I've been wondering about the quantum entanglement for years. This is the best explanation ever. Great script and animation for easier understanding. I appreciate people worked on this great video.
It seems to myself the two entangled say particles are like a cogs one is spinning clockwise the other anticlockwise then take them apart they stay synchronous with each other in all directions when measured However if they become out of sync or asynchronous in all directions they would loose mesh with each other and would break the wave function the synchronization Sorry for the gearbox analogy it was just a random throught floating around
As they all say, before the measurement you CAN'T know what the configuration of the particle is. In other words they cannot prove that this phenomenon is real. Attempts at proving that the phenomenon is real have only been carried out by varying a measurement of an already set configuration, so there is no proof at all that this phenomenon is real.
Thank you. This is the very best explanation that I've heard as to how Bell's Theorem detects that entanglement is not due to hidden variables. Great explanation!!!
That was the most original (and unusual!) way of breaking down QE I've ever witnessed. Dr Lincoln's creativity is simply as infinite as the Unobservable Universe!
Hahahaha The top two comments I was like, wait. Who the fuck are these people and what language are they speaking and I’m jealous. And then this comment. Thank god for it
What blew my mind about quantum entanglement is that entangled particles have the same wave functions not just in space but also in time. Thanks for posting a video about it Prof. Lincoln.
@ It is not interesting to regard the history of physics with the aim of deciding who was the best, a champion is not enough for physics. E.g. Schrödinger's articles published after EPR are an essential contribution to our understanding of entanglement. What would have been QM without von Neumann (hence Hilbert), Dirac, Feymann, just to name a few and not mentioning too many? From our perspective what is relevant is all the contributions of those people, and we are lucky to have *all* of them.
Sending a message faster than light... On the sending end, we measure up/down, when we want to say "1" and we measure left/right when we want to say "0". Just measuring 1 time, won't tell enough, but measuring 100 times, would fast let the recieving end see a pattern. Sender and receiver makes an agreement. They each have a box of great many entangled particals, where they have one of the entangled pairs each. Every hour, the sender will measure 100 particals. If they measure them to 1, then in 10 minutes from now, we will transmit a message. If the measure is 0, we wont transmit any. And then when the message is send, we just use regular computer messages, each bit requiring 100 (more? less? sure) mesurements, to determin if its a 0 or 1 being send.
I knew if I kept revisiting this subject I would eventually I’d gain a greater understanding. Thank you for being the first I’ve seen to break down vital details necessary for the average person (interested in this) to understand more meaningfully. You have been so helpful!
I would really have liked an explanation on why the wave function and hidden variables hypothesis gives different prediction of probability at say 20 degrees angle?
Think about it in terms of rotating both detectors instead of just one. If you rotate detector B 20 degrees you get X% difference, if you rotate it -20 degrees (i.e. 20 degrees in the opposite direction) you get the same X% difference. So if you assume hidden variables, then rotating detector B 20 degrees and detector A -20 degrees should yield no more than 2X% difference (since the particles are just following their hidden variable programming and neither has any idea what's happening at the other detector). If you picture both detectors rotating simultaneously in opposite directions, the percentage difference should be a linear progression as the difference from detector B is always equal to the difference from detector A. But quantum mechanics predicts *greater* than the 2X% difference (based on the overall angle of separation between both detectors), which is impossible unless the particle at detector A "knows" the angle of detector B and vice versa. Someone smarter can feel free to correct me, but I think that's the gist of it :)
@@RoboBoddicker could we not measure one particle in a certain position and hold for a specific amount of time and then measure the other in all directions and use the angles to send information? (This is assuming that the angle as stated in the video is a real angle and not an analogy to explain stuff easier)
@@SkyWave32 Once you measure the particle you change it's state (the wave function collapses). So after you measure the spin against the chosen alignment you cannot inquire any further what the particle's spin was before the measurement. Think of it trying to put a piece through a shaped hole. Either the piece fits through the hole and becomes the shape of the hole or it doesn't and becomes the exact opposite. Either way it can no longer be changed. edit: fixed my analogy a bit just to make it super clear
It’s the same as his explanation for 90 degrees in the video. The point is that it doesn’t matter how you measure the second particle, it will have the opposite spin from the measurement of the first particle.
A physicist friend of mine said this to me about the subject, and I'll never forget it: "It's only 'spooky' if you think about the behavior from a human's temporal point-of-view. Because for the photon, the events of entanglement, separation, and measurement effect all occur at the exact same time."
It is true that from light's "point of view", there is no passage of time. Quantum comms are still 'spooky' though, in that all macroscopic phenomena are limited by the speed of light - to anything with mass, time does exist, and light speed is a limit to transfer of information - yet quantum information travels infinitely fast. So how is it travelling? It's not by light - because as Don explains, that's been tested for and ruled out - it travels 'instantaneously'. However, the whole thing has never seemed too bizarre to me. The universe started from a single point of space-time, so it doesn't seem too implausible (to me) to suppose that stuff going on 'under the hood' has remained 'connected' in some fashion. And as Don says, it doesn't break relativity because we can't use this mechanism to break the speed of light limitation on movement of mass or information. And then too, I always found John Cramer's "Transactional Interpretation" of Quantum Mechanics to be more plausible and pleasing than the unreasonably-popular "Copenhagen Interpretation" (which has hung around well beyond its sell-by date mainly because of that bloody silly alive-and-dead cat being sexy to layman types). In addition to that, TI is mathematically more aesthetic - by interpreting 'negative time' solutions as being "information travelling back in time", rather than ignoring it as "obviously nonsense" (as Copenhagen and other interpretations do). Kids get told off for ignoring 'the other' root, and imaginary numbers seem to be 'used' in the universe, so it seems dodgy to not try to interpret them. Those signals ('advanced waves'), travelling back in time can form atemporal 'handshake' communications - which neatly explain a lot of 'spooky' stuff like the double slit experiment, that bloody cat, and perhaps spooky action at a distance, all in a more (to some, anyway) philosophically pleasing way, i.e., without requiring infinitely branching universes (Many Worlds), or the existence of intelligent (?) observers to actually make anything happen or the universe exist. See Wikipedia < en.wikipedia.org/wiki/Transactional_interpretation > or the 1995 book "Schrodinger's Kittens (and the Search for Reality)" by John Gribbin.
I'd like to thank Jada PS for bringing me here. Now I learnt something new and now I understand what she was talking about...2 particles in a single wave pattern. Brilliant!
This is the first time I have properly understood the concept, although had seen many videos on the topic earlier. Thanks a lot for the lucid explanation! Really mind blowing.
Lack of data points so they join the points with straight lines (isnt this what plagues all physics?); at a more subtle level this is fundamentally what is wrong with Quantum Physics we only have data at the points of measurement he he
The mathematical functions for hidden variables and quantum mechanics are continuous, so there's no need to join points or "extend the function". The real difference is that the QM function is probabilistic, and as such yields a gaussian distribution. The HV function is fully determined by initial conditions, so there is no probability game into play and the percent of what's measured (amount of measurement agreement) increases linearly to 100%, then decreases the same way. Given that QM yields a line that fits the experimental results much more closely, the scientists conclude that QM is better for describing the phenomenon and making predictions about it.
I see it as a problem with how they are imagining the hidden variables. If you have a random vector being detected it has a probability as well so Hidden variables can create sine waves.
If you assume the hidden variable is not time-varying, you get the anticipated straight line. But if you allow time-varying hidden variables, and admit that time-keeping varies from one location to another, then the time-varying hidden variables drift in and out of sync (e.g there is a non-vanishing "beat frequency'), and the straight line model gives way to the one we actually find in experimental measurements.
The triangle wave is linear. But the wave function is sinusoidal. Linear would be two separate clocks where you reading them at the same time. The graph is linear because you're dividing. Say 12 divided by 1 oclock.
The idea is (as far as my layman mind can grasp it): Hidden variables tells you that the two spins are in opposite directions, and the first one is "closer" to spin up than the second, but you can't know the actual, original spins. Quantum Mechanics says that when you measure the first spin to be up, the other one BECOMES spin down - without any probability weirdness. So you don't need to integrate over all possibilities - there is only one. And thus the result is different.
6:15 - 8:08 This is probably the most important educational physics video on RUclips, by virtue of the concept it explains, and especially the apparent paradox it reconciles.
Intriguing video. I took high school physics about 40 yrs ago, so I don't even know if this is even an intelligent question, but here goes: How is the spin of a particle observed or measured? How do we know that particles only spin up, down, left or right if we can never observe such a small thing?
When we measure the spin of any particle we are actually interacting it with field which means there are other particle involved ( meausuring device), thus measurement is another entanglement.
Interesting how Einstein made such significant contributions to quantum mechanics with his papers on Brownian Motion and the Photoelectric Effect, yet he is always remembered for his "God does not play dice" remark.
The video doesn't cover why the hidden variable must result in that particular probability line. At a surface level, it feels like there should be forms of hidden variable(s) that would deliver a curve similar to quantum mechanics.
You can't use a random function for describing any hidden variables. In this particular case, you have a result (value of measurement for the second particle) fully depending on the measurement on the first particle (because at the beginning there are only 1 blue and 1 red balls, so if one is red/spin up, the other must be blue/spin down). So the equation needs to be y=-x or more in general y=ax+b, which is a straight line equation
See Sabine H. I think what's going on is the hidden variable is what you measure. "What a quantum particle does depends on what measurement will take place. The 2022 Nobel was likely for proving Bell Wrong. See Measurement Independe. See Sabine H.
