Where did the CSHS thing come from? What happens to Victor and what do these particles have to do with echother? In a significantly larger scale, apples, oranges, and peaches look like particles. Victor sends an apple to Bob and a peach to Alice. So what?
Bell did not assume "realism". In fact he pointed out himself (!) that his theorem is about models, not about reality. He instead assumed a second property called "measurement independence". This was pointed out among others (ironically) by one of the recipients of the Nobel Prize, John Clauser.
@SabineHossenfelder The algorythm just recommended this video to me after watching your most recent video. You must have collapsed our entanglement and this was inevitibility (let me tell you I don't understand quantum entanglement without telling you).
John Bell was wrong! The EXPLICIT information (information describing the waveform) is utterly deterministic. Free Will arises out of the complexity of the RELATIONAL information (the information regarding the interrelationships between the various wave-forms). BTW, I'm a fan of your channel!
I'm guessing new assumptions were thrown in so people don't make unrealistic conjectures arguing moot points. Love your dry sense of humor you put in your videos.
One thing that is interesting is how much Einstein influenced Quantum Mechanics, even if he did not agree with the philosophy behind it. The EPR paper was the end result of a series of arguments between Einstein and Bohr over the underlying meaning of QM. Einstein would present an argument against the probabilistic nature of QM, and Bohr would provide a counterargument showing Einstein where he was wrong. Eventually Einstein came up with the argument in the EPR paper that Bohr could not answer. Bell also did not answer it, but he came up with a way to, in theory, answer the question about which interpretation was correct. And then the three Nobel winning scientists came up with experimental ways to use Bell's theorem. Without the EPR paper quantum entanglement would probably never have been looked at and measured. So even when wrong Einstein made a great advance in science.
The operative phrase here is "in theory". What physicists are supposed to answer is "in reality". That is what the subject is all about: "physical" reality, previously "natural philosophy". I doubt theoreticians of quantum mechanics are claiming the theory is complete, so I fail to see how this proves Einstein was wrong. What he was saying sounds axiomatic to the whole field of physics. Give it up if you wish, but that is giving up "physics".
John Stewart Bell's birth town of Belfast (and, of lesser significance, my own birth town) has a street interestingly named for the theory rather than its discoverer: 'Bell's Theorem Crescent'. I discovered it accidentally on a walk around Belfast a couple of years ago and have often wondered if it existed on Google Maps prior to my observing it!
That's funny next time I'm there I'll look it up - so much work has been done in other places that are not Stanford/MiT .. I found out while in Manchester
As Einstein said, “If you can't explain it simply, you don't understand it well enough.” you have shown that you indeed understand this completely! Thank you for the simple explanation and the example for us to try.
Yes, I agree that her simple explanation demonstrates that she thoroughly understands this subject. The quote is often attributed to Einstein, but I believe there is no record of him saying it. The source of this quotation is most likely Richard Feynman who once said, "I'll prepare a freshman lecture on it. If I can't explain it to a freshman, I don't understand it."
I see lots of comments about this being a clear explanation. What am I missing then? I feel like there's a considerable amount of information missing about the experiment that is crucial to understand anything about it. A and B are sent a particle and measure x or y projection. x and y projection of what? Some vector? No idea, but I can accept that they measure some kind of quantity that, after normalization, can only be -1 or 1. Then, after many runs of that, they average out their measurements and compute (Ax + Ay)Bx + (Ax-Ay)By. I understand that the outcome of that can not be >2. But, what does that have to do with locality or realism? I don't see a connection there at all? Then you quickly move to an example with Qbits and the fact that the outcome becomes ~2.8. The conclusion is that either particle moves faster than the speed of light, or realism is incorrect. Again, Why?? What does the speed of the particles have to do with measuring -1 or 1? What does realism have to do with measuring -1 or 1? If the outcome is higher than 2, namely ~2.8, that can only happen when some measurements have not been 1 or -1, but >1 or < -1? So yeah, this feels like one of those times an explanation is simplified and information is omitted up to a point where the whole explanation makes no sense at all anymore and is basically useless. Sorry for the harsh words, but this is frustrating, haha
My college physics teacher said that if we compressed the earth somehow so that every molecule was touching, it would then fit into a space the size of the classroom. And my smart friend said, "Yes, but that thing that fits into the classroom is itself made of a substrate that can be broken down into its components and again it is 99.9999999% nothing, and if you break that down, it would be true again." Because at each level there is information imposed on "stuff" and that stuff is again information imposed on different stuff, and that. So I think we still have a long ways to go to get a handle on things and I am with you and don't understand it either. Nor do I think I ever could. It is my own guess that if we can go through enough substrates we will eventually observe it as nothingness. But that statement means nothing (g)
@@marwanadel__ I agree with you. She exactly glides across the surface, precisely without explaining anything that wasn't already clear. On top of that, she does an ugly job of mangling Aspect's name. Careless. Unnecessary. Unprofessional. Anonymous "Inaugurated," on the other hand, is quite right not to sign their post: all they're complaining about is their own laziness or ignorance. Fake "Inaugurated" is correct only on the point that she cheats about that 2.8; all the other whines are be solved if Inaugurated simply pays a little attention.
Totally agree. She said absolutely nothing. I mean, suppose that instead of Alice and Bob taking measurements, how about we just let Victor keep a record of the properties of each particle he sends? Obviously, Victors table of data would be the same as any data collected by Bob and Alice, Right? The two tables constructed by Bob and Alice combined would would be equivalent to the table constructed by Victor as long as everyone accurately recorded their entries, wouldn't they? It seems to me that there can be only two possibilities for the '2.8' anomaly. Either, Victor, (Quantum Mechanics), is unconsciously biased and _prefers_ or _favours_ one property over another *_or,_* it is the case that the properties of the particles can change as they travel between Victor and Alice or Victor and Bob which would suggest that the Universe prefers one property over the other. Perhaps it is easier for 'left-handed' to become 'right-handed' than the other way around. Or maybe '+1' spin converts more easily to '-1' spin than the other way around. It may be the case that in a Universe made of anti-matter, Bell's Inequality would be measured as '-2.8'? I don't know but I do know that if it doesn't make sense then there is probably some problem with an assumption that has been made.
I can't agree to that. She might become a good salesman, but not a teacher or scientific presenter. From 4:20 to 8:30 she was laying down the content of thought experiment, but instead of showing how it leads to controversy, she just finished it with "now suppose that instead we use entangled particles, and you see, we actually going to measure a different result". In this presentation it looks like she insisted that "the math broke down", not some physics phenomenon, as "
Always thought a presenter was someone who got presents ready for people, like a third party service, kind of like an elf, but then I realised that they rarely came with gifts, mainly because they were a 3rd party I guess and I never saw them like that elusive fat jerk who eats all the cookies and leaves the neighbour's stolen badmington set as a "gift", and probably stole something while he was at it for the next kid and cookies. Then I realised that presents are only called that because they are presented to somebody, which preferebly would be myself (reciever, not giver (me receiving the the present and not the one labled a "presenter", nor a 3rd party in the mix who is preparing the present (or presentation))). Then I realised potentially that I would be receiving less presents, and figured that if I became a presenter myself, pehaps I could hijack the system of flow, thereby recieving my deserved and duly proportional amount. Then I realised that If you prepare a present that you intend to appropriate for yourself, it ceases to exist in the realm of "presents", as it is presented to none, except maybe from your left hand to your right. I toyed with the idea of concocting some big fake fanfare "presentation", where I first dressed as a "presenter", then call myself up to the stage to recieve a "suprise", duck behind the curtain, change clothes, then apear with a shocked and thankful expression as I walked to the podium to receive the present, but obviously with noboy there to present it, it fails the test on all levels. I had to concede that at least a 2nd party must be involved to be the "presenter". I think I finally found such a person.
Olivia, it is a joy to watch your presentations. I saw one from Al Khalili explaining Bells inequality, but yours has made it much clearer, which has increased my understanding of Quantum Physics to about 2%. :) Keep posting!
I did too; I had given up on understanding any of it after the laboriously detailed AlKhalili presentation on BBC. This made me feel there might be something to it. A note: I have learned from some of the AlKhalili series that I have watched in the past, but Bell's theorem wasn't one of those that made sense to me
It's worth pointing out *why* you can't build an ansible (FTL communicator) with entangled particles. When Alice interacts with her q-bit, the probability function does indeed collapse for *both* q-bits at the same time -- but Bob doesn't know that the probability function for his particle has collapsed. Further, when Bob *does* interact with his q-bit, he can't distinguish between the case "probability function has already collapsed due to Alice" and "Probability function just collapsed due to Bob's interaction". Finally, neither Alice nor Bob can influence *how* the probability function collapses to favor one value or the other. Thus, once Bob interacts with his q-bit he can say with certainty what value Alice will get when she interacts with *her* q-bit but not whether or not she has or hasn't. Since the measured value is random, no useful information has been transferred. Interestingly, entangled q-bits *do* have some use in communication -- they can be used to authenticate messages. In this scenario, Alice interacts with her q-bit and uses that value as part of the encryption key of a message. When Bob receives the message, he interacts with *his* q-bit to create the decryption key. While a single q-bit doesn't give Bob much confidence that Alice sent the message, if 256 q-bits are used...
While this is an interesting comment, it still doesn't prove or disprove faster than light travel or transfer of energy or information. It just doesn't.
I love how you used the words "at the same time". Delayed-choice experiments have shown that the wave-function collapse even transcends time. Which kinda makes sense if you accept the nonlocal collapse that seemingly violates c. But it goes against our intuition based on our ability to experience the universe.
This is a great explanation, thank you. One thing that I don't understand is: If Alice and Bob cannot tell whether their probability function has collapsed or not, how do we even know there is any probability function after the particles are entangled? To me, it seems like the act of entangling a particle simply synchronizes the states of the two particles so that they will have opposite values and the probability function itself is only a thought experiment to help explain behavior caused by the observer effect. Is Bell's Inequality theorizing that this cannot be the case because of that 2.8 value?
@@Kevin-ht1ox Yes, that's correct. Bell's Theory is one of the rare cases where you *can* prove a universal negative statement-- that is, there is no function can be constructed, even with perfect information, that can say with certainty what the the state of an undeterminate particle is. The MinutePhysics video does a much better job at illustrating this (ruclips.net/video/zcqZHYo7ONs/видео.html), with a bonus that it includes an experiment that you can conduct yourself if you are willing to sacrifice a pair of cheap polarizing sunglasses.
@@KastorFlux "...but also any other adjacent particles through localized communication..." If this were correct, then yes, entangled particles could be used for FTL communication. However, it isn't -- if there are any adjacent particles to interact with the probability waveform would have *already* collapsed. The only valid answers to the question "Has the quantum wave function of my particle collapsed" is "Yes" or "I don't know" -- unless, of course, you have a separate channel of communication with Alice. If you *do* have such a mechanism, then not only are you in line for a Nobel Prize, you would also make lots and lots of physicists very happy. As Einstein pointed out, lots of physicists are very, very disturbed by the consequences of Bell's Theory and quantum mechanics in general, and detecting a collapsed quantum wave form without collapsing the wave form would go a long way towards proving that quantum mechanics is only an approximation of the *actual* laws of physics. And you would likely be rich to boot -- stock traders are spending millions of dollars to reduce latency on trades from 10s of milliseconds to 8 milliseconds. 8f you could reduce we it to picoseconds over any distance... There is a market for an ansible even today.
all it proves as far as i can tell is that what (properties) we measure has no definite value split between two particles as per QM theory .. nothing more nothing less
So, this means Heisenberg (Walter White, Breaking Bad) was wrong about time travel being impossible? I'm too old to verify the math behind quantum theory, entropy, etc.
This was a little strange to me because you describe the initial scenario and show how it can be no greater than 2. Then you simply state that when using entanged cubits the number is ~2.8. How did you get there? Why is the number greater? I feel like there is something missing here.
John Bell was a technician in Queens for some years. People realised his genius and helped him get his degree encouraged him to get his PhD. He had died before I started there but by all accounts he was a lovely bloke.
@@BobbyT-yj1cw That's not quite correct, or at least potentially misleading. It is too often overlooked Bell was proponent of Bohmian mechanics, an alternative to Quantum Mechanics, that predicts the same experimental results, but where particles have position with out measurement.
Robin, I don't think you're paying attention. That's exactly what she *didn't* do. And her mispronunciation, "Elaine" Aspect, is fingernails on the blackboard horrible. When it came to the math she said "Go look in the caption, The actual stuff is in a paper there..." She teased us over why the value turns out to be 2.8 and then didn't tell. That's posing, not math.
