Is Wave-Particle Duality Really Real? An Analysis of the Double Slit Experiment

[eaglelake]

No... you missed my point entirely. The experiment involving Rubidium showed a single atom having a unique wavefront just as a single photon does. The fact that it takes multiple passes (as you say, a buildup) to make the pattern visible is a limitation of our detection methods. If one could image a photon more exactly there would be a wavefront causing an interference pattern, visible or not. The dual nature of the quanta seems pretty clear. That's a limitation of the experimental apparaturs, but it's clear from the distribution... built over time as you say... that each individual photon, atom, etc, while observed at any given time to be particle or wave -like... has both properties at all times.

I repeat, no experiment has ever “showed a single atom having a unique wavefront just as a single photon does.” ( A single photon doesn’t either). The detection of a single particle is seen as a single dot on the screen and no wave properties can be discerned from it! The quantum experiment does not reveal any wavefront for a single particle. I assume that the wave you refer to is the state function, which is a probability amplitude. It is defined in a linear vector space and no one has ever observed it in 3-space. The results of an experiment are always visible to us. Your interpretation sounds like deBroglie-Bohm, and that’s OK, but it is speculation about “what is really happening”. Both the quantum theory and experiment are silent on such things.

Further, Bohr’s complementarity principle is widely accepted and considered as a fundamental tenet of quantum mechanics; we never observe both particle and wave properties at the same time. The experiment does not reveal “both properties at all times.”

All we know for certain is that the double slit experiment yields an angular distribution of scattered particles that has maxima and minima, which we identify as constructive and destructive interference. Quantum mechanics was invented, in part, to explain such interference effects in particle scattering.

Best wishes.

 

[Galap]

To be fair to those scientists who stake their careers and reputations on various theories... it's easy to see politics stifling science in hindsight, but when your *** is on the line... not so easy. So, in some cases the debate is spirited for the sake of retaining one's viewpoint or standing, and sometimes it's spirited because the math says very strange things about the universe that we as humans do not see in our everyday lives (and recognize as such at least).

GR and SR have plenty of debate, including ideas such as treating time as separate from space. Einstein's theories however, have had the benefit of experiments which refute some counterclaims and support it. Time dilation, gravitational lensing, and more have been directly observed. By its very nature, QM defies that same degree of precision in the absence of new thinking, math, and technology.

Want to test GR? Make some really great telescopes and wait for the right time (or make some really good gyros and lasers in the extreme). Want to test SQM? Build the Large Hadron Collider and cross your fingers. You see the problem... ;)

There do exist alternative theories to GR, for example the Brans Dicke theory (http://en.wikipedia.org/wiki/Brans–Dicke_theory), which is also consistent with observations. The only reason it doesn't get much attention is that GR to most people just simply makes sense in and of itself and doesn't have 'disturbing' or 'wierd' elements like QM does.

Now because GR makes sense does it mean that Brans Dicke theory is unneccesary? No. Any theory is acceptable until experimental evidence shows it to be untrue. That's why we still use QM and GR: because of any two theories out there, they have probably given us the best predictions of anything. The only problems are that QM 'doesn't make sense' and that the two don't mesh very well.

 

[mintparasol]

Ok, I've read some of the links posted here and have gleaned a little more understanding of what's going on here by some of your replies. I won't pretend to understand the math but think I have a better understanding of what's going on here in layman's terms.

Basically, as I see it, we see no evidence of the wave property of light from the firing of a single photon. We fire it thru the slits and it hits the detector screen and is detected at a point. We have no way of determining in advance where it will hit the detector screen. It is only after firing a whole lot of photons, either all at once, or one at a time, that the wave nature of light is revealed to us by means of an interference pattern at the detector.
This means to me at least, that we get a more meaningful view of the properties of light by considering the properties of many photons rather than the properties of a single photon.
It's interesting that the time factor (i.e. whether you fire the photons all at once or one at a time) makes no difference to the result of the experiment.

 

[Frame Dragger]

Ok, I've read some of the links posted here and have gleaned a little more understanding of what's going on here by some of your replies. I won't pretend to understand the math but think I have a better understanding of what's going on here in layman's terms.

Basically, as I see it, we see no evidence of the wave property of light from the firing of a single photon. We fire it thru the slits and it hits the detector screen and is detected at a point. We have no way of determining in advance where it will hit the detector screen. It is only after firing a whole lot of photons, either all at once, or one at a time, that the wave nature of light is revealed to us by means of an interference pattern at the detector.
This means to me at least, that we get a more meaningful view of the properties of light by considering the properties of many photons rather than the properties of a single photon.
It's interesting that the time factor (i.e. whether you fire the photons all at once or one at a time) makes no difference to the result of the experiment.