@@TheNasaDude This is important: "What a quantum particle does depends on what measurement will take place." - Sabine H. It's likey Bell was proved wrong because he assume measurement independence. What if you understand what Sabine's saying what i am saying might make sense.
I feel like you didn't truly go into depth about what the hidden variable theory would predict, and what the results truly show us, for example if measured at the 45 degree angle. Another video showing a proof of Bell's inequality would help, I feel.
I would definitely love that. I never understood why hidden variable theory is supposed to be wrong and just stating that's what it'd predict without any explanation whatsoever makes the whole thing unconvincing for me
The best video I remember is from Minute Physics, but Veritasium also did one. I don't think Space Time or Science Asyluym did one, but I am not 100% sure. At least not until you measure me :P
I would guess. The hidden variable theory is linear like dividing times on a clock. A moving clock hand does not turn sinusoidal compared to the angle or time. It turns linear. But the wave function is sinusoidal compared to the angle.
My understanding of quantum entanglement hinges on knowing why the idea of hidden variables doesn't work. This helped that understanding, I see how the predictions are different, where one is a triangle wave and the other is a sine wave. Still don't know why the predictions are different.
That's in the graph at 12:50 -- I don't understand why you would even request that. Or do you mean measuring the first particle at 45º? That's trivial, we know the result: 225º for the entangled couple.
I was actually pleasantly surprised to NOT learn something new from one of your videos (for once)! This makes me feel like I have a decent grasp of this topic. I don't think this is going to hold for the quantum teleportation video! :) Could you also do one about quantum encryption? I feel like that would be both fascinating and enlightening. Thanks for the great videos!!!
It feels errant to say "therefore information can travel faster than light". Why are we assuming anything is being transmitted? What if these two point-like particles are intersections of some other higher-dimensional brane?
Do you think theorists coming up with concept of "brane" gave it such name just to troll? ;) Anyway, to be specific, it's "quantum information" and "traveling faster than light" is just a shortcut, a stopgap (like dark energy and dark matter) - a plaque saying "fix me". Don't know much about super- theories but wouldn't brane fall into hidden variables category?
I see that the quantum entanglement “red bell curve” is different in shape than the hidden variables “blue pyramid”; however, I don’t understand WHY they’re different. I think that extra bit of information would’ve been great to help us compare the predictions made by both interpretations, but perhaps it would’ve taken too long to go into the math that determines those probability predictions?
That's letf out because the only way to explain it is with math i think. This guy explains that part in his video ruclips.net/video/-WSWz1H3mJg/видео.html
This was fascinating, and very well explained for the most part. I really like that you just didn't explain it, but you also explained the experiment. Although it's still hard to wrap my mind around it, it's definitely better than not knowing how this was measured at all. (I'd still like to know more about how those two lines colored lines on the graph differ, though!)
Yes I understand why hidden variables gives the graph that it does but not 100% sure why quantum physics would predict the other graph. That would be a nice video for the future
For that same reason, I actually did not like this particular video. TBF, I didn't find a video yet which explains the experimentation and meaning behind it properly, just the inferences of the experiments, analogies and what it means for the phenomenon of Quantum Entanglement.
@@_sayan_roy_ Yeah, I get you. It's a complex topic and there were some good explanations, but the graph itself is not explained, and I'd like to see how those differing lines are arrived at (which was not done here...or apparently, anywhere else that is easily assessible and made for regular people).
@@Rationalific Hey, I got one Veritasium video which made me understand quite a bit, of course, after pondering a lot on that by myself. The video is 7 years old and you can search by quantum entanglement or spooky action at a distance. There is a video of Sabine as well but not as good as Veritasium's, on the details we want.
This helps a lot. I’ve taken several science for dummies courses on physics including his Theory of Everything with the Teaching Co. (No, I don’t even know anyone working for them.) However, I’ve struggled to understand this even after five or six courses for science dummies. This is simple and fascinating. By the way, it’s hard to blame Einstein for being bewildered by this and calling it spooky action. And he had a very human overreaction to it by not liking quantum mechanics or theory. (Dr. Lincoln gave a reassuring explanation that would probably reassure Einstein (and the rest of us) that he could appreciate his relativity and quantum mechanics.) Thanks for a great video!
Well we know that it's not physical spin, because we're talking about point particles with r=0. It's a specific property that we just call spin to make visualisation easier. That said, we know little more than that about spin, besides that it can be -1, -1/2, 0 , 1/2 or 1 (also values chosen for ease of grasp). Same goes for charge. We've figured out how it works, but what it is exactly? Scientist still cannot answer that question. What scientists do is make up theories that fit current data, and are testable for new variables or refinement of known variables. It's the only way forward on the path of knowledge.
Yes. Spin is an abstract form of angular momentum. And it is one of the bedrock principles that angular momentum is conserved. This is why if you measure the spin of one particle to be up, the other had to be down, assuming you specify the same direction in each measurement. What Bell showed is that the correlations observed cannot be reproduced by pre-assigning all possible outcomes to the particles when they first separate. This, combined with the purely randomness of each measurement in isolation (meaning they appear random at each end, but when the observers compare notes, spooky correlations emerge), rules out hidden variables. Here's a video that goes into more detail about that, giving examples of how hidden variables fail to explain the data: ruclips.net/video/ZuvK-od647c/видео.html
Listen, I'm still in high school and hadn't had physics in about 3 years. The last time I had it I almost got a D on my report card. For some reason I gained an interest in quantum physics. I would like for you know Dr. Don that your videos are amazing! I watched a lot of them and learned so so much! You explain it so well and eventhough English is not my native tounge I can understand and follow them very well. Thank you so much for these great videos. They make to facinating world of quantum phyics so much more accessable! Thank you.
For me, this was your best video. Quantum mechanics, prooves that the world is material and dialectic. This means that always is an existence of cause which is going to give e result but it is impossible to predict the exact probability of this result till it happens.
You say earlier on in the video (6:10) that measurements have shown that the information from one particle is transferred to the other faster than the speed of light. But at the end (13:34) you say that communication faster than the speed of light is not possible. That makes no sense, and you are contradicting yourself. Please can you clarify. Thank you.
Isn't it easier to assume we lack knowledge about (opposite) rotation, than to assume things travel faster than light? Couldn't said particles be set off in specific opposing rotations that we lack insight of?
.... it doesn't need to travel ftl, you can't compare the effect until after both measurements are made and you have brought the results together, we just get confused about it since we think of ourselves as being seperate from the wave function, when we are all part of it, the perception of it being probabilistic is just observation bias
I would compare it to sending 1 glove from a pair to 2 people far apart from each other. If person 1 opens theirs and it's the left glove, the other person immediately knows the other one is the right glove. No data has been transmitted to either person
@@dcquence That analogy is misleading, as which side is being sent which glove is theoretically knowable at the point where the gloves are packaged aka, hidden variables. Both of the possibilities happen, we know this from a variety of external tests where, as opposed to examining one particle, we make them interact with each other and see their interference, it's just, we have a huge bias against applying the math to ourselves when we interact with one of them, and get into the same superposition as it is in, at which point, we should not be surprised at all to find that interactions with someone that interacted with th other particle are consistent
Yah but how does the second person KNOW the first person has a left glove. How is that information being transmitted faster than light Further, that analogy would require that person one could suddenly make his left glove a right glove, and that persons twos glove would immediately become a left glove And they wouldn’t, plus the analogy breaks down in usefulness because gloves can’t switch left/right orientation
QUESTION: If the first particle is measured "up" and the second is measured "left", the angular momentum sum is not zero. Why does that not violate the conservation of angular momentum?
I have a simple question. If you are constantly looking at 2 entangled particles with known opposite spin direction, and you changed the direction of one particle's spin, would the other also change even though you did nothing to that particle?
You can't do that experiment. As soon as you measure a particle's spin, the particle is absorbed. All you can observe are the statistics of millions of particles.
@@ragnaarminnesota6703It is true that you can change spin without measuring it. Everything I wrote is true. You probably just don't understand QM. That's understandable.
@@david203 Reread everything. You said you can't do that experiment. Sabine was arguing against spooky action when she said what I am repeating. Given this video, are you arguing against spooky action? The PBS Space time guy said Einstein was proven wrong by spooky action. Was he?
That's what I tell people as well. People seem to misunderstand Einstein's comment, thinking that he was somehow scared. In reality, he called it "spukhafte Fernwirkung" in clear reference to what you mention. In German, Fernwirkung is legitimate physics terminology for the forces of Newtonian mechanics, i.e., forces acting instantaneously over finite distances. Wirkung in this usage comes from the old times, when even Newton was calling forces "actio." Given the context, I would assume that Einstein really meant it as a derisive description by putting a quantum phenomenon in the same category as a discredited idea from classical physics. The "spooky" is just added to emphasize the joke, to make it clear that he didn't really think that's what's going on.
@@noeckel I still think that Einstein is wrong by saying that light is constant, light is proved by quantum entanglement not to be, whene they say that 2 atoms are in 2 places at the same time, they see such effect because light goes IN then goes OUT way to fast that in a matter of a very, very, very small fraction of a second it comes and goes to where it needs to go so they only see the atom whene it stops in one side then whene it stops in the other side cause the atom acts as a marble in a band that goes in one direction then stops to change to the other side. Atoms entangled are like a band whene the up side goes left the bottom side goes to the right.
