#science #physics #ideas The Biggest Ideas in the Universe | 8. Entanglement

#science #physics #ideas The Biggest Ideas in the Universe | 8. Entanglement 211,773 viewsMay 12, 2020 Sean Carroll 154K subscribers The Biggest Ideas in the Universe is a series of videos where I talk informally about some of the fundamental concepts that help us understand our natural world. Exceedingly casual, not overly polished, and meant for absolutely everybody. This is Idea #8, "Entanglement." I talk about what entanglement means, how it showed up in classic work by Einstein, Schrödinger, and Bell, and the crucial role it plays in competing formulations of the foundations of quantum theory, including Many-Worlds and others. My web page: http://www.preposterousuniverse.com/ My YouTube channel: https://www.youtube.com/c/seancarroll Mindscape podcast: http://www.preposterousuniverse.com/p... The Biggest Ideas playlist: https://www.youtube.com/playlist?list... Blog posts for the series: http://www.preposterousuniverse.com/b... #science #physics #ideas #universe #learning #cosmology #philosophy #quantum #entanglement 566 Comments rongmaw lin Add a comment... Jeremy Roy Jeremy Roy 1 year ago (edited) Physics students of the 60s had the Feynman Lectures in print form. We have a Sean Carroll Youtube playlist. What a time to be alive. 297 NoGary No NoGary No 1 year ago (edited) Entanglement, yes! Been trying to get my head around it for awhile now, every time I think I have it there's more around the corner, angular momentum was an entire rabbit-hole on its own. Thank you for sharing your knowledge Sean, your videos are my favourite for explanations of complex ideas. 31 tom kuo tom kuo 1 year ago Sean, very smooth talk, I really like it. You used two particles/waves collision as an example for entanglement. It makes sense to me but this is the first time I hear that kind of use case in entanglement. The two particles collision case can be seen as following Newton’s 3rd law of action vs reaction, although this is QM which makes Newton’s law dubious. A more interesting case is the action over distance in gravitational force. Has anybody tried to apply the entanglement idea to explain action over distance in gravitational force? It seems there are different types of entanglement. The spin-based entanglement is one type, the two particles/waves collision you mentioned here is another and the action over distance in gravitational force is yet another. 5 alexrsnh alexrsnh 1 year ago This was my favorite of this series so far, and they're all great. Brian Greene also provides a really good explanation of Bell's Theorem in "The Fabric of the Cosmos." 1 Czeckie Czeckie 1 year ago This was so good, thank you Sean. Additionally, I really enjoyed Mindscape episodes with Adam Becker and your solo episode about this very topic, I really liked the idea how space is basically and emergent property - two things being close is defined as being able to entangle with each other. I've bought myself a copy, but haven't got the chance to read it yet. I have two questions about the video: 1) Decoherence. Why don't atoms destabilize? We saw that electron fired into a cloud chamber is behaving pretty classically and not like a blob of uncertainty. You explain it like it's getting entangled with everything around. I like that. But how come the electrons in atoms don't de-cohere when every other atom from vicinity is bouncing into them? As we've seen in the previous lecture, the work of Planck-Bohr-de Broglie-Schrödinger explained the electron in an atom needs to be quantum and classical particle just doesn't work. 2) There're projects of 'quantum reconstruction.' Mathematically minded people are trying to rediscover quantum mechanics from simple foundations and derive it mathematically. This is because some people are uneasy because Planck, Heisenberg, Schrödinger and others basically just guessed it. Some of these are based on quantum thermodynamics or quantum information theory. Are these approaches compatible with many worlds? 1 C.J. McELEAVY C.J. McELEAVY 1 year ago (edited) Love that every so often Sean's hand slips in and out of "phase spacetime" when he becomes more demonstratively excited! Always thought he might actually be a many worlds traveler. Confirmation; seeing is believing! 1 Helder Godinho Helder Godinho 1 year ago Thank you so much Mr. Carroll for these series of videos. It's my end of day everyday and I've been learning a lot about these subjects. More than the lectures and I've seen a lot of them. Thank you so much! Henry David Purple Henry David Purple 1 year ago You’re the man Sean. Thank you for doing these. 1 R C R C 1 year ago Another great video, Professor Carroll! Also, I have read the professor’s latest book, Something Deeply Hidden, and I highly recommend it to anyone who really enjoys this video and wants to learn more about the foundations of QM. 16 Tomas Kratochvil Tomas Kratochvil 1 year ago Hi Sean, what an amazing series! When I think about the reality through quantum physics eyes, and wonder how nature works, I was compelled by Many Worlds from the begining, though not sure about it, because I felt it is somehow wastefull, by splitting the universe with each interaction. Thanks to you, and your series, I have gained knowledge, in understanding QM as well as Many Worlds in the way I see it through different perspective now, and I like it even better. Always appreciate your lectures and appearances (WSF). Question about topic at hand. Decoherence seems to me like pretty strait concept and I wonder why it had appeared so long after concieving Quantum theory, why Shrodinger and others haven't thought about it? Regards to you, Sir and your very familiar cat in our branch of the wave function of our Universe bouble. Matko Smat Matko Smat 1 year ago Hello, Sean! Watching your videos has actually given me a pretty good picture of the current state of affairs, and I appreciate this immensely, being a total layman in physics. I have this question: if the Wave function is not only a tool to make predictions, but is instead something real, how do you even start studying it? Who sets its values? I'm a bit lost, I can't really formulate my question right, but the reality or unreality of the wave function stops me from even thinking about it. Help! Harley smith Harley smith 1 year ago quickly becoming my favourite series on YouTube. 63 Alex Cameron Alex Cameron 1 year ago This is really good informative stuff Prof Carroll. I really want to thank you for making all these videos - this one in particular. The nature of entanglement and quantum decoherence leaves me wondering if it will be possible to actually build a useful quantum computer - or if decoherence will present insurmountable technical problems Nga Nguyen Nga Nguyen 1 year ago This is the best ‘Many World Interpretation’ that I have heard! Thank you so much! I still don’t believe this is how it works. I personally like the ‘Wave Collapsing’ theory better! I’ll wait to see how it turns out! 1 Jens Roynlid Jens Roynlid 1 year ago Thanks for a fantastic lecture series! All of the lectures are clearly explained and easy to follow. I'm not sure about the many-worlds interpretation of quantum mechanics though: In the Copenhagen interpretation nature somehow chooses which of the possible outcomes the wave function collapses into. Doesn't nature likewise somehow choose which of the multiple possible worlds we end up in? Tamas Goltl Tamas Goltl 1 year ago The real “Mr. Universe”! Just awesome! Thank you for this video (too) Mr. Carroll! Me: never stop learning just sometimes “sleep a bit longer”! 