100 Years anniversary: Stern-Gerlach Experiment 1922 (U2-07-03)
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- Опубліковано 9 лип 2024
- The Stern-Gerlach experiment, performed in 1922, delivered the first experimental proof of the fascinating degree of freedom of an electron spin.
This video ist part of the online course www.quantumreflections.net dealing with quantum physics, produced by the institute for physics education research, Münster university (Germany)
For more videos on quantum physics, please visit:
www.quantumvisions.net/en/ - Наука та технологія
Btw, props for the video being pi minutes long
pi minutes is really around 3 minutes 8.5 seconds
Pi is irrational, a video has an INTEGER length.
Noice
Very observant. What a coincidence!?
Yeah man ..share Pi feelings ...it happens to much to be random
Anyone learn anything easily by 3d projections ..
Your video is really useful for me..
the explanation was clear and precise.thank you
Thank you ! Great explanation and great video!
I watched a dozen videos trying to explain spin for 20 minutes and none made it as clear as this one. Thanks!
it's not repeating.
It doesn't explain why there is only a spin up or down and not somewhere in between.
Any spin direction is possible before the interaction. Just upon measurement, there are only two eigenvalues of the 2x2 Hamiltonian. Interestingly, this formal description fits with experiment, as ony two peaks are observed. Meaning that the measurement basis is important for the definition of the "direction" of spin, and in this basis, only two "direction" are possible.
@@quantumvisionsumunster8208 "there are only two eigenvalues of the 2x2 Hamiltonian." I wonder if there's any alternate universe where I would understand this sentence
The amount that a magnet deflects in a magnetic field, depends on how long it takes to flip , so if the magnet flips immediately, it will separate exactly like the stern Gerlach experiment.
Large radius objects spend a lot more time turning than objects with a smaller radius.
Really nice video, You helped me a lot of to understand this experiment. Thanks!
Finally someone made a video with *perfect* explanation.
Thank you. 👍🏻👍🏻👍🏻
The explanation is clear, but not correct.
@@manuelpvmb2080 What's wrong with the video?
@@coreyanderson3288 Sorry for the delay, just noticed your question. Essentially, in the video the magnetic field forces the spin to take the decision of being either up or down (with a probability related to the initial direction). In reality this is not the case. What really happens is that any spin direction can be thought of as being a superposition of up or down. When the atom enters the Stern-Gerlach device, each of these components is deflected upwards or downwards (here I'm talking about the position of the atom, the spin is not changed!). So, inside the devise and afterwards, each single atom has BOTH spin up and down and moves BOTH upwards and downwards. This is the essence of quantum mechanics and qualitatively the same happens in a double slit experiment. That the atom has both spins and not either up or down can be tested experimentally putting a second ST device after the first one. Finally, when the atom hits screen, it does choose whether to be in one position or the other. Or equivalently this happens when you look at the screen. Or when you tell your physicist friend. Or in a many-world interpretation there are actually two yous and two friends, each seeing a different position of the spot... but this is another story.
I've always had trouble grasping the spin thank you
Danka..........great video...visualizing things always helps so much
Great job
Holy moly good quality
super. . thank you so much
Excellent!!!
Wow, great work brother. Thank you very much
You are welcome!
Thank you for this useful video
Great! I was confused about this experiment because I was thinking about it in the context of a uniform magnetic field.
oh dude your comment just made it click for me... the magnetic field is stronger at the top of the magnet 🤯🤯🤯
Beean Schnoodler I’m in grad school now. Glad this old comment is useful! 🤣
@@Slimbenzene139 im not in school, i just love learning about physics haha!
What difference would it make had it been a homogenous field? I'm not understanding what the inhomogeneous field does for the spin.
Then watch itagain
Tribute to great experimental physicist Otto Stern, who was born OTD in 1888 and who along with Gerlach discovered spin quantization 100 years ago in this month i.e. in Feb. 1922.
It's 2022 i.e 100 year anniversary of this experiment..🥰
Very good
Very easy to learn
Thanks
Awesome
Thanku
Great explanation
well Explained Sir
Super explanation👍
Great explanation, which Software is use for this kind of animation....
