# Double Slit with one particle

• I
Summary:
Is there an interference pattern using a single particle?
What I've seen of the experiment involves sending a stream of particles through the slits. I'm extrapolating when I say that the interference pattern could be caused by electromagnetic fields (in the case of massive particles), especially because the particles are moving and probably spinning as well.

I've also seen a single photon slowed down to nearly stopping, so it seems that sending a single photon (is possible and) might reveal whether or not a photon has a wave component (a position probability cloud). My guess is that it would not. It's tricky in my mind, because to send a single photon, the photon would already be a particle.

The question of mass: There are different forms of mass, so could some force similar to the emf be acting on mass-less photons?

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Dale
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2020 Award
How could a single photon experiment possibly demonstrate the presence or absence of an interference pattern? I.e. you get one spot somewhere on the screen, how do you interpret that one spot as an indication of the presence or absence of interference?

PeroK
Homework Helper
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2020 Award
Summary: Is there an interference pattern using a single particle?

What I've seen of the experiment involves sending a stream of particles through the slits. I'm extrapolating when I say that the interference pattern could be caused by electromagnetic fields, especially because the particles are moving and probably spinning as well. I've also seen a single photon slowed down to nearly stopping, so it seems that sending a single photon (is possible and) might reveal whether or not a photon has a wave component (a position probability cloud). My guess is that it would not. It's tricky in my mind, because to send a single photon, the photon would already be a particle.
None of this makes much sense.

In QM things don't go back and forward between being waves and particles.

vanhees71
Gold Member
A single particle always marks one point on a screen. Only shooting a lot of particles on the slit gives an interference pattern. That's the "wave-particle dualism" of old quantum theory, which only could be resolved with modern quantum theory and Born's probability interpretation of the quantum state.

The double-slit experiment with single electrons can be found even in Wikipedia:

https://en.wikipedia.org/wiki/File:Double-slit_experiment_results_Tanamura_2.jpg
It's from a famous AJP paper:

https://www.ifi.unicamp.br/~cabrera/teaching/aula 8 2010s1.pdf

dlgoff
Gold Member
... you get one spot somewhere on the screen, ...
Maybe this would be helpful for the OP.

Dale
A single particle always marks one point on a screen. Only shooting a lot of particles on the slit gives an interference pattern. That's the "wave-particle dualism" of old quantum theory, which only could be resolved with modern quantum theory and Born's probability interpretation of the quantum state.

The double-slit experiment with single electrons can be found even in Wikipedia:

https://en.wikipedia.org/wiki/File:Double-slit_experiment_results_Tanamura_2.jpg
It's from a famous AJP paper:

https://www.ifi.unicamp.br/~cabrera/teaching/aula 8 2010s1.pdf
The electron's electromagnetic field interacts with other waves, and maybe in this case it is running perpendicular to the Earth's magnetic field. With a group of electrons, although you can see an interference pattern, I don't understand how it can be inferred that an/the electron has superposition, or even a wave function from the results of this experiment. Just that it's difficult to find and see with a microscope. Is Born growing math (interpretation) to fit the theory?

Dale
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2020 Award
although you can see an interference pattern, I don't understand how it can be inferred that an/the electron has superposition, or even a wave function from the results of this experiment
This is a straightforward application of the scientific method. You assume that an electron behaves according to the Schrödinger equation. Then you predict how it would behave in the two slit experiment based on that assumption. Then you run the experiment. If the experiment agrees with the prediction then the assumption is validated. When many vastly different experiments validate the same assumption you infer that the assumption is a good model.

vanhees71
DrChinese
Gold Member
The electron's electromagnetic field interacts with other waves, and maybe in this case it is running perpendicular to the Earth's magnetic field.

In the presented wiki JPGs, it is a double slit setup which is interacting with the particles. The experiment shows that the pattern is NOT the sum of the two separate slits. I.e. it shows that there is something occurring when the path cannot be limited to a single slit. We call that interference.

Theory matches experiment in this case, the experimental result was known prior to modern particle theory.

vanhees71 and Dale
ZapperZ
Staff Emeritus
The electron's electromagnetic field interacts with other waves, and maybe in this case it is running perpendicular to the Earth's magnetic field. With a group of electrons, although you can see an interference pattern, I don't understand how it can be inferred that an/the electron has superposition, or even a wave function from the results of this experiment. Just that it's difficult to find and see with a microscope. Is Born growing math (interpretation) to fit the theory?

Talk is cheap.

Produce the math based on your model to reproduce the exact interference pattern. Then we'll talk.

Zz.

Dale and dlgoff
If I flip two coins should I expect to see the probability wave? I don't know. (A real question.)
Or are the experimental results like fluid dynamics, where the wave would be expected to draw an interference pattern having moved forward through the two slits.
Yet, it looks to me like the patterns are creating by randomizing the paths at origin, and then interfering with the paths of the particles, where upon they paint that particular randomization pattern. What if the slits were instead round holes, or hexagonal shaped holes. Wouldn't they draw different interference patterns as a result of the differing shapes? If each particle were shot straight through one of two slits I doubt if there would be any pattern at all.

[personal speculation removed by moderator]

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DennisN
Gold Member
2020 Award
What if the slits were instead round holes, or hexagonal shaped holes.
Actually you don't need slits or holes (or any other shape of holes) to get interference similar to the double slit experiment. You can fire a laser on a single thin barrier and get interference due to the two (or more) different paths around the barrier. If I remember correctly this is what was done when electrons were used in the first electron version of the double slit experiment; a stream of electrons were fired on a single filament, and the different possible paths around it resulted in interference.

In short, what is needed to get this kind of interference are different possible paths for the light (or massive particles) to take.

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Dale
DennisN
Gold Member
2020 Award
What if the slits were instead round holes, or hexagonal shaped holes. Wouldn't they draw different interference patterns as a result of the differing shapes?
Yes. Here are some examples of diffraction patterns from single slit/single apertures:

(source: Phys 102 – Lecture 23 Diffraction. http://slideplayer.com/slide/3866721/)

PeroK