😉 1 In Coath We Trust In Coath We Trust 1 year ago Sean, thanks for putting out these amazing lectures. You are an incredible teacher! I honestly feel that these videos have much more utility than all the nonsensical and pseudo-sophisticated "Theory of Everything" garbage being propagated by certain individuals (e.g. Weinstein and Wolfram) who are not even directly involved with the established physics community. Kudos to your efforts! I'll be looking for your undergrad QM textbook when it comes out. 12 Aus Blob Aus Blob 1 year ago Thank you for taking the time to do these videos they are great. You are respectful and dont assume you are talking to a room full of kids thanks for all the details and real explanantion this is a very valuable video series. ph ph 1 year ago I can't wait for the upcoming class/episode! Mr. Carroll is the best "teacher" (I've watched quite a few online) in QM I've come across. Really hope he continues to produce classes (and alike) about QM for the unforeseeable future! Argiris Vlastos Argiris Vlastos 1 year ago Thank you! for making more accessible, these highly abstract and technical concepts to those of us who love physics and...and assuming we're not stupid! SC a fantastic human being, thank you sir for sharing! Riddlix Riddlix 1 year ago Very interesting stuff explained in a way everyone can understand it. Thanks, Sean. 1 sunny sunny 1 year ago as an average layman when it comes to subjects like this, i always found it odd that Einstein was accused of being 'anti qm' given that he himself welcomed the oddness of the universe. maybe the biasness in humanity permeates to the scientific community. thank you dr. for your willingness to share youre knowledge to us all. 1 walkercatenaccio walkercatenaccio 1 year ago This is probably the best talk so far of a great series. I finally understand (a little) "Many Worlds," which had always seemed ridiculous to me. It was the orthogonal axes that did it. Jim McIntyre Jim McIntyre 1 year ago Does entanglement play a part in light slowing down when travelling through a medium? Some physicists say that the light is slower because scattering lengthens the photons' path while others say that it is because of the interaction of the light wave with the waves of the electrons in the medium. The latter hypothesis seems to reference entanglement. 2 Jayen Vaghani Jayen Vaghani 1 year ago Hi Sean, thanks so much for this video series! Was watching a video on Many Worlds by Sabine (yes, I'm sorry :-)), and she suggested that many worlds doesn't solve the measurement problem. Now, instead of collapsing the wave function, you branch it - but you can't say when exactly it will branch. Is it when a measurement is done, or...? Nicolas Argon Nicolas Argon 1 year ago Great lecture! Love the vids :) I have a few questions: 1. Are all functions vectors? I guess there's a few ways to pose the question. Conceptually I think that a function may have many representations, of which a vector is one. So on some level I feel like 'functions' can be represented by a vector as well as other things. On a more grounded level, maybe the claim is that physical reality manifests functions as a vector. So its less about "all functions = vectors" than, all functions in the real world manifest as vectors? At the beginning you (sean carroll) describe how the wave function "associates amplitudes with the entire configuration of a system not part by part". Two questions from that: 2. Is this a form of 'harmonization'? I know you called this 'entanglement' but when describing the state of the entire universe, how could the complexity of everything come to be defined in a single function? (keeping with the first question, as 1 vector?). I feel like there is this problem with abstraction, where if you abstract to a sufficient degree you are inclusive of all things without defining anything. Like saying "there is". Technically this is true. Its an abstraction which brackets every phenomenon, yet is so sparse as to be non-functional. Maybe I'm comparing things of too different a nature, but I still wonder about. 3. Does it make sense to have a 'closed quantum system'? If the wave function harmonizes or entangles everything, then the notion of a closed system (what schrodinger's cat seems to imply with 'the box') is a non-starter. How can we think about the notions of closed and open systems in the quantum framing, if it is at all possible to do so? Finally on to the many worlds, here're my questions. 4. You followed through with the Schrodinger's cat example, demonstrating how the 'environment' would be described completely differently in Hilbert space when comparing the dead cat vs. the live cat. On a technical level, how do you map states and particles onto Hildbert space? And how do we know that when comparing these two states (live vs dead cat) that the vectors would be orthogonal? Now disregarding the technical questions for a moment, you then suggest that since the vectors are orthogonal that these two systems could coexist without interference. Now I wonder what it looks like down the line. Keeping in mind that the wave function harmonizes or entangles throughout, then would the vectors ALWAYS stay orthogonal? They are independent worlds, and its not inconceivable (at least to me right now) that in each universe pursuing their existence that these vectors get continually shifted and bumped and entangled, an in a way that does not preserve the orthogonality with other universes... Is this possible? Or how is the orthogonal states of the different universe remain so for the next billions and billions of years? Thank you! TheKoopaKing TheKoopaKing 1 year ago Definitely the best video yet. My only question: Are there any leads on when quantum information decoheres? I remember hearing that we've sent entire molecules through double slit experiments and preserved a wave interference pattern. Do you think there is a hard line (if any) that separates quantum information from the environment? 2 life42theuniverse life42theuniverse 1 year ago 47:00 A interesting observation I had one day. I was entering the mall one day and some doors were automatic some were of the manual variation. You could see by the wear in the ground how much each was used. It reminded me of the double slit experiment. But it was people and shopping destinations. 1 PuppetPron PuppetPron 1 year ago Thank you for all of your lectures, you make complex subjects more understandable, (although I can't follow the math). I wish I had a instructor or they told us this stuff when I was a kid I might have gone into Quantum Mechanics. Nixon Nixon 1 year ago Thanks for posting, surprisingly easy to follow. 👍 1 bruinflight bruinflight 1 year ago OH MY LORD. I never thought I would understand entanglement. Sean you are AMAZING. Doug Kuykendoll Doug Kuykendoll 1 year ago Thank you for the Biggest Ideas. I was late with my question from the last video so I'm reposting it here. Why do we pose that the observables such as electrons or photons are acting like a wave but then a particle with the collapse of a wave function instead of posing that the electrons or photons act/are like particles interacting in a 'wavey' like background medium or some extra dimension(s) that force corpuscles into appearing to have interference? Alternately asked, is there a reason to believe that space-time could not be causing the interference patterns observed in the double slit experiment? Thanks Andrew Bond Andrew Bond 1 year ago What if there's a hidden dimension where entangled particles are still adjacent even when they are far apart in 3D space? 