Excekllent!
Thank u
had they done an experiment that conforms to their null hypothesis with this apparatus?
A beam of silver atoms were generated in an atomic beam furnace... please explain this process
Do U guys actually have the SG apparatus? If so:
What would happen if U first passed the silver atoms thru a homogenous magnetic field?
Would they all align parallel!?
teşekkürler
Buen video bro
I am stunned. This experiment does not seem to show what it has been purported to show:
The silver atom, being a spinning charge spinning around a nucleus, behaves like a magnet and this 'effect' increases when exposed to the magnetic force of the setup. Magnets either instantly align or go topsy turvy in a greater magnetic field. When I see this experiment I can only deduce that Spin up spin down is a result of the experimental setup, it is not inherent to the silver atom/electron. The fact that the magnetic field is inhomogeneous is a deceptive notion, because in reality the witness plate does not show the amount of tilt of the atom/electron. It merely shows that the only excluded position is perpendicular to the inhomogeneous magnetic field, which for spinning objects (such as vortices, gyroscopes) at the interface of two forces is entirely expected even in classical mechanical systems because that perpendicular position is unstable (example: a spinning gyroscope when spinning down skits away when the sides droop down and touch a surface/opposing force interface, it cannot remain in the latter position).
Please have a look in the standard textbooks: A constant field only leads to precession.
@@quantumvisionsumunster8208 Yes. The textbook you are using evidently is too simplistic because it does not account for the internal motion.
Repeat the given experiment with a second set of magnets at a given distance. It may be possible to refine the results.
So what are the two opposite spinning silver atoms considered once they have been deposited in an up and down orientation on the target or do they re-orient themselves back to their native or natural state at some point. ?
I think magnetic field forces their spin to orient during field passing. Afterward their spin direction would be any depend on interact to environment quantum action there after.
How fast is the sivel released -...+
Thank you for making this video. 🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗🤗
I didn't count, it must be 100 smileys for sure...Thanks.
@@quantumvisionsumunster8208 🤗
This universe reserves so many surprises... Quantum world is amazing
Awesome video! How can I get started in making animations like these for physics?
I started with no-budget-stop motion animations some 25 years ago.... Now, we work with a small team of designers and scientists. Good luck!
Blender is a free software you can use. The requirements and skills for this kind of animation and effect are reachable if you invest some time in the tools .
You don't necessarily need hight skills in rendering and modelling, to accomplish this kind of video. Animation will be the thing to focus on.
This is the first video that I could find that actually talked about the instrumentation that's used to actually measure any of this. I want to know what instruments they use to measure spin and how they calculate the 'spooky action at a distance' that sounds more and more like bullshit. Where are the instruments?
There is no entanglement in this experiment. Concerning instruments, have a look to the original publications.
What is it?
Este normal sa nu admiteti ce nu scrie in manuale. Dar dupa ce se descifreaza constanta de actiune h si cu legile electromagnetismului, rezulta structura bipolara a electronului. Inpartiti lungimea de unda a fotonului gama electronic la 137 si apoi la 2.pi si o sa obtineti raza clasica a electronului. Ceeace dovedeste ca electronul este unda stationara bipolara de mare amplitudine a fotonului gama electronic. Si ca fotonul gama, ca orisicare foton are exact masa particulei din care se naste prin mecanismul reactiei de anihilare.
It is normal not to admit what is not written in the manuals. But after deciphering the action constant h and the laws of electromagnetism, the bipolar structure of the electron results. Divide the wavelength of the electronic gamma photon by 137 and then by 2.pi and you will get the classical radius of the electron. Which proves that the electron is the high-amplitude bipolar standing wave of the electronic gamma photon. And that the gamma photon, like any photon, has exactly the mass of the particle from which it is born through the mechanism of the annihilation reaction.
Since it's polar, why doesn't it make sense that it would either get attracted up or down towards the magnets depending on the angle it was at when passing through the field? I don't like the coin slot idea.