@@noeckel light dobles each time that is why gravity in a free fall the speed doubles each second. The serie PHI goes kind about the same but not realy, you now 1pluss 1= 2, 2 and 1= 3, 3 and 2= 5 and so on that in a matter of few times passes light speed anlist the numbers.
@@Motorfirez gravity is the results of space-time bending and the variations of the bending (gravitational waves) propagate at the speed of light. Relativity sets the "speed of light" as the speed limit of causality, this is why quantum entanglement is out of rule.
I dont think that information is transported. What I mean: When you entangle quantum objects than you put them into a certain state. Than you can move the quantum objects apart. You don´t know what state these quantum objects are, but you know that if (for example) the spin on one object is to the left, the other must have a spin to the right. It is because you have prepared this behavior at the time of their formation (when they where close together). Information would be transported if when the objects are far apart and you change the spin on one object and the spin on the entangled other object chances. But as far as I know this is not the case.
I dropped physics last school year as we had a few topics in class I didn't totally understand and now I am grievously sad because this video made me want to have physic lessons at school again.
Quantum entanglement is a sketchy thing. Finaly this video connects it with worship of chaos gods. Should i now prepare to see The Pope as follower of Khorne or Slanesh?
Would you please make video about Light interference pattern? As far as I know interference pattern is different when we are observing and when we are not.
I have two unique balls, one blue and the other red. I place both inside sealed containers, so that you can't tell which is which until you open them. My brother chooses one of the containers at random, and flies off light-years away into a spaceship. I sometime decide to open my container and I find the red ball. I instantly know that my brother has the blue ball. No information traveled faster than light. EDIT: Omg, you used the same example! Now, that is probability in action. EDIT2: Oh well, I stand corrected. I was using the hidden variables hypothesis without realizing it, and it turns out to be false.
That's the hidden variables hypotheses. Quantum entanglement is this: You have two unique balls, both balls can have any color you wish. You chose one to be red and the other blue. You put them in boxes... you send your brother light years away... and before you open your box you start changing the color of your ball. So now, how would you instantly know the color of the ball that your brother has? Exactly... You can't. Your brother's ball can have any color... So anyway you start changing the color of your ball and your brother opens his box and observes the color of his ball changin too! And not randomly but according to the color that your ball has... So when your ball is red his ball is blue, when your ball is green his balls is yellow, when your ball is pink his ball is orange etc... In this case you can't instantly know anything, so you might have to conclude that somehow the other ball knew how to change its colors to correctly match the "opposite" color of your ball... So information about the state of your ball was traveling faster than light to reach the one your brother has!
Actually, no; what you (and Don) described is simply 'maximum correlation' - which, in QM, is represented by some vector in a _maximally_ entangled subspace. "HV" refers to the possibility of using classical probability distributions to describe the QM results - different thing altogether
Could it be that nothing is transmitted, but that the wave function collapse collapses backwards in time? This would allow the entangled information to be shared at the moment of entanglement, correct?
Great video as usual! Now I don't have much knowledge about quantum mechanics but I have two questions, firstly has there ever been an experiment that proves that information is transmitted faster than the speed of light ? and if so how was it conducted? Secondly, if hypothetically, there was a way to take a bunch of entangled particles and store one of each pair in a way in which they couldn't interact with anything else, separate them by a lightyear or whatever and have two people measure their spin in only the vertical direction. The two people agree to measure their particle, say every second but the second person measures it 0.5 seconds after the first person. Couldn't the first person's measurement ( UP or DOWN), be read as ( DOWN or UP) by the second person and if they agree that UP is 1 and DOWN is 0 or vice verca, wouldn't that enable them to communicate in Binary instantaneously over great distances? There must be some information I'm missing out on but if someone could explain why it isn't possible that would be cool :)
hi.. Sorry but i have to disagree with you on that you can not use this to transfer information. I will attempt to explain how to use this to transfer information. Lets assume technology is advanced enough so we can read the states of these entangled particles relatively quickly, although the speed of measurement does not invalidate this theory. If we had 1 particle on a mars rover, and 1 particle here on earth (lets say). Both particles are being measured at a default speed of say 100Hz. Lets assume Up is a 1 and down is a 0. If here on earth i want to transmit a 0 followed by a 1, the transmitter(earth particle) would ramp the measurement speed to say 1khz, the receiver stays at 100hz, the transmitter would continue to measure at this higher speed until it got a result that is down, the transmitter would then not measure again for 1 clock cycle of the receiver, the transmitter would repeat again of measuring at the high speed throwing away all the measurement results if it was up then hold again when a down is measured. If this is repeated about 10 times the receiver would see a block of downs. If the same is then repeated for up (i.e the transmitter throws away all the measured downs and hold on up), you have then transmitted at a relatively slow baud rate the bits 0 followed by a 1. The only limit that determines the baud rate of data flow is the rate at which one can perform a measurement on the particles, but nevertheless whatever the baud rate, that data was transmitted faster than light.. I hope you get a chance to read this and comment.. Many thx...
But if the first particle's spin is vertical (up), simultaneous measurement of the second particle's spin shouldn't be horizontal since it isn't opposite to the vertical spin of the first particle. (11:30) If the first particle's spin is up, then the second particle should be down, not at a horizontal angle. The fact that the spin of the second particle isn't down shows that the particles aren't entangled -- because their spins aren't simultaneously opposite to each other. Apparently, two simultaneous measurements can be made with spins in any direction, not just opposite to each other, so actually, there's no entanglement.
If spin is "up in the vertical" that tells you nothing about the spin in the horizontal. Worse, if you measure along the vertical and then along the horizontal, you lose all information about your first measurement. The same applies for entanglement. Perfect correlation only happens if you measure along the same axis.
@@narfwhals7843 ~ But the second particle shouldn't have a horizontal measurement if the first particle's measurement is vertically up. The second particle should only be down if entanglement is occurring. If the second particle's spin can be measured in any direction (not just in the opposite direction) to the first particle, where's the evidence of entanglement?
@@FrankCoffman Spin is _always_ up or down along the direction you're measuring. That's one of the reasons it doesn't really have a classical analog. If you're measuring along any axis, you're forcing the particle into that spin state regardless of entanglement. If you measure both along the same angle you force both into the spin state along the axis, and they always come out with the predicted correlation. The evidence of entanglement if you measure along different angles is still in the correlation, which is then related to the cosine of the angle.
Is the wave function a mathematical description or is it a "thing" that causes change itself, i.e causal? I cannot see how it is causal, which is implied by some of the "explanations" talked about. Non-locality remains as the most weird thing in the ultimate nature of existence, still.
what he says makes no sense. Be ok. You are smarter then him, that is why you do not understand what he says. Means you correctly get that it makes no sense. He is fermilab, he is the main stream.
hey fother mucker how are you doing? I just thought you could be happy to by one hour slot via skype to heal the wounds you carry.. 60usd/hour special price for you.
I want to get there in my studies some day. It is great to find a video like this in a situation where my instructors only killed my interest in physics.
Thanks for the lecture. I have a naïve question: Suppose you have three particles. How do they know which one to pair with To form the quantum entanglement? Thank you
I agree. There is no reason to think that correlation must be linear. If we think in "particles" as waves (as de Broglie suggested), why could not found hidden properties which depend on sin(x)?
Yet, some would have us believe that government is not capable of anything. Fermilab is under the US Dept. Of Energy. That makes Dr. Lincoln one of those "bureaucrats." He is a scientist. I'm very proud to see my tax dollars go to this national lab. This is a national treasure. Keep up the great work.
What if you use sequences of measurements to create statistical skew? If you use 3 entangled pairs and measure the first one for up/down spin it would be 50/50 until you measured it. As would the 2 others. If you got a up, you measure the second while knowing the other end measurements on the entangled particles would be a down for the first one. If the second is an up as well, you measure the third. You thus only perform all 3 measurements if the first two are up's. Measuring on the other end will then give a 50/50 spread for first value always, but you will know that if you get a down, the second measurement will be determined as opposite of the first since it will also have been measured. The same goes for the third assuming second was also a "down". Depending on how you look at this you are either picking possible outcomes, or you are just increasingly less likely to measure. I am wondering if the odds of measuring downs on second and third coupled measurements are affected by this decision or if the outcomes are still 50/50 but you now know what they were in first set of measurements.
The point at which the spin of entangled particles is determined is when the wave-function of the measurement device becomes entangled with the wave-function of the particles. It doesn't matter which particle is measured because both entangled particles share the same wave-function. The crucial point to understand is that these wave-functions don't travel through physical space-time, they propagate instantaneously throughout Configuration Space, a complex-valued domain of potentially limitless numbers of dimensions where the wave-function is defined. No information is transmitted between particles in physical space-time, all entangled particle properties derive from their entanglement with the measurement device in Configuration Space. Thus, there is no information that travels through space at any speed, hence nothing that exceeds the speed of light. What we observe in relativistic space-time is the quantum mechanical projection of events that evolve deterministically in Configuration Space. Such events appear random to us because the projection into space-time is probabilistic rather than deterministic. In short, the universe we observe exhibits non-local realism, exactly as demonstrated by Bell Inequality experiments. @12:44 "Quantum mechanics is correct and the whole idea of hidden variables is completely ruled out." That is an objectively incorrect claim, and it was the Nobel Prize-winning experiments of Bell's Inequalities by Aspect et al that proved it wrong. Reason being, Dr. Lincoln fails to distinguish between local and non-local hidden variable theories. While local HV theories do indeed make incorrect predictions, non-local hidden variable theories were demonstrated to be perfectly consistent with quantum mechanics, just as John Bell himself emphasized.