1 Pvte Pyle Pvte Pyle 1 year ago (edited) Really nice lecture, thank you very very much sean :) Nikki Tea Nikki Tea 1 year ago You’re really good at making the equations seem less scary, and explaining the reason behind the numbers. Dean Sundquist Dean Sundquist 1 year ago (edited) Favorite video in the series thus far! Thanks Dr C. 2 David Jewell David Jewell 1 year ago (edited) Thank you! Always instructive. I do wonder if the induced collapse hypothesis and the many worlds hypothesis, with a selected branch outcome, are not the same interpretation? For instance: The photon absorbance in the “wake cat” state could also be an induction, a decoherence event, that leads to the collapse of the wave equation into the “wake cat” state. I suppose the more detailed and rigorous statements of the QM equations and the probabilities of state are persuading you towards the Everett interpretation? If you could help me to understand where these two possibilities of Everett and Induced Collapse are not identical I would be most grateful. (Also, an accounting for the dof for changes in configurational entropy is not really being made here (branch selection or objective collapse) and I believe there is good mathematical reasoning available and might lend itself to a further understanding how the “macroscopic” branches of the QM ensembles, you are describing, are selected in the making of our reality.) Jerry Robbins Jerry Robbins 1 year ago (edited) best podcast ever. i had to rewind a few times to get things again. you're a great science communicator, thank you so much. John Joseph John Joseph 1 year ago Love this topic. Thanks Sean Petr Tisoň Petr Tisoň 1 year ago I have heard about entanglement many times. But this was super duper explanation Professor! Finally it does not seem as a pure magic for me anymore. Thank you for this. Henry Bronett Henry Bronett 1 year ago I so enjoy these lectures! With the entanglement episode, you made me think of the story about the blind men and the elephant. Each touching a different part of the animal and from that having an opinion about the nature of the creature. It is hard to state what the entirety of something is (and exciting!) - not knowing the whole creature… Thank you so much! Henry B. posseydon6891 posseydon6891 1 year ago Q: Can you please show us exactly why the "glove analogy" fails in explaining quantum entanglement ? (We buy 1 pair of gloves, put each individual glove into a box at random. Bob takes one box on a trip to some distant star. Once he opens the box and see right glove, he instantly knows that Alice has the left one) BTW. awesome video, thanks! 1 Theodor Samoladas Theodor Samoladas 1 year ago OMG! From the 1st lesson about basic calculus, Sean reached the point of negotiating the deepest questions of the present. I'm afraid this means that gradually this wonderful series is coming to an end... :( Anyway thank you so much Sean... Arpan Sircar Arpan Sircar 1 year ago Questions: - 1. In the spin example, can the wave function be of the form: 1/sqrt(3) [ (up,up) (down,down) (up,down) ] - in that case if A measures up, the measurement of B is not immediately determined - is this also an entangled system then ? 2. It seems that the concept of many worlds comes out as a result of Everett's 2 postulates. However, is it possible to design an experiment to test the concept of many worlds ? 3. A request: would you please re-do the double-slit experiment explanation from the point of view of many worlds rather than Copenhagen 8 Damian Erangey Damian Erangey 1 year ago (edited) This has finally answered my questions on entanglement, I love popular science descriptions, however at times, you just need to run through the fundamentals. Astronomy Notebook Astronomy Notebook 1 year ago These videos are very much appreciated thank you so much. joshuad31 joshuad31 1 year ago (edited) 1:10:58 "many worlds is plug and play ... for those of us who are interested in pushing the laws of physics beyond what we currently know into more speculative realms ... hidden variables are not nearly as compelling as many worlds." I seem to remember that Feynman stressed this point quite a bit. So can you elaborate a little bit and make some predictions to help better explain this point? The next big breakthrough in QM and QFT that incorporates gravity or solves some big problem, can you assign probabilities to what the authors of that paper are likely to believe as their preferred interpretation of Quantum Mechanics? Probability that the author is a believer in Everettian interpretations of QM? Probability that the author is a believer in Bohmian Mechanic interpretations of QM? Spontaneous Collapse? Cubism? Some variant of the Copenhagen interpretation? 3 Iain Mackenzie Iain Mackenzie 1 year ago 7:00. When two 'waves' meet, my sense is that they disturb one another at the moment of 'impact' but then move on through undisturbed. (This is what I teach my A-level students about superposition.) So could you please tell us in the QnA session: Why is this different with the wave function? Why do we get this 'spherical resultant wavefunction'. What is it about the wavefunction that makes it NOT like an emag wave for example... 2 dandelion dandelion 1 year ago I really appreciate how neutral you are with your preferred theory while being objective in fairly expressing the alternatives. That said, many worlds feels an awful lot like string theory to me, though instead of making up n dimensions, we make up n worlds. Something about it feels off to me. But that's just a suspicion! 1 Markoul11 Markoul11 1 year ago (edited) Thank you Prof. Sean Carroll for this passionate thorough and science loving presentation about the subject of QE and not only and specially for its interpretation in the the many worlds theory context. I kept and cherished specially your phrase that decoherence is the entanglement of the quantum particle with the "environment". QE, superposition and all the "quantum weirdness" could be resolved by simply examining that what is very obvious possibility for me and was all the time in front of our nose, that vacuum 3D Cartesian space is a medium in an underlying intrinsic superluminal energy state and that our matter Universe is actually the phase transition of this superluminous medium to luminous or lower energy states. In this context, all "spooky actions at a distance" in our spacetime domain and frame of reference, would appear instantaneous as actions would propagate instantly as it would appear to us and timeless intrinsically in this underlying vacuum space superluminous energy state connecting all actions and phenomena like a gel. Einstein said that there can be no superluminous energy state but he was referring to our spacetime 3D reality domain. That necessarily does not mean that there can not be an underlying higher energy state to our Universe which is completely invisible to us... well not completely, QE is one hint. smoozerish smoozerish 1 year ago Fantastic body of work with these videos. Well done. Keep it up. Brian Cohen-Doherty Brian Cohen-Doherty 1 year ago From the numerous videos I have watched from different presenters, it seems that the isn't enough emphasis on figuring out the "Observer". That appears to be a major gap in everything I have seen, but as it seems to be a foundational aspect of quantum mechanics, I feel like it needs deeper attention. I would love any references for things happening in that area as well!! Christine LaBeach Christine LaBeach 1 year ago Hello and thanks for these fantastic vides. However could you explain spin in maybe a future video? It's my understanding that particles don't actually spin but the term refers to a form of angular momentum without rotation? Does that sound right? 