Double slit mystery in relation to holography and the single slit?

In summary, the double slit mystery remains considering single slit can produce interference pattern as well. Holography does not fully explain those patterns behind any number of slits as a sort of "encoded image" of the slit(s). The equation that makes us think "single photon" equals only one wave is not the problem here. The problem is that a single photon, when detected, appears as a particle with a relatively well defined position, and not as a wave widely expanded in space. And yet the associated wave is widely expanded in space. It looks like a contradiction or at least a puzzle.
  • #1
Zelebg
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What part of double slit mystery remains considering single slit can produce interference pattern as well? Does holography not fully explain those patterns behind any number of slits as a sort of "encoded image" of the slit(s)?

Does the word "focus" have any meaning in these kinds of experiments?
 
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  • #2
The double slit "mystery" is a mystery when you consider a single photon, because the detection of a single photon does not show interference, and yet the statistics of many single photons does. To the extent that it is a "mystery" at all, it is a mystery even for a single slit interference.
 
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  • #3
The addition of a second slit highlights the wave nature of 'particles' better.
 
  • #4
Demystifier said:
The double slit "mystery" is a mystery when you consider a single photon, because the detection of a single photon does not show interference, and yet the statistics of many single photons does. To the extent that it is a "mystery" at all, it is a mystery even for a single slit interference.

What equation makes us think "single photon" equals only one wave? Why wouldn't a single wave interfere with itself like waves usually do?

To the extent that it is a "mystery" at all, it is a mystery even for a single slit interference.

What mystery are you referring to? In holography everything seems to work just perfectly, slits or no slits.
 
  • #5
Zelebg said:
What equation makes us think "single photon" equals only one wave? Why wouldn't a single wave interfere with itself like waves usually do?
The problem is that a single photon, when detected, appears as a particle with a relatively well defined position, and not as a wave widely expanded in space. And yet the associated wave is widely expanded in space. It looks like a contradiction or at least a puzzle.
 
  • #6
Demystifier said:
The problem is that a single photon, when detected, appears as a particle with a relatively well defined position, and not as a wave widely expanded in space. And yet the associated wave is widely expanded in space. It looks like a contradiction or at least a puzzle.

There was a problem with explaining the double slit experiment even before single photon were used, some explanations claimed it has something do with observation or measurement and such.

I don't consider wave-particle duality to be the problem here. The problem with the single photon double slit experiment is that single photon should not interfere with itself, but it’s not supposed to be a photon until it gets fully absorbed, so I ask where is the problem then if not photon, but a wave is interfering with itself?
 
  • #7
Zelebg said:
The problem with the single photon double slit experiment is that single photon should not interfere with itself, but it’s not supposed to be a photon until it gets fully absorbed, so I ask where is the problem then if not photon, but a wave is interfering with itself?

It's not just a wave. It lands as if it was a localised particle.
 
  • #8
EPR said:
It's not just a wave. It lands as if it was a localised particle.

When it lands, when it gets absorbed, yes. But until then, and at the time it's passing the slits, it's suposed to still be a 'radiation', a wave, not a photon yet. Right?
 
  • #9
Zelebg said:
but it’s not supposed to be a photon until it gets fully absorbed
Why do you think so?
 
  • #10
Demystifier said:
Why do you think so?

You do not?

https://en.m.wikipedia.org/wiki/Electromagnetic_radiation
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space...
 
  • #11
Those are single photons and single photons probably have very very small em wave width(due to very low energy).
 
  • #12
EPR said:
Those are single photons and single photons probably have very very small em wave width(due to very low energy).

Looks like it's wide enough to go through, otherwise it would get absorbed between the slits and there wouldn't be a pattern. Isn't it the wavelength that needs to be in some special relation to the slits separation?
 
  • #13
Zelebg said:
Looks like it's wide enough to go through, otherwise it would get absorbed between the slits and there wouldn't be a pattern. Isn't it the wavelength that needs to be in some special relation to the slits separation?
In the double slit it's the probability wave that goes through both slits. Or that's the predominant mode of thinking. It's nonsense but still...

No one understands this. I mean no one.
 
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  • #14
Zelebg said:
You do not?
I do not.

Zelebg said:
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space...
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space...

By my bolding, you see that photons can be propagating too.
 
  • #15
Demystifier said:
By my bolding, you see that photons can be propagating too.

Never heard of it before. If photons do not exhibit their wave nature while propagating through space, why would you expect them to interfere like waves?
 
  • #16
You misunderstand - 'photons' travel through space as oscillating EM waves.
If it's just 1 photon in question, that EM wave is extremely tiny in spread.
The photon(EM wave) also has a theoretical probability wave to it that makes it delocalised.
At measurement/observation this whole quantum arrangement becomes a dot(detection).