The main take away of the experiment was that resulted in an even distribution of up vs down, regardless of the polar angle of the particle.
Is it possible someone could explain or link to a resource that _would_ explain how particles can be concentrated into a beam? I was often confused with this in other experiments such as the Rutherford Gold Foil Experiment. I cannot wrap my head around it yet would appreciate an explanation! Thank you!
We do not have a simple beam like the idea would present a pure; uniformly coherent; Simple students idea of a beam; Some of the source gets abandoned; wasted;
*Commonly termed loss* this is a known → we simple accept okay it works - for demonstration of something - and get on with the work at hand; A candle behind common simple aluminum foil one can say it is a beam with a small orifice;
@@ChiDraconis Firstly I want to say thank you, I did not expect a response- and I am really grateful you took the time to answer! I also had never considered that a candle behind aluminum foil was to be considered a beam. I suppose my question is, even though I did not know that there was a certain amount of imprecision when making what we know as a "beam"- how from a technical perspective are the beams we _do_ have made at all? Perhaps this should be intuitive to me, but it is nevertheless a concept I struggle to understand. Perhaps I need to do some independent research on this, I just don't know how they work. But again thank you very much for your time!
@@scisarah3770 Not only _not_ a «certain» ( euro quotes ) the amount - which is Quanta in the lingo - is non-definite also •• «certain amount of imprecision» can be narrowed to not only how far it might be of but how uncertain that measure of is also; Believe it or not Gravity was just disproved but I suggest not to plan your life around that;
Additionally this Stern-Gerlach also we see some fudge → they choose up / down & say North but who came up with that why:
Zeeman and Stark effect for example; If we have machines that are tweaked those effects also are non-definite; North on the magnet was up due to human nature but now we have folks telling others that Proton Spin Axis is up & down but really spin was just a name; Handy & obvious but electrons are clouds or similarly
Wild stuff awaits if you do not spend bucks on textbooks published by people make more money if they sell textbooks that do not really answer; You will take a lot of flak for this but is a professionals 1-st lesson
So, is the magnet measuring the silver atoms, and that’s why it acts like particles, not a wave?
Seems reasonable
I think that's not quite applicable here. While the state of the 47th, unpaired electron is what gets measured, it is part of an atom and the atom is what gets registered.
Cartoon animstions. 0:22 how did she balanced both the S & N magnets mass placing it on the table like that.
wow
Oh my godd.....
I assume they've used silver because it was easier to expose it based on known photographic methods of the time (e.g. Daguerrotypes). Indeed it turns black due to spontaneous formation of silver oxide (AgO).
Or was there another reason for picking that particular metal?
That's correct - in addition, it is perfectly suited since there is one unpaired spin in Ag.
And why does it have to be either up or down? Why not somewhere in between? The apartus is forcing the electron to one of two sides because there is only a single magnetic plane. Doesn't seem like a very scientific way of telling the direction of spin.
how did they prof that the single silver atoms are not charged? Or get charged on the way.
Atoms don't get charged randomly. You have to ionize the atoms to charge them.
why is it called quanitized when spin are random and are oriented only because of magnetic fields.
That’s the point: Quantization is in geometric terms orientation of nodes of the wave function. Smallest unit is h. Nodes are random unless interaction forces to align them.
The most intuitive way to explain how or why a particle like a photon (or electron, etc) might behave as an uncertain location particle while also like a polarizable axial or helical wave ''packet'', given that everything in the universe from electrons to solar systems are in orbit with something else pulling them into polarizable axial or helical apparent waves depending on the orientation of their orbits as they travel thru space, and given that we know we’re in a sea of undetectable dark matter but don’t know where it’s disbursed, is that they’re in orbit with an undetectable dark matter particle pulling them into polarizable axial or helical apparent waves as they travel where the speed of their orbit determines the wavelength and the diameter is the amplitude which would explain the double slit, uncertainty, etc. No?
Can i use this video?
Yes, if you provide the source.
How can there be a up or down in non - homogeneous magnetic field.
