This guy should be proud to be one of the best teachers around. He is able to explain complicated concepts unlike most any other person. Kudos.

Bro, two paticles being actually the same one regardless of the distance is actually a more astonishing explanation than spooky action at a distance.

This guy really is so great. The remote lecture he gave on quantum weirdness is the best introduction to the subject anyone could ever do.

Love the RI videos more than I can say. Keep 'em coming!

At 9:14 no coherent explanation is given as to why you are producing rabbits for Bob in Alice's 2 pound column. Sure, there's a bit of word salad thrown into the world as if it was a necessity that this be the case, but given the information provided up to that point in the video, nothing compels rabbits in Alice's 2 pound column. Note that I am not claiming that the conclusion is false. I am saying that the logic of the analogy is incoherent. It's perfectly possible to reach a true conclusion from invalid reasoning, but it doesn't help anyone else understand why the conclusion is true! I will provide the required logic to reach the (as it happens, true) conclusion at the end of this comment. The explanation provided was this combination of sentences: 1) "If alice has produced a rabbit with one pound, then the only way we can get a dog is if they both put in 2 pounds. 2) So alice has already put in 1 pound. 3) So bob's box has to produce a rabbit in both of those cases". Statement 1 is contains a non sequitur and is incoherent. If alice has put in one pound, then alice cannot have put in two pounds. There is no "if - then" relationship between the first and second part of the sentence because they describe two completely different cases. You can't create an "if-then" relationship between a case where Alice has put in 1 pound and a case where alice has put in two pounds. The second part of the sentence (1) is false. It is not true that the only way we can get a dog is if they both put in two pounds. We can also get at least one dog if alice puts in 2 pounds and bob puts in 1 pound, and two dogs result. This still satisfies all three rules. Statement (2) is just restating the premise, ie, we are looking at the scenario where alice has put in 1 pound. No problem here, but be careful with use of the word "so....". When making a logical argument, "so..." implies "what I am about to state follows from that which I have just stated", ie, it's often used as a synonym for "therefore". But statement 2 doesn't follow logically from statement 1, therefore use of the word "so..." is confusing. Statement (3) is unclear about which two cases are implied by "both". There are two axes here, the bob axis and the alice axis. If "both" means "both when bob puts in 1 pound, and when bob puts in 2 pounds", then the statement is correct. If alice has put in one pound, then in both of those cases bob must produce a rabbit. But in the graphic, you filled in both of those cases, AS WELL AS both cases where alice puts in 2 pounds. This is "both boths", as it were, and is not justified by the rules. These are the reasons why your explanation is considered unhelpful. Nobody can follow the logic because the logic isn't valid. The resolution to the invalidity is to bring in rule 4, which is the "NB" in italics in the rule slide, but which you do not actually state. That rule *seems* to mean that one box must always produce the same output for a given input. IE, it cannot be the case that bob's box can produce a rabbit on a 1 pound input on some occasions, and can also produce a dog on a 1 pound input.on other occasions. If that is the case then we cannot produce two dogs with the combination (alice 2, bob 1) as I previously suggested, because we have established that the combination (alice 1, bob 1) must produce (rabbit, rabbit) from the combination of rules 1 and 3, so (bob 1) -> rabbit, so we cannot also have (bob 1) -> dog. But this critical part of the logic is *never stated* during your explanation.

‘And then I entered into a quantum entanglement with August’

Since we have moved on to rabbits and dogs, Am I to assume Schrodinger's cat is dead?

He lost me at "hello"

Thank you Phil. I also didn’t understand the example in the initial lecture, so I found this and now understand it. This is a fault with me not you. If my brain was a bit faster I would have understood it in the first place. QM is one of the most fascinating disciplines I have ever ventured into.

I for one am astounded and amazed at these teaching skills- I can´t believe that I- as a somewhat logically challenged and abstract minded and scatterbrained layperson- managed to follow through this lecture and actually felt like I grasped the concepts! Well done!

I adore the clarity of your explanations.

thanks! A very helpful clarification. Also, I like the book, having followed our suggestion and got it.

Great talk. And I like the final point a lot. Quantum mechanics is a window into a deeper theory, one where either time or space is emergent. And this 85% limitation may be a clue about what lies beyond it.