@@ragnaarminnesota6703 - Invalidating measurement independence is legitimate, so long as you're fine with undermining all expermental science in favor of superdeterminism. Personally, I prefer science to predestination.
@@QuicksilverSG "In short, the universe we observe exhibits non-local realism..." Science with non-locality. I have decided FTL isn't real. Do you except determinism? If you don't, you seem to be knocking out one of the pillars of science.
@@ragnaarminnesota6703 The quantum wave-function is defined on Configuration Space, which is inherently non-local and deterministic. Consequently, all quantum events in Configuration Space occur instantaneously, without requiring FTL transmission of information across relativistic space-time.
Love your video. It's very instructive. When I think about the why of quantum entanglement, and how the spin measurement of one particle determines the spin of the other, at seemingly faster than light speed - there's a lot of "why" left on the table to explain. One idea that I think deserves more attention is quantized spacetime. If there is such a thing as quantized spacetime, then the particles of such spacetime would have the properties of superposition, and entanglement. In this scenario, two entangled electrons could exist in the confines of entangled spacetime. What appears to us as two electrons, separated by a vast distance, is actually local as far as the electrons are concerned. The entangled spacetime in which they reside, makes it appear to us that the electrons are far apart - when they are actually right next to each other. In this hypothesis, there's no violation of special relativity. And most importantly, no violation of causality. The entangled spacetime implies an extra dimension that we cannot see directly - but this dimension manifests in such a way that two electrons, from our viewpoint, can be far apart - and yet appear to be communicating faster than light allows. To take physics to the next level - it's my opinion that the key problem to solve is the "why" of quantum entanglement. Quantized spacetime may offer an answer. Quantized spacetime may also help with ideas related to quantum gravity - which is another reason to further develop this field of study. The one thing we do know, that we cannot allow in our theories, is a violation of causality - because if that happens, Physics becomes a land of anything goes. Please carry on.
The explanation lies in a single word: relativity. If you don't understand why that's enough, then you are simply admitting that you weren't paying enough attention in undergrad physics.
@@lepidoptera9337 But the "why" behavior of quantum entanglement does not lie in a single word. However, I don't think special relativity is being violated by QE. That's why it's such a puzzle. How to reconcile the apparent contradiction? Something else is going on that perhaps involves additional dimensions arising from quantized spacetime, or perhaps the so-called many-worlds hypothesis explains QE's apparent faster-than-light collapse of the wave function. Or maybe, as some have speculated, the wild idea the QE creates the spacetime in which it operates. In any case, causality must be preserved - which implies that special relativity must be obeyed. And here we are in 2024, and we still don't have a solid explanation for the apparent violation of SR by QE. Instead, we have a lot of head scratching - a few ideas on the table - and a mystery with no definitive answer.
That was a very clear and easy to understand explanation of quantum entanglement. There is some kind of link between entangled particles. When that is understood, other mysteries will be revealed.
I get it, but I don't understand it! The thing that confuses me the most is the measurement of the spin direction. How can you truly determine what direction you are measuring in a 3 dimensional space without a frame of reference? I imagine it to be be like floating in space, there is no way of knowing which way is 'up'? Someone please explain this to me as its driving me insane :)
At 13:05, '' the hidden variable is wrong '' . Well, that's not true! It only means that the Bell test say LOCAL hidden variable is unlikely but there can be non local variable, like fields permeating the whole universe for example, at play!
True but since it's "common knowledge" that local HVs are what (experimental tests of) Bell's theorem(s) ruled out I would say that that's a forgiveable error in this context. The more serious error there in my view is the assertion that standard QM forces us to accept that there must've been some kind of ('spooky') transfer of information. There are other serious errors in this video too. Physicists are generally terribly ignorant of quantum foundational matters.
It would be nice to explain more about: 9:56 why the measurement of the 2nd particle is "Right or Left". Shouldn't it be zero? ;D and 12:18 the reason for "Hidden Var" having a straight line. why it is a straight line?
1:53 if that's truly the case, let's say you assign two students to the exact same problem, but one decides to choose vertical and the other one chooses horizontal. They both get their answer and Student A's Up while Student B is right. Once you find out the answer there's no going back and if it's to the same problem and the only variation is the direction then if both people are correct but it can't be anything else but what their answer is then aren't both people actually wrong at the same time. As you've said before, once it's determined that the direction is up, any other direction is considered wrong. Therefore if the person has a choice to choose a random direction and their choices, either up down or left or right once they've made that decision and figured out the equation based off of that limited contradictive measurement, then at that point the whole the whole way of figuring out the answer is contradictive and paradoxical. If they Can't be wrong and anyone else who tries to mess with it is wrong then it's a paradox.
Dr. Lincoln, what is the most significant question or questions relating to quantum entanglement that have not been scientifically answered as of yet? Question or questions that are important to you for any reason, I have many but yours would be very interesting to me.
Could the entangled particles be joined in a higher dimension ? If this higher dimension was consciousness , would this also explain the “ measurement problem “ ?
I recommend Sabine Hossenfelder's channel for physics. Although she's German, she's far more articulate (in English) than most native speakers. She's also very intelligent, so her understanding and explanation of topics is at a significantly higher level than what you typically find on RUclips.
I've been wondering about the quantum entanglement for years. This is the best explanation ever. Great script and animation for easier understanding. I appreciate people worked on this great video.
It seems to myself the two entangled say particles are like a cogs one is spinning clockwise the other anticlockwise then take them apart they stay synchronous with each other in all directions when measured However if they become out of sync or asynchronous in all directions they would loose mesh with each other and would break the wave function the synchronization Sorry for the gearbox analogy it was just a random throught floating around
Dr. Don, It literally makes my day when I see a new video of yours has been uploaded. Thank you VERY much for all that you do!
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I love this guy. I understood maybe 20% of the information he talked about, but I 100% know he’s the man .
As they all say, before the measurement you CAN'T know what the configuration of the particle is. In other words they cannot prove that this phenomenon is real. Attempts at proving that the phenomenon is real have only been carried out by varying a measurement of an already set configuration, so there is no proof at all that this phenomenon is real.
I'm just a cabinetmaker and writer of novels, but I love that you explain physics in a way I can understand. (mostly lol)
Multi-skilled!
Thank you. This is the very best explanation that I've heard as to how Bell's Theorem detects that entanglement is not due to hidden variables. Great explanation!!!
That was the most original (and unusual!) way of breaking down QE I've ever witnessed.
Dr Lincoln's creativity is simply as infinite as the Unobservable Universe!
That was really helpful, can you just explain that part again about everything?
Me too. It would help if my mind wasn't blown by the video. But heck, if Einstein found it weird...
Lol. I would appreciate it if he focused more on each sentence he said.
Is that you Fry?
Hahahaha
The top two comments I was like, wait. Who the fuck are these people and what language are they speaking and I’m jealous. And then this comment. Thank god for it
Rewind the video
What blew my mind about quantum entanglement is that entangled particles have the same wave functions not just in space but also in time. Thanks for posting a video about it Prof. Lincoln.
Drop a pebble in a complex (real+imaginary) pond at low signal levels and square-law quantizing detectors, and un-blow your mind.
@ It is not interesting to regard the history of physics with the aim of deciding who was the best, a champion is not enough for physics. E.g. Schrödinger's articles published after EPR are an essential contribution to our understanding of entanglement. What would have been QM without von Neumann (hence Hilbert), Dirac, Feymann, just to name a few and not mentioning too many?
From our perspective what is relevant is all the contributions of those people, and we are lucky to have *all* of them.
There are no sine wave functions in this explanation.
There is no space and time, it's just spacetime.
Sending a message faster than light...
On the sending end, we measure up/down, when we want to say "1" and we measure left/right when we want to say "0".
Just measuring 1 time, won't tell enough, but measuring 100 times, would fast let the recieving end see a pattern.
Sender and receiver makes an agreement. They each have a box of great many entangled particals, where they have one of the entangled pairs each.
Every hour, the sender will measure 100 particals. If they measure them to 1, then in 10 minutes from now, we will transmit a message.
If the measure is 0, we wont transmit any.
And then when the message is send, we just use regular computer messages, each bit requiring 100 (more? less? sure) mesurements, to determin if its a 0 or 1 being send.
I knew if I kept revisiting this subject I would eventually I’d gain a greater understanding. Thank you for being the first I’ve seen to break down vital details necessary for the average person (interested in this) to understand more meaningfully. You have been so helpful!
Thank you Dr. Don, you are an exceptional person and scientist.
I'm grateful for the thoughtful and clear explanation .
I would really have liked an explanation on why the wave function and hidden variables hypothesis gives different prediction of probability at say 20 degrees angle?
Veritasium: "Quantum Entanglement & Spooky Action at a Distance" ruclips.net/video/ZuvK-od647c/видео.html
minutephysics: "Bell's Theorem: The Quantum Venn Diagram Paradox" ruclips.net/video/zcqZHYo7ONs/видео.html
Think about it in terms of rotating both detectors instead of just one. If you rotate detector B 20 degrees you get X% difference, if you rotate it -20 degrees (i.e. 20 degrees in the opposite direction) you get the same X% difference. So if you assume hidden variables, then rotating detector B 20 degrees and detector A -20 degrees should yield no more than 2X% difference (since the particles are just following their hidden variable programming and neither has any idea what's happening at the other detector).