This is somewhat past my mathematical understanding but I really appreciate your taking the time to break it down so I can understand it and hence expand/bend my mind a little. At 61yo I do regret not pushing myself more in my mathematics study- just a word to the young scientists and mathematicians out there: keep grinding!!
Ditto for me. Have gone back to studying high school and first year universities maths in my retirement and now regret that I didn’t do more in my youth!
Thanks for this - I did think of Bell when the Nobel prize awards were announced. I often think of him because I live a few hundred metres from where he was born, in Belfast - and cycle past his house most days.
Maybe he can, he just can't tell at what points his self belief as a medium, meets his probability of self delusion, making the convergent outcome evident, but not quantifiable in a meaningful way.
Well done. I understand some of it; I am still learning. At 77 it is difficult to comprehend since everything I learned is now passe. The universe is joyfully weird.
Fantastic distillation of "spooky action at a distance!" I wish the prof who taught my graduate quantum class had been as effective at describing Bell's inequality as you are.
One of the coolest explanations of bell inequality I've seen and you literally fulfilled fenyman's idea of being able to explain the idea in the coolest possible way.
I love this channel so much. There are always super interesting things going on in the Quantum Computing field and the explanations are actually approachable. I appreciate all of these posts.
To each his own, of course, but I happen to disagree. Here is a much better explanation (IMHO) by Sixty Symbols: ruclips.net/video/0RiAxvb_qI4/видео.html
Fantastic video but I would say it is missing one thing. For Bell's theorem, he also assumed statistical independence of the system, that is P(x|ab) != P(x) where x is a specific event of a quantum particle and a and b are measurements taken of the particle. In other words, if the "choice" the particle makes with regards to its waveform collapse is based on the measurements that WILL be taken of the particle in the future, then none of Bell's theorem, including the inequality, apply. I think this is important to think about, since no one has ever proven that statistical independence actually holds.
My personal take is that measurement information retroactively determines agreement on state. I’ll throw away causality in hopes of a deterministic reality.
Thank you, Olivia. I didn’t understand half of it but your presentation allowed me to grasp some of it. 🤣 I hope you’re teaching somewhere; you have a wonderful, open style of communicating ideas clearly.
lol She literally said nothing. Suppose that instead of Bob and Alice making measurements, we let Victor keep a record of the properties of the particles he sends to them. Where then would the 2.8 figure come from? Clearly, Victor is biased in some way.
Yeah Victor is suspect...He likely voided his honesty by being a supporter of donald duck, he can't be trusted. His maga hat is definetly on a few snaps too tight...That in and of itself makes him untruthful, like his esteemed(he thinks)leader...Yes I'm sorry to tell you but, in the spooky action at a distance of quantum theory makes Victor nothing but a liar, so vote blue and save our local reality!!!...lol
It's wonderful what can result from people doing what they are truly passionate about. Paths are drawn so much cleaner and we can conclude collectively, so much more efficiently. Thank you again for another thoughtful and extremely well-presented piece, Olivia ♡
Enjoyed this exposition, and I'm far from being a physicist or understanding the nuts and bolts of quantum mechanics. It adds to the many, many things I know I don't know enough about and that no matter how much I try I'll only ever have a tenuous grasp of!. Every day is a school day.
Back in the 70s, there was a physics Nobel laureate in my meditation class at Cambridge. Afterwards we had tea and a chat, and someone asked him why a scientist was drawn to this mystic practice He replied: "Oh, we're all mystics at the Cavendish - and once anyone begins to understand the profound weirdness of reality the way that we understand it, they would become a mystic too!".
@@tullochgorum6323 if you could go back in time to stop Rutherford splitting the atom , and prevent the development of what Russia is threatning to use today.....would you stop Rutherford, or not.?
@@tullochgorum6323 that is a great story. On a technical note, Rutherford didn't split the atom. Splitting the atom happened the year after he died. He did a lot in physics, though. Thank you for sharing :)
@@fierce-green-fire8887 Thanks for the information on Rutherford - I'd better read it up because I seem to have misunderstood something about his work. As you will have gathered, I'm very much a lay person when it comes to the mysteries of physics!
Yes I loved the fact that there was no annoying background music and Yes I agree with all others that you are an excellent presenter. If I may mention that the Nobel Prize work was not all done in a lab. I watched and loved the presentation on Nova, Eisnstein's Quantum Riddle where an experiment in the Canary Islands Observatory have done some amazing experiments.
Thanks! That was super clear. I never really knew what Bell's Inequality was claiming, only that it sealed the truth of non-realism. For me, the double-slit experiment was my introduction to non-realism. I just read that the "single electron" version of that experiment (which is the version that blew me away) wasn't done until 2002, years after Einstein died. So he never got to see that. Now I understand how non-realism was established in a more thorough way using the violation of Bells Inequality. I also don't feel as disappointed in my high school physics teacher whose explanation of the particle vs wave nature of light left out telling us about the underlying quantum weirdness it suggests. Since that was before 2002 he couldn't have known . Tying up a lot of loose ends here ...
> only that it sealed the truth of non-realism. It didn't the explanation is wrong. It only sealed local hidden variable theory one of many local realistic theory. There was and it is still a lot of research on a local realist description of quantum mechanics.
It most certainly did not "seal the truth of non-realism". You can have realism or you can have locality, but you can't have both. Remember that these words have technical descriptions in the theory so don't load other meanings onto them.
@@nehocm123 You can have both. Deutsch worked on it in the early 2000. There are even more recent result of making local-realist description of quantum mechanics. That is the point. It's unbelievable to some physicist but the bell theorem doesn't exclude it. If you want i can send you the link of papers.
@@coot33 I am familiar with the many worlds escape from this conundrum and I will grant its formal consistency but until one of its forms is shown to be testable, at least in theory, I would prefer to give up locality and keep realism. This is of course a philosophical stance and I don't begrudge you or Dr. Deutsch for believing otherwise. Keep in mind that the non-local phenomena we are discussing do not involve FTL signaling. I also suggest that a likely more fruitful approach is work on objective collapse interpretations and the nature of time and entropy in spacetimes with realism.
There are so many explanation out there of this last Nobel in Physics than either oversimplified the issue to the point of being wrong or they enter into so many details that I need a PhD in Physics to have any chance to get something out of them. However, this explanation hits the nail on the head. Brilliant.
@@pavelvedernikov8502 Then you're probably a bit like me. I can grasp a lot (actually most) of the concepts and theorems of physics when it's explained to me in words. I'm just not a beta person by nature. Therefor I've always struggled to understand the underlying proof. Which of course is always expressed in the beautiful language of maths. It takes me a lot of effort to actually understand those equations. Just rewind that part of the clip a couple more times and try to do the equations step by step with her. It eventually clicked with me.
I'm surprised people think this is a good explanation. She wrote out a simple mathematical expression that can't be more than 2, because the Ax, Ay, Bx, By values, she said, are each 1 or -1. Then she says they measured it and it's 2.8 - wow, isn't QM weird. That's not a violation of classical physics, it's a violation of arithmetic. There is no world in which `(Ax + Ay)Bx + (Ax - Ay)By` is greater than 2, given the variables are 1 or -1. So... it seems like the video hid the "weirdness" somewhere and didn't show it. I'm guessing it's in the logical connection between the QM and that simple math expression. In other words, something about QM makes you think it should follow that math expression, but it doesn't. But this video never shows why they thought it should follow that math expression in the first place.
This woman is "miraculous" herself. Even someone as limited as myself could understand every major concept she described and that amazes me. Thank You so very much miss.
I spent the last hours trying to understand what this nobel prize was really about and the closer i could get to it was with this video. Thank you very much
Thank you for explaining it so well! Definitely leaves us with some interesting things to explore regarding the relationship between entangled particles.
Never heard an explanation that is crystal clear like this. IBM is truly world clsss. They many 11corporate research labs all over the US and the world as well. They hire the best young PhDs in Physics and bring the best out of them in their labs. Hope this tradition is continued endlessly as many other corporate research labs had shut down citing the expenditure of running such labs like Bell labs, Lucent technologies.
@@KastorFlux There is no requirement for a claim to be falsfiable. Again, can the "spooky action at a distance" be used or not isn't relevant. Unless you believe in superdeterminism, you can't rationally deny that spooky action. Relativity is a local theory, so that spooky action demonstrated it's at the least "not complete", like Einstein suggested about QM. "Does it rely on esoteric bs that can not be proven? Yes. " As I said, unless you are a proponent of superdeterminism, it has already been proven. There isn't anything that needs to be proven anymore. "Does it make wild and unbelievable claims? Yes. " Argument from incredulity is a fallacy. "Does it rely on superstition, faith, or social pressure to propagate its validity? Yes." Empirical experiments are not superstition.
Thank you Jesus for not only no background music, but also for no camera movement. Thank you for letting Lanes present and for not goobering up her presentation with unnecessary production clichés.
The Bell's inequality experiments are great! Probably a good choice for the Nobel Prize. My amateur guess is that they show that reality is nonlocally interconnected. Maybe with waves. Stephen Hawking wrote that there might be only waves, and that particles with locality are just our interpretation of the underlaying waves and that there isn't even any need for uncertainty in quantum mechanics.
I have always subscribed to this interpretation of reality, as it is anchored in relative Spatio-Temporal Unity… however, it has to be justified and proven first for it to hold any substance in the community and society as a whole
"Quantum mechanics brings us to the brink of the impossible, to the point at which we shouldn't be able to fully comprehend what's going on, but NO FURTHER THAN THAT." Really like this description
The entangled pair, had selected a state before any were measured, else they would not have become entangled. The uncertainty is entirely because of the problem of measurement. It is a fundamental problem, not something to write into a theory. The universe operates completely well outside our observations or measurements. We need a whole new approach.
I have been struggling to understand Bell's theorem for years and I'm afraid that this presentation leaves me just as confused as before! But what I would love to know is whether there are any practical applications of these strange phenomena.
@@carlgrove8793 «@Evi Hofkens I just read what Wikipedia says about that and frankly I couldn't understand it at all! Thanks for the info, anyway!» ---- Dear friend, imho the reason you cannot understand it is that of being sincere and honest. If you want to understand it in a way many others understand it, you should (re)read The Emperor's New Clothes. Btw Clothes that were made using bits that had jumpy levels of sawing energy coming out of cryptically nested sub-dimensions of the inner quantum not-space.
The main problem I have with this video is that she completely dismisses locality and emphasizes the experiment disproved realism when the results of the experiment show neither locality nor realism is true in quantum mechanics. The information of entangled objects does travel faster then the speed of light. While the persons in the experiment cannot communicate faster then light, the entangled cubits can which means the instant one person knows the state of one cubit, the other knows instantly what the state of other cubit is.
It's poorly explained: X and Y are never measured at the same time. Either X is measured or Y. So, for a single experiment the CHSH is not even defined... it's only computed on average.
This is not merely a statement about the weirdness of Quantum Mechanics, but the weirdness of the ultimate/inherent nature of space itself that we still don’t know anything about. Much in the same way that we still don’t know what gives rise to the Higgs Field, for instance; and still ascribe it to the inherent and unknowable nature/property of space itself.
So either we agree with quantum mechanics saying everything that makes up reality (i.e., particles) aren't there until we measure them. Or we agree with Einstein, that quantum mechanics is an incomplete theory... After listening to this explanation, sure get the feeling Einstein was right, again.
that may be right clauser tried to show john bell about how he forgot to include meausrement independence but only about 6 mathamaticians and physicists are brave enough to talk about it.
Thanks for the explanation. I had heard of Bells theorem but this helped me understand it better as a non-physicist. The idea that realism does not exist sparked many of my own "thought experiments" about the nature of reality and the universe. I think we may be close to unlocking some of the secrets of reality itself, the consequences of which we cannot comprehend at this point.
Can’t disagree with slip’s conclusion here but it’s looking to me like either it’s gonna be a Trojan horse orapandoras box. Third favourite has to be the lair of the Minotaur with or without heroic intruders. Here’s one I’ve never wondered about much until now; what did the Minotaur do if they accidentally left it’s lair unsecured?
But it's not "reality" like a normal English meaning of that word. The point is just that we've disproved the idea that "measurement" tells you about properties of a system that existed before you took the measurement. I'm not 100% sure why the word "reality" is used in this way, not the word I would have chosen, I think. I think it had something to do with a quote from the EPR paper.
