I always found that Feynman quote very unfortunate. It sounds like quantum mechanics is some kind of wizardry, and physicists don't really understand what they're doing with it (well, in a way they don't, but if that standard is applied to most other subjects, then nobody understands anything but the most trivial things, maybe with the exception of mathematical theorems). For most quantum mechanics is "unintuitive", and what means is, that our experience of the world is much closer to classical mechanics. But one *can* develop an intuition for quantum mechanics by studying quantum mechanical systems in theory and in experiments, in fact that is much easier now, since with the maturing of quantum mechanics the didactics has also made a lot of progress, as has notation. When comparing our understanding of e.g. the precession of a rotating solid object to the understanding of the double slit experiment I'd even think the latter is a bit easier to comprehend. In both cases one will need mathematical abstractions to "understand" (i.e. visualize) what's going on. If one goes down the rabbit hole, one will lead to Newtons law of motion, the other to the Schrödinger equation. And Newtons law of motion also needs some getting used to, since our experience typically includes frictional forces and gravity taken for granted.
I don't buy into the "consciousness causes collpase" theory but to be fair, the idea that decoherence always causes collapse is not necessarily true there are several interaction free experiments that have been made sure Decoherence is a collapsing mechanism but experiments show it isn't the only collapsing mechanism
I believe AE was right. However, imagine this. You and I have a a dice. The goal is to add up to 7. I show a 2 and you show a 5. We do this many times and it never fail. You must be reading my mind. 4 +3. 6+1. How are you doing that. Even you don't know! That is spooky action at a distance in Bhor's mind. How are we correlated?
For the second one, doesn't the absurdity of Schrodinger's cat show that quantum mechanical effects like superposition doesn't apply to macroscopic objects?
That's an excellent question! So the idea behind Schrodinger's cat experiment actually doesn't make any claims on the size of the system, but instead on the interpretation of quantum systems themselves. In fact, in the original thought experiment, the quantum system is indeed microscopic (radioactive decay). So Schrodinger's argument applies no matter the size of the quantum mechanical system. It's purpose was to call into question the interpretation of the quantum mechanical state that it can exist in a superposition until an observation is made, which collapses the wavefunction.
The cat experiment is very misunderstood by popular media and it really is a question about how the reality around us is in a collapsed wave state. (This includes galaxies billions of light-years away) There are a few different scientific opinions of how the collapse happens - One is the multiverse branching theory (or parallel universes), then there's the conscious universe interpretation and finally, the way we perceive conciousness is wrong interpretation. These are the most prominent interpretations because they agree with the laws of physics that we're familiar with. Google them to understand them better and you'll see what I mean.
Superposition is the norm. We only think it’s weird because adding up human-scale quantities of waveparticles-all of them independently imparting information about themselves to *us and everything else in the similarly-highly-interactive immediate vicinity*-reduces all unintuitive superpositionality to a level many orders of magnitude below our ability to perceive it (hence the phenomenon we call “waveform collapse”). So a “Shrodinger’s cat box” has to be made of an impossible, black-hole-event-horizonlike material to create sufficient causal separation, but sticking the cat in orbit around another planet is enough to create an equally meaningful, actually possible, time-delay-based causal separation on human scales. So, knowing these things, the concept which *should* be plainly absurd is the *non-reality* of an alive/dead superposition.
If we don't observe the state of the detector, we will still only see two bright spots, not interference fringes (assuming the detectors are turned on). This is because, regardless of whether or not we look at the data, the detectors are still interacting with the system enough to collapse the wavefunction.