3dlabs99 3dlabs99 1 year ago Amazing how fast you can make these videos -- I love the quarantine :) 2 D L D L 1 year ago Got the first notification but could not view ... for a few hours I was worried the wave function collapsed 🤣. Thank you for producing and sharing such interesting content ... yay !!! 14 Robby Johnson Robby Johnson 1 year ago I am artist with very little understanding of physics. I have been so interested in my whole life, and five or so years ago, gave up on my attempt to understand or appreciate the subjects that you've been teaching in this series. This is exactly what I've been hoping for for so damn long! I have the drive to learn more about this stuff again. Every episode starts with me doubting myself, that I'm too stupid to get it, and ends with my mind being blown, and feeling like I have a new outlook on my ability to understand... well, anything. 1 Andrew C. Mumm Andrew C. Mumm 1 year ago If I was studying quantum mechanics at uni, I would be thrilled to have these "big picture" videos Dave Wilson Dave Wilson 1 year ago Thanks for the podcasts and videos. I appreciate you. Chuck Cecil Chuck Cecil 1 year ago Dang! I thought I understood Sean's answer to the question in the last video of "What is waving in the wave function?" until this video came and shattered that perception. I thought he was talking about spacetime, but now I see he wasn't. It goes deeper than that. Incredibly fascinating stuff, but I am continually cursing the limits of my intellect. I know I wont' ever fully comprehend these concepts, but the challenge is great fun. Keep 'em coming, Sean. Scott Stuart Scott Stuart 1 year ago Question: In the many-worlds interpretation, how do you think about the "reality" of the multiple branches of the wavefunction? And what ensures that they never interact with each other after decoherence? John Lawrence John Lawrence 1 year ago Entanglement: one of those words whose meaning changes as the year passes. Like iconic. I am old enough to remember when it involved splitting a quantum particle in two, consigning each of the halves to opposite sides of the universe, then tapping one to make the other jump simultaneously. The logistics of such an experiment were always rather fascinating, I thought. But then I can remember when an icon was a small painting on wood of a Christian subject created in the Byzantine era of the Roman Empire in Constantinople Ah me, those were the days 2 Dr10Jeeps Dr10Jeeps 1 year ago How lucky we are to have people like Dr. Carroll willing to share their knowledge of physics with us! I love it. 1 Don Dovahkiin Don Dovahkiin 1 year ago Great stuff, professor, Now I can understand why physicists are so frustrated, Watching all of these lectures, I can but wonder that the human brain is so limited. Barry Kort Barry Kort 1 year ago (edited) At about 4 minutes into the video, where you take up the case of a collection of N of particles distributed in space, it occurs to me there is a caveat about keeping a single shared value of time in the Schrödinger Equation for all of them. Time-keeping is local, so if the collection is confined to a local neighborhood, then it's not terribly unrealistic to assume that they all age in unison according to a single shared local clock. But for the whole universe, what the devil do you plug in for time? The (Newtonian) assumption of one absolute universal time is perhaps the most startling and important distinction between QM and GR. And it is in the EPR scenario where this disparity comes to the fore (especially in the derivation of Bell's Inequality). If you consider the case (e.g. as in the EPR scenario), where the distance between the particles can become arbitrarily large, then each particle ages according to its own independent local clock. So, for example, if there is a gravitational gradient present, particles ascending the gravitation gradient will age faster then those descending the gravitational gradient. The one place where this caveat is especially crucial is not so much for Schrödinger's Equation, but for derivations like those found in Bell's Inequality. In that case, by assuming a universal cosmic clock, it's possible to exactly cancel out any time-varying model for the states of the particles as they speed apart. But if you admit that time-keeping is local to each particle, then instead of perfect cancelation, you would end up with a non-vanishing "beat frequency" term that survives to the bottom line. To my mind, that's why Bell's Inequality does not hold in our cosmos. We live in a cosmos where time-keeping does vary from one spacial location to the next. Time itself is the not-so-hidden variable, and "spooky timekeeping at a distance" is one of the features of GR that QM calculations must not ignore. There are gravitational gradients all over the cosmos which perturb timekeeping from one spacial location to the next. Now you might ask how this applies to Quantum Spin. Feynman noticed that if you spin a plate (like spinning a Frisbee) it wobbles as it spins. Moreover he noticed that the frequency of the wobble was half the RPM of the spinning plate, which gave him some insight to the concept of Spin ½. Now the wobble of the spinning plate corresponds to precession of a spinning top. One model of Quantum Spin is that there is an associated 45° precession, such that the instantaneous spin axis is sweeping out a 45° cone. The mean axis of spin is fixed along the axis of the cone, but the instantaneous axis is time varying as it precesses. Two twin particles might be like two spinning tops precessing in perfect phase-locked synchrony, but as they separate in space, they are no longer governed by the same clock, and so they “decohere” with respect to the time-varying precession around their mean spin axis. This is why you can choose any axis to measure the spin. If Bob and Alice choose orthogonal axes, their measurements will be confounded by having no shared clock to determine the instantaneous phase of a spin that includes a 45° precession as a time-varying term in the spin model. 2 Jon Olsen Jon Olsen 1 year ago Is it possible to simulate the wave function for a small quantum system and potentially get results that can support any of the interpretations? Tanio Diaz Santos Tanio Diaz Santos 1 year ago Thanks a lot for the videos. I have some Qs for the Q&A: 1) Is there any kind of "profound" connection between each of the conservation laws and each pair of conjugate variables in Heisenberg's unc. principle(s)? Is there a one-to-one relation, or one can arise from the other? 2) Isn't the dismissal of "super-determinism" at odds with the acceptance of the Anthropic principle (which I'm also fond of but...)? If I understand well, it's not about the experiments being able to be imagined, but whether some outcomes will ever happen or not. Accepting the Anthropic principle implies that many of them won't, because those are not the outcomes that would allow us to be here to measure them. And that's very similar to the idea of "super-determinism". 