If you picture both detectors rotating simultaneously in opposite directions, the percentage difference should be a linear progression as the difference from detector B is always equal to the difference from detector A. But quantum mechanics predicts *greater* than the 2X% difference (based on the overall angle of separation between both detectors), which is impossible unless the particle at detector A "knows" the angle of detector B and vice versa.
Someone smarter can feel free to correct me, but I think that's the gist of it :)
@@RoboBoddicker could we not measure one particle in a certain position and hold for a specific amount of time and then measure the other in all directions and use the angles to send information? (This is assuming that the angle as stated in the video is a real angle and not an analogy to explain stuff easier)
@@SkyWave32 Once you measure the particle you change it's state (the wave function collapses). So after you measure the spin against the chosen alignment you cannot inquire any further what the particle's spin was before the measurement. Think of it trying to put a piece through a shaped hole. Either the piece fits through the hole and becomes the shape of the hole or it doesn't and becomes the exact opposite. Either way it can no longer be changed.
edit: fixed my analogy a bit just to make it super clear
It’s the same as his explanation for 90 degrees in the video. The point is that it doesn’t matter how you measure the second particle, it will have the opposite spin from the measurement of the first particle.
I watched many videos on these. This is the most explanatory one. Thank you Dr. Lincoln and FermiLab members who made this possible.
Yeah same here.
A physicist friend of mine said this to me about the subject, and I'll never forget it:
"It's only 'spooky' if you think about the behavior from a human's temporal point-of-view. Because for the photon, the events of entanglement, separation, and measurement effect all occur at the exact same time."
It is true that from light's "point of view", there is no passage of time. Quantum comms are still 'spooky' though, in that all macroscopic phenomena are limited by the speed of light - to anything with mass, time does exist, and light speed is a limit to transfer of information - yet quantum information travels infinitely fast. So how is it travelling? It's not by light - because as Don explains, that's been tested for and ruled out - it travels 'instantaneously'.
However, the whole thing has never seemed too bizarre to me. The universe started from a single point of space-time, so it doesn't seem too implausible (to me) to suppose that stuff going on 'under the hood' has remained 'connected' in some fashion. And as Don says, it doesn't break relativity because we can't use this mechanism to break the speed of light limitation on movement of mass or information.
And then too, I always found John Cramer's "Transactional Interpretation" of Quantum Mechanics to be more plausible and pleasing than the unreasonably-popular "Copenhagen Interpretation" (which has hung around well beyond its sell-by date mainly because of that bloody silly alive-and-dead cat being sexy to layman types). In addition to that, TI is mathematically more aesthetic - by interpreting 'negative time' solutions as being "information travelling back in time", rather than ignoring it as "obviously nonsense" (as Copenhagen and other interpretations do). Kids get told off for ignoring 'the other' root, and imaginary numbers seem to be 'used' in the universe, so it seems dodgy to not try to interpret them.
Those signals ('advanced waves'), travelling back in time can form atemporal 'handshake' communications - which neatly explain a lot of 'spooky' stuff like the double slit experiment, that bloody cat, and perhaps spooky action at a distance, all in a more (to some, anyway) philosophically pleasing way, i.e., without requiring infinitely branching universes (Many Worlds), or the existence of intelligent (?) observers to actually make anything happen or the universe exist.
See Wikipedia < en.wikipedia.org/wiki/Transactional_interpretation > or the 1995 book "Schrodinger's Kittens (and the Search for Reality)" by John Gribbin.
as a skeptic, I wonder if you even have "physicist friend"
If you watched the video that is called hidden variables and has already been accounted for and disproven so your 'physicist friend' is wrong
It's made up by mathematicians.
@@jonz23m That's nothing. The entire universe is a figment of my imagination, and no one can prove me wrong, so it must be true! 😁
I'd like to thank Jada PS for bringing me here. Now I learnt something new and now I understand what she was talking about...2 particles in a single wave pattern. Brilliant!
LMAOOO
That's freaky action at a distance, not spooky (unless you are Will of course).
This is the first time I have properly understood the concept, although had seen many videos on the topic earlier. Thanks a lot for the lucid explanation! Really mind blowing.
I'm curious to see how/why hidden variables yields straight lines, whereas quantum mechanics yields a sine wave.
Lack of data points so they join the points with straight lines (isnt this what plagues all physics?); at a more subtle level this is fundamentally what is wrong with Quantum Physics we only have data at the points of measurement he he
I thought I missed the explanation at first for the straight line prediction, but I researched and didn't find it
The mathematical functions for hidden variables and quantum mechanics are continuous, so there's no need to join points or "extend the function".
The real difference is that the QM function is probabilistic, and as such yields a gaussian distribution. The HV function is fully determined by initial conditions, so there is no probability game into play and the percent of what's measured (amount of measurement agreement) increases linearly to 100%, then decreases the same way.
Given that QM yields a line that fits the experimental results much more closely, the scientists conclude that QM is better for describing the phenomenon and making predictions about it.
I see it as a problem with how they are imagining the hidden variables. If you have a random vector being detected it has a probability as well so Hidden variables can create sine waves.
If you assume the hidden variable is not time-varying, you get the anticipated straight line. But if you allow time-varying hidden variables, and admit that time-keeping varies from one location to another, then the time-varying hidden variables drift in and out of sync (e.g there is a non-vanishing "beat frequency'), and the straight line model gives way to the one we actually find in experimental measurements.
This is the clearest and most understandable explanation of the topic that I've encountered. Thank you.
You explained everything except the most important part, which is why the hidden variables and quantum mechanical predictions are different.
are you talking about the pilot wave interpretation?
The triangle wave is linear. But the wave function is sinusoidal. Linear would be two separate clocks where you reading them at the same time. The graph is linear because you're dividing. Say 12 divided by 1 oclock.
The idea is (as far as my layman mind can grasp it):
Hidden variables tells you that the two spins are in opposite directions, and the first one is "closer" to spin up than the second, but you can't know the actual, original spins.
Quantum Mechanics says that when you measure the first spin to be up, the other one BECOMES spin down - without any probability weirdness. So you don't need to integrate over all possibilities - there is only one. And thus the result is different.
+1
There's a video that explains it !! its from veritasium ,and he explians the experiment, and how the probabilities work
6:15 - 8:08 This is probably the most important educational physics video on RUclips, by virtue of the concept it explains, and especially the apparent paradox it reconciles.
Intriguing video. I took high school physics about 40 yrs ago, so I don't even know if this is even an intelligent question, but here goes: How is the spin of a particle observed or measured? How do we know that particles only spin up, down, left or right if we can never observe such a small thing?
When we measure the spin of any particle we are actually interacting it with field which means there are other particle involved ( meausuring device), thus measurement is another entanglement.
Oh boy
Yes, the observer also obeys the shrodinger equation and becomes entangled with the object being measured
"No matter where you go, there you are." - Buckaroo Banzai
Corollary: No matter where you are, there you go.
Hmm
@Mr. H impossible, you are always moving.
This is such an underrated channel.
This is the clearest presentation on this subject that I have ever seen.
Interesting how Einstein made such significant contributions to quantum mechanics with his papers on Brownian Motion and the Photoelectric Effect, yet he is always remembered for his "God does not play dice" remark.
The video doesn't cover why the hidden variable must result in that particular probability line. At a surface level, it feels like there should be forms of hidden variable(s) that would deliver a curve similar to quantum mechanics.
You can't use a random function for describing any hidden variables. In this particular case, you have a result (value of measurement for the second particle) fully depending on the measurement on the first particle (because at the beginning there are only 1 blue and 1 red balls, so if one is red/spin up, the other must be blue/spin down). So the equation needs to be y=-x or more in general y=ax+b, which is a straight line equation
Yes, I thought very similar.
@@TheNasaDude You just explained what I disagree with.
See Sabine H. I think what's going on is the hidden variable is what you measure. "What a quantum particle does depends on what measurement will take place. The 2022 Nobel was likely for proving Bell Wrong. See Measurement Independe. See Sabine H.
@@TheNasaDude This is important: "What a quantum particle does depends on what measurement will take place." - Sabine H. It's likey Bell was proved wrong because he assume measurement independence. What if you understand what Sabine's saying what i am saying might make sense.
I feel like you didn't truly go into depth about what the hidden variable theory would predict, and what the results truly show us, for example if measured at the 45 degree angle.
Another video showing a proof of Bell's inequality would help, I feel.
I would definitely love that. I never understood why hidden variable theory is supposed to be wrong and just stating that's what it'd predict without any explanation whatsoever makes the whole thing unconvincing for me
The best video I remember is from Minute Physics, but Veritasium also did one.
I don't think Space Time or Science Asyluym did one, but I am not 100% sure.
At least not until you measure me :P
I would guess. The hidden variable theory is linear like dividing times on a clock. A moving clock hand does not turn sinusoidal compared to the angle or time. It turns linear. But the wave function is sinusoidal compared to the angle.
My understanding of quantum entanglement hinges on knowing why the idea of hidden variables doesn't work. This helped that understanding, I see how the predictions are different, where one is a triangle wave and the other is a sine wave. Still don't know why the predictions are different.
That's in the graph at 12:50 -- I don't understand why you would even request that. Or do you mean measuring the first particle at 45º? That's trivial, we know the result: 225º for the entangled couple.