Uhhhhh what about superdeterminism? When properly understood, it explains the results of Bell's experiments, preserves locality, reframes 'wave function' as ignorance of the observer, keeps Einstein and Newton happy, and still makes room for a robust understanding of free will.
It is not explained fully in the video since the equation values can never all be measured simultaneously. The 2.8 comes from averaging across component values measured many times (not simultaneously) and then summing these average component values.
5:00 What I don't understand, assuming Alice, Victor & Bob are in the same "Frame of Reference" (Train for ex.) that moves with 0.5c to the right (Bob-direction). - First, because of dopplershift, one photon becomes blueshifted and the other redshifted, even if they are entangled. - Second, even worse. Alice gets the photon first for external viewers. So she knows the outcome of the measurement, while it's still in superposition for Bob. Because within the train, both Alice & Bob get the entangled Photons at the same time. So, it has to be in superposition for Bob, and not collapsed to a value when it arrives. Does this make any sense? 🧐😵💫🤯
The consequences of special relativity would only manifest if they are moving relative to each other. If they are all on the same train moving at a constant speed, anything perceived by the people on that train, are exactly the same as if they were all standing still, so there's no doppler shifting or time dilation from their perspectives.
More to the point, the particles being exchanged in the experiment are *not* photons. Instead, entangled electrons are exchanged, quite possibly in a briefcase. Thus: 1) The measurement of the values doesn't occur immediately upon receipt. 2) Alice and Bob may perform the measurement at different times, perhaps even on different days. Thus, relativity isn't a significant factor in the experiment. I'm not even certain we know how to entangle photons, but even if we do, *keeping* them entangled is going to be very, very difficult. Electrons, on the 9ther hand, are reasonably easy to entangle.
@@jmr5125 Actually, it’s way easier to create a pair of entangled photons, in fact that’s what the Nobel laureates used. The most common way to do this is using spontaneous parametric down conversion (SPDC), which creates 2 photons with orthogonal polarizations. The coherence lifetime of a photon is practically infinite while an electron will suffer decoherence extremely rapidly unless it’s in ultra low vacuum at temperature close to absolute zero.
@@nikhilmathur9952 Thanks! I did see MinutePhysics video on this same topic, so I should have realized that it's easy to create quantum entangled photons. My bad.
@@nikhilmathur9952 ~ The actual time dilation comes from the fact that there are gravitational gradients all over the place. (They cause the tides, for example). Timekeeping is elastic, varying with local gravitational field strength.
You can't tell the difference between gravity and acceleration, because gravity is acceleration. Gravity doesn't just bend space time, it absorbs it. Black holes prove this.
This is fascinating! Quick question: is there a specific "max speed" beyond the speed of light, such that the 2 ~ 2.8 equation would actually balance out correctly? Like, if we pitch lightspeed and keep realism, do we get a specific number for max speed beyond our (easily? currently?) perceived max?
Um, idk the answer to this question but i think the implications of this experiment is not that the speed of light is violated but that local realism is violated. Although i believe there was a study done by swedish physicists with mirrors and virtual photons that postulated that the speed of light was not in fact a constant but relative to the number of subatomic particles in existence so that it appeared constant.
@probablyup I was so immediately excited after reading this comment that I googled to get reading and now I'm not even sure if I'm being punked or not, that's how hard it is to learn science online in current year
Thanks Olivia and the rest of the team. I'm recovering from series of mini strokes. I use videos such as yours as weight lifting exercises. The brain is a muscle. It needs the exercises you kindly provide. Thanks again for the knowledge and a little bit of befuddlement!
I’m not sure to whom this video was intended, those with little to no understanding of quantum physics or those who are actively studying it. You spent so much time setting up this AxyBxy equation, you set limitations of +/-1 and showed it’s equal to or less than 2. But you gave no reason that I heard about why the measurement is only +/-1. Then you jumped to entangled particles and just told us the measurement is about 2.8 without an equation demonstrating why. And what does it matter than the opposite value was known immediately? You remind me of my high school biology teacher who tells the tale of an experiment where someone cut off the tails of mice for 50 generations and no mouse produced offspring with missing tails because acquired traits are not inherited. Then she goes on to say, giraffes had normal length necks but would have to stretch their necks to reach higher than others. As they continued to stretch and stretch, their offspring have the long necks we know today.
Sublayperson sounds similar to my self designated 'amateur layperson'. Maybe in a few years, already 67, I can become an experienced amateur layperson'. 😂😅. I did really like this explanation and surely wouldn't try to paraphrase it.
I’m not a physicist. But I have a problem with “entanglement”. I have yet to see anyone explain entanglement. And what is the difference between entangled and not entangled particles? When 2 particles are viewed by 2 separate observers, how is it they know for sure any particle was entangled at the source? What is the physical process of entangling particles? What kind of measurement is made at the time of entanglement? How can an observer be confident that they were actually observing an entangled particle? How is just one particle produced at a given time? There are a number of questions associated with the concept of entanglement that I’ve seen no “empirical” proof of. If something is simply mathematics, is that to be accepted as proof of something in the real world? Logic for example doesn’t necessarily draw empirical conclusions. Correct conclusions are based upon the premises being true. A logical argument can be made even with false premises.
Maybe bob and alice were both cooking a egg, and as 4 minutes approched they both looked at the toast at exaclty the same time and said 'grab the butter', then they looked at eachother and both said 'jinx'.. and loled, we all loled and ate dippy eggs.
I have to admit I was expecting some information about the 2.8 result. Also, for people who are not familiar with these things -like me- I would like to have quick words about what are X and Y in the first experiment you are mentioning
X and Y are usual ways to denote directions in which you measure the spin of a particle, for example. Measuring spin in one direction leaves the other (perpendicular) direction free to take any value, but measuring spin twice in a row in the same direction makes the second measure be equal to the first. Measuring at intermediate directions creates correlations which are not 100%, but which can be calculated. All of this is important to get the result shown. You might want to look up the Stern-Gerlach experiment, it isn't too complicated, but illustrates all of this very well (some textbooks on quantum mechanics even open with it)
The link holds quite some clues but as it was said this needs a bit more math and physics to fully understand. what I can fit in a comment to lift some mystery it is not 2.8 really the exact value is 2*sqrt(2) which is related to the binary nature of this particular problem description and perpendicularity.
I have had many attempts to understand Bell's Inequality/Theorem, and this video has gotten me further down that road. I think I can now at least see which bits I understand, and which I don't. I still don't totally get why apparently "instant" effects can't produce instant communication. Even if it doesn't in this particular case, maybe in the future someone will design an experiment that behaves differently.
Yes, great explanation but I still do not understand why there is any probability function at all if the only thing we can really know is that the two particles have opposite values and when we read the values, we cannot tell whether or not either particle was already "read". This behavior seems no different than if I were to split an apple in half, place each in a box and randomly give Bob and Alice one of the boxes. Opening the box only reveals to Alice or Bob which side of the apple they received however every quantum theory explanation says that the apple halves have superpositions where they are both values until they're observed. That superposition theory seems like a gross misinterpretation of the statistical measurements. A tree falling in the forest will make a sound whether or not someone is there to hear it and there is no evidence that suggests otherwise. What is it about the quantum world that leads us to believe it is any different?
To understand or see how the quantum world is different from classical physics explaining the world we normally experience it helps to look at Young's double slit experiment and read on the wave-particle duality. It shows that particles are also waves and behave as such. It's actually an observable effect, not just a theory, even for particles that have mass. The particles are not just in one place, but with a certain probability they are also in other places. One effect of this is tunneling, which explains radioactivity, for example. It's probably best to hear about some basics first. Makes understanding things like entanglement much easier.
@@Kevin-ht1ox the whole point of the theorum is to see if the apple example you mentioned is how it works. It's worth noting that Bell was hoping that's how it was, he was in favour of hidden variables but was a good enough scientist to go with the result. If the apple scenario was true it predicts certain values, however quantum mechanics predicts different values that are not possible if the states are fixed before hand. Experiments show it to be right. I strongly recommends the Sixty Symbols video if you want more detail as he goes into way more depth about how the experiment works and the maths. m.ruclips.net/video/0RiAxvb_qI4/видео.html Realism feels intuitively true beacuse it is our experience, but we can dismiss the facts bexause they are unintuitive the universe is under no obligation to work in a way that feels right to us.
@@Kevin-ht1ox this is bells inequality, both apples should add up to one, in the same vein, the sum of all outcomes should end up being something specific, but they are not they are actually more, which is proven by experiments, so imagine you put two slices of an apple in two separate boxes and later measure the contents and find the material for 1.4 apples. That doesn’t make any sense? That’s with the vectors of the quantum particles they don’t add up to two but 2.8 which is too high. So they go above the bounds of bells inequality which makes it weird.
@@NeoRetroX i don't know that it doesn't make sense. I just know it doesn't fall within the belief systems of mathematics or logic. And they are belief systems. Everyone has to before hand agree to accept certain truths before you can proceed. An axiom, a statement that is accepted as true without proof. 1 and 1 only adds up to 2 because everyone agrees its so. Belief system. Its essentially just agreeing on the rules of the game before we begin the game
"Now, in quantum mechanics we say there exists this thing called the wave function which describes all the properties of your Quantum system and upon measurement it collapses into a single quantity that was only described probabilistically before you measured it." Good Gal! Best, most succinct, rendition of wave function collapse l've ever read. WFC's reaIly just like snagging a flipped coin. Its position is indeterminate tilI you snag it. The coin position wasn't fixed tiIl you snagged it and stopped it. In the same way your quantum properties aren't fixed tiIl you 'snag' the system by measuring it. Good Gal! Thx. Man. This quantum mex is SO counterintuitive. Crazy.
Yes, that's total bullshit. Absolutely nobody who knows quantum mechanics will ever say that the wave function "exists" or that it contains any information about an individual quantum system. Only people who don't understand quantum mechanics will say such nonsense. ;-)
Bells experiment assumes that the experimenters have a free choice in configuring their experiment (Choosing the spatial orientation of their detectors). This assumption sounds insane to me because if there are hidden variables and the universe does work like a deterministic 'machine' then why would the experimenters be special (in that they don't work like machines but have free choice)? When are we finaly going to loose the 'human = special' assumption in physics. It has turned out to be wrong so often already...
You misunderstood the nature of the free choice. In practice, the experiments use random inputs to make the choice, not humans. As random as possible, with no plausible correlation between the choices... for example using random bits generated by noise from the Cosmic Microwave Background.
@@brothermine2292 Yeah but you didn't solve anything with that. Where is the cosmic microwave background "randomness" determined from? You can't just assume that something super complicated is perfectly random. At best the CMB is pseudo-random and still deterministically intertwined with everything else on earth.
@@seanmcalevey4566 : Even if it's merely pseudo-random, it's implausible that the effect would create the coordination between the measurement orientation setting of Alice's detector & the measurement orientation setting of Bob's detector that would be needed to result in statistics that imitate the non-classical prediction of quantum mechanics. It's like the implausibility of an untrained monkey at a typewriter producing only plays of Shakespeare, never producing unintelligible garbage (or foolish youtube comments).
That is a valid objection. What if the whole experiment was predetermined? An experiment was set up where the observers didn't TRY to make a random choice; instead they used information from ancient stars to make the choice. And the two observers used two stars so far apart that they could not have communicated in any way, due to speed-of-light restrictions. Sorry if I am not clear on this, but basically they handled your objection.
This is very interesting and thank you for the explanation. A bit I'm struggling with is that while Bob and Alice aren't communicating, the particles either must be, or they each have a real value that is hidden, or somehow otherwise exists outside our current understanding of what's "real". Am I missing something about the definition of either local or real?
Thank you for the effort. I didn't actually follow along properly, there were a few yhimgs I wish you had clarified a few things in the video. 1) what is CHSH? (Full form, meaning) 2) Why was that inequality constructed the way. Adding 3 terms and subtracting 1, sort of randomly in a hand wavy fashion. 3) Would have liked a better example of realism, didnt quite get that. There is more, but I won't go into it. The overall quality of the video is great but the explanation could have been a bit better. Thanks. (Ps, I am a computer scientist who has studied quantum mechanics at a bachelor's level, so noy a complete beginner).
It’s a tragedy that Bell died only a few years ago and so was excluded from the Noble. Remember his theory was so weird at the time that all the mainstream physics journals rejected his paper. Now it’s the definitive proof of entangled interactions.