ZAP Physics wow this information is actually really important. Many will assume they’d leave the detector on and not observe the results as a way to eliminate doubt during tests. It’s almost like they’d rather keep it interesting and make people think that their consciousness is more meaningful than it actually is.
premed2 you have to be very careful when you talk about destroying quantum information. But semantics aside, it isn't the fact that the detector collected data that changed the pattern on the screen. It's the fact that the detector being turned on while part of the experiment changed the physical state of the system. Just ignoring or throwing out the data that the detector collects will never restore the interference fringes. Now, there are theoretical experiments known as "quantum erasers" (although this name tends to be misleading), where by e.g. adding or removing a polarizer destroys or restores interference patterns. However, to do this, one must use pairs of entangled particles and one of these entangled particles is sent through a double slit. The subtlety is that the entangled particle is very different from a particle in a pure state. So it turns out that the interference pattern can essentially be decoupled from the "which way" information and even if you destroy the interference pattern, you still can't determine which slit the particle went through. This is why the interference can be restored in this case.
The gravity of the particle traveling through the slit isn’t an interactive detector? Any wall is essentially a large spring with a really small spring constant. Something is missing in your description. Maybe some fancy decoherence math. But awesome videos.
After the electron passes the slit with the detector why the wavefunction doesn't evolve again to give us a pattern like the one without the detector? Thanks in advance.
Good question. So if you look at Higgsino's animations at 4:36 and 5:13 you can see that when the wavefunction goes through the slits, each slit basically acts as a new "source" for the wavefunction. The interference comes from the fact that the wavefunction goes through both slits simultaneously, since you now have two "sources." Now keep in mind that these aren't physical waves like ripples on a lake but more like a wavy probability distribution. When you make the measurement of which slit the electron goes through, you are saying that there is a 0% probability that the electron went through the opposite slit. This effectively "closes off" that slit to the wavefunction so it now is only going through the single slit you measured it through. This eliminates one of the two wave "sources" and stops the interference entirely. Hopefully that answers your question!
@@zapphysics Thanks for the reply. So it is that the second slit stops to act like a source but the wavefunction is not localized right? (the pattern just changes-the wave nature is still here)
Oh yes, the wave nature is definitely still there. For example, if I were to set up a detector on this set of slits and then set up a second screen with two slits and no detectors, I would recover an interference pattern again!
Sorry, saying that observing one of the two balls affects the other simply because they shared a wavefunction ignores the reality that *something* connected to both balls has to inform the complementary ball of the event. This is a case of providing a mathematical explanation as a cover for not being able to provide a physical explanation for the phenomena.
I do have to ask though: why is there a difference between the existence of a detector behind a slit and the existence of the slit itself? Why does the former collapse the wavefunction while the latter does not? Have I stumbled into the measurement problem of the Copenhagen interpretation or am I off base?
The particle doesn't interact with the slit in any way that leaves a record of its passage. It does, however, interact with the detector in such a way. That's pretty much the definition of a detector!
I think that this kind of depends on what you mean by "intuitively." We have a sort of natural physical intuition that we build up from everyday experiences. For example, you can toss a ball back and forth with a toddler and they will be able to catch the ball (sometimes at least) even though this requires them to predict where the ball will be before it gets there. In a sense, the toddler is doing some "intuitive physics" based on how they have seen objects move through the air previously. They aren't really doing any calculations and don't have any understanding of Newton's laws or anything, but that intuitive understanding of physics is there. I would say that that sort of intuition does not exist for quantum mechanics, simply because we don't experience quantum effects in our day-to-day lives. The same could be said for relativistic phenomena. There is, however, what I would call a "physicists intuition" which is a bit different. This comes from deep study of the laws of the theory and working through many different problems yourself. By doing this, you form a sort of pattern recognition where for example, if someone were to draw some potential on a sheet of paper, you could probably draw a rough estimate of what the wavefunction of a particle in that potential would look like. Whether or not you call this true intuition is sort of up to you, but I would argue that this is essentially the best that you can do. However, this isn't always going to be 100% accurate and should really be used as a "test" to make sure that the results you get from an actual calculation actually make sense.
@@zapphysics I didn't even thought you would respond to my comment and that too this big. Thanks for responding I love your channel. By intuition I meant to able to imagine things that happen at quantum level without pure mathematics. Your reply makes absolute sense. Thank you.
