Feynman Double Slit

Cangas,

You have quoted a book written by Werner Heisenberg in, if I recall, the 1920s. We have a slightly more revised interpretation of quantum mechanics from then. I've also read Heisenberg's book, but I've also read a lot more than that. If all you've read are sixty year old Dover editions, I strongly advise that you pick up something from about 1985 onward.
 
PhysMach:

As usual, in your self elevating mode, you have misstated circumstances. The old book, from 1930, as you well know, if you really know very much about the subject, was plainly presented as a means of acquainting a new student with the math of Quantum Physics.

It will be of great interest to anyone who actually does know something about Quantum Physics to hear from a really knowledgeable expert like yourself: specifically which mathematics and concepts in the old book are now PROVEN WRONG? Maybe some are. Tell us which ones. And do a better job than when you fumbled and bumbled around and did not know that an electron goes through BOTH slits of the double slit experiment.

It is completely unbelievable that you can claim to be some kind of expert about Quantum Physics and yet you did not know to plainly state the universally accepted, among professional Quantum Physicists, conclusion that each electron goes through both slits.

And obviously your seeing eye dog did not inform you that, in the same post that I mentioned the old book, I also mentioned a new book, The Fabric Of Reality, written by a real expert, in 1997.

You do this kind of misleading dodge so often. How can it be an honest mistake?

I am tired of argueing with you about things you know I did not say and things I know you do not understand.
 
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Heisenberg's book, as I recall (can't seem to find my copy around), was mostly listing out the experimental evidence regarding quantum mechanics, and discusses the mathematics a little bit. The fact is that this book predates the concept of path integration by at least a decade, and most modern books don't look at quantum particles as being in some sort of "wave function" to begin with. That's viewed as the position representation of some underlying state that is basis-independent. Our understanding has evolved quite a bit since the 1930s.

As for your second book, I shouldn't have to be critical of a piece of pop-sci to get the point across that using it as a reference is silly and does not give you much leg to stand on. I don't care if this Deutch fellow is an expert in his field, popular science books are inevitably misleading with regards to the interpretations they give, and they frequently talk about the author's views, which may not be the general views of the community as a whole (I haven't read Deutch's book or studied his writings with much detail, but this rule generally holds even for the most credible of writers).

Try reading Sakurai, Shankar, or Baym. Any one of those three gives a much more modern interpretation of quantum mechanics. I also strongly advise you against criticizing someone else's qualifications when (a) you haven't presented your own and (b) you don't know theirs. It's like walking into a dark cave without know what's going to come back and bite you on the ass.
 
When a self alledged Quantum Physics EXPERT claims, as you have done openly, that electrons in the double slit experiment do not go through both slits, then that self claimed EXPERT has no alternative but to be known as a fraud, no matter how much crap they spew out of their keyboard.

I have never mentioned qualifications. You have raised the issue, obviously as a Red Herring.

Qualifications are not the issue here, although you desperately try to divert attention. Facts are the issue. You have blatantly misrepresented the fact that you have claimed that electrons do not go through both slits, while every real expert, from Feynman on down has plainly stated that they undeniably do go through both slits.

Why don't you edit your prior post? Maybe I have not saved it to my hard drive as proof.

If qualifications are the issue, why isn't your dumb ass impressed that you are directly contradicting Feynman?

Are you halucinating that you, not Feynman won the Nobel , because you say they do not go through both slits, whereas he said they do?

And, Fizz, I have challenged you to show us what writings of Heisenberg, in your infinite wisdom, you declare to be PROVEN WRONG. I ain't seen nothin' yet.

You do realize that you are essentially implying that everybody from Heisenberg through Feynman Through Deutsch has it wrong but YOU have it right?

YOU are going to bite MY ass? IN YOUR HALUCINATION. GET STARTED, M F. Oops, typo, of course I mean F M. ( Fizzix Munchkin ).
 
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CANGUS, I had no problem understanding PhysMachine's posts. Why do you? Suppose
you tell us which state of the electron passes through both slits, the wave function
or the particle.

Now for a question I have. If a single electron is emitted towards two open slits and
measurements are taken behind each of the slits simultaneously, how many electrons
will be measured? ONE, correct? Behind only one of the slits, correct?
 
CANGAS:

A little spellchecking can go a long way. Your semiclassical attempt to understand quantum mechanics is outdated. It makes no sense to say "the electron went through this slit" or "the electron went through a slit" unless you measure that it goes through some slit. You've misunderstood everything that I've said from the beginning. What I'm saying, and what is the generally accepted interpretation, is that it is nonsensical to ask the question "which slit did the electron go through?" unless you are measuring as such. If you don't make this measurement, the distribution you get on the other side of the two slits looks as if a classical wave has passed through both slits. But this is for a classical wave: electrons are in no way classical. Until you can get past your attempts to classically describe a quantum particle, nothing you say to me has any meaning.

2inquisitive, you will measure one electron hit on the detector past the two slits. If you do this measurement many times with one electron at a time, you will observe that the particles randomly distribute themselves with diffraction patterns and such that are identical to those of a classical wave. Don't let that fool you, thought. There is nothing at all classical about an electron.
 
PhysMachine, my example was using TWO detectors, one behind each slit to determine
which of the two slits the electron passed through. In this version of the double slit experiment, only one electron is measured to pass through one or the other of the slits
and the fringe pattern disappears, no diffraction pattern, due to the collapse of the wave function upon measurement. The electron is neither particle or wave, but something else not completely understood by current physics.
 
2inquisitive,

The electrons will form a distribution over the entire wall behind the two slits, so putting a detector behind each one will lead to large losses in data, and won't tell you anything.

