Bell's Inequality: The weirdest theorem in the world | Nobel Prize 2022
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- Опубликовано: 6 окт 2022
- Last year, in 2022, John Clauser, Alain Aspect, and Anton Zeilinger were awarded the Nobel Prize in physics. Their groundbreaking work was built upon one of the most significant discoveries in the history of physics: Bell's Theorem, which was originally formulated by the late John Stewart Bell. In this video, we delve into the reasons why Bell's Theorem stands as one of the most important and perplexing results in the annals of physics. Join us as we celebrate the achievements of these three remarkable scientists who, through their contributions, laid the foundation for cutting-edge technologies rooted in quantum information.
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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.
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.
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
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
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.
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
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.
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.
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.
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.
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 ♡
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.
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.
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.
Thank you for explaining it so well! Definitely leaves us with some interesting things to explore regarding the relationship between entangled particles.
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.
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.
That was wonderfully clear and well presented. Excellent stuff !
I wanted to see the physical experiment
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.
I did my undergraduate thesis on Bell's Theorem and loopholes in experimental tests of the theorem.
I was pleasently surprised to see Alain Aspect winning the prize because I read a lot of his research.
I am curious to hear more about quantum-tunnelling experiments that seem to show information being transmitted faster than light. Particularly since some of the claims that what was being transmitted (a piece of classical music in one experiment that I recall) was not really “information”, seemed just a little bit dubious.
A slowly paced video that explains things with the goal of actually understanding them. Finally! Subscribed!
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.
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
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.
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.
Great presenting skills, well done! It was even a pleasure just to listen to your presentation and explanation 😆
Outstanding pragmatic explanation! This opens up a whole new perspective for me! Thank you for your remarkable review!!!
Excellent work--your depth of knowledge and enthusiasm shine through. Clear and easy to understand with minimal previous knowledge
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?
This person is a terrific teacher and explicator of very complex ideas with clarity and ease. Brava!
You have proven you might now know you did not know what you thought you might have known or not known. As well, your words, it’s miraculous. Good work!
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.
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.
Nice production quality - excellent speaker - great engagement! This video presents an introduction to Bell's theorem. Great work!
Thank you so much…🙏🙏🙏 way above my maths/ comprehension at near midnight.., but a huge privilege to have the theory behind a noble price explained🙏🙏
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 very much for such a wonderful explanation. I wonder if these experiments ultimately confirm that there is "something" that we are not taking into account. And that is precisely what we could call "hidden variables", or better, "unknown variables", because in fact we know what happens but not exactly why.
Terrific video. A very easy, digestible demonstration of quantum weirdness. Thank you, Olivia.
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 fact that I can test Bell's Inequality online is crazy!!! Very cool. Makes me want to study computation theory.
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.
Thank you for a clear explanation. If you measure one particle, is it true that the wave function collapses for the other particle and that can be detected (perhaps through something along the lines of a double slit experiment)? If so, how come that is not a way to communicate (measuring the collapse of the wave function)?
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.
Fantastic explanation! Thank you for doing this video.
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?
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.
EXCELLENT PRESENTATION 👏 ...thank you 👍.....super impressed with how you presented the ideas and I see others are as well so I am not alone in that regard
I loved that ending. It felt like a heartfelt and genuine thank you to the Nobel prize winners.
Also Olivia, you’re doing pioneering work in quantum computing. The rest of us thank you for the applications that will come from your work and many of OUR future jobs.
Appreciate it!
In the first set-up, Victor sends two non-entangled particles/qubits, one in Alices' direction and the other in Bob's direction.
A very nice explanation, kudos for clarity. But I thought that Bell also recognized the need for measurement independence i.e. the notion that the choice of detector axes were made independently by Alice and Bob. If their choices are correlated, as in super-determinism, it provides yet another route to violation of the Bell Inequalities, albeit no less "spooky"
Where does this equation come from? Is x and y spatial coordinates or base values for cubits? The circuit calculator? Is it sufficient to calculate a simulated logic/diffraction gate using entangled particles for a computational hologram?