In a homogeneous field you just would have Lamor precession. If it is inhomogeneous, the gradient defines a direction, and with respect to this direction, a mixed state emerges. As observation, you find discrete values for the spin.
Magnetic field ????
What is meant by homogeneous magnetic field
spectre Films That the magnetic field lines are parallel. Inhomogeneous therefore means that the lines aren’t parallel, which is visualized at the beginning of the video.
Figura obtinuta pe ecranul tubului de experienta, din cadrul experimentului Stern-Gerlach, reflecta cu fidelitate structura de unda bipolara a electronului, formata din doua semiunde diametral opuse. Prin rotatia foarte rapida a semiundelor cu viteza de c/137 (m/s), este generat in jur campul electric pulsatoriu al electronului, camp care face sarcina electrica elementara.
The figure obtained on the screen of the test tube, from the Stern-Gerlach experiment, faithfully reflects the bipolar wave structure of the electron, consisting of two diametrically opposite half-waves. Through the very fast rotation of the half-waves with a speed of c/137 (m/s), the pulsating electric field of the electron is generated around, a field that makes the elementary electric charge.
I do not agree to this statement from the point of view of theory. Just use the Schrödinger equation, and you get all you need.
I don't get why the spin is either up or down AND has a random direction which is forced into up or down by the magnetic field.
Before the interaction, it has a random direction. Due to the interaction, a certain direction is selected (that of the magnetic field). Then, there are probabilities for either up or down on the screen. See also: ua-cam.com/video/Piwh5h9ly2o/v-deo.html
@@quantumvisionsumunster8208 how do we know that electrons dont have the spin all the time and they just get quickly oriented getting into magnetic field?
0:50 - Well, finally know what "spin" is actually derived from even when today's physicist confuse us about the talks of "spin" this or that in a verb sense. Just for those who were wondering, electrons don't spin unless it was caused to spin. 0:58 - What exactly is this chart?
"Spin" is not a motion in real space. It is just a geoemtric property of the electron.
@@quantumvisionsumunster8208 Yes I know, but today's physicist confuse us and they themselves do not know what spin really is. They literally like their listeners to think the "spin" as if it's spinning in motion or in 3D space of some sort, hence why I was so confused before until I had to do my own research for the sake of "sureness" of what exactly is "spin". Everyone knows this, even physicists who did their homework, they all agree that many physicists today misuse the term of "spin".
Let's open youtuversity!
If we shoot the silver atom one by one, then we get two separate lines. But if we shoot many silver atoms at the same time, then we get only one line?
No, in both cases two lines. It is just not predictible for a single sivler atom, but on the long run, 50% probabilities lead to equiportions in the distributions with small fluctuations, decreasing with 1/sqrt(N)
@@quantumvisionsumunster8208 So the electron is never in a superposition or passing through the magnet forces it into a position? How do we know it was ever in a superposition then?
@@ploppyploppy that was discovered way later - scientists at that time tried to explain things like triplets in spectral lines of hydrogen - note this is before the dawn of quantum physics
there are different experiments with two magnets at different orientations to show there is superposition
ahh yes, imagine if this experiment done in schools.
what type of civilization we will be? type 5? 6? or type omega?
Why this should tell anything about "spin" and not just that some of the atoms can have charge?
In case of charge, you would have a continuious spectrum. Moreover, the Ag is neutral.
@@quantumvisionsumunster8208 Thank you. Can I have one more question? If the Ag atom is neutral by itself, but it interacts with magnetic field that means it should have a magnetic field by itself, right? If it's true, than moving magnetic field should also produce electricity. So.. is the spin of unpaired electron in Ag, what makes it electrical conductor?
Forget the discovery of electron spin--they seem to have discovered magnetic monopoles and how to levitate them.
@@xenomyr Spin of Indivisible Particle : Watch...
ua-cam.com/video/nnkvoIHztPw/v-deo.html
Is not the magnetic field which produces the measurement of the spin but the screen. In fact if this would be true the extended version of the experiment would not work.