Actually, the electron is pretty well understood by current physics. It's just not a classical thing, so any attempt to base intuition on an electron based on classical thought is doomed to failure.
 
In a bizarre twist of Physics, lets suppose that light rays were discovered to travel backwards from detector to emitter. Lets imagine that in this bizarre new world the so-called emitter does quite the opposite to what one would expect. Rather than the orthodox view of the emitter releasing its store of energy to its surroundings, instead please consider the emitter to be extracting energy from its surroundings in whatever form the emitter is constructed to do so. In other words, energy flows the opposite way. I am fully aware that this is REALLY stupid but I want some feedback so I can further develop my thought processes regarding quantum dilemmas. I’m interested to learn more about the possibilities of instantaneous communication between source and detector and this will help me develop more ideas.

So, just for one minute lets say that the emitter (a laser) works the opposite way round such that when we “charge” its battery, in actual fact we are taking energy AWAY from it wrt its surroundings and turning the laser on means that the laser resonates with its surroundings and “sucks” back the energy to gain net equilibrium. The laser looks brighter to our eyes because it is resonating with our eyes more vigorously and “sucking” more energy. (Yes, I know – stark raving bonkers!!!)

I know this is a weird thought experiment but how would this affect the way we think about the double slit experiment and quantum mysteries if this were the case?
 
dav57 said:
...(Yes, I know – stark raving bonkers!!!)...
Click to expand...
Yes it is, but you may want to investigate what the Greeks thought about vision as for them it consisted of two parts. One was the sunlight falling on an object and interacting* with it. The other part came out of the eyes, ray like, also struck the object and felt the interaction that the sunlight had produced. Sort of like you can feel the difference between sandpaper and glass surface.

All vision worked this way, so of course you could not see the rays passing thru space towards the object, any more than you can feel the tactical nerves that are working for you. - You only feel the object with your tactile system's nerves or see the object with your visual system's rays.

* faint light could not produce the color part of the interaction, and opaque objects blocked the eye rays so you could not see thru opaque thing to the objects behind. All in all, not a bad theory.
 
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CANGAS said:
When a self alledged Quantum Physics EXPERT claims, as you have done openly, that electrons in the double slit experiment do not go through both slits, then that self claimed EXPERT has no alternative but to be known as a fraud, ...
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No, Physics Machine is correct. The "alternative" you are omitting applies to you. It can happen that someone, who does not even understand QM, makes many claims about it. This does not prove you are a "fraud" - only that you have not studies QM enough, never actually used it for calculations, etc.
 
Ok, so although this notion is impossible, if there were a kind of carrier wave that communicated information, how might this help Quantum mechanics enigmas, I wonder?

This is why I am asking you for one moment to imagine that experiments using down converters and beam splitters would be anywhere near as perplexing if we imagined the light reversing its direction throughout the experiment, as explained above.
 
Cheese.

Why have so many of the most highly respected quantum physics experts gone on public record saying that one electron goes through both slits?

Are they all nutz, but you good old boys REALLY know was hapni'n?
 
Why have so many of the most highly respected quantum physics experts gone on public record saying that one electron goes through both slits?

Are they all nutz, but you good old boys REALLY know was hapni'n?
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cangas,

I think you are mistaken. An electron will seemingly go through both slits OR only one slit depending on how the experiement is performed. Let me clarify. Say you are to perform the double slit experiment by shooting only one electron at a time and you DON'T make any experimental attempts to determine the actual position of the electron as it passes through the slits. Then, on the screen you will see the classical interference pattern. However, if you experimentally track the position of the electron as it passes through the slits then you will see that the same electron only pass through one slit. So, the interference pattern is lost and we just see a seemingly random pattern on the screen which is consistent with Heisenberg's uncertainty principle. So, as you can see, the results of the former experiment are explained by concluding that the electron must have passed through both slits while the latter results clearly show that the electron only passed through one slit. So it's both!

Acutally, as an aside, interestingly enough the whole basis of Quantum Computing is based on this superposition principle--that the electron is in "two places at once" which will drastically increase computer processing .....facinating topic.

If you still don't believe me, check out this site for a really good explanation complete with animations:

http://www.upscale.utoronto.ca/GeneralInterest/Harrison/DoubleSlit/DoubleSlit.html#TwoSlitsElectrons

So it appears that they are not "all nutz" and the "good old boys" really do know what they're taking about. In the future it would be wise to actually read and understand the previous posts before making sweeping accusations that really do nothing but reveal your own ineptitude.
 
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I would like to understand WHY observation changes the outcome.

Simple enough question, is there a decently formulated answer?
 
sleeper555 said:
I would like to understand WHY observation changes the outcome.

Simple enough question, is there a decently formulated answer?
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This is not a technical answer. That is I only want to make a general point. If your assumption that observation means seeing it then you would be wrong.

Observation in this context means "measurement" of some sort which normally entails some form of interference.
 
That nuance was understood.

Does anyone have a reasonable theory as to why measurement influences the outcome?
 
sleeper555 said:
That nuance was understood.

Does anyone have a reasonable theory as to why measurement influences the outcome?
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I think it is just because in order to measure it you have to hit it with a photon. The photon changes its motion.

Of course, that seems to presuppose the "particle" view of the electron. And until you hit it with that photon it seems to be more of a wave. So I guess it is not really a satisfying answer.

-Dale
 
Ok, so you have one photon with no certain locality heading for an interaction with another wave/particle with no certainty of locality? How do non localized waves interact, and what is it about this interaction that generates what we percieve to be localized particle phenomena?
 
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