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?
As a lay person who studied analytical chem and no physics courses, I think I'm following. This host is a great science communicator.
As a follow up vid, I am curious to see how the experiments of Clauser et al were conducted. An overview of the instruments and data/analysis that resulted would be much appreciated.
She's an incredible presenter of information / data. Very well explained despite the complexity of the material.
This is such a well done explanation, thank you!
Wow. This is the best explanation on this I've heard so far. Great job and thank you! 😊
It wasn't, her hairy arms were distracting me from being able to focus
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.
Wow. Very good explanation. I was waiting for the "usual" error that screws up the logic.
It didn't come. None of us really know what is going on, but in terms of what we theorize - this presentation is wonderful.
Excellent video, with very clear explanations. Thank you!
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!
Wow great walk through.. Olivia should start a lecture series on QM stuff here on youtube. Really cool!
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
Really well explained - thank you. Einstein is right in the sense that there is still a mystery here.
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 enjoyed this very much! It''s my first video watched from this channel, I'm a new subscriber!
Masterfully done. Thank you!
Intelligent speaker and explained in a down to earth manner even a layman like me can understand. Thank you.
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.
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!
Great explanation because I'd been wondering if we could communicate faster than light with entangled particles. I understand it is not possible thanks to this video, but even more importantly I now understand WHY it's not possible!
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 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!»
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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.
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.
What is interesting is during '50s, '60s and even '70s working in quantum theoretical field and challenging the Copenhagen interpretation was a kiss of death for your career. That was clearly stated by Clauser himself. Even John Bell, after writing his not so famous at that time Bell's theorem, left it for like 20 years and picked it only later on during 70s. This behavior was generated by the "Shut up and calculate!" mentality that arose after WWII.
Great explanation of Bell's results. After reading Wikipedia's entry on his theorem and watching RUclips videos, I only finally understood your explanation! I've got a few questions from curiosity, and, to ensure I'm on the same page:
1) does normalizing mean we make a value easier to work with by first converting it to a simpler number like 1? (or -1)
2) is the result at 9:00 inviting us to choose between 'faster than light' or 'indefinite until measured' when you say "it is incompatible with local realism, so either: something is moving faster than the speed of light, or these particles do not have definite values before they are measured"?
Or, it it simply saying: the result cannot be violating the speed of light, so it must mean that the values were indefinite until measured? (which means it's different than classical)
3) does classical include Einstein's relativity? (in context of your video)
4) when Bob and Alice know they received a particle, isn't that by interacting with it so it'll already be collapsed? (in other words there isn't any way to have or carry an uncollapsed particle after knowing you received it)
1) Normalizing simply garantuees you that you are working with a probability distribution - one where all values sum up to 1. Which is important when talking about probabilities.
2) Not really. This mechanism of entanglement is probabilistic in nature. You can not chose the message youre sending. On that topic, there is the no-communication theorem and others if you want to read more.
3) Relativity (both special and general) are classical theories, yes. Note that this is simply a classification and basically, anything non-quantum is classified as classical.
4) I am actually not exactly sure on this. But I think its possible to interact with a system such that is collapses into a subsystem, still being able to collapse further. So I guess it depends on how you find out that you received it. And even if thats wrong, there is no problem here, right? If the measurement you are interested in gives you a result, you know that you received a particle.
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 like the theory that quantum superpositioned entanglement is a kind of encryption state, and a measurement of any entangled partner creates a "consistent history" signal that is effectively a deencryption key for all other entangled partners (by flowing past decohered channels and only interacting with cohered channel that maintain a coherent signal chain). So it first deencrypts the local encrypted partner to a resolved state (creating the first node in a "consistent history"), and then, when the resulting chain of coherence-maintaining signals eventually arrives to the entangled partner, the distant partner is deencrypted by that same mechanism to the same "consistent history" state.