I was actually pleasantly surprised to NOT learn something new from one of your videos (for once)! This makes me feel like I have a decent grasp of this topic. I don't think this is going to hold for the quantum teleportation video! :) Could you also do one about quantum encryption? I feel like that would be both fascinating and enlightening. Thanks for the great videos!!!
One of best general explanations of quantum entanglement I've seen on the web.
This is one of the best plain language explanations of Bell's inequality ever done. Thanks!
It feels errant to say "therefore information can travel faster than light". Why are we assuming anything is being transmitted? What if these two point-like particles are intersections of some other higher-dimensional brane?
Why are we even assuming that space time is anything but a perceptual construct?
Why are you assuming that reality exists and it's not just a flux of ideas projected in your mind by God?
Do you think theorists coming up with concept of "brane" gave it such name just to troll? ;)
Anyway, to be specific, it's "quantum information" and "traveling faster than light" is just a shortcut, a stopgap (like dark energy and dark matter) - a plaque saying "fix me". Don't know much about super- theories but wouldn't brane fall into hidden variables category?
Why are we even assuming pineapple pizza could taste good.
@@charlesjohnson9879 Because it's not the matrix.
I see that the quantum entanglement “red bell curve” is different in shape than the hidden variables “blue pyramid”; however, I don’t understand WHY they’re different. I think that extra bit of information would’ve been great to help us compare the predictions made by both interpretations, but perhaps it would’ve taken too long to go into the math that determines those probability predictions?
That's letf out because the only way to explain it is with math i think.
This guy explains that part in his video
ruclips.net/video/-WSWz1H3mJg/видео.html
quantum entanglement can be mesured as data and hidden variables are posibilities, so it's a perfect "line", data vs predictions
This was fascinating, and very well explained for the most part. I really like that you just didn't explain it, but you also explained the experiment. Although it's still hard to wrap my mind around it, it's definitely better than not knowing how this was measured at all. (I'd still like to know more about how those two lines colored lines on the graph differ, though!)
Yes I understand why hidden variables gives the graph that it does but not 100% sure why quantum physics would predict the other graph. That would be a nice video for the future
For that same reason, I actually did not like this particular video. TBF, I didn't find a video yet which explains the experimentation and meaning behind it properly, just the inferences of the experiments, analogies and what it means for the phenomenon of Quantum Entanglement.
@@_sayan_roy_ Yeah, I get you. It's a complex topic and there were some good explanations, but the graph itself is not explained, and I'd like to see how those differing lines are arrived at (which was not done here...or apparently, anywhere else that is easily assessible and made for regular people).
@@Rationalific Hey, I got one Veritasium video which made me understand quite a bit, of course, after pondering a lot on that by myself. The video is 7 years old and you can search by quantum entanglement or spooky action at a distance. There is a video of Sabine as well but not as good as Veritasium's, on the details we want.
@@_sayan_roy_ Thanks! I'll check it out.
Best video on quantum entanglement I've seen so far. Well explained for dummies as well as deep facts for physicists.
This helps a lot. I’ve taken several science for dummies courses on physics including his Theory of Everything with the Teaching Co. (No, I don’t even know anyone working for them.) However, I’ve struggled to understand this even after five or six courses for science dummies. This is simple and fascinating. By the way, it’s hard to blame Einstein for being bewildered by this and calling it spooky action. And he had a very human overreaction to it by not liking quantum mechanics or theory. (Dr. Lincoln gave a reassuring explanation that would probably reassure Einstein (and the rest of us) that he could appreciate his relativity and quantum mechanics.) Thanks for a great video!
Thank you Dr. Don.
B...but have we understood this property we're calling "spin" well enough to try to reason so much more about it?
Well we know that it's not physical spin, because we're talking about point particles with r=0. It's a specific property that we just call spin to make visualisation easier. That said, we know little more than that about spin, besides that it can be -1, -1/2, 0 , 1/2 or 1 (also values chosen for ease of grasp). Same goes for charge. We've figured out how it works, but what it is exactly? Scientist still cannot answer that question. What scientists do is make up theories that fit current data, and are testable for new variables or refinement of known variables. It's the only way forward on the path of knowledge.
Yes. Spin is an abstract form of angular momentum. And it is one of the bedrock principles that angular momentum is conserved. This is why if you measure the spin of one particle to be up, the other had to be down, assuming you specify the same direction in each measurement. What Bell showed is that the correlations observed cannot be reproduced by pre-assigning all possible outcomes to the particles when they first separate. This, combined with the purely randomness of each measurement in isolation (meaning they appear random at each end, but when the observers compare notes, spooky correlations emerge), rules out hidden variables.
Here's a video that goes into more detail about that, giving examples of how hidden variables fail to explain the data:
ruclips.net/video/ZuvK-od647c/видео.html
Listen, I'm still in high school and hadn't had physics in about 3 years. The last time I had it I almost got a D on my report card. For some reason I gained an interest in quantum physics.
I would like for you know Dr. Don that your videos are amazing! I watched a lot of them and learned so so much! You explain it so well and eventhough English is not my native tounge I can understand and follow them very well. Thank you so much for these great videos. They make to facinating world of quantum phyics so much more accessable! Thank you.
For me, this was your best video. Quantum mechanics, prooves that the world is material and dialectic. This means that always is an existence of cause which is going to give e result but it is impossible to predict the exact probability of this result till it happens.
You say earlier on in the video (6:10) that measurements have shown that the information from one particle is transferred to the other faster than the speed of light. But at the end (13:34) you say that communication faster than the speed of light is not possible. That makes no sense, and you are contradicting yourself. Please can you clarify. Thank you.
I need to buy the whole collection of his t-shirts!
Isn't it easier to assume we lack knowledge about (opposite) rotation, than to assume things travel faster than light? Couldn't said particles be set off in specific opposing rotations that we lack insight of?
No, that would be hidden variables
@@ekotar1 Instant communication good, hidden variables bad?
That is what is called determinism.
@@ekotar1 Hidden variables have not been ruled out. See Sabine H.
@@paulmichaelfreedman8334 Super Determinism is the right path.
.... it doesn't need to travel ftl, you can't compare the effect until after both measurements are made and you have brought the results together, we just get confused about it since we think of ourselves as being seperate from the wave function, when we are all part of it, the perception of it being probabilistic is just observation bias
I would compare it to sending 1 glove from a pair to 2 people far apart from each other. If person 1 opens theirs and it's the left glove, the other person immediately knows the other one is the right glove. No data has been transmitted to either person
@@dcquence That analogy is misleading, as which side is being sent which glove is theoretically knowable at the point where the gloves are packaged aka, hidden variables. Both of the possibilities happen, we know this from a variety of external tests where, as opposed to examining one particle, we make them interact with each other and see their interference, it's just, we have a huge bias against applying the math to ourselves when we interact with one of them, and get into the same superposition as it is in, at which point, we should not be surprised at all to find that interactions with someone that interacted with th other particle are consistent
Yah but how does the second person KNOW the first person has a left glove. How is that information being transmitted faster than light
Further, that analogy would require that person one could suddenly make his left glove a right glove, and that persons twos glove would immediately become a left glove
And they wouldn’t, plus the analogy breaks down in usefulness because gloves can’t switch left/right orientation
QUESTION: If the first particle is measured "up" and the second is measured "left", the angular momentum sum is not zero. Why does that not violate the conservation of angular momentum?
The sum is zero if there was no spin before the decay. This is accepted.
I have a simple question. If you are constantly looking at 2 entangled particles with known opposite spin direction, and you changed the direction of one particle's spin, would the other also change even though you did nothing to that particle?
You can't do that experiment. As soon as you measure a particle's spin, the particle is absorbed. All you can observe are the statistics of millions of particles.
@@david203 Wrong. See Sabine H. You can change the spin w/o measuring it. They've done it.
You can change the spin of one of them w/o measuring it. It doesn't do anything to other particle. See Sabine H.
@@ragnaarminnesota6703It is true that you can change spin without measuring it. Everything I wrote is true. You probably just don't understand QM. That's understandable.
@@david203 Reread everything. You said you can't do that experiment. Sabine was arguing against spooky action when she said what I am repeating. Given this video, are you arguing against spooky action? The PBS Space time guy said Einstein was proven wrong by spooky action. Was he?
Could you talk about delayed choice quantum eraser experiment?
Answers with Joe made a great and funny video about it
Yo is this about jada and aug?
Yup, she's been getting some Spooky Action distant from Will's eyes.
Newton's gravitational force was also "spooky action at a distance"
That's what I tell people as well. People seem to misunderstand Einstein's comment, thinking that he was somehow scared. In reality, he called it "spukhafte Fernwirkung" in clear reference to what you mention. In German, Fernwirkung is legitimate physics terminology for the forces of Newtonian mechanics, i.e., forces acting instantaneously over finite distances. Wirkung in this usage comes from the old times, when even Newton was calling forces "actio." Given the context, I would assume that Einstein really meant it as a derisive description by putting a quantum phenomenon in the same category as a discredited idea from classical physics. The "spooky" is just added to emphasize the joke, to make it clear that he didn't really think that's what's going on.