Thank you for making this video. It's the best one I've seen on quantum entanglement, and I've seen a lot, trying to wrap my head around it!

That is one of the best talks I've seen and heard. I studied QM at Uni, and his talk gave me a real insight into what I learned through number crunching the equations, but not really being able to form some sort of mental picture about what was going on in that weird QM space. It really is like a "Fairyland of Weirdness", if you study it. It's better than The Adventures of Alice In Wonderland. Bells Inequality and Bell's Theorem are mind bending concepts to get one's head around.

How appropriate to try explaining such a convoluted and hard to understand concept using a convoluted and hard to understand example. Bravo!

I came here trying to understand what Jada meant by Entanglement

As commenter 'allmhuran' pointed out, the rather offhandedly included line, "NB - these are simple, unconnected mechanical boxes with one given output (animal) per input (coin)" was the single thing that had to be understood (and should've been explained) to make this analogy sensical.

Brilliant conversation Sir,,it seems to me we could expand our understandings of quantum entanglement by interjecting into the conversation models,and examples of the different types of electrons and how they function,AC/DC,,and differences between single phase electrical systems,and three phase electrical systems, such as Delta,and Y,, ..either way I love having and hearing these conversations.In doing so maybe one day we will be able to explain it and understand it in such a manner that we could at the least refrain ourselves from having Wars with each other.God Bless!

Excellent 👌! I appreciate the enthusiasm you have about QM.

"Quantum nonlocality" are just words describing a phenomenon that is still spooky.

Definitely something going on when we turn our attention to measuring quantum objects, the double slit experiment also, our thoughts change particle behaviour somehow. Thankyou very much for hashing it out a bit more, it is a mind blowing concept, letting go of preconceptions and being amazed but something that is measurable and real is refreshing.

I love these vids and take the material seriously... I still smile when we discuss Alice's box though.

Excellent video.. i understood the whole phenomenon.. thank you sir.. your way of presenting was really good..

A lot of the confusion is due to a tiny omission: the same coin in the same box always produces the same animal throughout the thought experiment. This isn't intuitive in the realms of symbolic logic. (I don't think the "NB" solves much, since even it doesn't explicitly state that that output will always be the same if the coin and the box in question are the same.)

Thank you for clarifying once and for all that quantum physicists are awful at analogies. :)

Thank you this is the best description of quantum entanglement I’ve seen👍🏾.

Thanks for making this video, it's brilliant, it helped clear my head, at least I've got a toe hold on a cliff face of unknown depth or height. "The mind has chasms, cliffs of fall, sheer steep no man fathomed."

I lost it as soon as he mentioned rule 2 & rule 3.

You should explain this 85% !

Dear Phil, thank you for making this video. I have a question regarding fields that I hope you could address. In QFT a particle is a wave-like perturbation on a field, the speed of a wave is determined by the media, but the speed of a particle is determined by the source. How these two are reconciled in QFT. QFT reconstructs the particle-like behavior by adding an infinite number of planar waves. However, in experiments we can have a particle traveling with any speed we like (less than c). On the other hand, it is known of waves that their speed is determined by the media on which they travel. I couldn't have a wave on the surface of a pond travel at any speed I like. The speed is determined by the characteristics of the pond. So, how these two are reconciled in QFT. Any pointers of where to find the answer are highly appreciated. Thank you very much, Juan.

Nice explanation. Puts Bells theorem into context.

Quantum is the word that some day Scientists would equate with Cosmic Intelligence. We are waiting for that day to come. Thank you for your interesting talk Dr. Phillip Ball.

That was so good...I nearly understood.

Inspired me to watch the whole talk :)

Great talk, it makes one think. To me it exposes the issue with only having 4 dimensions, X,Y,Z, and t, and it sort of steers one into the idea of extra dimensions, these being the ones of particle interaction. Say A,B,C, and d are dimensions in which very specific particle properties exist or are modified through, and in this dimensional reality distance and time (or whatever they are) are completely different than XYZt. The abstract idea of extra dimensions can make more sense if we can relate them to things in our own tangible dimensions. It may even be possible to map other dimensions based on these "spooky" particle relationships. I've always had an issue with the idea of extra dimensions, the concept makes no sense, but this talk gets one wondering.