This was a great video - I myself have suffered from the fallacy of entanglement allowing for FTL information passage. Good explanation of the “collapse” of the entangled wave function not implying information. I’ve found no intuition for quantum mechanics. It’s all just been studying that has allowed me to see further. Definitely defies our logic of the natural world. Thanks for taking me a step further on that journey :)
How can we confirm with a measurement if two particles are entangled before we run experiments with them, or do we just say they are entangled because we believe some process they go through gets them in a state of entanglement? It all sounds like a scientific charlatanism. In reality, Everything measures everything therefore the Universe is deterministic but not necessarily self-knowable. (The state of Schrodinger's cat located in any given Plank point of space-time is determined because any Plank point of space-time is measured by its neighbouring points of Plank space-time)
When you explain the fact that these particles are not transferring information faster than the speed of light it's still a little confusing. It's mentioned that the particles are entangled and their wave functions become one. It also mentioned the the particles are sent to Alice and Bob before the measurement. So, because entangled particles consist of the same wave combined wave function, they can be thought of as the same quantum object. When the two objects are transferred to both locations at less than the speed of light before the measurement then the information traveled at sub light speed to their measurement locations. Then when a measurement is made of one of the particles, then the combined wave function or quantum object collapses into a opposite values for both particles at the same time. The fact that you can have an quantum object that is essentially in two places in once until measured and it breaks into individual particles again is really the crazy idea here.
I am always amazed that anyone can understand this stuff to begin with. The fact that nobody understands, including themselves, where they end up to end with is the challenge of this life.
I am a physicist and I want to explain the “observation” problem in quantum mechanics because it is often misunderstood even by many physicists. In quantum mechanics the physical system is described through a wave function whose evolution over time is determined by the Schrodinger equation. The wave function represents infinite different possible results for the physical quantities related to the system, but when we take a measurement, only one of these infinite possibilities becomes real; after the measurement, we must therefore modify the wave function “by hand” to eliminate all other possible results, and this modification is called the “collapse” of the wave function. If all other results are not eliminated by imposing the collapse "by hand" on the wave function, the predictions of subsequent measurements on the same system will be wrong. The fundamental problem with quantum mechanics is that interactions among particles are already included in the Schrodinger equation and such equation does not predict any collapse. The collapse of the wave function is a violation of the Schrodinger equation, i.e. a violation of the most fundamental laws of physics and therefore the cause of the collapse cannot be determined by the same laws of physics, in particular, it cannot be determined by the interactions already included in the Schrodinger equation. The Schrodinger equation is what allows us to make quantitative predictions about the outcomes of future measurements; everytime we make a measurement, we receive new information about the system, and we need to "update" our wave function, i.e. to collapse it, otherwise the Schrodinger equation would provides wrong predictions relative to successive measurements. After one century of debates, the problem of measurement in quantum mechanics is still open and still represents the crucial problem for all interpretations of quantum mechanics. In fact, on the one hand it represents a violation of the Schrodinger equation, that is, a violation of the fundamental laws of physics. On the other hand, it is necessary for the laws of quantum physics to make sense, and to be applied in the interpretation and prediction of the phenomena we observe. This is the inescapable contradiction against which, all attempts to reconcile quantum physics with realism, break. Quantum mechanics is incompatible with realism (that's why Einstein never accepted quantum mechanics); all alleged attempts to reconcile quantum mechanics with realism are flawed. Quantum mechanics implies that physical reality (the universe) consists of the collection of all observed phenomena and such phenomena do not exist independently of consciousness. In fact, the properties of a physical system are determined only after the collapse of the wave function; when the properties of the system are not yet determined, the system is not real, but only an idea, a hypothesis. Only when collapse occurs do properties become real because they take on a definite value. It makes no sense to assume that the system exists but its properties are indeterminate, because properties are an intrinsic aspect of the system itself. The collapse represents the transition from a hypothetical system to an actual system. The collapse of the wave function represents a non-physical event, since it violates the fundamental laws of physics, and can be associated with the only non-physical event we know of, consciousness. Therefore, the only consistent rational explanation of the collapse is that it occurs because consciousness is involved in the process. However, the fact that properties are created when a conscious mind observes the system in no way implies that it is the observer or his mind that creates those properties and causes the collapse; I regard this hypothesis as totally unreasonable (by the way, the universe is supposed to have existed even before the existence of humans). The point is that there must be a correlation between the collapse of the wave function (=violation of the physical laws) and the interaction with a non-physical agent (the human mind); however, correlation does not mean causation because the concomitance of two events does not imply a causal link. The consciousness that causes the collapse of the wave function must be an eternal consciousness, that is, a conscious God. This is the idealistic perspective, which implies that physical reality exists as a concept in the mind of God who directly creates the phenomena we observe, according to the matematical models through which He conceived the universe (the laws of physics); the collapse of the wave function is a representation of the moment when God creates the observed phenomenon. This is essentially the view of the Irish philosopher George Berkeley, and in this view God is not only the Creator, but also the Sustainer of the universe. Idealism provides the only logically consistent interpretation of quantum mechanics, but most physicists do not accept idealism because it contradicts their personal beliefs, so they prefer an objectively wrong interpretation that gives them the illusion that quantum mechanics is compatible with realism.
This may be a related topic. In our experiments we have observed that nearfield electromagnetic fields propagate nearly instantaneously, but reduce to the speed of light in the farfield, about 1 wavelength from the source. The result is predicted by Maxwell equations by solving the inhomogenous wave equation and analyzing the speed of the fields. And this result corresponds to the phase speed, group speed, and front speed (ie. information speed). As you mentioned, instantaneous communication has observed been observed in quantum systems, and likely also explains the phenomena we are observing in the nearfield. But until now it was not though possible to control and transmit the information nearly instantaneously. Our results show that normal narrowband AM or FM modulated radio waves propagate instantaneously in the nearfield of the antenna source and clearly can be used to speed up communications over large distances by lowering the carrier frequency. A quantum explanation of this phenomena can be shown using Heisenberg's uncertainty (HUP) where Δx and Δp are interpreted as averages according to the Pilot Wave interpretation of Quantum Mechanics. In this interpretation HUP is: Δx Δp = h, where Δx and Δp correspond to average values. So in HUP: Δx Δp = h, where Δp=mΔv, thus HUP becomes: Δx Δv = h/m. In the nearfield where the field is created, Δx=0, therefore Δv=infinity. In the farfield, HUP: Δx Δp = h, where p = h/λ. HUP then becomes: Δx h/λ = h, or Δx=λ. Also in the farfield HUP becomes: λmΔv=h, thus Δv=h/(mλ). Since p=h/λ, then Δv=p/m. Also since p=mc, then Δv=c. So in summary, in the nearfield Δv=infinity, and in the farfield Δv=c, where Δv is the average velocity of the photon according to Pilot Wave theory. The fact that Instantaneous nearfield electromagnetic fields have been observed both theoretically and experimentally, favors the Pilot Wave interpretation and not the Copenhagen Interpretation of Quantum Mechanics, where in the Copenhagen Interpretation, Δx and Δp are interpreted as probabilities. It should be mentioned that both the Ensemble Interpretation of Quantum Mechanics also interprets the Heisenberg uncertainty principle (HUP) in terms of averages. But the Ensemble Interpretation does not support instantaneous propagation of information, whereas Pilot Wave theory does. *RUclips presentation of above arguments: ruclips.net/video/sePdJ7vSQvQ/видео.html *More extensive paper for the above arguments: William D. Walker and Dag Stranneby, A New Interpretation of Relativity, 2023: vixra.org/abs/2309.0145 *Electromagnetic pulse experiment paper: www.techrxiv.org/doi/full/10.36227/techrxiv.170862178.82175798/v1 Dr. William Walker
Thank you for not playing annoying music whilst we're trying to follow the explanation.👍
Actually underrated comment. People these days have no attention span whatsoever
@@TimEnjoysGnocchis "span" not spawn. But yes, I hate unnecessary background noise.
Some ones Thenthive!!!
They need to spaun their attention
I to am glad that there is no annoying background music.
Understanding it is one thing but then explaining it in a simple way to ordinary people is a craft in itself. Excellent lesson.
No one understands it. All we know is the effects that are measurable, not how it actually works.
It sounds like a scientific charlatanism. Everything measures everything therefore the Universe is deterministic but not necessarily self-knowable.
@@hoochygucci9432 Anyone who recognizes that the Everettian interpretation is self consistent understands how it actually works.
Where did the CSHS thing come from?
What happens to Victor and what do these particles have to do with echother?
In a significantly larger scale, apples, oranges, and peaches look like particles. Victor sends an apple to Bob and a peach to Alice. So what?
Very smart individual.
Bell did not assume "realism". In fact he pointed out himself (!) that his theorem is about models, not about reality. He instead assumed a second property called "measurement independence". This was pointed out among others (ironically) by one of the recipients of the Nobel Prize, John Clauser.
@SabineHossenfelder The algorythm just recommended this video to me after watching your most recent video. You must have collapsed our entanglement and this was inevitibility (let me tell you I don't understand quantum entanglement without telling you).
John Bell was wrong! The EXPLICIT information (information describing the waveform) is utterly deterministic. Free Will arises out of the complexity of the RELATIONAL information (the information regarding the interrelationships between the various wave-forms). BTW, I'm a fan of your channel!
I'm guessing new assumptions were thrown in so people don't make unrealistic conjectures arguing moot points. Love your dry sense of humor you put in your videos.
@@ThePonymaster2160 Id love to read your paper, got a link?
damn @@chilloutnostress2586
One thing that is interesting is how much Einstein influenced Quantum Mechanics, even if he did not agree with the philosophy behind it. The EPR paper was the end result of a series of arguments between Einstein and Bohr over the underlying meaning of QM. Einstein would present an argument against the probabilistic nature of QM, and Bohr would provide a counterargument showing Einstein where he was wrong. Eventually Einstein came up with the argument in the EPR paper that Bohr could not answer. Bell also did not answer it, but he came up with a way to, in theory, answer the question about which interpretation was correct. And then the three Nobel winning scientists came up with experimental ways to use Bell's theorem.
Without the EPR paper quantum entanglement would probably never have been looked at and measured. So even when wrong Einstein made a great advance in science.
The operative phrase here is "in theory". What physicists are supposed to answer is "in reality". That is what the subject is all about: "physical" reality, previously "natural philosophy". I doubt theoreticians of quantum mechanics are claiming the theory is complete, so I fail to see how this proves Einstein was wrong. What he was saying sounds axiomatic to the whole field of physics. Give it up if you wish, but that is giving up "physics".
@@jamescaley9942 This year Nobel Price was given to people who proved this "in reality". It was an experiment-based prove that Eistein was wrong.
Think we should get over Einstein - nobody has a problem with Newton but we moved on - great thought leader as time-sensitive lol
@@jamescaley9942 This sounds like something ppl would have said about Newton, if anything modern physics have already proven Einstein wrong so 🤷♂️
@@franknugent2801 That will and should not happen until an accurate theory of quantum-gravity is developed.
John Stewart Bell's birth town of Belfast (and, of lesser significance, my own birth town) has a street interestingly named for the theory rather than its discoverer: 'Bell's Theorem Crescent'. I discovered it accidentally on a walk around Belfast a couple of years ago and have often wondered if it existed on Google Maps prior to my observing it!
No way to know now you've collapsed that sign
That's funny, I saw it as 'Bell's Theorem Loop."
LOL
Was it a random walk?
That's funny next time I'm there I'll look it up - so much work has been done in other places that are not Stanford/MiT .. I found out while in Manchester
As Einstein said, “If you can't explain it simply, you don't understand it well enough.” you have shown that you indeed understand this completely! Thank you for the simple explanation and the example for us to try.
It sounds like a scientific charlatanism. Everything measures everything therefore the Universe is deterministic but not necessarily self-knowable.
Obviously not if she didn't win the Nobel Prize lol
Simple my ass !!! There is nothing simple about Quantum Mechanics !
Yes, I agree that her simple explanation demonstrates that she thoroughly understands this subject. The quote is often attributed to Einstein, but I believe there is no record of him saying it. The source of this quotation is most likely Richard Feynman who once said, "I'll prepare a freshman lecture on it. If I can't explain it to a freshman, I don't understand it."
that saying has served me well in evaluating my own understanding, love it
I see lots of comments about this being a clear explanation. What am I missing then? I feel like there's a considerable amount of information missing about the experiment that is crucial to understand anything about it.
A and B are sent a particle and measure x or y projection. x and y projection of what? Some vector? No idea, but I can accept that they measure some kind of quantity that, after normalization, can only be -1 or 1. Then, after many runs of that, they average out their measurements and compute (Ax + Ay)Bx + (Ax-Ay)By. I understand that the outcome of that can not be >2. But, what does that have to do with locality or realism? I don't see a connection there at all?