@@noeckel I still think that Einstein is wrong by saying that light is constant, light is proved by quantum entanglement not to be, whene they say that 2 atoms are in 2 places at the same time, they see such effect because light goes IN then goes OUT way to fast that in a matter of a very, very, very small fraction of a second it comes and goes to where it needs to go so they only see the atom whene it stops in one side then whene it stops in the other side cause the atom acts as a marble in a band that goes in one direction then stops to change to the other side. Atoms entangled are like a band whene the up side goes left the bottom side goes to the right.
@@noeckel light dobles each time that is why gravity in a free fall the speed doubles each second. The serie PHI goes kind about the same but not realy, you now 1pluss 1= 2, 2 and 1= 3, 3 and 2= 5 and so on that in a matter of few times passes light speed anlist the numbers.
@@noeckel vielen dank for your comment, I like the original version of "spooky action at a distant", to foreigners it really sounds "scary" :-)
@@Motorfirez gravity is the results of space-time bending and the variations of the bending (gravitational waves) propagate at the speed of light. Relativity sets the "speed of light" as the speed limit of causality, this is why quantum entanglement is out of rule.
I dont think that information is transported. What I mean: When you entangle quantum objects than you put them into a certain state. Than you can move the quantum objects apart. You don´t know what state these quantum objects are, but you know that if (for example) the spin on one object is to the left, the other must have a spin to the right. It is because you have prepared this behavior at the time of their formation (when they where close together). Information would be transported if when the objects are far apart and you change the spin on one object and the spin on the entangled other object chances. But as far as I know this is not the case.
exactly!!!
Watching it today 05.07.2020. This is the best explantion one can deliver. Thank you Fermilab and Linclon.
Thank you for giving today's date. I wondered when I was.
8:13 could it be that the 2 particles are merely 2 lower-dimensional projections of the same higher-dimensional meta-particle?
Interesting
Why, yes, it is entirely possible. 😮
"This video is long".
No, Dr. Lincoln, none of your videos will be ever long enough.
came here to say this
OK Dr. Don, gonna ask it anyway: What about Shrödinger's dog?
Thanks Don, you're the only one that explained this in a way that I was finally able to understand. You're the man!
I dropped physics last school year as we had a few topics in class I didn't totally understand and now I am grievously sad because this video made me want to have physic lessons at school again.
It sounds an awful lot like a plain old "IF THEN" statement in some sort of natural rendering engine.
Would make sense since the coding language processes faster than the simulation
Chaos worship going on in your thumbnail.
Seems Dr Don is a Tzeentch worshipper. Heresy
Quantum entanglement is a sketchy thing. Finaly this video connects it with worship of chaos gods. Should i now prepare to see The Pope as follower of Khorne or Slanesh?
Posted 49 seconds ago, yet already 30 views. Yay, science!
Would you please make video about Light interference pattern?
As far as I know interference pattern is different when we are observing and when we are not.
Damn, equally weird phenomenon...
Hexanitrobenzene yes
Real good comprehensive explanatipn on quantum entanglement. Thanks to prof. Don.
❤
Let's try different model for hidden variable theory.
I have two unique balls, one blue and the other red. I place both inside sealed containers, so that you can't tell which is which until you open them. My brother chooses one of the containers at random, and flies off light-years away into a spaceship. I sometime decide to open my container and I find the red ball. I instantly know that my brother has the blue ball. No information traveled faster than light.
EDIT: Omg, you used the same example! Now, that is probability in action.
EDIT2: Oh well, I stand corrected. I was using the hidden variables hypothesis without realizing it, and it turns out to be false.
That's the hidden variables hypotheses.
Quantum entanglement is this:
You have two unique balls, both balls can have any color you wish. You chose one to be red and the other blue. You put them in boxes... you send your brother light years away... and before you open your box you start changing the color of your ball. So now, how would you instantly know the color of the ball that your brother has?
Exactly... You can't.
Your brother's ball can have any color...
So anyway you start changing the color of your ball and your brother opens his box and observes the color of his ball changin too! And not randomly but according to the color that your ball has... So when your ball is red his ball is blue, when your ball is green his balls is yellow, when your ball is pink his ball is orange etc...
In this case you can't instantly know anything, so you might have to conclude that somehow the other ball knew how to change its colors to correctly match the "opposite" color of your ball... So information about the state of your ball was traveling faster than light to reach the one your brother has!
I was thinking same thing
@@-_Nuke_- Very nice analogy, thanks!
Actually, no; what you (and Don) described is simply 'maximum correlation' - which, in QM, is represented by some vector in a _maximally_ entangled subspace. "HV" refers to the possibility of using classical probability distributions to describe the QM results - different thing altogether
That would mean that nothing is traveling from one particle to the other but that it was already there such as an outreaching entangled quantum field!
Could it be that nothing is transmitted, but that the wave function collapse collapses backwards in time? This would allow the entangled information to be shared at the moment of entanglement, correct?
You just discovered the key to time travel!
Great video as usual! Now I don't have much knowledge about quantum mechanics but I have two questions, firstly has there ever been an experiment that proves that information is transmitted faster than the speed of light ? and if so how was it conducted?
Secondly, if hypothetically, there was a way to take a bunch of entangled particles and store one of each pair in a way in which they couldn't interact with anything else, separate them by a lightyear or whatever and have two people measure their spin in only the vertical direction. The two people agree to measure their particle, say every second but the second person measures it 0.5 seconds after the first person. Couldn't the first person's measurement ( UP or DOWN), be read as ( DOWN or UP) by the second person and if they agree that UP is 1 and DOWN is 0 or vice verca, wouldn't that enable them to communicate in Binary instantaneously over great distances? There must be some information I'm missing out on but if someone could explain why it isn't possible that would be cool :)
See Sabine H. There is no FTL comminication. C is the speed of like. What does the C stand for?
hi.. Sorry but i have to disagree with you on that you can not use this to transfer information. I will attempt to explain how to use this to transfer information. Lets assume technology is advanced enough so we can read the states of these entangled particles relatively quickly, although the speed of measurement does not invalidate this theory. If we had 1 particle on a mars rover, and 1 particle here on earth (lets say). Both particles are being measured at a default speed of say 100Hz. Lets assume Up is a 1 and down is a 0. If here on earth i want to transmit a 0 followed by a 1, the transmitter(earth particle) would ramp the measurement speed to say 1khz, the receiver stays at 100hz, the transmitter would continue to measure at this higher speed until it got a result that is down, the transmitter would then not measure again for 1 clock cycle of the receiver, the transmitter would repeat again of measuring at the high speed throwing away all the measurement results if it was up then hold again when a down is measured. If this is repeated about 10 times the receiver would see a block of downs. If the same is then repeated for up (i.e the transmitter throws away all the measured downs and hold on up), you have then transmitted at a relatively slow baud rate the bits 0 followed by a 1. The only limit that determines the baud rate of data flow is the rate at which one can perform a measurement on the particles, but nevertheless whatever the baud rate, that data was transmitted faster than light.. I hope you get a chance to read this and comment.. Many thx...
Troll.....😂
So, quantum entanglement is not local because "data".
Most unsatisfactory ending since GoT...
Lol. Seriously, I just laughed out loud at work. Thanks a lot. 😆
@@nickgivent3157 you're welcome.
Quantum entanglement blew my mind at one time .then I started believing in simulated universe theories and everything started making sense.
Well shit.... That does make alot of sense.
But if the first particle's spin is vertical (up), simultaneous measurement of the second particle's spin shouldn't be horizontal since it isn't opposite to the vertical spin of the first particle. (11:30) If the first particle's spin is up, then the second particle should be down, not at a horizontal angle. The fact that the spin of the second particle isn't down shows that the particles aren't entangled -- because their spins aren't simultaneously opposite to each other. Apparently, two simultaneous measurements can be made with spins in any direction, not just opposite to each other, so actually, there's no entanglement.
If spin is "up in the vertical" that tells you nothing about the spin in the horizontal. Worse, if you measure along the vertical and then along the horizontal, you lose all information about your first measurement. The same applies for entanglement. Perfect correlation only happens if you measure along the same axis.
@@narfwhals7843 ~ But the second particle shouldn't have a horizontal measurement if the first particle's measurement is vertically up. The second particle should only be down if entanglement is occurring. If the second particle's spin can be measured in any direction (not just in the opposite direction) to the first particle, where's the evidence of entanglement?
@@FrankCoffman Spin is _always_ up or down along the direction you're measuring. That's one of the reasons it doesn't really have a classical analog. If you're measuring along any axis, you're forcing the particle into that spin state regardless of entanglement. If you measure both along the same angle you force both into the spin state along the axis, and they always come out with the predicted correlation. The evidence of entanglement if you measure along different angles is still in the correlation, which is then related to the cosine of the angle.
Is the wave function a mathematical description or is it a "thing" that causes change itself, i.e causal? I cannot see how it is causal, which is implied by some of the "explanations" talked about. Non-locality remains as the most weird thing in the ultimate nature of existence, still.
I wish I was half as smart as Don Lincoln. Then I would be at least 10 times smarter than I am now.
what he says makes no sense. Be ok. You are smarter then him, that is why you do not understand what he says. Means you correctly get that it makes no sense. He is fermilab, he is the main stream.
Move to Trump country and raise the average IQ in both places.
Don't listen to science deniers like lukas. Even at 1/20th as smart as Don, you're already 100 times smarter than the science deniers around here.
@@EnglishMike mike tell me, what is the smallest particle that is influenced by gravity?
hey fother mucker how are you doing? I just thought you could be happy to by one hour slot via skype to heal the wounds you carry.. 60usd/hour special price for you.