Before the big bang, all the space time, and energy and mass that we observe today was crushed in a tiny quantum state. So doesn't this mean that entire space is entangled ?

am still slightly confused ; just means i was paying attention. most coherent, concise explanation delivered in a very pleasurable voice. thank you, truly, for making and then sharing this video with us. let us watch and be nourished

Clear and concise explanation of a complex phenomena in physics

Amazing explanation, it did make the topic easier

Oh No, the analogy example was awful, not the e explanation! The author should have come with a different example or best would be to explain simply the real experiment. Trying to explain the same bad analogy again in a longer detailed video is pointless!

Not quite sure if quantum mechanics broke any laws of physic but I do know it broke my brain.

One question regarding the "action at the distance" part and how it's not a thing. It seems that saying that two particles are the same is overlooking the part that they remain connected no matter the distance between them. Meaning that the factor of the distance not mattering seems to be overlooked or, at least, de-emphasized by simply saying they are one object.

Excellent explanation of a difficult concept . Perhaps explaining how the " rules " of this scenario apply to the quantum world specifically would wrap things up neatly .

I'm here because Martha said 'Quantum entanglement' while explaining a phenomenon. Had to know what it meant!

Sometimes you get a lecture that 'clicks ' when the explanation just fits with stuff you have heard before. I was lucky to experience this from this lecture. I nearly 'lost it' at the Alice and Bob box analogy, My big takeaway was confirmation of the 'no spooky action' understanding.

I love these videos. Its 4 in the morning - ive got insomnia but I have some very very bright physicist chatting to me about Entanglement. How incredible is that. He doesn't need to hear my input (wow spooky action at a distance er... that's spooky man)

If you have 2 electrons and one is observed to be left spin then you know the other is right spin, assuming this is a correct interpretation, is the determination of the spins confined to the sub atomic level and if yes then, at the sub atomic level can these same 2 electrons be 299 792 458 m / s apart? How is the quantum entanglement of these 2 electrons extrapolated to universe size by physicists? In the Alice / Bob example you present when Alice knows the glove is left handed, she also knows Bob's glove is right handed but only Alice knows this as Bob may not have looked at the glove to know which he has? (if that makes sense)

Well done , a great lecture and well delivered. I loved the glove analogy , excellent and clever. Makes it clear to a novice.

Entangled particles act like c++ pointers :). Different variables pointing to the same memory block.

When I think about spin up and spin down, I think of a seesaw, where one end spins about a pivot, so that the opposite end is always the inverse and never the same. So I have a question: If I push up at one end of an arbitrary seesaw, does the other end go down instantly? Is there a delay in the force applied or does this force travel at a finite speed? What if this pivot approaches an infinitesimal point in size and the seesaw is contructed by an infinitesimally thin line of arbitrary length passing through the pivot - would pushing one end up instantly push the other end down? If there are two entangled electrons analogous to a pivoted seesaw as above, maybe we should be looking for the pivot?

I like that you use examples. Thanks.

Hi Mr. Philip. I have to say you did such a fantastic job explaining this and it just feels awesome listing to you talk about this topic. I really love physics so much but never gone beyond first year university physics. But I think I have a great real life example of quantum entanglement which I think is really true. I have a little 3 year old daughter. And whenever I think about her I can feel exactly what she is doing. It's totally like the quantum entanglement. When she was a baby every time I would think about her she would start crying. And this was so strong I said to my self I'm going to stop thinking about it. It's hard to explain but in my view entanglement doesn't have a physical "explainable" property to it. But I think a mother/daughter thoughts are entangled. And no matter where she is in the world I can be thinking and knowing exactly what she is doing.

I’m starting to love physics man🤩

Thanks for that. Much clearer.