Very good remarc indeed! I agree to it. We have a more refined version of the explanation here: www.quantenspiegelungen.de/subdimension-linie-u3/permutationen-und-transformation/operationen-mit-qubits/
Was the stern gerlach done with atoms or electrons?
They talk about silver atoms.
So a certain electron wave function for silver atoms.
I mean think about it.
The experiment was done with neutral silver atoms, but only a single electron has a spin which is not entangled with a partner electron within the orbitals. So there is effectively a single spin 1/2 wave-function of an electron to be considered, all other add to zero.
@@quantumvisionsumunster8208 oh that explains it perfectly. Thank you very much Sir!
Ein Magnetfeld ist, wenn ein Magnet fällt.
If the magnetic field is homogenes.Can this happen again?
No, in a homogeneous magnetic field, you just have Larmor precession. Classicaly speaking, no force acts on the atoms in this case.
what it would be the case if the magnetic field is Homogeneous ?
Then, you would just have Larmor spin precession
@@quantumvisionsumunster8208 thank you bro, thanks for the effort. Keep making videos.
@@quantumvisionsumunster8208 one more question I have, and that is, if I'm sending an unknown particle having 6 (let's say) spin state through that inhomogeneous magnetic field, now in this case would the result show me 6 maxima/peaks in graph ???
@@pritamroy3766 If total spin is j, then you have (2j+1) peaks. Für j=1/2, these are the two oberserved here.
@@quantumvisionsumunster8208 thanks bro...really appreciated
.
this video made me feel dumb as shit. but now i know the about the quantized spin.
This experiment was done in 1922. Schrodinger introduce his equation in 1926. The conclusion that the z-component of magnetic dipole moment of a silver atom has two possible values was based on the assumption that the silver atom has a well defined position at all time so the magnetic force acting on it are also well defined at all time. But this is not true because uncertainty principle says there is always a spread of values in the position of the wave packet of one silver atom, and from this it follows that the magnetic force, which depends on position, should also be random. When the wave packet reaches the magnetic field it should be scattered into two blobs, one is deflected up and the other one down. The concept of force is alrite but it should be expectation-valued. How can classical physics predict quantum effect (z-component is quantised)? Is it because the number of silver atoms in the beam is so huge that it can be explained by classical concept ?
Thanks for the interesting question. Indeed, Stern and Gerlach did not know modern quantum physics. For this reason, they were so excited about the result. The relation to the concept of "force" and quantum physics can be described using the Ehrenfest theorem. Uncertainty in position of order h is decribed by commutators. In fact, as the experiment is about 100 years old, these questions are all well settled.
Shaggy!!!!! scobydoooooo where are you
Looks suspiciously like a wave interference pattern. Hm.
So it’s UP and DOWN because of the magnetic field? Kind of doesn’t make sense... think about it.
Why we learn this at age 15/16
So that the weird truth of nature feels more intuitive, maybe? Like for kids who started playing with their phones feel it intuitive but boomers it doesn't.
@@atithi8 Spin of Indivisible Particle : Watch...
ua-cam.com/video/nnkvoIHztPw/v-deo.html
Silver enters randomly oriented, and has the “freedom” to align any way it wants, but always does so in only one if two directions.
So in an inhomogenes magnetic field; the silver atoms must therefore also be inhomogeneous for this to work, with 50% of the atoms with the North side of its magnetic moment concentrated and 50% of the atoms with the south side of their magnetic moment concentrated. The complimentary pole must therefore be relatively diffused in comparison. A homogeneous magnetic moment on the silver would still give a randomized scatter. Thus “Spin” must be inhomogenes with a greater *concentration of spin* in one of two directions.
এইটা বি এস সি তে পড়েছি.....
Finally, a real physics explanation, in plain English, from who else but der Germans,
instead of all that meaningless math/s, from all those bloody parrots,
who just keep repeating that bloody math/s without even understanding the physics, of it.
But can U please do another one and explain how a particle gets aligned antiparallel.
Yes we can. Indeed, there will be the complete line U3 in www.quantumvisions.net/ launched soon (I hope in August 2021). I will upload the videos also here. To your question in short: It depends on the energy difference between the states up/down, and on the initial state. In case of Stern-Gerlach, the energy difference is small, so the dependence on inital state is dominant. The rest is statistics....