You now understand the SQM interpreation of the experiment. I'd call the thread a rousing success! Differences in whether the experiment reveals the wave nature of light, or if it is the result of an ensemble, or pilot wave... you have the actual details of the mechanics down pat.

Finally, remember that if you CAN add an additional measuring device, it doesn't matter if you use the data or not. The fact that you COULD have by deploying more observation means that you can't see evidence of duality.

 

[mintparasol]

You now understand the SQM interpreation of the experiment. I'd call the thread a rousing success! Differences in whether the experiment reveals the wave nature of light, or if it is the result of an ensemble, or pilot wave... you have the actual details of the mechanics down pat.

Finally, remember that if you CAN add an additional measuring device, it doesn't matter if you use the data or not. The fact that you COULD have by deploying more observation means that you can't see evidence of duality.

Hmmm, is it right to say then that we observe individual photons as particles and we find wave properties only when we measure the properties of many photons emanating from the same source. To me, this clears up the 'mystery' of duality completely

 

[Mentz114]

This means to me at least, that we get a more meaningful view of the properties of light by considering the properties of many photons rather than the properties of a single photon.

Yes, Maxwell's equations are the classical way. Light is waves.

It's interesting that the time factor (i.e. whether you fire the photons all at once or one at a time) makes no difference to the result of the experiment..

Agreed. This is what led Feynman to say that the photon interferes with itself.

In the deB-B pilot wave model, the trajectory depends only on the initial conditions and there's no randomness except there.

[Edit : I posted simultaneously with the post above ...]

 

[Frame Dragger]

Hmmm, is it right to say then that we observe individual photons as particles and we find wave properties only when we measure the properties of many photons emanating from the same source. To me, this clears up the 'mystery' of duality completely

It leads you to an Interpretation probably. Mentz is offering the De-Broglie Bohm Pilot Wave Interpretation, I'm for SQM. They are on equal empirical footing, if not political footing (not their fault).

The more I learn about dBB, the more I find myself on the fence. I'm no convert, but it strikes me as a guess on par with SQM.

 

[DrChinese]

Basically, as I see it, we see no evidence of the wave property of light from the firing of a single photon.

I would say that is true with the double slit setup itself. However, there are other setups that show the wave nature of light on a single particle basis. I am thinking of certain special interferometer setups, for example (assuming that you accept that an interferometer shows wave effects). Not sure if that is relevant to your thinking, but thought I would mention it, see Figure 2 of this:

Non-local generation of entanglement of photons which do not meet each other

 

[mintparasol]

Thanks again to everyone, this thread has really helped my understanding.

I have some more questions, I hope you don't mind!

:- If I conduct the double slit experiment by firing one photon at a time, do I find that every now and again, a photon is 'blocked' by the dark part of the slitted screen or do all the photons always find a way thru the slits to the detector screen?

:- Is there any relationship between the frequency/wavelength of light emitted by a particular atom and the physical size/circumference of said atom?

:- I'd be grateful if someone could spend the time explaining exactly how the protons are generated and focussed down the tube in the double slit experiment. Also, to help refresh my memory of how photons are emitted from atoms in the first place. I understand it's to do with the excitement of atom-bound electrons and that the electron emits a photon as it 'jumps' from one state to another but could do with a refresher course!

Thanks again,
ad

 

[huffypuffy]

J12345 - are you attributing consciousness to particles? Bohr would just say that the measurement is the collapsing of the wave function, and that's the easy way out that physicists have followed for decades. You miss the subtle questions that we need to start asking again.

No man. Cause the device is used a day prior to the decision. which means for the statement "The measurement collapses the wave function" to be true, As soon as the device measured the gate, the wave function would collapse at the instant the device measured and the result would be set in stone. But that's not the case. our (human) measurement breaks down the wave function. Devices have been seemingly seen to collapse the function in sophisticated experiments. But we don't know if it is due to our influence now do we? We can think we had nothing to do with it. But A human built it.

Like global warming programs were no good cause the guy writing the program must agree with the hypothesis or the program won't give the results they created it to give.

Now if someone can set up an experiment that could show a human is not needed, you still can't ignore the fact that human observation breaks down the wave function as proven in the original experiment.

Does anyone know where the results are from the original delayed decision portion of the experiment? Before wheeler expanded on it years later. I really do smell a rat.

 

[Dmitry67]

This is yet another good example while CI (and other collapse interpetations) do more harm then good.

I understand that there are no experimental data that can favor say BM over MWI or vice versa, but after the discovery of Quanrtum Decoherence the 'wavefunction collapse' should follow the 'either', 'Phlogiston' et catera

 

[mintparasol]

Thanks again to everyone, this thread has really helped my understanding.

I have some more questions, I hope you don't mind!

:- If I conduct the double slit experiment by firing one photon at a time, do I find that every now and again, a photon is 'blocked' by the dark part of the slitted screen or do all the photons always find a way thru the slits to the detector screen?