Respected sir,🌟 how single slit interference pattern is been formed....it is so wierd to hear... single wave interfered with itself. ... when and why this happens...will water undergo single slit interference....if so why you did not mention In this vedio....?? Thank you sir 🌟
@gowri ssshanker Single-slit diffraction is a bit more complicated imo than double-slit interference. The whole idea of single-slit diffraction comes from the fact that the slit has some finite width to it (in the double-slit case, you typically approximate the slits as infinitesimally small). The basic idea is that each point along the slit can be treated as a "point-source" for the waves just meaning that we can imagine all of these points radially emitting waves simultaneously. All of these sources would interfere with each other. In quantum mechanics, there is a different way of seeing this with the path integral, where a particle will take every path available simultaneously and the total amplitude is given in terms of a sum over all of these paths. Again, since the slit has finite width, there will be many (in principle, an infinite number) of paths which travel through the different parts of the slit. When we calculate the probability by squaring the amplitude, we get cross-terms due to the fact that the amplitude is a sum. These cross-terms are what lead to interference.
I disagree that QM goes against intuition, but then I'm miserable at math--instinct is all I have. I agree 100% with Richard Feinman. We'll never understand QM. Max Planck admitted openly that he didn't quite understand his own theory, if I recall correctly. Maybe that is the essence of QM, the "serious mysterious" in physics. I'm subscribed now, BTW: girl gearhead, geek & SciFi freak! 🐒😁
I always found that Feynman quote very unfortunate.
It sounds like quantum mechanics is some kind of wizardry, and physicists don't really understand what they're doing with it (well, in a way they don't, but if that standard is applied to most other subjects, then nobody understands anything but the most trivial things, maybe with the exception of mathematical theorems).
For most quantum mechanics is "unintuitive", and what means is, that our experience of the world is much closer to classical mechanics. But one *can* develop an intuition for quantum mechanics by studying quantum mechanical systems in theory and in experiments, in fact that is much easier now, since with the maturing of quantum mechanics the didactics has also made a lot of progress, as has notation.
When comparing our understanding of e.g. the precession of a rotating solid object to the understanding of the double slit experiment I'd even think the latter is a bit easier to comprehend. In both cases one will need mathematical abstractions to "understand" (i.e. visualize) what's going on. If one goes down the rabbit hole, one will lead to Newtons law of motion, the other to the Schrödinger equation. And Newtons law of motion also needs some getting used to, since our experience typically includes frictional forces and gravity taken for granted.
I had a blast creating this video with you! Thanks for inviting me to contribute to this fun topic :)
Great video! Especially the entanglement ≠ interaction was easy to understand 👍
That's what I still find confusing actually.
Good work. Much needed when pop culture is drenched with misinformation. You both got my sub.
I don't buy into the "consciousness causes collpase" theory but to be fair, the idea that decoherence always causes collapse is not necessarily true
there are several interaction free experiments that have been made
sure Decoherence is a collapsing mechanism but experiments show it isn't the only collapsing mechanism
I believe AE was right. However, imagine this. You and I have a a dice. The goal is to add up to 7. I show a 2 and you show a 5. We do this many times and it never fail. You must be reading my mind. 4 +3. 6+1. How are you doing that. Even you don't know! That is spooky action at a distance in Bhor's mind. How are we correlated?
AE's reply when they spoke you already know!
some explanations about misconceptions contains some misconceptions. Like the explanation of entanglement and observer effect.
Nice video, thanks! And good luck to your channel!
Came from Reddit, well done dude!
For the second one, doesn't the absurdity of Schrodinger's cat show that quantum mechanical effects like superposition doesn't apply to macroscopic objects?
That's an excellent question! So the idea behind Schrodinger's cat experiment actually doesn't make any claims on the size of the system, but instead on the interpretation of quantum systems themselves. In fact, in the original thought experiment, the quantum system is indeed microscopic (radioactive decay). So Schrodinger's argument applies no matter the size of the quantum mechanical system. It's purpose was to call into question the interpretation of the quantum mechanical state that it can exist in a superposition until an observation is made, which collapses the wavefunction.