@@quantumvisionsumunster8208 Danke schon, mein Herr/en.
I really want to understand the physics/al/mechanism/science of this.
Can U explain the Larmor precession, a bit, more?
I suspect U are not talking about the dipole swinging over but the spin axis wobbling.
@@quantumvisionsumunster8208 In particular,
is there a real/physical/classical explanation, for this, or not?
Or does it have to be quantum/virtual? My high school physics text/book said
that there was no classical explanation for this n/or the MRI machine!?
@@quantumvisionsumunster8208
Sorry about the edits. I just realised
(that) U probably get an email each time!
I'll be more careful and sparing next time.
Yes I do appreciate the "irony" of this. Sorry.
I try to restrict my comment/s to 4 lines,
so it can all be seen, easily. Except this time.
I have actually simulated this (effect), in SW,
and I have no doubt/s that that dipole gets aligned
with the magnetic field, the shortest way it can,
even if that means going antiparallel, somehow.
How can a magnetic dipole get aligned antiparallel,
in/side a magnetic field, even if it's nonhomogenuous,
so we can ignore the weak/er side?
It's a spinning charge, with its associated magnetic
field and gyroscopic effect, in/side a magnetic field!
It's just too many components, for me, e/specially
since I work everything out from basic principles.
That's all I know.
Would it get aligned inside a homogenuous field!?
Actually, U mentioned the Larmor precession.
I never even heard of him, before. I must look into it. UH!
Why hasn't someone explained this, away, already?
It can't be THAT hard.
@@curiouscat8396 The case of a constant magnetic field is treated in my paper here: www.mdpi.com/2073-8994/12/7/1135?TrendMD&Symmetry_TrendMD_0
The geometry of a non-homogeneous case is more involved, I cannot do in this chat.Good luck!
I'm always wondering why the actual experiment is never shown in a video. Always cartoons. Only cartoons. Only abstracts.
Simply because it was done 100 years ago. The photo shown in the video is a copy of the original results. If you want to see actual experiments, see e.g. xqp.physik.uni-muenchen.de/research/index.html
or many other groups worldwide.
@@quantumvisionsumunster8208 Thanks for the link to more cartoons and diagrams. Truly, I am very curious to see the actual thing at work, the actual experiment, somewhere. I would like to buy or make the apparatus.
(I'm sure there is some rabbit hole in that link I can follow to get what I want, but I'm just too tired from yesterday's *exhausting* search.)
It's not only this. It would be nice to see the Milikan experiment too, and other "spookily" missing things (from mainstream), which I feel should have an apparatus in every physics classroom across the world.
Not being facetious I've wondered about the lack of sharing the experiments before. It's that the more I do "private study" on it, the more I find lacking... hands-on, eyes-to-see, ears-to-hear information.
I've seen many demonstrations of various physical phenomenon and I love it! I love doing the experiments myself if I can. The spin thing, however, seems the worst culprit.
(I'm retired electronics guy and theoretical physics has always been an interest. In electronics, everyday was like experimenting with something, with a tonne of theory backing it. With theoretical physics, however, it's like *abstract everything* , almost never giving us _curious ones_ the beef in the burger.)
The petulance in me is screaming, "Where's the beef!?"
@@schitlipz You can of course buy the Millikan-Experiment (e.g. www.phywe.de/versuche-sets/nobelpreisversuche/elementarladung-und-millikan-versuch_9229_10160/) oir other stuff (spin: qutools.com/qunv/), but the best would be to get intouch with a university close to you.
Turkish translate please
We only have german and english versions yet. See www.quantumvisions.net
Allah razı olsun sonunda bir türk bulabildim ya.
Ulaştın mı türkçesine ?
