference, etc., but I've never seen an experiment in which a constant beam is used but both slits are analyzed or the energy required for measurement is attempted to be applied to all photons passing through both slits.

Thank you.

Do you have an experimental set-up in mind?

Note that photons do not interfere with each other. A photon may loosely be said to interfere with itself, in the sense that there may be an interference term in its probability amplitude.

 

[Kurt Mueller]

So then is the interference pattern seen in the double slits, even if you used many photons versus one, considered to always be this probability expression of single photons? I likely was just then under a misapprehension.

And I didn't have an experimental setup in mind. I'm just curious.

 

[PeroK]

So then is the interference pattern seen in the double slits, even if you used many photons versus one, considered to always be this probability expression of single photons? I likely was just then under a misapprehension.

Yes, exactly. The interference pattern is created by each photon interfering with itself. However, with QM nothing is ever quite that simple:

https://physics.stackexchange.com/questions/6234/does-a-photon-interfere-only-with-itself

 

[Nugatory]

So then is the interference pattern seen in the double slits...

A subtlety that is often left out of non-technical discussions is that in quantum mechanical double-slit experiments we do not look at the screen and see interference. Instead the screen is something like a piece of photographic film. We send photons at the barrier one at a time, and each one lands at a single point on the film; when we develop the film there's a dot at that point. To "see" the interference pattern we have to let the experiment run long enough for many dots to form; then when we develop the film we find alternating regions with many dots and few dots indicating that the each photon had a higher probability of landing in some regions than in others. The pattern is the same as long as the number of dots is the same; 1000 photons arriving in one second or one photon arriving every second for 1000 seconds yield the same pattern, which is a fairly convincing argument that the interference is a single-photon phenomenon.

But to continue to your question

So then is the interference pattern seen in the double slits, even if you used many photons versus one, considered to always be this probability expression of single photons?

Yes. You don't see much quantum mechanical discussion of this case because it is just the ordinary classical double-slit experiment first done by Thomas Young around 1805 (shine a light source at a barrier containing two slits, observe alternating brighter and darker illuminated regions on the screen) which doesn't provide any insight about quantum behavior. We explain Young's results with two equivalent descriptions:
1) We have electromagnetic waves, they interfere to produce alternating regions of high intensity and low intensity according to well-known wave principles.
2) We do various appallingly complex and abstract calculations with the theory of quantum electrodynamics, we use the fact that the energy carried by the beam is large compared with the energy of any single photon, and we end up with a result that says that the energy delivered per unit time (that's "intensity") at any point on the screen is proportional to the probability of photon arrival at that point.

So when we're done the #2 calculation gives us the same result as the #1 calculation and doesn't demonstrate any uniquely quantum effect - and that's why you won't see as much discussion of it. It's the dot-at-a-time experiments working with single particles that distinguish the quantum electrodynamic photon model from the classical electromagnetic wave model.

 

[DrChinese]

Summary:: Has an experiment been attempted wherein all photons in a beam are interacted with?

I keep seeing that it's assumed that photons interfere with each other, and there are other points of proof for this like destructive interference, etc., but I've never seen an experiment in which a constant beam is used but both slits are analyzed or the energy required for measurement is attempted to be applied to all photons passing through both slits.

Thank you.

This is a fairly complex experiment, but it does demonstrate that the "interaction" (your term) is applied to all photons. Polarizers are used, and the key thing that varies is their relative orientation.

https://sciencedemonstrations.fas.h...-demonstrations/files/single_photon_paper.pdf

 

[Kurt Mueller]

Thank you all for your in-depth responses. You're amazing people. I hope to be like you one day.