Philip Ball is one of the few people in foundations of physics who recognized the value of the quantum reconstruction program (QRP) early on. He was advocating for that approach as early as 2009 in a UKposts video and shared Dakic and Brukner's information-theoretic reconstruction in a UKposts video on quantum entanglement years ago. Well, it turns out Philip was prescient. Quantum information theorists have now rendered quantum mechanics (QM) a principle theory based on the relativity principle exactly like special relativity (SR), which shows QM is as complete as possible and totally compatible with SR (many believe quantum entanglement renders QM at odds with SR). With that understanding of QM one can rule out the existence of Popescu-Rohrlich joint probabilities (the PR-box) because they violate conservation per the relativity principle. We explain that in "Why the Tsirelson Bound? Bub’s Question and Fuchs’ Desideratum" Entropy 2019, 21(7), 69. We explain the conservation principle itself in "Answering Mermin’s challenge with conservation per no preferred reference frame" Scientific Reports volume 10, Article number: 15771 (2020). [Those are open access, but I can't provide the links or UKposts will delete this post.] Those articles are a bit technical, but we have it all explained for the "general reader" forthcoming in "Einstein's Entanglement: Bell Inequalities, Relativity, and the Qubit" due out in June 2024 with Oxford UP (see Chapter 8 specifically for the PR-box). Here's a brief summary. The mystery of quantum entanglement arises because we are looking for a 'causal mechanism' behind its correlations, what Einstein called "constructive efforts." Einstein was faced with a very similar situation concerning constructive accounts of length contraction (and time dilation) to explain the Michelson-Morley experiment. Einstein wrote: "By and by I despaired of the possibility of discovering the true laws by means of constructive efforts based on known facts. The longer and the more despairingly I tried, the more I came to the conviction that only the discovery of a universal formal principle could lead us to assured results." That is, he gave up looking for causal mechanisms ("constructive efforts") that would shrink meter sticks and slow down clocks to fool everyone into measuring the same value for the speed of light c, regardless of their relative motions (an empirically discovered fact known as the light postulate). Instead, he said c is a constant of Nature per Maxwell's equations, so the relativity principle -- the laws of physics (including their constants of Nature) are the same in all inertial reference frames -- demands that everyone measure the same value for c, regardless of their relative motions. The Lorentz transformations of SR follow from the light postulate as justified by the relativity principle. As it turns out, the same opportunity for QM has been provided by quantum information theorists. That is, they have reconstructed QM based on an empirically discovered fact called Information Invariance & Continuity that (in non-information-theoretic terms) means everyone measures the same value for Planck's constant h, regardless of their relative spatial orientations. How does that solve the mystery of quantum entanglement? Suppose you send a vertical spin up electron to Stern-Gerlach (SG) magnets oriented at 60 deg relative to the vertical. Since spin is a form of angular momentum, classical mechanics says the angular momentum you should measure is (hbar/2)cos(60) = hbar/4 in that direction of SG spatial orientation. But, the SG measurement of electron spin constitutes a measurement of h, so everyone has to get the same +/- hbar/2 for a spin measurement in any SG spatial orientation, which means you can't get what you expect from common sense classical physics. Instead, QM says the measurement of a vertical spin up electron at 60 deg will produce +hbar/2 with a probability of 0.75 and it will produce -hbar/2 with a probability of 0.25, so the average is (hbar/2 + hbar/2 + hbar/2 - hbar/2)/4 = hbar/4. In other words, quantum mechanics says you get the common sense classical result on 'average only' because of the observer-independence of h. Now suppose Alice and Bob are measuring the spin singlet state (the two spins are anti-aligned when measured in the same direction) and Alice obtains +hbar/2 vertically and Bob measures his particle at 120 deg relative to Alice. Obviously, if Bob had measured vertically he would have obtained -hbar/2, so at 120 deg Alice says he should get hbar/4 per our single particle example. But of course, Bob must measure the same value for h that Alice does, so he can't get the fractional value of h Alice says he should (otherwise, Alice would be in a preferred reference frame). Instead, his outcomes at 120 deg corresponding to Alice's +hbar/2 outcomes vertically average to hbar/4 just like the single particle case. And, of course, the data are symmetric so Bob can partition the results according to -*-his-*- +/- hbar/2 outcomes and show that Alice's results satisfy conservation of spin angular momentum on 'average only'. In the end, Alice partitions the data per her +/- hbar/2 outcomes and says Bob's results must be averaged to satisfy conservation of spin angular momentum while Bob's partition shows it's Alice's outcomes that must be averaged. This should remind you immediately of an analogous situation in SR. There when Alice and Bob occupy different references frames via relative motion, they partition spacetime events per their own surfaces of simultaneity and show clearly that each other's meter sticks are short and their clocks run slow. In other words, the mystery of quantum entanglement resides in 'average-only' conservation that results from "no preferred reference frame" (NPRF) giving the observer-independence of h (NPRF + h). And, the mystery of length contraction resides in the relativity of simultaneity that results from "no preferred reference frame" giving the observer-independence of c (NPRF + c). Give up your constructive bias for QM just as is done for SR and physics makes perfect sense. But, the implications for your worldview are profound; you have to accept that physics is most fundamentally about constraints on the 4-dimensional (spatiotemporal) organization of worldtubes per NPRF + c and the distribution of quanta therein per NPRF + h.