Photons like ordinary matter have both quantum and classical-like properties depending on the context.
 
  • #17
EPR said:
In the double slit it's the probability wave that goes through both slits. Or that's the predominant mode of thinking. It's nonsense but still...

No one understands this. I mean no one.
Well, nearly no-one.

https://arxiv.org/abs/1103.0100
 
  • #18
EPR said:
'photons' travel through space as oscillating EM waves

This is not correct; you are either trying to mix together two different theoretical models of light, or conflating two very different kinds of states.

In the classical EM model, which is the most common one people mean when they use the term "oscillating EM waves", there is no such thing as a "photon".

In the QED model, which is the applicable one if you are using the term "photon", states of the quantum EM field that are usefully described as "photon" states are very different from states of the quantum EM field that are usefully described as "oscillating EM waves". Better still would be to use neither ordinary language term and instead specify in math the particular kind of quantum EM field state you are talking about: Fock state, coherent state, etc.
 
  • #19
Mentz114 said:
Well, nearly no-one.

https://arxiv.org/abs/1103.0100
Optics?

The double slit experiment has been performed with matter as large as C60.
Explain the interference.
 
  • #20
Zelebg said:
https://en.m.wikipedia.org/wiki/Electromagnetic_radiationIn physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space...
Stuff like this is why Wikipedia is not in general an acceptable source under the Physics Forums rules. The struck-through part above is just plain wrong.

You will also find that it has been removed from the most recent version of the article.
 
  • #21
Zelebg said:
Never heard of it before. If photons do not exhibit their wave nature while propagating through space, why would you expect them to interfere like waves?
Who said that photons do not exhibit their wave nature while propagating through space?
 
  • #22
Nugatory said:
Stuff like this is why Wikipedia is not in general an acceptable source under the Physics Forums rules. The struck-through part above is just plain wrong.

You will also find that it has been removed from the most recent version of the article.

I agree, and it's why 'photon' has its own page.

So we ended up talking about semantics, in a way, and I don't think my questions were addressed, or at least I don't get it yet. Let me unpack and focus on the points I am asking about.

Double slit - single photon experiment
Mystery: why is the pattern still there when emitting single photons.

Q1. Why is this a mystery, why would not a single EM wave interfere with itself like other kinds of waves do?Double slit - which way experiment
Mystery: why the pattern disappears when we monitor one of the slits.

Q2. It seems in the holograpy the pattern on the screen behind the slits is just an "encoded inverse-shadow" of the object that is in the "field of view" of the laser beam. Here I'm interested in actual physical arrangement of the experiment to see whether the results are incompatible with what would be expected in holography.
 
  • #23
Demystifier said:
The double slit "mystery" is a mystery when you consider a single photon, because the detection of a single photon does not show interference, and yet the statistics of many single photons does.
Just to make this explicit, you get the same type of "mystery" for a single slit. The only difference is in the shape of the probability distribution for many photons, which corresponds to the difference in the intensity patterns for classical light waves:

Single slit

Double slit
 
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  • #24
EPR said:
Optics?

The double slit experiment has been performed with matter as large as C60.
Explain the interference.
Read the paper I cited. QFT gives the correct prediction for 'matter-waves'.
 
  • #25
Zelebg said:
Double slit - single photon experiment
Mystery: why is the pattern still there when emitting single photons.

Q1. Why is this a mystery, why would not a single EM wave interfere with itself like other kinds of waves do?

I think you are asking the wrong question. The interesting question is why single photons show interference in a double slit and antibunching in a Hanbury Brown-Twiss experiment at the same time. In case you are not familiar with it: The HBT experiment is simply realized by directing a light field to a beamsplitter and placing single-photon-sensitive diodes at both output ports. If you send single photons towards the beamsplitter, you will find that both detectors will never click simultaneously and for each photon only one of the detectors will receive a detection event. This cannot be realized by considering only EM waves. In fact, the detectors can be placed arbitrarily far apart. Even so far apart that they are not within each others light cone.
 
  • #26
Cthugha said:
I think you are asking the wrong question. The interesting question is why single photons show interference in a double slit and antibunching in a Hanbury Brown-Twiss experiment at the same time. In case you are not familiar with it: The HBT experiment is simply realized by directing a light field to a beamsplitter and placing single-photon-sensitive diodes at both output ports. If you send single photons towards the beamsplitter, you will find that both detectors will never click simultaneously and for each photon only one of the detectors will receive a detection event. This cannot be realized by considering only EM waves. In fact, the detectors can be placed arbitrarily far apart. Even so far apart that they are not within each others light cone.