The cat experiment is very misunderstood by popular media and it really is a question about how the reality around us is in a collapsed wave state. (This includes galaxies billions of light-years away)
There are a few different scientific opinions of how the collapse happens -
One is the multiverse branching theory (or parallel universes), then there's the conscious universe interpretation and finally, the way we perceive conciousness is wrong interpretation.
These are the most prominent interpretations because they agree with the laws of physics that we're familiar with. Google them to understand them better and you'll see what I mean.
Superposition is the norm. We only think it’s weird because adding up human-scale quantities of waveparticles-all of them independently imparting information about themselves to *us and everything else in the similarly-highly-interactive immediate vicinity*-reduces all unintuitive superpositionality to a level many orders of magnitude below our ability to perceive it (hence the phenomenon we call “waveform collapse”).
So a “Shrodinger’s cat box” has to be made of an impossible, black-hole-event-horizonlike material to create sufficient causal separation, but sticking the cat in orbit around another planet is enough to create an equally meaningful, actually possible, time-delay-based causal separation on human scales.
So, knowing these things, the concept which *should* be plainly absurd is the *non-reality* of an alive/dead superposition.
Sir you explain meserment problem but device effect Superpostion Or not ?
What about red/red and bue/blue?
And if we don't observe the state of the detector...
If we don't observe the state of the detector, we will still only see two bright spots, not interference fringes (assuming the detectors are turned on). This is because, regardless of whether or not we look at the data, the detectors are still interacting with the system enough to collapse the wavefunction.
ZAP Physics wow this information is actually really important. Many will assume they’d leave the detector on and not observe the results as a way to eliminate doubt during tests.
It’s almost like they’d rather keep it interesting and make people think that their consciousness is more meaningful than it actually is.
And if before looking at the screen, or the detector, we destroy the information in the detector...
AJ Lynch Thanks! Fortunately for physicists, nature doesn't really care what people think is interesting ;)
premed2 you have to be very careful when you talk about destroying quantum information. But semantics aside, it isn't the fact that the detector collected data that changed the pattern on the screen. It's the fact that the detector being turned on while part of the experiment changed the physical state of the system. Just ignoring or throwing out the data that the detector collects will never restore the interference fringes.
Now, there are theoretical experiments known as "quantum erasers" (although this name tends to be misleading), where by e.g. adding or removing a polarizer destroys or restores interference patterns. However, to do this, one must use pairs of entangled particles and one of these entangled particles is sent through a double slit. The subtlety is that the entangled particle is very different from a particle in a pure state. So it turns out that the interference pattern can essentially be decoupled from the "which way" information and even if you destroy the interference pattern, you still can't determine which slit the particle went through. This is why the interference can be restored in this case.
The gravity of the particle traveling through the slit isn’t an interactive detector? Any wall is essentially a large spring with a really small spring constant. Something is missing in your description. Maybe some fancy decoherence math. But awesome videos.
After the electron passes the slit with the detector why the wavefunction doesn't evolve again to give us a pattern like the one without the detector? Thanks in advance.
Good question. So if you look at Higgsino's animations at 4:36 and 5:13 you can see that when the wavefunction goes through the slits, each slit basically acts as a new "source" for the wavefunction. The interference comes from the fact that the wavefunction goes through both slits simultaneously, since you now have two "sources." Now keep in mind that these aren't physical waves like ripples on a lake but more like a wavy probability distribution. When you make the measurement of which slit the electron goes through, you are saying that there is a 0% probability that the electron went through the opposite slit. This effectively "closes off" that slit to the wavefunction so it now is only going through the single slit you measured it through. This eliminates one of the two wave "sources" and stops the interference entirely. Hopefully that answers your question!