3) Could you comment a bit more on how non-locality fits in the MW interpretation? The idea of decoherence being triggered by the environment seems somewhat local to me (or at least it appears; maybe it's just the word). Does decoherence/branching happen instantaneously everywhere or does it propagate at c? Also, can be particles entangled in any property that is not part of any of the Heisenberg unc. principle(s)? (or conservation laws?). Thanks again! Dave Muller Dave Muller 1 year ago Sean, thank you for making this complicated topic so easy to understand conceptually. Even though the maths is above my head. I do have a question about the future of Quantum Mechanics. I would like to know "what's next" in a few areas, namely: - What's next if something like QBism is experimentally proven or many worlds falsified - Can you imagine any other new interpretations that have no theories, just speculative as to what the bounds are of what it could all mean - what are practical applications of understanding this more or is that unimaginable until it is understood more? And what is day to day life like as a physicist in lunch room talk on these topics? e.g. I'm a programmer and we get into debates about languages, libraries, programming techniques etc. Do you and your colleagues discuss it much or is this a taboo topic? Imager Imager 1 year ago Curious, when you say position, would there also be a wave function of the momentum? 1 Stephen Bryant Stephen Bryant 1 year ago Feynman, Susskind, Carroll ... three great explainers, but with very different styles and emphases. I can’t say which is more influential, but I am so glad that Sean has decided that this is a good use of his time. For me, these talks are very accessible. PuppetPron PuppetPron 1 year ago (edited) A definite Oh DUDE question. Can you alter the spin of a particle, make it fluctuate, vibrate, or spin in opposite direction, or is the SPIN set once measured? CyrusTheGreat CyrusTheGreat 1 year ago Hey Sean, do you mind sharing the name of the apps that you use to create a chalkboard and put yourself there? I am a professor and I'd like to use this idea, of course giving you absolute credit for that :) Bruno Teixeira Bruno Teixeira 1 year ago Question: How did Quantum Mechanics allowed us to make transistors? PS: I left this question in the previous video and got an answer from another viewer but I wasn't convinced :) (sorry Brian) crush537 crush537 1 year ago You have quite the visual style, Dr. Carroll. It reminds me of '80s era VCR tapes for some reason. Love all your content. John P John P 1 year ago Question: can entanglement be used as a form of communication, in your example, between Alice and Bob? Does what Bob would learn from his measurement depend on what Alice decides to measure? overTIMe overTIMe 1 year ago When writing the wave fn of the universe at the beginning, you gave in brackets (x1, x2, ... xN, t). How does QM deal with the relativistic notion that every electron technically should have its own time frame and that there is no absolute time? 1 bartk07 bartk07 1 year ago Professor Carroll, could you explain what is going on after the measurement with, say, a particle and its wave function? When we see "collapsed" wavefunction giving us the position, does it somehow "recombines" from this definite "peaked" value to fuzzy wavefunction again? When and how it is done and how does it look like in all of those theories (or interpretations) you mentioned? ivan flores ivan flores 1 year ago Hi sir! I am a big fan of your work, I don't know if you've already answered this but I want to ask why is the theory of a multiverse considered to be a dead end of physics? Jeff Bass Jeff Bass 1 year ago This all makes perfect sense for simple entanglement like spin-up and spin-down, but I still just can't wrap my head around position entanglement. Wouldn't the universe split infinitely often for every different position that an electron could be in, for example? 1 aman neelappa aman neelappa 1 year ago (edited) Thanks again Sean!! A couple of questions 1. What determines the basis states of a quantum system? Are they an artefact of the formulation of the quantum system, of the measurement setup or an actual "element of reality"? 2. Decoherence seems to be riding on the orthogonality of the basis states of the environment. Which, probably, comes from the Euclidean nature of Hilbert space. Is there any other physical phenomenon to it? Also, if the preceding is correct,is it surprising/interesting that the "space" of reality has nice right angles while GR spacetime has this complex geometry? Paulina Gently Paulina Gently 1 year ago Thank you, Professor Carroll. Pavlos Papageorgiou Pavlos Papageorgiou 1 year ago Are you able to start from wave functions and describe a classical process like two particles bumping into each other and scattering in different directions? DomainRider DomainRider 1 year ago Wow! - Entanglement in a purple hot tub! Isolation doesn't get much better than this!! Thank you Sean, for the highlight of my week :) 3 Shinsei01 Shinsei01 1 year ago Question: Is it possible to continuously measure both entangled particles without break the entanglement? Also is it possible while this is occurring to manipulate one particle's Spin or Charge there by observing the instantaneous change in the other particle? Pavlos Papageorgiou Pavlos Papageorgiou 1 year ago (edited) Is every interaction phenomenon a change of entanglement, and does the uncertainty principle come from having to entangle your quantum states with the experiment? Jim McIntyre Jim McIntyre 1 year ago Also, do you have any thoughts about how the branching to many worlds happens? Does the split happen at light speed or faster (because there is a superposition), or is it futile to think in terms of speed? If there is a superposition that causes the branching doesn't that mean that there is one wave function for the many worlds? supergoodguy supergoodguy 1 year ago Could it be so that Spooky action at a distance is a way that architects are logging the events happening in our reality straight into their database? 🤔 2 Wordy Smithsonism Wordy Smithsonism 1 year ago Great lecture. Thank you. Be sure to get enough rest. Dean Batha Dean Batha 1 year ago The best explanation of entanglement I've ever heard. 2 Morten Brønsby Morten Brønsby 1 year ago (edited) At 9:12 Sean refers to particle 1, but he should have said particle 2. At least as I see it. Afterwards he explains what happens in more detail, and here he gets it right. Phil Jamieson Phil Jamieson 1 year ago I'm glad that I live in a universe that has people like Sean Carroll. I never get tired of reading his stuff. markweitzman's wannabe a theoretical physicist school markweitzman's wannabe a theoretical physicist school 1 year ago (edited) I think it would be better to say that Bell's theorem (and experimental confirmation) says no local realistic theory can match the predictions of QM. 1 Jadyn Anczarski Jadyn Anczarski 1 year ago Can quantum computers give any insight into these "interpretations"? Do some interpretations predict different capabilities of quantum computers? I can see some tangential, yet interesting, questions related to consciousness and our brain being more of a quantum computer than a regular computer. Wenlie Li CN Wenlie Li CN 9 months ago "It's not a bug, it's a feature" made me laugh, as I'm a programmer. 