What happens "instantaneously" upon measurement of the first entangled partner isn't the distant deencryption of the distant partner, but the creation of the deencryption key, in the form of a coherence-maintaining chain of signals, that will later deencrypt the distant partner, by the preservation of a coherent signal chain, into a unique consistent history signal when it arrives to it. The deencryption key still travels at or less than the speed of light, so it doesn't violate special relativity, and the final state of the distant partner was present encrypted in the superposition state since the entangling event (along with many other possible final states encrypted with it), just waiting to be resolved to a unique final state by interacting with the unique deencryption key.
The catch is that, by the symmetry of superposition, each unique consistent history key should have to deencrypt the superposition encryption to its own unique consistent history channel, which is to say it works best with the Everettian multiple worlds interpretation (unless you argue that only one unique key is ever made upon measurement, which requires some extra mechanism to explain that we don't know yet; whereas MWI is supposed to work right out of the Schroedinger Equation box. Also, if there is a superposition of measurements of the distant partner, one of them would have to occur and be destroyed, which I don't know is so much better than many worlds). All consistent histories should get resolved, but in their own channels, since the other channels are, by the same mechanism of decoherence, mutually encrypted to each other. What I like about it is that the mechanism is quantum decoherence, with which we have daily experience with. You can explain it with something we already understand pretty well.
I feel like I've been waiting my whole life for this.
Great content... thanks for sharing
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
The more interesting idea is that the measurers themselves are in a superposition until they measure one of the entangled particles, which collapses them into a state where both particles have been measured.
I have understood the concept of entanglement for some time. I wish this was the first explanation I heard because it was presented in a way so that us non-scientific people can grasp the concept.
This satiates my queries so much while also firing so many neurons for further inquiries.
Brilliantly communicated the phenomenon 👏
@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.
I have a PhD in quantum optics. Why should Bell's Inequality be the weirdest theorem in the world? It makes perfectly sense and is no stranger than other parts of quantum theory.
very nice explanation and video, well done! It helps me , thanks.
That presentation was interesting and your delivery was appropriately technical and charming- a combination of science with humanity. Thanks-
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
Thank you, Olivia. At 9:36 you said (slightly paraphrasing): “When you measure Particle 1, we know that instantaneously, the other particle, Particle 2, is going to choose the opposite correlated value. But that does not mean they are able to communicate with each other.”
My question is: If the two particles can’t communicate with each other, how does the measurement of Particle 1 affect Particle 2, which could be in another galaxy?
Good question.
If A always got the opposite value of B wouldn't the final number be 2 or less? Did they actually check each case and see that A and B got opposite values. I highly doubt that check was done.
I think the answer has to depend on your interpretation of quantum mechanics, and to the extent that disagree about that, they'd disagree about how the measurement of P1 ends up affecting P2.
One answer is it affects it through a "hidden variable" which must be non-local. Sometimes you hear talk of a wormhole connecting them through which the measurement of one very quickly resolves the other, so they are local to each other (in their private hidden space), but not in "our" space. But since it's hidden to us, we can't see it or know about it. I think this is part of the ER=EPR hypothesis (i.e., entanglement = wormhole) that Leonard Susskind talks about, which you can find videos on. But I'm not too clear about how it works.
Another answer is the Many Worlds Interpretation, where quantum decoherence acts like a deencryption key. The measurement of P1 creates a chain of signals that flies through inconsistent histories (by decoherence, washing out any signal chain) and interacts coherently only with consistent histories to maintain a coherent signal chain with a consistent history. When that coherent signal chain finally arrives at P2 (at the speed of light or less), it's like a deencryption key that, when they interact, deencrypts the distant superposition state into the same consistent history for its channel.
So say the scientist measuring P1, Alice, finds "spin-up" (Alice1), then when the chain of signals finally gets to the scientist measuring P2, Bob, there is a superposition state there. The Bob that measured the inconsistent state of P2 (spin-up, call him Bob2) is effectively invisible to the chain (or any coherent signal chain is washed out by it), and only the Bob that measured the consistent state of P2 (spin-down, Bob1) is coherent with it, so there is an interaction continuing the consistent chain, so Alice1 and Bob1 find themselves in the same reality, and Bob2 is encrypted to both of them. Similarly Bob2 finds himself in the same reality as Alice2 that measured spin-down, and Alice1 and Bob1 remain encrypted to them.