OK THEN. NOW HOW TO WE CHANGE THIS TO MAKE WIFI FASTER??????
The final conclusion drawn from all this, all you need is love.
I want to get there in my studies some day. It is great to find a video like this in a situation where my instructors only killed my interest in physics.
Love the shirt... Fermilab is great; This is my 2nd time viewing all of the uploads. Thank you for making Physics fun.
I just like to avoid any Imperial entanglement..
That'll cost you extra.
Chaos symbol detected! Purge the heretic!
Thanks for the lecture. I have a naïve question: Suppose you have three particles. How do they know which one to pair with To form the quantum entanglement? Thank you
If you have three entangled particles, they are all mutually entangled. You're welcome.
So, question… why is the Hidden variable graph linear while the quantum mechanical graph sinusoidal? Wouldn’t they both be sinusoidal?
I agree. There is no reason to think that correlation must be linear. If we think in "particles" as waves (as de Broglie suggested), why could not found hidden properties which depend on sin(x)?
Yet, some would have us believe that government is not capable of anything.
Fermilab is under the US Dept. Of Energy.
That makes Dr. Lincoln one of those "bureaucrats."
He is a scientist. I'm very proud to see my tax dollars go to this national lab. This is a national treasure.
Keep up the great work.
The very first time I learned about Quantum Entenglement, my mind just exploded!
This man's explanation is the best i've seen. Thank you so much!
Thank you!! One of the best no bs explanations of entanglement and Bell's Theorem!
The best video on entanglement thanks to 12:00👍
Hidden variables > Bell theorem, though.
What if you use sequences of measurements to create statistical skew?
If you use 3 entangled pairs and measure the first one for up/down spin it would be 50/50 until you measured it. As would the 2 others. If you got a up, you measure the second while knowing the other end measurements on the entangled particles would be a down for the first one. If the second is an up as well, you measure the third. You thus only perform all 3 measurements if the first two are up's. Measuring on the other end will then give a 50/50 spread for first value always, but you will know that if you get a down, the second measurement will be determined as opposite of the first since it will also have been measured. The same goes for the third assuming second was also a "down". Depending on how you look at this you are either picking possible outcomes, or you are just increasingly less likely to measure. I am wondering if the odds of measuring downs on second and third coupled measurements are affected by this decision or if the outcomes are still 50/50 but you now know what they were in first set of measurements.
I wouldn’t utter another word until you are thoroughly conversant with the Electric Universe and the work of Halton Arp.
The point at which the spin of entangled particles is determined is when the wave-function of the measurement device becomes entangled with the wave-function of the particles. It doesn't matter which particle is measured because both entangled particles share the same wave-function. The crucial point to understand is that these wave-functions don't travel through physical space-time, they propagate instantaneously throughout Configuration Space, a complex-valued domain of potentially limitless numbers of dimensions where the wave-function is defined. No information is transmitted between particles in physical space-time, all entangled particle properties derive from their entanglement with the measurement device in Configuration Space. Thus, there is no information that travels through space at any speed, hence nothing that exceeds the speed of light.
What we observe in relativistic space-time is the quantum mechanical projection of events that evolve deterministically in Configuration Space. Such events appear random to us because the projection into space-time is probabilistic rather than deterministic. In short, the universe we observe exhibits non-local realism, exactly as demonstrated by Bell Inequality experiments.
@12:44 "Quantum mechanics is correct and the whole idea of hidden variables is completely ruled out."
That is an objectively incorrect claim, and it was the Nobel Prize-winning experiments of Bell's Inequalities by Aspect et al that proved it wrong. Reason being, Dr. Lincoln fails to distinguish between local and non-local hidden variable theories. While local HV theories do indeed make incorrect predictions, non-local hidden variable theories were demonstrated to be perfectly consistent with quantum mechanics, just as John Bell himself emphasized.
Bell assumed measurement independence. A Mach-Zehnder interferometer has been used to show that's not always true. See Sabine H.
@@ragnaarminnesota6703 - Invalidating measurement independence is legitimate, so long as you're fine with undermining all expermental science in favor of superdeterminism. Personally, I prefer science to predestination.
@@QuicksilverSG "In short, the universe we observe exhibits non-local realism..." Science with non-locality. I have decided FTL isn't real. Do you except determinism? If you don't, you seem to be knocking out one of the pillars of science.
@@ragnaarminnesota6703 The quantum wave-function is defined on Configuration Space, which is inherently non-local and deterministic. Consequently, all quantum events in Configuration Space occur instantaneously, without requiring FTL transmission of information across relativistic space-time.
Love your video. It's very instructive. When I think about the why of quantum entanglement, and how the spin measurement of one particle determines the spin of the other, at seemingly faster than light speed - there's a lot of "why" left on the table to explain. One idea that I think deserves more attention is quantized spacetime. If there is such a thing as quantized spacetime, then the particles of such spacetime would have the properties of superposition, and entanglement. In this scenario, two entangled electrons could exist in the confines of entangled spacetime. What appears to us as two electrons, separated by a vast distance, is actually local as far as the electrons are concerned. The entangled spacetime in which they reside, makes it appear to us that the electrons are far apart - when they are actually right next to each other. In this hypothesis, there's no violation of special relativity. And most importantly, no violation of causality. The entangled spacetime implies an extra dimension that we cannot see directly - but this dimension manifests in such a way that two electrons, from our viewpoint, can be far apart - and yet appear to be communicating faster than light allows. To take physics to the next level - it's my opinion that the key problem to solve is the "why" of quantum entanglement. Quantized spacetime may offer an answer. Quantized spacetime may also help with ideas related to quantum gravity - which is another reason to further develop this field of study. The one thing we do know, that we cannot allow in our theories, is a violation of causality - because if that happens, Physics becomes a land of anything goes. Please carry on.
The explanation lies in a single word: relativity. If you don't understand why that's enough, then you are simply admitting that you weren't paying enough attention in undergrad physics.
@@lepidoptera9337 But the "why" behavior of quantum entanglement does not lie in a single word. However, I don't think special relativity is being violated by QE. That's why it's such a puzzle. How to reconcile the apparent contradiction? Something else is going on that perhaps involves additional dimensions arising from quantized spacetime, or perhaps the so-called many-worlds hypothesis explains QE's apparent faster-than-light collapse of the wave function. Or maybe, as some have speculated, the wild idea the QE creates the spacetime in which it operates. In any case, causality must be preserved - which implies that special relativity must be obeyed. And here we are in 2024, and we still don't have a solid explanation for the apparent violation of SR by QE. Instead, we have a lot of head scratching - a few ideas on the table - and a mystery with no definitive answer.
That was a very clear and easy to understand explanation of quantum entanglement. There is some kind of link between entangled particles. When that is understood, other mysteries will be revealed.
So the graphs show that spin is not always conserved, that the spins are sometimes measured both up or both down. Is that right?
I get it, but I don't understand it! The thing that confuses me the most is the measurement of the spin direction. How can you truly determine what direction you are measuring in a 3 dimensional space without a frame of reference? I imagine it to be be like floating in space, there is no way of knowing which way is 'up'? Someone please explain this to me as its driving me insane :)
At 13:05, '' the hidden variable is wrong '' .
Well, that's not true! It only means that the Bell test say LOCAL hidden variable is unlikely but there can be non local variable, like fields permeating the whole universe for example, at play!
True but since it's "common knowledge" that local HVs are what (experimental tests of) Bell's theorem(s) ruled out I would say that that's a forgiveable error in this context. The more serious error there in my view is the assertion that standard QM forces us to accept that there must've been some kind of ('spooky') transfer of information. There are other serious errors in this video too. Physicists are generally terribly ignorant of quantum foundational matters.
excellent explanation!!! It took me to watch several videos until I found this one and now I can understand it much better.
Best video on quantum entanglement.... Really helpful ❤
It would be nice to explain more about:
9:56 why the measurement of the 2nd particle is "Right or Left". Shouldn't it be zero? ;D
and 12:18 the reason for "Hidden Var" having a straight line. why it is a straight line?
1:53 if that's truly the case, let's say you assign two students to the exact same problem, but one decides to choose vertical and the other one chooses horizontal. They both get their answer and Student A's Up while Student B is right.
Once you find out the answer there's no going back and if it's to the same problem and the only variation is the direction then if both people are correct but it can't be anything else but what their answer is then aren't both people actually wrong at the same time.
As you've said before, once it's determined that the direction is up, any other direction is considered wrong.
Therefore if the person has a choice to choose a random direction and their choices, either up down or left or right once they've made that decision and figured out the equation based off of that limited contradictive measurement, then at that point the whole the whole way of figuring out the answer is contradictive and paradoxical.
If they Can't be wrong and anyone else who tries to mess with it is wrong then it's a paradox.
Certainly helps me visualize quantum entanglement. Well done.
Dr. Lincoln, what is the most significant question or questions relating to quantum entanglement that have not been scientifically answered as of yet? Question or questions that are important to you for any reason, I have many but yours would be very interesting to me.
Could the entangled particles be joined in a higher dimension ? If this higher dimension was consciousness , would this also explain the “ measurement problem “ ?
I recommend Sabine Hossenfelder's channel for physics. Although she's German, she's far more articulate (in English) than most native speakers. She's also very intelligent, so her understanding and explanation of topics is at a significantly higher level than what you typically find on RUclips.
And higher than this guy's. Spooky action has not been proved. 2022 Nobel Prize.