@@zapphysics Thanks for the reply. So it is that the second slit stops to act like a source but the wavefunction is not localized right? (the pattern just changes-the wave nature is still here)
Oh yes, the wave nature is definitely still there. For example, if I were to set up a detector on this set of slits and then set up a second screen with two slits and no detectors, I would recover an interference pattern again!
Sorry, saying that observing one of the two balls affects the other simply because they shared a wavefunction ignores the reality that *something* connected to both balls has to inform the complementary ball of the event. This is a case of providing a mathematical explanation as a cover for not being able to provide a physical explanation for the phenomena.
I do have to ask though: why is there a difference between the existence of a detector behind a slit and the existence of the slit itself? Why does the former collapse the wavefunction while the latter does not? Have I stumbled into the measurement problem of the Copenhagen interpretation or am I off base?
The particle doesn't interact with the slit in any way that leaves a record of its passage. It does, however, interact with the detector in such a way. That's pretty much the definition of a detector!
Sir large scale object including humans have a quantam effects
In daily life? Pls answer
Is it impossible to understand quantum mechanics intuitively?
I think that this kind of depends on what you mean by "intuitively." We have a sort of natural physical intuition that we build up from everyday experiences. For example, you can toss a ball back and forth with a toddler and they will be able to catch the ball (sometimes at least) even though this requires them to predict where the ball will be before it gets there. In a sense, the toddler is doing some "intuitive physics" based on how they have seen objects move through the air previously. They aren't really doing any calculations and don't have any understanding of Newton's laws or anything, but that intuitive understanding of physics is there.
I would say that that sort of intuition does not exist for quantum mechanics, simply because we don't experience quantum effects in our day-to-day lives. The same could be said for relativistic phenomena.
There is, however, what I would call a "physicists intuition" which is a bit different. This comes from deep study of the laws of the theory and working through many different problems yourself. By doing this, you form a sort of pattern recognition where for example, if someone were to draw some potential on a sheet of paper, you could probably draw a rough estimate of what the wavefunction of a particle in that potential would look like. Whether or not you call this true intuition is sort of up to you, but I would argue that this is essentially the best that you can do. However, this isn't always going to be 100% accurate and should really be used as a "test" to make sure that the results you get from an actual calculation actually make sense.
@@zapphysics I didn't even thought you would respond to my comment and that too this big. Thanks for responding I love your channel. By intuition I meant to able to imagine things that happen at quantum level without pure mathematics. Your reply makes absolute sense. Thank you.
Respected sir,🌟 how single slit interference pattern is been formed....it is so wierd to hear... single wave interfered with itself.
... when and why this happens...will water undergo single slit interference....if so why you did not mention In this vedio....??
Thank you sir 🌟
@gowri ssshanker Single-slit diffraction is a bit more complicated imo than double-slit interference. The whole idea of single-slit diffraction comes from the fact that the slit has some finite width to it (in the double-slit case, you typically approximate the slits as infinitesimally small). The basic idea is that each point along the slit can be treated as a "point-source" for the waves just meaning that we can imagine all of these points radially emitting waves simultaneously. All of these sources would interfere with each other.
In quantum mechanics, there is a different way of seeing this with the path integral, where a particle will take every path available simultaneously and the total amplitude is given in terms of a sum over all of these paths. Again, since the slit has finite width, there will be many (in principle, an infinite number) of paths which travel through the different parts of the slit. When we calculate the probability by squaring the amplitude, we get cross-terms due to the fact that the amplitude is a sum. These cross-terms are what lead to interference.
"Higgsino Physics" lives in Denmark but his accent sounds more German than Danish sometimes. What's going on? A German in Denmark? A guy from Duborg?
I disagree that QM goes against intuition, but then I'm miserable at math--instinct is all I have. I agree 100% with Richard Feinman. We'll never understand QM. Max Planck admitted openly that he didn't quite understand his own theory, if I recall correctly. Maybe that is the essence of QM, the "serious mysterious" in physics. I'm subscribed now, BTW: girl gearhead, geek & SciFi freak! 🐒😁