Then you quickly move to an example with Qbits and the fact that the outcome becomes ~2.8. The conclusion is that either particle moves faster than the speed of light, or realism is incorrect. Again, Why?? What does the speed of the particles have to do with measuring -1 or 1? What does realism have to do with measuring -1 or 1? If the outcome is higher than 2, namely ~2.8, that can only happen when some measurements have not been 1 or -1, but >1 or < -1?
So yeah, this feels like one of those times an explanation is simplified and information is omitted up to a point where the whole explanation makes no sense at all anymore and is basically useless. Sorry for the harsh words, but this is frustrating, haha
Yes, I don't understand why people are saying it's well explained. There're many jumps and conclusions that don't make sense unless explained!
My college physics teacher said that if we compressed the earth somehow so that every molecule was touching, it would then fit into a space the size of the classroom. And my smart friend said, "Yes, but that thing that fits into the classroom is itself made of a substrate that can be broken down into its components and again it is 99.9999999% nothing, and if you break that down, it would be true again." Because at each level there is information imposed on "stuff" and that stuff is again information imposed on different stuff, and that.
So I think we still have a long ways to go to get a handle on things and I am with you and don't understand it either. Nor do I think I ever could.
It is my own guess that if we can go through enough substrates we will eventually observe it as nothingness. But that statement means nothing (g)
It means you are a clear-thinking individual and haven't been brainwashed. Everything from Einstein forward was made up nonsense.
@@marwanadel__
I agree with you. She exactly glides across the surface, precisely without explaining anything that wasn't already clear. On top of that, she does an ugly job of mangling Aspect's name. Careless. Unnecessary. Unprofessional.
Anonymous "Inaugurated," on the other hand, is quite right not to sign their post: all they're complaining about is their own laziness or ignorance. Fake "Inaugurated" is correct only on the point that she cheats about that 2.8; all the other whines are be solved if Inaugurated simply pays a little attention.
Totally agree. She said absolutely nothing. I mean, suppose that instead of Alice and Bob taking measurements, how about we just let Victor keep a record of the properties of each particle he sends? Obviously, Victors table of data would be the same as any data collected by Bob and Alice, Right? The two tables constructed by Bob and Alice combined would would be equivalent to the table constructed by Victor as long as everyone accurately recorded their entries, wouldn't they?
It seems to me that there can be only two possibilities for the '2.8' anomaly. Either, Victor, (Quantum Mechanics), is unconsciously biased and _prefers_ or _favours_ one property over another *_or,_* it is the case that the properties of the particles can change as they travel between Victor and Alice or Victor and Bob which would suggest that the Universe prefers one property over the other. Perhaps it is easier for 'left-handed' to become 'right-handed' than the other way around. Or maybe '+1' spin converts more easily to '-1' spin than the other way around. It may be the case that in a Universe made of anti-matter, Bell's Inequality would be measured as '-2.8'?
I don't know but I do know that if it doesn't make sense then there is probably some problem with an assumption that has been made.
What an excellent presenter; you can feel the respect for the material and the people involved.
@@amoxzi jeez man... you forgot to point out her necklace is a bit crooked.
@@stark-hampton3118 Okay thanks.. Now that is all I can focus on :(
@@brakgeluid should've read the critiques after enjoying it lol.
I can't agree to that. She might become a good salesman, but not a teacher or scientific presenter. From 4:20 to 8:30 she was laying down the content of thought experiment, but instead of showing how it leads to controversy, she just finished it with "now suppose that instead we use entangled particles, and you see, we actually going to measure a different result". In this presentation it looks like she insisted that "the math broke down", not some physics phenomenon, as "
Always thought a presenter was someone who got presents ready for people, like a third party service, kind of like an elf, but then I realised that they rarely came with gifts, mainly because they were a 3rd party I guess and I never saw them like that elusive fat jerk who eats all the cookies and leaves the neighbour's stolen badmington set as a "gift", and probably stole something while he was at it for the next kid and cookies. Then I realised that presents are only called that because they are presented to somebody, which preferebly would be myself (reciever, not giver (me receiving the the present and not the one labled a "presenter", nor a 3rd party in the mix who is preparing the present (or presentation))). Then I realised potentially that I would be receiving less presents, and figured that if I became a presenter myself, pehaps I could hijack the system of flow, thereby recieving my deserved and duly proportional amount. Then I realised that If you prepare a present that you intend to appropriate for yourself, it ceases to exist in the realm of "presents", as it is presented to none, except maybe from your left hand to your right. I toyed with the idea of concocting some big fake fanfare "presentation", where I first dressed as a "presenter", then call myself up to the stage to recieve a "suprise", duck behind the curtain, change clothes, then apear with a shocked and thankful expression as I walked to the podium to receive the present, but obviously with noboy there to present it, it fails the test on all levels. I had to concede that at least a 2nd party must be involved to be the "presenter". I think I finally found such a person.
Olivia, it is a joy to watch your presentations. I saw one from Al Khalili explaining Bells inequality, but yours has made it much clearer, which has increased my understanding of Quantum Physics to about 2%. :) Keep posting!
Stick with it! Keep coming back to Quantum Physics long enough, and it's inevitable you will tunnel through.
The only way I see to tunnel through to 28 is 10008 divided by 10007999717. Who knows?🤷♀️weirder than you think.
I did too; I had given up on understanding any of it after the laboriously detailed AlKhalili presentation on BBC. This made me feel there might be something to it. A note: I have learned from some of the AlKhalili series that I have watched in the past, but Bell's theorem wasn't one of those that made sense to me
It's worth pointing out *why* you can't build an ansible (FTL communicator) with entangled particles. When Alice interacts with her q-bit, the probability function does indeed collapse for *both* q-bits at the same time -- but Bob doesn't know that the probability function for his particle has collapsed. Further, when Bob *does* interact with his q-bit, he can't distinguish between the case "probability function has already collapsed due to Alice" and "Probability function just collapsed due to Bob's interaction". Finally, neither Alice nor Bob can influence *how* the probability function collapses to favor one value or the other.
Thus, once Bob interacts with his q-bit he can say with certainty what value Alice will get when she interacts with *her* q-bit but not whether or not she has or hasn't. Since the measured value is random, no useful information has been transferred.
Interestingly, entangled q-bits *do* have some use in communication -- they can be used to authenticate messages. In this scenario, Alice interacts with her q-bit and uses that value as part of the encryption key of a message. When Bob receives the message, he interacts with *his* q-bit to create the decryption key. While a single q-bit doesn't give Bob much confidence that Alice sent the message, if 256 q-bits are used...
While this is an interesting comment, it still doesn't prove or disprove faster than light travel or transfer of energy or information. It just doesn't.
I love how you used the words "at the same time". Delayed-choice experiments have shown that the wave-function collapse even transcends time. Which kinda makes sense if you accept the nonlocal collapse that seemingly violates c. But it goes against our intuition based on our ability to experience the universe.
This is a great explanation, thank you.
One thing that I don't understand is: If Alice and Bob cannot tell whether their probability function has collapsed or not, how do we even know there is any probability function after the particles are entangled? To me, it seems like the act of entangling a particle simply synchronizes the states of the two particles so that they will have opposite values and the probability function itself is only a thought experiment to help explain behavior caused by the observer effect. Is Bell's Inequality theorizing that this cannot be the case because of that 2.8 value?
@@Kevin-ht1ox Yes, that's correct. Bell's Theory is one of the rare cases where you *can* prove a universal negative statement-- that is, there is no function can be constructed, even with perfect information, that can say with certainty what the the state of an undeterminate particle is.
The MinutePhysics video does a much better job at illustrating this (ruclips.net/video/zcqZHYo7ONs/видео.html), with a bonus that it includes an experiment that you can conduct yourself if you are willing to sacrifice a pair of cheap polarizing sunglasses.
@@KastorFlux "...but also any other adjacent particles through localized communication..." If this were correct, then yes, entangled particles could be used for FTL communication.
However, it isn't -- if there are any adjacent particles to interact with the probability waveform would have *already* collapsed. The only valid answers to the question "Has the quantum wave function of my particle collapsed" is "Yes" or "I don't know" -- unless, of course, you have a separate channel of communication with Alice.
If you *do* have such a mechanism, then not only are you in line for a Nobel Prize, you would also make lots and lots of physicists very happy. As Einstein pointed out, lots of physicists are very, very disturbed by the consequences of Bell's Theory and quantum mechanics in general, and detecting a collapsed quantum wave form without collapsing the wave form would go a long way towards proving that quantum mechanics is only an approximation of the *actual* laws of physics.
And you would likely be rich to boot -- stock traders are spending millions of dollars to reduce latency on trades from 10s of milliseconds to 8 milliseconds. 8f you could reduce we it to picoseconds over any distance... There is a market for an ansible even today.
Love how they proved quantum mechanics is real and it just leads to "we have no idea what the hell is going on"
all it proves as far as i can tell is that what (properties) we measure has no definite value split between two particles as per QM theory .. nothing more nothing less
So, this means Heisenberg (Walter White, Breaking Bad) was wrong about time travel being impossible? I'm too old to verify the math behind quantum theory, entropy, etc.
should have figured out by the "Miraculous" experiments...
I love how everyone and their brother is dumping on Einstein, then have to admit quantum mechanics is incomplete, after all. 😃
Outside of entanglement. It is still a HUGE consequential thing to demonstrate with an experiment.
This was a little strange to me because you describe the initial scenario and show how it can be no greater than 2. Then you simply state that when using entanged cubits the number is ~2.8. How did you get there? Why is the number greater? I feel like there is something missing here.
John Bell was a technician in Queens for some years. People realised his genius and helped him get his degree encouraged him to get his PhD. He had died before I started there but by all accounts he was a lovely bloke.
um that is ridiculous and wrong. he was irish, and received all of his education in the UK. he was never any form of technician prior to his phd.
@@mabmab100I can't speak to the technician part, but FYI Queens is a university in Northern Ireland, UK
You meant he was broke...like tesla. This happens to most genius. Sad
@@BobbyT-yj1cw That's not quite correct, or at least potentially misleading. It is too often overlooked Bell was proponent of Bohmian mechanics, an alternative to Quantum Mechanics, that predicts the same experimental results, but where particles have position with out measurement.
Finally, a channel that isn’t scared to show some of the maths that is so crucial to the underlying physics of this exciting news.
Robin,
I don't think you're paying attention. That's exactly what she *didn't* do. And her mispronunciation, "Elaine" Aspect, is fingernails on the blackboard horrible.
When it came to the math she said "Go look in the caption, The actual stuff is in a paper there..."
She teased us over why the value turns out to be 2.8 and then didn't tell. That's posing, not math.
Lol. Calm down. It's going to be okay. The video is meant to encourage people to look more into the topic.
This is somewhat past my mathematical understanding but I really appreciate your taking the time to break it down so I can understand it and hence expand/bend my mind a little. At 61yo I do regret not pushing myself more in my mathematics study- just a word to the young scientists and mathematicians out there: keep grinding!!
Not sure how true it is but I have heard that Einstein expressed regrets for not investing more in mathematics on his deathbed.
Ditto for me. Have gone back to studying high school and first year universities maths in my retirement and now regret that I didn’t do more in my youth!
Wise words. Trying to impress importance of good maths skills on my kids
U r just 61yrs old u can easily become a Mathematician if u want to
Thanks for this. I needed to hear it.
This speaker is great. She is able to communicate clearly and make it simple to understand and relate to. Thanks for the great explanation.
The clarity is due to the writer of her script. If she wrote it, applause. If not, she is still a great presenter.
Thanks for this - I did think of Bell when the Nobel prize awards were announced. I often think of him because I live a few hundred metres from where he was born, in Belfast - and cycle past his house most days.
...but of course, you can't communicate with him.
Maybe he can, he just can't tell at what points his self belief as a medium, meets his probability of self delusion, making the convergent outcome evident, but not quantifiable in a meaningful way.
Well done. I understand some of it; I am still learning. At 77 it is difficult to comprehend since everything I learned is now passe. The universe is joyfully weird.
everything that you learned that was true is still true, nothing is wasted
Fantastic distillation of "spooky action at a distance!" I wish the prof who taught my graduate quantum class had been as effective at describing Bell's inequality as you are.
A slowly paced video that explains things with the goal of actually understanding them. Finally! Subscribed!
One of the coolest explanations of bell inequality I've seen and you literally fulfilled fenyman's idea of being able to explain the idea in the coolest possible way.