:- Is there any relationship between the frequency/wavelength of light emitted by a particular atom and the physical size/circumference of said atom?

:- I'd be grateful if someone could spend the time explaining exactly how the protons are generated and focussed down the tube in the double slit experiment. Also, to help refresh my memory of how photons are emitted from atoms in the first place. I understand it's to do with the excitement of atom-bound electrons and that the electron emits a photon as it 'jumps' from one state to another but could do with a refresher course!

Thanks again,
ad

Anyone?

 

[DrChinese]

Thanks again to everyone, this thread has really helped my understanding.

I have some more questions, I hope you don't mind!

:- 1. If I conduct the double slit experiment by firing one photon at a time, do I find that every now and again, a photon is 'blocked' by the dark part of the slitted screen or do all the photons always find a way thru the slits to the detector screen?

:- 2. Is there any relationship between the frequency/wavelength of light emitted by a particular atom and the physical size/circumference of said atom?

:- 3. I'd be grateful if someone could spend the time explaining exactly how the photons are generated and focussed down the tube in the double slit experiment. Also, to help refresh my memory of how photons are emitted from atoms in the first place. I understand it's to do with the excitement of atom-bound electrons and that the electron emits a photon as it 'jumps' from one state to another but could do with a refresher course!

Thanks again,
ad

1. Yes, that happens frequently.

2. "Size" of an atom has nothing to do with it. When a electron drops from one shell to another, a photon of a specific frequency is emitted and that frequency is a function of the energy difference between the shells.

3. You can use a variety of sources to get the double slit effect. The usual requirement is that the light be coherent, and a laser produces such light. Coherent light is light in which the waves are - in basic terms - lined up so that there is constructive interference but no destructive interference between photons. (So the peaks are at the same points...)

 

[mintparasol]

1. Yes, that happens frequently.

2. "Size" of an atom has nothing to do with it. When a electron drops from one shell to another, a photon of a specific frequency is emitted and that frequency is a function of the energy difference between the shells.

3. You can use a variety of sources to get the double slit effect. The usual requirement is that the light be coherent, and a laser produces such light. Coherent light is light in which the waves are - in basic terms - lined up so that there is constructive interference but no destructive interference between photons. (So the peaks are at the same points...)

Thanks,
I had a strong 'vision' of what's going on with duality the night before last, hence the questions.

I've no doubt that this vision is flawed due to incomplete understanding of the processes so I'll keep my mouth shut for fear of ridicule but will ask another question:-

Is the energy difference between the shells a function of the radial distance of the shells from the nucleus of the atom?

 

[mintparasol]

Is the energy difference between the shells a function of the radial distance of the shells from the nucleus of the atom?

Anyone?

 

[Frame Dragger]

Anyone?

The further from the nucleas of the atom, the faster and more energetic you get, so, yes. I don't know the exact numerical relationship, and I suspect it varies by atom, and how many electrons can 'occupy' each shell.

 

[Dmitry67]

The most interesting example is the 21cm Hydrogen radiation
How tiny the hydrogen atom is. And it emits 21cm wave!

 

[Frame Dragger]

The most interesting example is the 21cm Hydrogen radiation
How tiny the hydrogen atom is. And it emits 21cm wave!

Gotcha lol, well said.

 

[housefull]

Thanks!The reason is that interactions with the environment (the air) changes the statistical properties of the molecules, as more and more information about the paths taken can (in principle) be inferred by performing measurements on the state of the air. This proves that "wavefunction collapse" isn't a sudden and discontinuous physical process, and that "wave-particle duality" isn't about the system being either a wave or a particle. Apparently it's a little bit of both. For more information about this, see a book or a review article about decoherence.

__________________
Watch The Wolfman Online Free

 

[jtbell]

Is the energy difference between the shells a function of the radial distance of the shells from the nucleus of the atom?

The shells are "smeared out" so you can't really think of them as having a definite distance from the nucleus. See these graphs of the radial probability distributions for hydrogen:

http://hyperphysics.phy-astr.gsu.edu/hbase/hydwf.html#c1

In multi-electron atoms, things get messier.

 

[mintparasol]

The further from the nucleas of the atom, the faster and more energetic you get, so, yes. I don't know the exact numerical relationship, and I suspect it varies by atom, and how many electrons can 'occupy' each shell.

The most interesting example is the 21cm Hydrogen radiation
How tiny the hydrogen atom is. And it emits 21cm wave!

The shells are "smeared out" so you can't really think of them as having a definite distance from the nucleus. See these graphs of the radial probability distributions for hydrogen:

http://hyperphysics.phy-astr.gsu.edu/hbase/hydwf.html#c1

In multi-electron atoms, things get messier.

There goes my 'vision', ha!