1 Tikoty Tikoty 1 year ago Question:(the obvious one) The Wave Function of the Universe has parameters for the position of every particle. Why does it have only one time parameter for all the particles? Is this not a contradiction with Relativity, light cones, causality, etc? Erin Morton Erin Morton 1 year ago Biggest entanglement in your lockdown hair X I so enjoy your stuff. Thank you. Alexander Catton Alexander Catton 1 year ago I have a thought ( I'm no physicist), but instead of treating entanglement between 2! particles, has anyone considered that the two entangled particles are in fact the SAME particle? This can occur if spacetime (if modelled as a flat plane) folds in such a way that it interacts itself and the 'entangled' particle is found at the intersection. I Would be keen to have my idea completely dismissed or taken as a possibility 🤔 Mickolas21928 Mickolas21928 1 year ago (edited) Are two different branches of the wave function physically located in different places in the universe so that they do not impact one another under Everett's "many worlds?" Another way of asking: why would two possible waveforms in Hilbert space not affect one another unless they are physically distant from each other? MadderHat MadderHat 1 year ago (edited) Is it weird that I'm more into the 1% of the ideas? Must be my science/philosopher/artist brain. 1:18:30 Totally agree with your wrap up for the show. Art Williams Art Williams 1 year ago In my recent question, I misused the Higgs example. So, forget that part. In one illustration you have two "me" worlds. Don't both of them have the mass we think of as total? Iain Mackenzie Iain Mackenzie 1 year ago Question: In the many worlds model, I am getting the notion that some/most (all but our) worlds will collapse or be invalid / non-existent in some way. If this is true, how is that different to the notion of a collapsing wave function where all but the 'observed' part is lost? Chris Chris 1 year ago "...and is an actual physical theory, unlike the Copenhagen interpretation..." Shots fired. Trying to entangle with the universe in which they bounced off the bow and everyone realized many worlds was the truth. So far, I've decohered into a state of consideration. There are certainly many worlds in which I reject your reality and substitute my own. 1 Dean Batha Dean Batha 1 year ago (edited) Sean, I downloaded the "Universe Splitter" app that you mentioned In your book, "Something Deeply Hidden," which I am still enjoying reading. I asked it if I should "Study physics" or "Waste my time." It told me to waste my time. A few minutes later, I asked the same question again. It told me to "Study physics." I now feel myself in a superposition between studying physics and wasting my time. MEF MEF 1 year ago I have maybe a silly question but I hope it’ll be picked for the Q&A please please. What happens to the particles after measuring them? I kind of get (kinda not really) that measuring collapses the wave function. But what happens if you re-measure at some later time? The particle has permanence, right? It remains in existence after the measurement. If the wave function was collapsed by one observation does it remain collapsed for all/any subsequent observations? Or does it revert back to wave-like? e.g. if the first measurement is spin up, and the next day you measure it again, will it still be spin up? Also, are entangled pairs still entangled after the measurement? So that if you take a second measurement of “Alice” you can still predict “Bob”? Thank you so much for these videos. You’re a great teacher. I’m understanding more than I thought I would. Jeremy McManus Jeremy McManus 1 year ago Dear Professor Carroll Many thanks indeed for your very clear explanation. One particular puzzle stood out for me, though. You point out (at about 21:03) that in the wavefunction Psi [2] measurement the result of Alice finding her particle having spin up is that she instantly knows that Bob's will also be spin up too. You then go on to say that in a variation of the measurement, wavefunction Psi [3], particles can be anti-correlated, so that when Alice measures her particle to be spin up, Bob will measure his to be spin down. How are Alice and Bob able tell which of the two types of wavefunction they're dealing with? I suppose they must have some way of telling otherwise neither Alice nor Bob can have any knowledge of the other's particle. Does this mean, then, that it's possible for the two wavefunctions Psi [2] and Psi [3] to be set up in advance to be either correlated or uncorrelated, thus having some control of the outcome of the measurement? 1 Joe Taber Joe Taber 1 year ago Since quantum mechanics must reject locality, it contradicts general relativity. But GR is where space comes from, if we ditch it we have to reinvent spacetime as a solution to the Schrodinger equation. (Which ideally can be approximated into something which looks like GR.) I'd be interested in what spacetime would look like if formulated in terms of quantum mechanics. Greg Killmaster Greg Killmaster 1 year ago This is so great and these videos are so illuminating and valuable to me personally. There is an item I am unclear about. I was watching an Arvin Ash video and he said that observing something doesn't cause entanglement. Colliding with a measurement device does since its a quantum system that comes into contact with another quantum system.. So it's the direct interaction or collision of "particles" that results in entanglement. In this video it sounds like you are saying it's merely observation that could create entanglement. Would be great for this to be clarified if it's possible to explain. When you say observation, do you mean it as a metaphor or literally the act of putting your attention on something? Thank you! Edward Martinez Edward Martinez 1 year ago The wave function for Methane hydrate is at 41 degrees. The entanglement is duplex delta in both directions. The quantum delta is compounded for 8100 times squared. John Wollenbecker John Wollenbecker 1 year ago Fun times to be so entangled with YouTube. 5 İnanç Onur İnanç Onur 5 months ago A 1:20:29 long video on solely entanglement. This is unique Charles Murphy Charles Murphy 1 year ago I have a question, Mr Carroll. Why do complex numbers are necessary to describe a wave function? I've never had a satisfactory answer to this question during my undergraduate studies in physics. 1 Brent Meeker Brent Meeker 1 year ago You didn't mention an interpretation of QM I find attractive, the transactional interpretation of John Cramer and Ruth Kastner. I'm also sympathetic to Roland Omnes' view that "QM is a probabilistic theory. So it predicts probabilities." TheFluxgate TheFluxgate 1 year ago I was just thinking.. What if entanglement is really an imprint of some sort from the moment of creation when the universe was a single infinitely dense particle? Sean Carroll Sean Carroll 1 year ago Hey, sorry for the mixup with the previous version of this video! Somehow I uploaded the wrong version, I had to delete it. This one should be better in both audio and video quality. 