Exactly how do two photons get ‘entangled’ ? Are they entangled indefinitely? Can a photon get re-intangled with a different photon later ?

Awesome teacher and explanation.

Beautifully put. Well done and bravo to you!!!!!👍👍👍💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚💚 and also, it may seem complicated too many but it is actually very simple. There is also a beautiful love story out of this and that would be love itself

@12min: Is it possible that in the classical example, the boxes are connected by time (ie. The wire is time). Would this not reconcile both the observer effect and special relativity? Unless I am mistake you cannot observe an event in the same moment it happens. Likewise is light not bent slightly by gravitational fields? So large observers (us) could witness sub-atomic events (electron spin) closer to the moment they occur, thereby increasing the probability of an accurate result.

Schrodinger to Heisenberg “so is the cat dead or alive Werner.” Heisenberg to Schrodinger “well Erwin I’m uncertain about that” 🤣

I saw the talk a while ago and didn't understand the boxes. Now you've told it here again... and it makes no sense what so ever as far as I can discern. Truly, I think that people should just admit that they don't yet understand the quantum scale and how things work there.

Such a good English - just supa to hear from somebody that learned english in school - brilliant Mind too !!

Maybe it's the way you explained it or maybe it's my ignorance to this matter but Bohr's Copenhagen Interpretation actually makes sense. The whole idea of the spin being uncertain until she measures it. cuz if electrons are constantly moving etc you could also assume their spin to not have a definite state?

Quantum Entanglement is what happens when physicists try to understand quantum theory.

Keep in mind the pencil through the paper worm hole analogy when I say. This is consistent with quantum particles being 4d items while atoms are the 3d effect of those particles. Like a flock vs birds. Since we are made of atoms we can not see the 4d universe.

Fantastic explanation of a very difficult concept.

Does resonance frequency reflect back at a continuous resonance when it hit's a void or build up and create a pulse back at the resonance? Especially when the resonance is produced from something the size of the black whole.

One take?!? Cheers

I was waiting for the 85%, then I got entangled.

Thanks for clarifying that for me. My question is, if the entangled particles are not fixed, would it be possible to use then as a long distance telegraph or Morse code for faster than light communication?

Why should any spinning (electron and it’s associated negative charge) produce a bipolar magnetic field? Or is that we assume it does without further understanding or experimentation, or because we said so? Spinning? Is spinning axis orientation well defined and with respect to what? What else we did we misunderstand or missed when we made the peculiar observation have concluded such observation?

if you think of time-space as a grid laid upon a nondimensional void, then entanglement makes sense. "local" is universal in that sense.

Nice video! Also, I'm happy to give you a haircut for free!!!

is it possible to build in the next 10 years a Quantum Entanglement receiver and transmitter? , also, what is the total energy of the particles when acting like one. Thank you.

What “any two quantum particles” means? Randomly or conditionally paired or anything else?

Jada Pinkett Smith brought me here.