@@Hermione5144 hayır ya nerden bul cam kaç yaşındasın peki
Actually, this is how I explain it, away, now:
Upon entering the magnetic field the silver atom's valence electron's
electric field aligns itself at right angle/s to the magnetic field,
the quickest/shortest way it can, as they are wont, to do, and the rest
follows, naturally. And if U are thinking "Why not just say that its
magnetic field aligns itself anti/parallel, to it"? Well, I can
understand how it would align parallel but how about antiparellel? Even
though I think I can actually explain it, in a nonhomogenous field, by
ignoring the weak/er side. But I am thinking ahead to an MRI machine,
which I think uses a homogenous field, even though I think I have an
alternative explanation. But the main reason, I prefer the electric
field, explanation, is because that leaves the option of it going into a
quantum superposition, of both. Or, is that the act of measurement?
I really wish I knew the answer to that, one.
This presents the measurement as if it takes place when the electron enters the magnetic field, which is WRONG!!!!!! The measurement happens when the electron hits the screen.............
You are right! I just didn't know how to visualize a superposition.
Nice video. Too bad the explanation is wrong.
We model the transition of a pure state to a mixed state due to interaction. In fact, this kind of transition is even more general than just the example shown here.
@@quantumvisionsumunster8208 Let me expand my comment. The interpretation starting at 2:30 is wrong. The magnetic field does NOT act as a filter. It does not measure any component of the spin and so it does not collapse the state. If the state is pure before the atom goes through the S-G device, it continuous to be pure afterwards, in a linear superposition of spin up and spin down, until the final measurement when the atom hits the screen. Actually the spin state after the S-G is the same as it was before: the orientation of the spin does not change! The only effect of the S-G is to entangle, via unitary evolution, the spin state with the position of the atom. For a real filter you can block one of the two beams, or watch with high-frequency photons the atom as it goes through the S-G. Your interpretation does not agree with the postulates of QM. That it is wrong can be shown experimentally putting another S-G with different orientation of the magnetic field between the first S-G and the screen. All this is standard and well explained in Sakurai or in Feynman lectures, for instance. It would be great if you could correct the video with an extended (and correct) discussion.
@@manuelpvmb2080 I agree with the fact that unitary time evolution creates entanglement. The mixed state indeed only emerges when taking the partial trace (ignoring the environment), that is, interaction with the screen. (e.g. going from equation (9) to (10) in iopscience.iop.org/article/10.1088/1751-8121/ac8f74). I see no contradiction to what you have written in your comment.
@@quantumvisionsumunster8208 I'm discussing the video, not your papers or your comments. I think you decided to simplify the explanation for non-experts, but in my view this simplification is too drastic and then the explanation misses the essence (and the beauty) of the quantum mechanical phenomenon. At 2:30 you say that the magnetic field "acts as a filter", and at 2:32 you say that "it forces the spin to take a random orientation either in line with the inhomogeneous magnetic field or in the opposite direction". But in reality the magnetic field does not act as a filter and doesn't do anything on the spin. Then you speak about likelyness of changing up or down, which is again wrong.
My proposal for a correct and still simple explanation in the video is that each arrow splits before entering the SG device into two arrows, one up and one down (you would need to explain before that this is just another way of representing the very same spin state. Maybe you could draw the two resulting arrows, that is, the two components, with different lengths or intensities, according to the initial direction.) Then, when they enter the SG, each of these components deviate upwards and a downwards, respectively. In the video, the spin of each atom has to make a choice to be either up or down but in reality it is in general up and down at the same time and the magnetic field just pushes each possibility in the corresponding direction. Finally, when the two arrows hit the screen, (for all practical purposes) one of them would dissappear and the other produce an imprint on the screen.
@@manuelpvmb2080 You wrote " In the video, the spin of each atom has to make a choice to be either up or down but in reality it is in general up and down at the same time and the magnetic field just pushes each possibility in the corresponding direction". I agree to that statement! I made a simplification by just showing this spatial separation of the two spin components, ignoring the difference between a mixed state and a superposition state. The double-arrow is a good idea, however, it cannot be shown in the spatial seperation which is important in this experiment. This is the general problem: How to visualize a superposition? Thanks for the discussion, which shows the difficulty to find good visulizations.