143 Dauer S. Dauer S. 1 year ago This is amazing thank you. 1 FlockOfHawks FlockOfHawks 1 year ago (edited) in hindsight i left university just in time :o) one thing i do seem to remember though : "spin" has nothing to do with rotation QM being a theory about atomic and smaller scales , entanglement across lightyears is - imo - a totally ridiculous concept Lewis Shrubb Lewis Shrubb 1 year ago (edited) would it be possible to use entanglement to seperate hydrogen atoms from oxygen in water? entangle one group to spin up, the other to spin down run it through a magnetic field? I read that physicist have managed to entangle large groups of atoms no just single particles, if that is the case then surely it would be possible, though probably not yet efficient Brian Cannard Brian Cannard 1 year ago Thank you so much Sean! Thedudeabides803 Thedudeabides803 1 year ago I barely understand algebra, but I still listen to these beginning to end with complete interest. thanks sean Vincent Romano Vincent Romano 1 year ago (edited) A few questions: What relation does many worlds have to the arrow of time? Can wave functions branch "backward" in time? If not, why is the wave function time asymmetric? Does the present moment have multiple possible pasts? Is entropy related to many worlds in any way? Could many worlds be emergent from a more fundamental law of the universe, such as for example, "all things that can exist do" and the branching then happens when different logically consistent possible realities can no longer logically exist together anymore? Could the laws of physics as we observe them be the original branches of the universe? Could other branches have other laws of physics or different values for universal constants? Also, thanks so much for making these videos! I hope you truly understand and internalize the impact they have on the world and especially to your viewers. 2 Mediocre Dude Mediocre Dude 1 year ago If multiple worlds is to be believed, what happens when you make a measurement? Does the wave function change? Are you just figuring out what branch of the wave function you inhabit? Or something else? Walt Rogers Walt Rogers 1 year ago If I sense (see, touch) something, will that cause me to be entangled with it? Do things become entangled simply by interacting? Thank you. Javi Kroonenburg Javi Kroonenburg 1 year ago I would love to see his QM3 lectures at calltech! 7 Lauren Doe Lauren Doe 1 year ago I admit I am by no means an expert on the Many Worlds Theory. I like it because it seems simple and explains a lot. My only problem with it is that I see no experiment that could confirm or refute it. Any experiment I can imagine would have to conclude: You exist in the world where this experiment ended that way. bartk07 bartk07 1 year ago The perfect duet - Sean Carroll with The Biggest Ideas and Brian Greene with Your daily equation. I could hear and learn from them all day long. Avadhut D Avadhut D 1 year ago (edited) Hi Sean , Many thanks form India for great great lecture But I want to ask one thing 1.whats Ur thought on experiment that monkey is sit on type writer and one of possible worlds it creates Shakespeare play ,or quantum immortality,these are the weird implications What's Ur thought folks please share 1 Christine LaBeach Christine LaBeach 1 year ago (edited) If you entangled 2 uranium atoms and one decayed how would that effect the entangled partner? Also is it possible that virtual particles are entangled and if so then how would that effect Hawking radiation? I mean would entanglement still be preserved with one particle in the black hole and the other escaped? Alex Tritt Alex Tritt 1 year ago (edited) I was wondering if you could give the Sean Carroll treatment to the Heisenberg picture vs the Schroedinger picture? The seem pretty relevant in the quest to find the “correct” perspective on quantum mechanics. Do you think one of the pictures looks at things the way things are “really going on” better than the other? Glen Wilson Glen Wilson 1 year ago You discussed Objective Collapse and that experiments could validate it. And explained its importance. Wikipedia just briefly mentions the different tests but doesn't say the outcome. Given this started in the 70's, why haven't the experiments settled this? Jim Lake Jim Lake 1 year ago This raises a question in my mind. You have two balls, a red one and a blue one. Pick one at random, don't look at it, and send it to Pluto. Then look at the one you kept. If it is red, you know the other one on Pluto is blue. There's nothing spooky about that. No FTL travel required. Please explain how what you are saying is different. 1 Gabe E. Gabe E. 1 year ago Entanglement finally clicked! While the spin example is simpler to write down, the conservation of momentum illustration is much more intuitive. Christine LaBeach Christine LaBeach 1 year ago Can photon entanglement be compared to electron entanglement with the nature of their spins being so different? Photon spin is related to their polarization while electron spin is related to their angular momentum. With that being said, perhaps entangled photons don't interact with the double slit experiment in the same way as entangled electrons. If that's true then what does that mean for the experimental results? Charon ME Charon ME 1 year ago in which videos do you talk more about the probabilities mentioned at 1:07:56 ? Music Video Vault Music Video Vault 10 months ago (edited) Fantastic work! The main three issues I have are: 1. I am having some trouble with the given description of what superdeterminism is. I understand it differently and I am not sure superdeterminism is getting a fair chance by the given explanation. 2. Electrons do not spin in a classical way, a small disclaimer that quantum spinning is yet another strange quantum phenomenon would have avoided people taking spinning literally. 3. The decoherence argument I find totally unconvincing. To quote: "they evolve completely independently, they do not affect each other....", well, that's not true since they are in superposition so one does have to continue to take the "sum" of it. Jamie Gairns Jamie Gairns 1 year ago Sean, if you ever read comments, do you believe the universe has a creator? Someone I know says you do make that claim. Many thanks!! Robert Shirley Robert Shirley 1 year ago Here’s the idea : Maybe space has another way of delivering information that does not need time. Well, the information through waves( gravitational wave and light) has speed of light limitation. Maybe there is a non-wave way of delivering information? Erik Dahlgren Erik Dahlgren 1 year ago (edited) Question: So an electron can be in super position, spin up in 1 world and spin down in another world. Does it travel between the worlds? Or is it always spin up in 1 world and vice versa. There is already existing infinte worlds or does it create more worlds. Reiner Wilhelms-Tricarico Reiner Wilhelms-Tricarico 1 year ago (edited) This is what went through my head following your interesting lecture: Isn't the Schrödinger cat problematic just a consequence of our thinking in categories, which we turn in a slight of hand into discrete states of nature? It reminds very much of the cow as a point mass. I have never seen a cat that is in the state of being asleep, or in the state of hunting mice (but I have seen a cat sleeping and possibly dreaming about hunting mice). This whole idea of physical state is great, especially when you can assess it quantitatively and make predictions about it, but for almost everything else of greater complexity it remains just an empty abstraction. How many possible states has a large molecule made up of 10,000 atoms? How many states has your brain with all its10^11 neurons, each one of which being as complex as a little universe? And, since you mention of course the Schrödinger equation of which that monstrosity is supposed to be a solution, one might challenge you to write down the Hamiltonian for that :-) The "solution" of integrating the cat, the entire apparatus, and the observer (with brain and