I love this channel so much. There are always super interesting things going on in the Quantum Computing field and the explanations are actually approachable. I appreciate all of these posts.
Thank you!
and she is looking good! very important for us!
@@ikillwithyourtruthholdagai2000 hhaah true
@@ikillwithyourtruthholdagai2000 sigh 🙄
Maybe someday the way a person looks won’t have anything to do with whether their intelligence is acknowledged.
Beautifully explained. The fact that we can actually do this experiment with Qiskit is just awesome.
To each his own, of course, but I happen to disagree. Here is a much better explanation (IMHO) by Sixty Symbols: ruclips.net/video/0RiAxvb_qI4/видео.html
@@robinswamidasan Just had a look, indeed, it's a remarkably explained
@@robinswamidasan oh by the way, how did RUclips allow you to post a URL, don't tell me it's quantum computing🤣
@@robinswamidasan I like this too.
That was wonderfully clear and well presented. Excellent stuff !
I wanted to see the physical experiment
Fantastic video but I would say it is missing one thing. For Bell's theorem, he also assumed statistical independence of the system, that is P(x|ab) != P(x) where x is a specific event of a quantum particle and a and b are measurements taken of the particle. In other words, if the "choice" the particle makes with regards to its waveform collapse is based on the measurements that WILL be taken of the particle in the future, then none of Bell's theorem, including the inequality, apply. I think this is important to think about, since no one has ever proven that statistical independence actually holds.
It's turtles all the way down.
My personal take is that measurement information retroactively determines agreement on state. I’ll throw away causality in hopes of a deterministic reality.
Re: Turtles. I thought it was elephants😢
Superdeterminism follows?
Thank you, Olivia. I didn’t understand half of it but your presentation allowed me to grasp some of it. 🤣 I hope you’re teaching somewhere; you have a wonderful, open style of communicating ideas clearly.
And you still understood 10x as much as me
lol She literally said nothing. Suppose that instead of Bob and Alice making measurements, we let Victor keep a record of the properties of the particles he sends to them. Where then would the 2.8 figure come from? Clearly, Victor is biased in some way.
They would still have to be measured in order to have a record
Yeah Victor is suspect...He likely voided his honesty by being a supporter of donald duck, he can't be trusted. His maga hat is definetly on a few snaps too tight...That in and of itself makes him untruthful, like his esteemed(he thinks)leader...Yes I'm sorry to tell you but, in the spooky action at a distance of quantum theory makes Victor nothing but a liar, so vote blue and save our local reality!!!...lol
She can communicate ideas clearly but you didn't understand half of what she said?
I went from not understanding this to sort of understanding it. Thank you for the logical and articulate presentation which helped me make this leap.
The crispness and clarity of this explanation of the mysteries of quantum mechanics was inspiring, downright chilling, thank you! I'll look for more.
It's wonderful what can result from people doing what they are truly passionate about. Paths are drawn so much cleaner and we can conclude collectively, so much more efficiently. Thank you again for another thoughtful and extremely well-presented piece, Olivia ♡
Nice production quality - excellent speaker - great engagement! This video presents an introduction to Bell's theorem. Great work!
Enjoyed this exposition, and I'm far from being a physicist or understanding the nuts and bolts of quantum mechanics. It adds to the many, many things I know I don't know enough about and that no matter how much I try I'll only ever have a tenuous grasp of!. Every day is a school day.
This person is a terrific teacher and explicator of very complex ideas with clarity and ease. Brava!
Love Bell’s Theorem-so simple, yet so hard to grasp. (I’ve been trying for 40 years. Getting there.🤨 I think.)
Quantum particles can become entangled, that’s it really
Back in the 70s, there was a physics Nobel laureate in my meditation class at Cambridge. Afterwards we had tea and a chat, and someone asked him why a scientist was drawn to this mystic practice He replied: "Oh, we're all mystics at the Cavendish - and once anyone begins to understand the profound weirdness of reality the way that we understand it, they would become a mystic too!".
What’s “the Rutherford”?
@@shyampadmanabhan4171I misremembered - it's the famous Cavendish Lab where Rutherford first split the atom.
Will edit.
@@tullochgorum6323 if you could go back in time to stop Rutherford splitting the atom , and prevent the development of what Russia is threatning to use today.....would you stop Rutherford, or not.?
@@tullochgorum6323 that is a great story. On a technical note, Rutherford didn't split the atom. Splitting the atom happened the year after he died. He did a lot in physics, though. Thank you for sharing :)
@@fierce-green-fire8887 Thanks for the information on Rutherford - I'd better read it up because I seem to have misunderstood something about his work.
As you will have gathered, I'm very much a lay person when it comes to the mysteries of physics!
Fantastic explanation! Thank you for doing this video.
Yes I loved the fact that there was no annoying background music and Yes I agree with all others that you are an excellent presenter. If I may mention that the Nobel Prize work was not all done in a lab. I watched and loved the presentation on Nova, Eisnstein's Quantum Riddle where an experiment in the Canary Islands Observatory have done some amazing experiments.
Thanks! That was super clear. I never really knew what Bell's Inequality was claiming, only that it sealed the truth of non-realism. For me, the double-slit experiment was my introduction to non-realism. I just read that the "single electron" version of that experiment (which is the version that blew me away) wasn't done until 2002, years after Einstein died. So he never got to see that. Now I understand how non-realism was established in a more thorough way using the violation of Bells Inequality. I also don't feel as disappointed in my high school physics teacher whose explanation of the particle vs wave nature of light left out telling us about the underlying quantum weirdness it suggests. Since that was before 2002 he couldn't have known . Tying up a lot of loose ends here ...
> only that it sealed the truth of non-realism.
It didn't the explanation is wrong. It only sealed local hidden variable theory one of many local realistic theory. There was and it is still a lot of research on a local realist description of quantum mechanics.
It most certainly did not "seal the truth of non-realism". You can have realism or you can have locality, but you can't have both. Remember that these words have technical descriptions in the theory so don't load other meanings onto them.
@@coot33 Maybe I should have said the "reasonableness" of non-realism. "Truth" is a pretty high bar.
@@nehocm123 You can have both. Deutsch worked on it in the early 2000. There are even more recent result of making local-realist description of quantum mechanics. That is the point. It's unbelievable to some physicist but the bell theorem doesn't exclude it. If you want i can send you the link of papers.
@@coot33 I am familiar with the many worlds escape from this conundrum and I will grant its formal consistency but until one of its forms is shown to be testable, at least in theory, I would prefer to give up locality and keep realism. This is of course a philosophical stance and I don't begrudge you or Dr. Deutsch for believing otherwise. Keep in mind that the non-local phenomena we are discussing do not involve FTL signaling.
I also suggest that a likely more fruitful approach is work on objective collapse interpretations and the nature of time and entropy in spacetimes with realism.
There are so many explanation out there of this last Nobel in Physics than either oversimplified the issue to the point of being wrong or they enter into so many details that I need a PhD in Physics to have any chance to get something out of them. However, this explanation hits the nail on the head. Brilliant.
I still dont get it
@@pavelvedernikov8502 Then you're probably a bit like me. I can grasp a lot (actually most) of the concepts and theorems of physics when it's explained to me in words. I'm just not a beta person by nature. Therefor I've always struggled to understand the underlying proof. Which of course is always expressed in the beautiful language of maths. It takes me a lot of effort to actually understand those equations. Just rewind that part of the clip a couple more times and try to do the equations step by step with her. It eventually clicked with me.
I'm surprised people think this is a good explanation. She wrote out a simple mathematical expression that can't be more than 2, because the Ax, Ay, Bx, By values, she said, are each 1 or -1. Then she says they measured it and it's 2.8 - wow, isn't QM weird. That's not a violation of classical physics, it's a violation of arithmetic. There is no world in which `(Ax + Ay)Bx + (Ax - Ay)By` is greater than 2, given the variables are 1 or -1. So... it seems like the video hid the "weirdness" somewhere and didn't show it. I'm guessing it's in the logical connection between the QM and that simple math expression. In other words, something about QM makes you think it should follow that math expression, but it doesn't. But this video never shows why they thought it should follow that math expression in the first place.
This woman is "miraculous" herself. Even someone as limited as myself could understand every major concept she described and that amazes me. Thank You so very much miss.
The best part was she wasn't reading off a teleprompter, she was explaining things she actually understood
I spent the last hours trying to understand what this nobel prize was really about and the closer i could get to it was with this video. Thank you very much
Thank you for explaining it so well! Definitely leaves us with some interesting things to explore regarding the relationship between entangled particles.
The fact that I can test Bell's Inequality online is crazy!!! Very cool. Makes me want to study computation theory.
Never heard an explanation that is crystal clear like this. IBM is truly world clsss. They many 11corporate research labs all over the US and the world as well. They hire the best young PhDs in Physics and bring the best out of them in their labs. Hope this tradition is continued endlessly as many other corporate research labs had shut down citing the expenditure of running such labs like Bell labs, Lucent technologies.
If the explantion was crystal clear, what is the justification/explanation/source for the ""AxBx + AxBy + AyBx - AyBy" ?
@@KastorFlux The issue isn't if it's usefull but does it happen. If something travels faster than speed of light, then relativity has been refuted.
@@KastorFlux There is no requirement for a claim to be falsfiable. Again, can the "spooky action at a distance" be used or not isn't relevant. Unless you believe in superdeterminism, you can't rationally deny that spooky action. Relativity is a local theory, so that spooky action demonstrated it's at the least "not complete", like Einstein suggested about QM.
"Does it rely on esoteric bs that can not be proven? Yes. "
As I said, unless you are a proponent of superdeterminism, it has already been proven. There isn't anything that needs to be proven anymore.
"Does it make wild and unbelievable claims? Yes. "
Argument from incredulity is a fallacy.
"Does it rely on superstition, faith, or social pressure to propagate its validity? Yes."
Empirical experiments are not superstition.
Thank you Jesus for not only no background music, but also for no camera movement. Thank you for letting Lanes present and for not goobering up her presentation with unnecessary production clichés.
In the first set-up, Victor sends two non-entangled particles/qubits, one in Alices' direction and the other in Bob's direction.
My favorite line: "It's not just weird on paper, it's weird in the real world."
Well, if a Higgs likes it...
12:26 "...us in the field..." are we not all in the field, seeing a few wave-tops and thinking it reality?
Dude, where's my boson?
And the results are: Bob is NOT the father.
Worse. Bob may or may not be the father.
@@Rosenthal00 Worse. Bob may and may not be the father.
Daddy is here.hi
Wow great walk through.. Olivia should start a lecture series on QM stuff here on youtube. Really cool!
The Bell's inequality experiments are great! Probably a good choice for the Nobel Prize. My amateur guess is that they show that reality is nonlocally interconnected. Maybe with waves. Stephen Hawking wrote that there might be only waves, and that particles with locality are just our interpretation of the underlaying waves and that there isn't even any need for uncertainty in quantum mechanics.
I have always subscribed to this interpretation of reality, as it is anchored in relative Spatio-Temporal Unity… however, it has to be justified and proven first for it to hold any substance in the community and society as a whole
"Quantum mechanics brings us to the brink of the impossible, to the point at which we shouldn't be able to fully comprehend what's going on, but NO FURTHER THAN THAT."
Really like this description
Excellent work--your depth of knowledge and enthusiasm shine through. Clear and easy to understand with minimal previous knowledge
@6:29 "it really doesn't matter where this quantity comes from" - I would like to know where the equation comes from.
That‘s what I thought as well.
exceptional delivery. Nice work, Olivia.
Intelligent speaker and explained in a down to earth manner even a layman like me can understand. Thank you.
That presentation was interesting and your delivery was appropriately technical and charming- a combination of science with humanity. Thanks-
The entangled pair, had selected a state before any were measured, else they would not have become entangled. The uncertainty is entirely because of the problem of measurement. It is a fundamental problem, not something to write into a theory. The universe operates completely well outside our observations or measurements. We need a whole new approach.
I have been struggling to understand Bell's theorem for years and I'm afraid that this presentation leaves me just as confused as before! But what I would love to know is whether there are any practical applications of these strange phenomena.
Yes, quantum encryption
@@evihofkens9530 I just read what Wikipedia says about that and frankly I couldn't understand it at all! Thanks for the info, anyway!
Philosophically, quantum physicists have proved a negative!
You can prove that men and wolves exist, but you can't prove that werewolves don't exist!
@@carlgrove8793 «@Evi Hofkens I just read what Wikipedia says about that and frankly I couldn't understand it at all! Thanks for the info, anyway!»