I don't see a problem with HBT. I would be surprised if a single photon could split in two. It seems there is an assumption that for a photon to interfere with itself it would first need to split, but in holography interference pattern is not the result of wave interference, but wave diffraction, which is simply direction bending of EM wave. So I guess my question about holography can be rephrased: is there anything diffraction can not explain in any of these experiments?
 
  • #27
Zelebg said:
I don't see a problem with HBT. I would be surprised if a single photon could split in two. It seems there is an assumption that for a photon to interfere with itself it would first need to split, but in holography interference pattern is not the result of wave interference, but wave diffraction, which is simply direction bending of EM wave.

I think you still avoid the relevant problem. A photon certainly carries energy. If the photon is detected, all of the energy arrives exactly at the position of the detector. One may naively assume that the energy travels to the detector in a localized manner. Then the appearance of the double slit pattern is puzzling. One may also naively assume that the energy is somehow delocalized within the wave. In that case at the time of the detection, all the other positions of the wavefront must be "updated" instantaneously in order to ensure that the photon gets detected only once at the position of the detector. In this scenario the double slit pattern is trivial, but you run into problems with relativity and have non-locality as this "update" would happen faster than the speed of light. Of course you may also assume that this property is simply undefined between emission and detection. However, not everybody considers this as a satisfying answer.
 
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  • #28
Cthugha said:
I think you still avoid the relevant problem. A photon certainly carries energy. If the photon is detected, all of the energy arrives exactly at the position of the detector. One may naively assume that the energy travels to the detector in a localized manner. Then the appearance of the double slit pattern is puzzling. One may also naively assume that the energy is somehow delocalized within the wave. In that case at the time of the detection, all the other positions of the wavefront must be "updated" instantaneously in order to ensure that the photon gets detected only once at the position of the detector. In this scenario the double slit pattern is trivial, but you run into problems with relativity and have non-locality as this "update" would happen faster than the speed of light. Of course you may also assume that this property is simply undefined between emission and detection. However, not everybody considers this as a satisfying answer.
With respect, surely using analogies like of wavefronts and updates is old-fashioned, as is looking for mechanisms. The problem is handled in QFT by creating whatever is required in the inputs of the BS and evolving this state. The calculation agrees with experiment but it tells us nothing about a 'mechanism'. Perhaps assuming these things will lead to apparent paradoxes.
 
  • #29
Mentz114 said:
With respect, surely using analogies like of wavefronts and updates is old-fashioned, as is looking for mechanisms. The problem is handled in QFT by creating whatever is required in the inputs of the BS and evolving this state. The calculation agrees with experiment but it tells us nothing about a 'mechanism'. Perhaps assuming these things will lead to apparent paradoxes.

Sure, but this is an I-level thread and I do not think that just saying "QFT handles this well" is going to solve the question. I especially think that it is not needed to understand the problem at hand. Assuming instantaneous updates is just a different name for nonlocality. However, the OP asked the question where the mystery of the double slit is rooted. Of course the math handles the double slit well in the ensemble average and on a probabilistic level. But the intrinsic mystery is that the double slit with single photons already carries all the basic problems of EPR. And this is indeed not a problem of the math, but of its implications: local realism is not a tenable position. I do not want to enter interpretation territory, but the mechanism taking place in a single run is the single mystery here. The math for ensemble averages surely is not. We do know the results pretty well.
 
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  • #30
Moderator's note: Moved thread to the QM interpretations and foundations forum since the thread topic is more about foundations than about the predictions of the QM math.
 
  • #31
Cthugha said:
I think you still avoid the relevant problem. A photon certainly carries energy. If the photon is detected, all of the energy arrives exactly at the position of the detector. One may naively assume that the energy travels to the detector in a localized manner. Then the appearance of the double slit pattern is puzzling. One may also naively assume that the energy is somehow delocalized within the wave. In that case at the time of the detection, all the other positions of the wavefront must be "updated" instantaneously in order to ensure that the photon gets detected only once at the position of the detector. In this scenario the double slit pattern is trivial, but you run into problems with relativity and have non-locality as this "update" would happen faster than the speed of light. Of course you may also assume that this property is simply undefined between emission and detection. However, not everybody considers this as a satisfying answer.

Before that I would like to understand why use QM to address optical problem in the first place. I want to step back into the 19th century, there was Huygens–Fresnel principle which is supposed to explain diffraction. I would like to know why and how exactly this principle fails in any kind of double slit experiment.
 
  • #32
It's not diffraction. Single photon diffraction would produce markings on both slits for every photon's wave landing on the plate. Not one.
QM is needed to explain the observations and the inherent nonlocality of the process.
At the tiniest scales, classical electromagnetism fails. You should use QED.
 