I keep thinking that quantum waves and ghosts are related, two sides of the same coin. Like yin and yang. It's the only conclusion that makes sense. Remember that nature uses the least action principle. The universe is inheritance lazy. But there is no reason to disallow a complex life form of very low energy content. QM should predict the existence of ghosts. A ghost is a special kind of wave function that has free will, consciousness, but has to creep between potential energy wells to move around. If you don't see it, then you are being intellectually avoidant.

we have taught that while creating entanglement between 2 particles via photon there is conservation of charge which means if a particle have positive charge the other would have negative charge, there is also conservation of spin which means that if one particle have up spin then the other must definitely have down spin .These r the 2 conditions to justify that 2 particles r entangled or not and there is conservation of charge and conservation of spin because to produce the net effect zero as photons don't have charge as well as spin . But the interesting thing here is to note that that there is no conservation of mass between the 2 particles so as to produce the net effect zero as photon mass is zero. My biggest dought which implies that if there is no conservation of charge that particles (not photons) cant be entangled at all. If anyone get some info about this pls inform me in the replies section.

That's a great job of simplification

The explaination is always how entaglement works, that has been stated over and over again. What always seems to be passed over is why particles gets entagled?

01:45 🤬 telling me I don't need to know about spin/angular momentum.

What is the 100% experiment (set of rules 17:52)?

Care to explain how you verify that both entangled particles collapse at the same time, when measuring one of them? If you measure both of them simultaneously they would have collapsed even if they were not entangled. If you measure one and not the other, how do you know that the other did in fact collapse, and did so at the time of measuring the first one? If you measure the other one later, you still would not know when the collapse took place.

There's a dead cat in one of the boxes.

"When we observe it..." Isn't this always the misleading phrase? Shouldn't it be "When there is an interaction..."? Whether we observe it or not? Whether we measure it or not? Why imply that we somehow have to be part of what makes a wave function collapse? When surely they collapse all the time all over the universe far beyond any possible role we might have in them doing so...

Hi, Question... As particles have wave nature too, is not entanglement really like Frequency Modulation ?

What if we measure both entangled particle at same time? Then will both particle continuously in Superposition or what?

Hold it with the lies. Nobody understands entanglement. The truth is this is what happens. It's spooky, bazaar, can't possibly work that way but it does. That is really our understanding of it.

Familiar with the subject, yet I couldn't follow the talk. Probably an out of context edit? Maybe it would be a good idea to leave aside Alice, Bob and weird imaginary boxes with strange cooked-up rules, and just state the facts. Nobody needs coins and rabbits here. Those are just adding confusion. It is not a board game with strange invented rules, it's reality, so start by describing real experiments and their results, and build from there. Only afterwords start discussing what abstract rules might be in place, so we see such experimental results.

Thank you for the most impressive science video I ever randomly clicked on in my Bell inequality UKposts watch later video list. Best description of this topic I have seen for now. "Entanglement flag" is a nice term, in not just one way, I like it.

Excellent. Thanks you.

Quantum mechanics is very Bohring!

Not sure why physics has become so dogmatic in the last 20-30 years. What if Special relativity doesnt apply in all cases? Maybe space/time is an illusion and there is really no separation between the entagled particles!? We assume same rules for Gravity apply everywhere in the Universe with the same constants and then we 'invent' Dark Energy/Matter which we havent been able to detect. Same way we 'invented' the INLATION theory (post Big Bang). I hope the young generation of Physicists/Mathematicians is looking at other options to explain some of these Quantum phenomena without the Dogmatic assumptions.

I was thinking if we can think of quantum entanglement as a wave. if we suggest that the crests and troughs of the wave are nothing but two particles, one with up and other with down spin, while these two are together its easy to identify them as a wave, but if they move apart and the wavelength increases, they stay harmoniously synchronized yet bound in a way, yet separate in a way. they interact with each other but very weakly and harmoniously one is not sending its info to the other. Is there a case where one can say that two parts of a wave is moving apart extending its wavelength while maintaining that harmonious motion? I like to think of particles as wave like phenomena rather than actual objects. somehow the idea of entanglement seems to manifest in waves where the crest and troughs are predictors of each other instantaneously regardless of the wavelength. Any thoughts on this idea? can a wave length span across the universe and maintain its harmonious motion?

Fascinating subject.

I don’t know dude, I got lost at long division in my head.

this experiment reminds me of an x & y chromosomes

Your explantion is clearer, I guess i saw so many videos and read few basics