----
Dear friend, imho the reason you cannot understand it is that of being sincere and honest. If you want to understand it in a way many others understand it, you should (re)read The Emperor's New Clothes. Btw Clothes that were made using bits that had jumpy levels of sawing energy coming out of cryptically nested sub-dimensions of the inner quantum not-space.
The main problem I have with this video is that she completely dismisses locality and emphasizes the experiment disproved realism when the results of the experiment show neither locality nor realism is true in quantum mechanics. The information of entangled objects does travel faster then the speed of light. While the persons in the experiment cannot communicate faster then light, the entangled cubits can which means the instant one person knows the state of one cubit, the other knows instantly what the state of other cubit is.
I am very confused: if the x and y values can still only be 1 or -1, how can the CHSH value ever be greater than 2, algebraically?
my confusion as well 😒
Could it be that both values could be +1 at the same time? And that the lower boundary is -2? But yes, confusing
It's poorly explained: X and Y are never measured at the same time. Either X is measured or Y. So, for a single experiment the CHSH is not even defined... it's only computed on average.
@@Jooolse that maked a LOT more sense. This video has loads of jumps in logic i failed to connect
This is not merely a statement about the weirdness of Quantum Mechanics, but the weirdness of the ultimate/inherent nature of space itself that we still don’t know anything about. Much in the same way that we still don’t know what gives rise to the Higgs Field, for instance; and still ascribe it to the inherent and unknowable nature/property of space itself.
12:05 - “The only way of discovering the limits of the possible is to venture a little way past them to the impossible." Arthur C. Clarke
So either we agree with quantum mechanics saying everything that makes up reality (i.e., particles) aren't there until we measure them. Or we agree with Einstein, that quantum mechanics is an incomplete theory... After listening to this explanation, sure get the feeling Einstein was right, again.
that may be right
clauser tried to show john bell about how he forgot to include meausrement independence but only about 6 mathamaticians and physicists are brave enough to talk about it.
@@benf2532 and yet, Brian Cox remains steadfastly silent on the topic, afaik.
Whenever someone names the character in their example as Alice it reminds me of Leonard Susskind :D Great video!
Thanks for the explanation. I had heard of Bells theorem but this helped me understand it better as a non-physicist. The idea that realism does not exist sparked many of my own "thought experiments" about the nature of reality and the universe. I think we may be close to unlocking some of the secrets of reality itself, the consequences of which we cannot comprehend at this point.
Can’t disagree with slip’s conclusion here but it’s looking to me like either it’s gonna be a Trojan horse orapandoras box. Third favourite has to be the lair of the Minotaur with or without heroic intruders. Here’s one I’ve never wondered about much until now; what did the Minotaur do if they accidentally left it’s lair unsecured?
But it's not "reality" like a normal English meaning of that word. The point is just that we've disproved the idea that "measurement" tells you about properties of a system that existed before you took the measurement. I'm not 100% sure why the word "reality" is used in this way, not the word I would have chosen, I think. I think it had something to do with a quote from the EPR paper.
Uhhhhh what about superdeterminism? When properly understood, it explains the results of Bell's experiments, preserves locality, reframes 'wave function' as ignorance of the observer, keeps Einstein and Newton happy, and still makes room for a robust understanding of free will.
can you give an example of measurement values when the outcome is 2.8?
Or 3, or 4, or anything greater than 2
It is not explained fully in the video since the equation values can never all be measured simultaneously. The 2.8 comes from averaging across component values measured many times (not simultaneously) and then summing these average component values.
This satiates my queries so much while also firing so many neurons for further inquiries.
Brilliantly communicated the phenomenon 👏
To save the energy and resource, the universe renders objects only when it's necessary, just like any MMORPG games.
5:00 What I don't understand, assuming Alice, Victor & Bob are in the same "Frame of Reference" (Train for ex.) that moves with 0.5c to the right (Bob-direction).
- First, because of dopplershift, one photon becomes blueshifted and the other redshifted, even if they are entangled.
- Second, even worse. Alice gets the photon first for external viewers. So she knows the outcome of the measurement, while it's still in superposition for Bob.
Because within the train, both Alice & Bob get the entangled Photons at the same time. So, it has to be in superposition for Bob, and not collapsed to a value when it arrives.
Does this make any sense? 🧐😵💫🤯
The consequences of special relativity would only manifest if they are moving relative to each other. If they are all on the same train moving at a constant speed, anything perceived by the people on that train, are exactly the same as if they were all standing still, so there's no doppler shifting or time dilation from their perspectives.
More to the point, the particles being exchanged in the experiment are *not* photons. Instead, entangled electrons are exchanged, quite possibly in a briefcase. Thus:
1) The measurement of the values doesn't occur immediately upon receipt.
2) Alice and Bob may perform the measurement at different times, perhaps even on different days.
Thus, relativity isn't a significant factor in the experiment. I'm not even certain we know how to entangle photons, but even if we do, *keeping* them entangled is going to be very, very difficult. Electrons, on the 9ther hand, are reasonably easy to entangle.
@@jmr5125 Actually, it’s way easier to create a pair of entangled photons, in fact that’s what the Nobel laureates used. The most common way to do this is using spontaneous parametric down conversion (SPDC), which creates 2 photons with orthogonal polarizations. The coherence lifetime of a photon is practically infinite while an electron will suffer decoherence extremely rapidly unless it’s in ultra low vacuum at temperature close to absolute zero.
@@nikhilmathur9952 Thanks! I did see MinutePhysics video on this same topic, so I should have realized that it's easy to create quantum entangled photons. My bad.
@@nikhilmathur9952 ~ The actual time dilation comes from the fact that there are gravitational gradients all over the place. (They cause the tides, for example). Timekeeping is elastic, varying with local gravitational field strength.
Really well explained - thank you. Einstein is right in the sense that there is still a mystery here.
You can't tell the difference between gravity and acceleration, because gravity is acceleration. Gravity doesn't just bend space time, it absorbs it. Black holes prove this.
This is fascinating! Quick question: is there a specific "max speed" beyond the speed of light, such that the 2 ~ 2.8 equation would actually balance out correctly? Like, if we pitch lightspeed and keep realism, do we get a specific number for max speed beyond our (easily? currently?) perceived max?
Um, idk the answer to this question but i think the implications of this experiment is not that the speed of light is violated but that local realism is violated. Although i believe there was a study done by swedish physicists with mirrors and virtual photons that postulated that the speed of light was not in fact a constant but relative to the number of subatomic particles in existence so that it appeared constant.
@@Ben-rz9cf See yeah, exactly. I'm just wondering what we can gain if we throw the speed of light out instead.
Sports almanac for future gambling endeavours
Planck speed
@probablyup I was so immediately excited after reading this comment that I googled to get reading and now I'm not even sure if I'm being punked or not, that's how hard it is to learn science online in current year
Thanks Olivia and the rest of the team. I'm recovering from series of mini strokes. I use videos such as yours as weight lifting exercises. The brain is a muscle. It needs the exercises you kindly provide. Thanks again for the knowledge and a little bit of befuddlement!
I would argue that the assumption of realism is unrealistic.
I enjoyed this very much! It''s my first video watched from this channel, I'm a new subscriber!
This is so well explained - grabbed my attention throughout! You are such a talented presenter :)
We are getting closer to this possibility with laser communication
You are an excellent presenter! I knew the Quantum world was weird, but not that weird!
Great presenting skills, well done! It was even a pleasure just to listen to your presentation and explanation 😆
With intelligent young people such as yourself there is hope for our future. Beautifully presented.
I’m not sure to whom this video was intended, those with little to no understanding of quantum physics or those who are actively studying it.
You spent so much time setting up this AxyBxy equation, you set limitations of +/-1 and showed it’s equal to or less than 2. But you gave no reason that I heard about why the measurement is only +/-1. Then you jumped to entangled particles and just told us the measurement is about 2.8 without an equation demonstrating why. And what does it matter than the opposite value was known immediately?
You remind me of my high school biology teacher who tells the tale of an experiment where someone cut off the tails of mice for 50 generations and no mouse produced offspring with missing tails because acquired traits are not inherited. Then she goes on to say, giraffes had normal length necks but would have to stretch their necks to reach higher than others. As they continued to stretch and stretch, their offspring have the long necks we know today.
Thank you for so clearly explaining to this sublayperson the meaning of this NOBEL event.
Sublayperson sounds similar to my self designated 'amateur layperson'. Maybe in a few years, already 67, I can become an experienced amateur layperson'. 😂😅. I did really like this explanation and surely wouldn't try to paraphrase it.
I’m not a physicist. But I have a problem with “entanglement”. I have yet to see anyone explain entanglement. And what is the difference between entangled and not entangled particles? When 2 particles are viewed by 2 separate observers, how is it they know for sure any particle was entangled at the source? What is the physical process of entangling particles? What kind of measurement is made at the time of entanglement? How can an observer be confident that they were actually observing an entangled particle? How is just one particle produced at a given time? There are a number of questions associated with the concept of entanglement that I’ve seen no “empirical” proof of. If something is simply mathematics, is that to be accepted as proof of something in the real world? Logic for example doesn’t necessarily draw empirical conclusions. Correct conclusions are based upon the premises being true. A logical argument can be made even with false premises.
There are no particles. You are simply watching too much RUclips. ;-)
You’re a great presenter! Thanks!
Maybe bob and alice were both cooking a egg, and as 4 minutes approched they both looked at the toast at exaclty the same time and said 'grab the butter', then they looked at eachother and both said 'jinx'.. and loled, we all loled and ate dippy eggs.
I have to admit I was expecting some information about the 2.8 result. Also, for people who are not familiar with these things -like me- I would like to have quick words about what are X and Y in the first experiment you are mentioning
X and Y are usual ways to denote directions in which you measure the spin of a particle, for example. Measuring spin in one direction leaves the other (perpendicular) direction free to take any value, but measuring spin twice in a row in the same direction makes the second measure be equal to the first. Measuring at intermediate directions creates correlations which are not 100%, but which can be calculated. All of this is important to get the result shown.
You might want to look up the Stern-Gerlach experiment, it isn't too complicated, but illustrates all of this very well (some textbooks on quantum mechanics even open with it)
Yes. This makes the whole thing obscure.
agreed
The link holds quite some clues but as it was said this needs a bit more math and physics to fully understand. what I can fit in a comment to lift some mystery it is not 2.8 really the exact value is 2*sqrt(2) which is related to the binary nature of this particular problem description and perpendicularity.
@@user-sl6gn1ss8p thanks a lot, it is very helpful! 👍
I have had many attempts to understand Bell's Inequality/Theorem, and this video has gotten me further down that road. I think I can now at least see which bits I understand, and which I don't.
I still don't totally get why apparently "instant" effects can't produce instant communication. Even if it doesn't in this particular case, maybe in the future someone will design an experiment that behaves differently.
Yes, great explanation but I still do not understand why there is any probability function at all if the only thing we can really know is that the two particles have opposite values and when we read the values, we cannot tell whether or not either particle was already "read". This behavior seems no different than if I were to split an apple in half, place each in a box and randomly give Bob and Alice one of the boxes. Opening the box only reveals to Alice or Bob which side of the apple they received however every quantum theory explanation says that the apple halves have superpositions where they are both values until they're observed. That superposition theory seems like a gross misinterpretation of the statistical measurements. A tree falling in the forest will make a sound whether or not someone is there to hear it and there is no evidence that suggests otherwise. What is it about the quantum world that leads us to believe it is any different?
To understand or see how the quantum world is different from classical physics explaining the world we normally experience it helps to look at Young's double slit experiment and read on the wave-particle duality. It shows that particles are also waves and behave as such. It's actually an observable effect, not just a theory, even for particles that have mass. The particles are not just in one place, but with a certain probability they are also in other places. One effect of this is tunneling, which explains radioactivity, for example. It's probably best to hear about some basics first. Makes understanding things like entanglement much easier.
@@Kevin-ht1ox the whole point of the theorum is to see if the apple example you mentioned is how it works. It's worth noting that Bell was hoping that's how it was, he was in favour of hidden variables but was a good enough scientist to go with the result.
If the apple scenario was true it predicts certain values, however quantum mechanics predicts different values that are not possible if the states are fixed before hand. Experiments show it to be right.
I strongly recommends the Sixty Symbols video if you want more detail as he goes into way more depth about how the experiment works and the maths.
m.ruclips.net/video/0RiAxvb_qI4/видео.html
Realism feels intuitively true beacuse it is our experience, but we can dismiss the facts bexause they are unintuitive the universe is under no obligation to work in a way that feels right to us.