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  • #33
EPR said:
Single photon diffraction would produce markings on both slits for every photon's wave landing on the plate.

No, it wouldn't, because putting anything at the slits that can detect the passage of a photon changes the results: only one slit gets a detection for each photon, and the interference pattern disappears.
 
  • #34
Zelebg said:
I would like to know why and how exactly this principle fails in any kind of double slit experiment.

Because this principle predicts that, as you make the light source fainter and fainter, what appears on the detector will still be an interference pattern, just a fainter and fainter one. But that's not what actually happens. What actually happens is that, as you make the light source fainter and fainter, what appears on the detector becomes individual dots, which build up an interference pattern over time. Classical EM cannot explain the individual dots.
 
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  • #35
PeterDonis said:
No, it wouldn't, because putting anything at the slits that can detect the passage of a photon changes the results: only one slit gets a detection for each photon, and the interference pattern disappears.
I wonder if you may have misunderstood my post. No doubt about the detectors but he was saying the 'classical' electromagnetic wave of a single photon was traveling through both slits and causing the interference. If this was the case(assume a 19 century knowledge and setup - prior to qm), one would probably expect interference effects from a single photon on the plate(provided the electromagnetic wave spread is bigger than the distance between the slits). I simply said what you said in your second post. Not sure if i did understand his question correctly but he seemed intent on using classical electrodynamics to explain single photon interference pattern. Which is impossible.
 
<h2>1. What is the double slit experiment and how does it relate to holography?</h2><p>The double slit experiment is a classic experiment in physics that demonstrates the wave-particle duality of light. It involves shining a beam of light through two narrow slits and observing the resulting interference pattern on a screen. This experiment is also closely related to holography, as both involve the interference of light waves to create a 3D image.</p><h2>2. How does the single slit experiment relate to the double slit experiment?</h2><p>The single slit experiment is a simpler version of the double slit experiment, where light is only passed through one narrow slit. This experiment also demonstrates the wave-like nature of light, as it produces an interference pattern similar to the double slit experiment. The single slit experiment is often used to explain the concept of diffraction, which is an important principle in holography.</p><h2>3. What is the significance of the double slit experiment for our understanding of light and matter?</h2><p>The double slit experiment has significant implications for our understanding of light and matter. It shows that light can behave as both a wave and a particle, which was a major breakthrough in physics. This experiment also laid the foundation for the development of quantum mechanics, which has revolutionized our understanding of the microscopic world.</p><h2>4. Can the double slit experiment be applied to other fields besides physics?</h2><p>Yes, the principles of the double slit experiment can be applied to other fields such as optics, acoustics, and even electron microscopy. In fact, holography, which is based on the interference of light waves, has many practical applications in areas such as security, data storage, and medical imaging.</p><h2>5. How does the double slit experiment support the holographic principle?</h2><p>The holographic principle states that all the information about a 3D object can be encoded on a 2D surface. This is similar to how a hologram can store and display a 3D image on a 2D surface. The double slit experiment supports this principle by demonstrating how a 3D image can be created through the interference of 2D waves. This concept is also applied in the development of holographic technology.</p>

1. What is the double slit experiment and how does it relate to holography?

The double slit experiment is a classic experiment in physics that demonstrates the wave-particle duality of light. It involves shining a beam of light through two narrow slits and observing the resulting interference pattern on a screen. This experiment is also closely related to holography, as both involve the interference of light waves to create a 3D image.

2. How does the single slit experiment relate to the double slit experiment?

The single slit experiment is a simpler version of the double slit experiment, where light is only passed through one narrow slit. This experiment also demonstrates the wave-like nature of light, as it produces an interference pattern similar to the double slit experiment. The single slit experiment is often used to explain the concept of diffraction, which is an important principle in holography.

3. What is the significance of the double slit experiment for our understanding of light and matter?

The double slit experiment has significant implications for our understanding of light and matter. It shows that light can behave as both a wave and a particle, which was a major breakthrough in physics. This experiment also laid the foundation for the development of quantum mechanics, which has revolutionized our understanding of the microscopic world.

4. Can the double slit experiment be applied to other fields besides physics?

Yes, the principles of the double slit experiment can be applied to other fields such as optics, acoustics, and even electron microscopy. In fact, holography, which is based on the interference of light waves, has many practical applications in areas such as security, data storage, and medical imaging.

5. How does the double slit experiment support the holographic principle?

The holographic principle states that all the information about a 3D object can be encoded on a 2D surface. This is similar to how a hologram can store and display a 3D image on a 2D surface. The double slit experiment supports this principle by demonstrating how a 3D image can be created through the interference of 2D waves. This concept is also applied in the development of holographic technology.

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