@@cademosley4886I haven't heard of the Many World Interpretation and quantum decoherence. It sounds intriguing but I don't know enough about it to say one way or another. What resonated with me, no pun intended, is the idea you mentioned that the particles could, in some sense, be local to each other (in their own private hidden space), yet not in "our" space.
I have a feeling that that is what is going on, but it is only an intuition. In a similar way, I have a feeling that although the universe, as we know it, is almost 100 billion light-years in span, and the furthest points from us are moving away from us faster than even the speed of light, somehow, in some other kind of space, all those points are accessible. Local even.
Just an intuition, one that is perhaps born out of the feeling of being overwhelmed by an unknowable universe that is expanding away from us faster than the speed of light, AND at an accelerating rate. I think to myself, there has got to be some other dimension where these unimaginable scales are manageable. The afterlife, perhaps.
The RUclips algorithm recommended this video to me on the evening after I read the chapter on Bell's Inequality in Heinz R. Pagels's 1982 book "The Cosmic Code: Quantum Mechanics as the Language of Nature." I'm tempted to joke about attributing the coincidence to nonlocal causation or spooky action at a distance -- but instead will just recommend the book, despite its age, as a highly readable and enjoyable introduction to the subject. The description of the standard model in the second half of the book has been overtaken by events, but the first half, discussing the historical development of quantum mechanics and thought experiments illustrating concepts like indeterminacy, complementarity, and the observer-created reality, has not lost its luster after 40 years.
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.
Even though there's no useful communication between 2 entangled particles, I believe information can be embedded beforehand for certain cryptographic application. It's like writing 2 encoded letters and giving them to 2 receivers who would then each travel to a far distant corner of the universe, when the time comes they'd be able to open the letter that can only be read once. Such an exciting prospect.
But the letters are written by two different people once they separated, so what would be the chances that the contents would contain the same information about e.g. location to meet? I think, from my limited information, that this is why QM is described as "weird" and lacking in realism.
Or rather.. perhaps both were given the same letter but neither contained the exact location / time to meet.
@@laestrella9727 My take, it's the same set of predetermined instructions given to both parties, within which each instruction is assigned to 2 pairs of entangled particles; 1 pair represents no and the other yes. If one party decides to switch on the yes pair, it means to the other party that that respective instruction is good to execute, if they choose the no pair it means don't use that instruction. Better yet, they can have a large and complex system of instructions to convey a whole bunch of information.
Anyway, some others have also suggested about how a pair of entangled particles would collapse upon observation thus renders it useless of any meaningful communication. Doh!
@@quasicesium Begs the question still: "how" are they even communicating faster than light?! Unless it's all somehow connected to the 4th dimension.. like how you can draw a circle around a dot without your pen ever leaving the paper by folding a corner just a bit and drawing the dot at the tip then backing the pen onto the folded bit then drawing the circle while smoothing out the fold to complete the circle.
There must be a reason instant communication is possible. Or maybe an undetectable thread / connection remains between the entangled particles that we haven't discovered (and possibly can't due to our inability to detect it).
@@laestrella9727 Einstein used to hate this faster than light notion on the quantum scale, however, the prevailing theory is that entangled particles share the same wave function that's connected via non-local space, that is they somehow affect each other NOT through the normal space. It's like quantum particles have their own "playground" that's beyond our current understanding, I suppose.
Great job explaining. Thank you.
Excellent lesson, presenting a complex topic in an intuitive manner.
You’re a great presenter! Thanks!
I would love to spend years hanging out with you and talking about so many other things. You did a great job with this.
is there a statistics artifact involved that would cause a result near the natural log?
This is an awesome explanation of the Bell's inequality! Thank you for being concise!
Amazingly distilled and well explained. Ironic how physics is stranger than fiction. Congrats to the winners this year.
It's "stranger than fiction" because it actually is just fiction. These are all just "thought experiments." No real-world experiments at all.
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