@@Kevin-ht1ox this is bells inequality, both apples should add up to one, in the same vein, the sum of all outcomes should end up being something specific, but they are not they are actually more, which is proven by experiments, so imagine you put two slices of an apple in two separate boxes and later measure the contents and find the material for 1.4 apples. That doesn’t make any sense?
That’s with the vectors of the quantum particles they don’t add up to two but 2.8 which is too high. So they go above the bounds of bells inequality which makes it weird.
@@NeoRetroX i don't know that it doesn't make sense. I just know it doesn't fall within the belief systems of mathematics or logic. And they are belief systems. Everyone has to before hand agree to accept certain truths before you can proceed. An axiom, a statement that is accepted as true without proof. 1 and 1 only adds up to 2 because everyone agrees its so. Belief system. Its essentially just agreeing on the rules of the game before we begin the game
"Now, in quantum mechanics we say there exists this thing called the wave function which describes all the properties of your Quantum system and upon measurement it collapses into a single quantity that was only described probabilistically before you measured it."
Good Gal! Best, most succinct, rendition of wave function collapse l've ever read. WFC's reaIly just like snagging a flipped coin. Its position is indeterminate tilI you snag it. The coin position wasn't fixed tiIl you snagged it and stopped it. In the same way your quantum properties aren't fixed tiIl you 'snag' the system by measuring it.
Good Gal! Thx.
Man. This quantum mex is SO counterintuitive. Crazy.
Yes, that's total bullshit. Absolutely nobody who knows quantum mechanics will ever say that the wave function "exists" or that it contains any information about an individual quantum system. Only people who don't understand quantum mechanics will say such nonsense. ;-)
Great content... thanks for sharing
Bells experiment assumes that the experimenters have a free choice in configuring their experiment (Choosing the spatial orientation of their detectors). This assumption sounds insane to me because if there are hidden variables and the universe does work like a deterministic 'machine' then why would the experimenters be special (in that they don't work like machines but have free choice)? When are we finaly going to loose the 'human = special' assumption in physics. It has turned out to be wrong so often already...
You misunderstood the nature of the free choice. In practice, the experiments use random inputs to make the choice, not humans. As random as possible, with no plausible correlation between the choices... for example using random bits generated by noise from the Cosmic Microwave Background.
@@brothermine2292 Yeah but you didn't solve anything with that. Where is the cosmic microwave background "randomness" determined from? You can't just assume that something super complicated is perfectly random. At best the CMB is pseudo-random and still deterministically intertwined with everything else on earth.
@@seanmcalevey4566 : Even if it's merely pseudo-random, it's implausible that the effect would create the coordination between the measurement orientation setting of Alice's detector & the measurement orientation setting of Bob's detector that would be needed to result in statistics that imitate the non-classical prediction of quantum mechanics. It's like the implausibility of an untrained monkey at a typewriter producing only plays of Shakespeare, never producing unintelligible garbage (or foolish youtube comments).
That is a valid objection. What if the whole experiment was predetermined?
An experiment was set up where the observers didn't TRY to make a random choice; instead they used information from ancient stars to make the choice.
And the two observers used two stars so far apart that they could not have communicated in any way, due to speed-of-light restrictions.
Sorry if I am not clear on this, but basically they handled your objection.
What a great presentation of some really complex problems. Really well done,thank you, I was thoroughly impressed.
This is very interesting and thank you for the explanation. A bit I'm struggling with is that while Bob and Alice aren't communicating, the particles either must be, or they each have a real value that is hidden, or somehow otherwise exists outside our current understanding of what's "real". Am I missing something about the definition of either local or real?
No, I think that was basically Einstein's point... I think he thought there was some hidden information that we simply can't access
Beautiful explanation Olivia, thank you!
My name is Olivia but thank you!
@@livlanes I'm sorry, long week.
Thank you for the effort. I didn't actually follow along properly, there were a few yhimgs I wish you had clarified a few things in the video.
1) what is CHSH? (Full form, meaning)
2) Why was that inequality constructed the way. Adding 3 terms and subtracting 1, sort of randomly in a hand wavy fashion.
3) Would have liked a better example of realism, didnt quite get that.
There is more, but I won't go into it. The overall quality of the video is great but the explanation could have been a bit better. Thanks.
(Ps, I am a computer scientist who has studied quantum mechanics at a bachelor's level, so noy a complete beginner).
It’s a tragedy that Bell died only a few years ago and so was excluded from the Noble. Remember his theory was so weird at the time that all the mainstream physics journals rejected his paper. Now it’s the definitive proof of entangled interactions.
He died over 30 years ago.
This was a great video - I myself have suffered from the fallacy of entanglement allowing for FTL information passage. Good explanation of the “collapse” of the entangled wave function not implying information.
I’ve found no intuition for quantum mechanics. It’s all just been studying that has allowed me to see further. Definitely defies our logic of the natural world.
Thanks for taking me a step further on that journey :)
How can we confirm with a measurement if two particles are entangled before we run experiments with them, or do we just say they are entangled because we believe some process they go through gets them in a state of entanglement?
It all sounds like a scientific charlatanism.
In reality, Everything measures everything therefore the Universe is deterministic but not necessarily self-knowable.
(The state of Schrodinger's cat located in any given Plank point of space-time is determined because any Plank point of space-time is measured by its neighbouring points of Plank space-time)
When you explain the fact that these particles are not transferring information faster than the speed of light it's still a little confusing. It's mentioned that the particles are entangled and their wave functions become one. It also mentioned the the particles are sent to Alice and Bob before the measurement. So, because entangled particles consist of the same wave combined wave function, they can be thought of as the same quantum object. When the two objects are transferred to both locations at less than the speed of light before the measurement then the information traveled at sub light speed to their measurement locations. Then when a measurement is made of one of the particles, then the combined wave function or quantum object collapses into a opposite values for both particles at the same time. The fact that you can have an quantum object that is essentially in two places in once until measured and it breaks into individual particles again is really the crazy idea here.
I am always amazed that anyone can understand this stuff to begin with. The fact that nobody understands, including themselves, where they end up to end with is the challenge of this life.
How did he win the Nobel if his name is Bell?
Asking the real question here.
Louder, for the people in the back.
(More decibels)
Should have had a yesbell okay sorry
I am a physicist and I want to explain the “observation” problem in quantum mechanics because it is often misunderstood even by many physicists.
In quantum mechanics the physical system is described through a wave function whose evolution over time is determined by the Schrodinger equation. The wave function represents infinite different possible results for the physical quantities related to the system, but when we take a measurement, only one of these infinite possibilities becomes real; after the measurement, we must therefore modify the wave function “by hand” to eliminate all other possible results, and this modification is called the “collapse” of the wave function. If all other results are not eliminated by imposing the collapse "by hand" on the wave function, the predictions of subsequent measurements on the same system will be wrong.
The fundamental problem with quantum mechanics is that interactions among particles are already included in the Schrodinger equation and such equation does not predict any collapse. The collapse of the wave function is a violation of the Schrodinger equation, i.e. a violation of the most fundamental laws of physics and therefore the cause of the collapse cannot be determined by the same laws of physics, in particular, it cannot be determined by the interactions already included in the Schrodinger equation. The Schrodinger equation is what allows us to make quantitative predictions about the outcomes of future measurements; everytime we make a measurement, we receive new information about the system, and we need to "update" our wave function, i.e. to collapse it, otherwise the Schrodinger equation would provides wrong predictions relative to successive measurements. After one century of debates, the problem of measurement in quantum mechanics is still open and still represents the crucial problem for all interpretations of quantum mechanics. In fact, on the one hand it represents a violation of the Schrodinger equation, that is, a violation of the fundamental laws of physics. On the other hand, it is necessary for the laws of quantum physics to make sense, and to be applied in the interpretation and prediction of the phenomena we observe. This is the inescapable contradiction against which, all attempts to reconcile quantum physics with realism, break.
Quantum mechanics is incompatible with realism (that's why Einstein never accepted quantum mechanics); all alleged attempts to reconcile quantum mechanics with realism are flawed. Quantum mechanics implies that physical reality (the universe) consists of the collection of all observed phenomena and such phenomena do not exist independently of consciousness. In fact, the properties of a physical system are determined only after the collapse of the wave function; when the properties of the system are not yet determined, the system is not real, but only an idea, a hypothesis. Only when collapse occurs do properties become real because they take on a definite value. It makes no sense to assume that the system exists but its properties are indeterminate, because properties are an intrinsic aspect of the system itself. The collapse represents the transition from a hypothetical system to an actual system.
The collapse of the wave function represents a non-physical event, since it violates the fundamental laws of physics, and can be associated with the only non-physical event we know of, consciousness. Therefore, the only consistent rational explanation of the collapse is that it occurs because consciousness is involved in the process. However, the fact that properties are created when a conscious mind observes the system in no way implies that it is the observer or his mind that creates those properties and causes the collapse; I regard this hypothesis as totally unreasonable (by the way, the universe is supposed to have existed even before the existence of humans). The point is that there must be a correlation between the collapse of the wave function (=violation of the physical laws) and the interaction with a non-physical agent (the human mind); however, correlation does not mean causation because the concomitance of two events does not imply a causal link. The consciousness that causes the collapse of the wave function must be an eternal consciousness, that is, a conscious God. This is the idealistic perspective, which implies that physical reality exists as a concept in the mind of God who directly creates the phenomena we observe, according to the matematical models through which He conceived the universe (the laws of physics); the collapse of the wave function is a representation of the moment when God creates the observed phenomenon. This is essentially the view of the Irish philosopher George Berkeley, and in this view God is not only the Creator, but also the Sustainer of the universe. Idealism provides the only logically consistent interpretation of quantum mechanics, but most physicists do not accept idealism because it contradicts their personal beliefs, so they prefer an objectively wrong interpretation that gives them the illusion that quantum mechanics is compatible with realism.
This may be a related topic. In our experiments we have observed that nearfield electromagnetic fields propagate nearly instantaneously, but reduce to the speed of light in the farfield, about 1 wavelength from the source. The result is predicted by Maxwell equations by solving the inhomogenous wave equation and analyzing the speed of the fields. And this result corresponds to the phase speed, group speed, and front speed (ie. information speed). As you mentioned, instantaneous communication has observed been observed in quantum systems, and likely also explains the phenomena we are observing in the nearfield. But until now it was not though possible to control and transmit the information nearly instantaneously. Our results show that normal narrowband AM or FM modulated radio waves propagate instantaneously in the nearfield of the antenna source and clearly can be used to speed up communications over large distances by lowering the carrier frequency.
A quantum explanation of this phenomena can be shown using Heisenberg's uncertainty (HUP) where Δx and Δp are interpreted as averages according to the Pilot Wave interpretation of Quantum Mechanics. In this interpretation HUP is: Δx Δp = h, where Δx and Δp correspond to average values. So in HUP: Δx Δp = h, where Δp=mΔv, thus HUP becomes: Δx Δv = h/m. In the nearfield where the field is created, Δx=0, therefore Δv=infinity. In the farfield, HUP: Δx Δp = h, where p = h/λ. HUP then becomes: Δx h/λ = h, or Δx=λ. Also in the farfield HUP becomes: λmΔv=h, thus Δv=h/(mλ). Since p=h/λ, then Δv=p/m. Also since p=mc, then Δv=c. So in summary, in the nearfield Δv=infinity, and in the farfield Δv=c, where Δv is the average velocity of the photon according to Pilot Wave theory. The fact that Instantaneous nearfield electromagnetic fields have been observed both theoretically and experimentally, favors the Pilot Wave interpretation and not the Copenhagen Interpretation of Quantum Mechanics, where in the Copenhagen Interpretation, Δx and Δp are interpreted as probabilities. It should be mentioned that both the Ensemble Interpretation of Quantum Mechanics also interprets the Heisenberg uncertainty principle (HUP) in terms of averages. But the Ensemble Interpretation does not support instantaneous propagation of information, whereas Pilot Wave theory does.
*RUclips presentation of above arguments:
ruclips.net/video/sePdJ7vSQvQ/видео.html
*More extensive paper for the above arguments:
William D. Walker and Dag Stranneby, A New Interpretation of Relativity, 2023:
vixra.org/abs/2309.0145
*Electromagnetic pulse experiment paper: www.techrxiv.org/doi/full/10.36227/techrxiv.170862178.82175798/v1
Dr. William Walker
The only problem there, is that there is no god.