guts and laptop) into one grand wave function seems attractive on first glance, but it is still an unbelievably great leap of faith to generalize from an entangled state of a few atoms (or even a million atoms) to "the Psi function of the universe". Some religious person might ask - does it include God? How far have we really moved away from trying to answer the question how many angels fit on a needle tip? bondmode bondmode 1 year ago press 40:47 for Sean laughing at his own statement and improve your day Jon Olsen Jon Olsen 1 year ago (edited) Let`s say that we setup the cat experiment and unknowingly two separate identical experiments are set up elsewhere. If everyone opens their boxes at the same exact point of time and observe all cats are asleep, are they all in the same world/universe or does it create a world for all three? Im just curious if planck time has anything to do with how the branching happens. Joe schmo Joe schmo 1 year ago it helped me so much to read his book first and then watch these videos :) host_runner host_runner 1 year ago If you want to see a great man with no pretentious ego, Sean Carroll is one such !!! 1 Cooking for One Cooking for One 1 year ago I was considering an element I don’t recall covered in your talks. Phase shift. If there are waves then should there be phase? If a shift is outside our means of measurement, yet, then could it be the explanation for the 90% of missing stuff? If the “other” universe if just a phase shift away of ours and just right there, it might manifest itself in interesting ways. Tex Texin Tex Texin 1 year ago Given entanglement, why do we need virtual particles to carry forces between particles or to cause events to happen? Entanglement #science #physics #ideas The Biggest Ideas in the Universe | Q&A 8 - Entanglement 68,821 viewsMay 16, 2020 Sean Carroll 154K subscribers The Biggest Ideas in the Universe is a series of videos where I talk informally about some of the fundamental concepts that help us understand our natural world. Exceedingly casual, not overly polished, and meant for absolutely everybody. This is the Q&A video associated with Idea #8, "Entanglement." Using spins as a model system, I try to explain why entanglement is much more subtle than classical correlations (as in gloves or socks). And I talk a bit more about Many Worlds and the origin of probability. My web page: http://www.preposterousuniverse.com/ My YouTube channel: https://www.youtube.com/c/seancarroll Mindscape podcast: http://www.preposterousuniverse.com/p... The Biggest Ideas playlist: https://www.youtube.com/playlist?list... Blog posts for the series: http://www.preposterousuniverse.com/b... Background image: https://woowpaper.blogspot.com/2020/0... #science #physics #ideas #universe #learning #cosmology #philosophy #quantum 201 Comments rongmaw lin Add a comment... Pavlos Papageorgiou Pavlos Papageorgiou 1 year ago Is there anything interesting to make of the fact that in MW the absolute amplitudes of each branch must be astronomically small, because the universe has been splitting for billions of years, but from existing inside each branch we always experience the probabilities as summing up to 1? 9 Enrique Arriola Enrique Arriola 1 year ago Thank you for creating these videos, Dr. Carroll, they are truly great! I hope many people tune in and watch them in order to have a better understanding of how science and the universe works, something that we desperately need to happen if we are going to successfully navigate these surreal times we are living in. Cheers! 5 BileTooth BileTooth 1 year ago (edited) 53:15 This reminds me of the independence of irrelevant alternatives (IIA) axiom in decision theory. Assigning equal credence or probability to all branches is like assuming IIA holds. The example of deciding to do another measurement in one branch and not measuring anything in the other branch is like the "red bus blue bus" example, which shows that IIA can lead to nonsensical conclusions. Edit: Never mind, I kept watching and Sean did indeed mention decision theory at 57:45, so I guess I was on to something in connecting the two. 1 Hal McKinney Hal McKinney 1 year ago My favorite nugget of information so far in this series occurs around the 15:00 mark where Sean reveals that “this is the origin of the Uncertainty Principle”... I feel like a big part of understanding concepts is knowing how they were first imagined... this was like finding gold to me. ❤️ 1 HollowThere HollowThere 1 year ago Hey Sean thank you for this very informative as always! Has anyone ever postulated or written any theories about the possibility of the big bang creating a "big expanding black hole" that we're basically living in? I've day dreamed about the largest explosion ever presumed (the big bang) creating a big expanding "black hole" that we exist within. Could explain weird dark matter and acceleration possibly? Or is this maybe just a good way to dream about what we are as a universe but it isn't necessarily a "black hole". 1 qcxcq qcxcq 1 year ago Love the content as always. I just noticed this is the 2nd or 3rd video that features a somewhat irritating ~120Hz hum in most parts. Especially obvious when it goes away e.g. at 8:38. 4 Tony D'Arcy Tony D'Arcy 1 year ago Sean's explanation reminds me of Bach's music, - very intricate and pleasing, yet I have no idea of what is going on ! As to Hilbert and his Grand Hotel with an infinite number of rooms, no problem if a further infinite number of guests turn up. Plenty of room in the ballroom for the dancers to spin and entangle and a high probability of a good meal in the dining room. There is no charge for neutrons in the bar, but quantum tunnelling on the golf course is against the rules. Now I'm all puckered out and need to find my rest mass. 6 Brian Cannard Brian Cannard 1 year ago Thank you for great answers! Finally got the EPR and Bell's through the uncertainty principle. So, position, momentum, spin do emerge from the complex amplitudes of wavefunctions right? Although we write in one direction as mapping from (RealSpace^3)^N to ComplexSpace, because wavefunction is one for the entire universe, intuitively it seems that the mapping should be in the opposite direction, from ComplexSpace to emergent variants in the "permutation space" (configuration space). Thanks again! :-) Sean Whetten Sean Whetten 1 year ago (edited) Watching this series through for the second time. It's good. Near the end of the video, Sean uses an example where the particles have spins with un-equally weighted probabilities: 1/root(3)*(up) + 2/root(3)*(down) Sean sorta "hand waived" when he set it up and said, "it's my experiment, I can do it how I want" which suggests that such a system is not really possible. However, if we could make a system like that that was also entangled, then we could do faster than light communication. e.g. If we imagine a system in this configuration (up and down here are with respect to Z): 1/root(3)*(aliceIsUp, bobIsUp) + 2/root(3)*(aliceIsDown, bobIsDown) Let's also imagine that spacetime is flat, so that having agreed beforehand on a predetermined "time" and "afterwards" to make the measurements might make sense. Then, we could make a big box of particles entangled in such a way and give one box to Bob and the other to Alice and move them far apart. At some predetermined "time", Alice could either a) not measure her particles, or she could b) measure all the particles in her box in the Y direction, which would give them a definite spin in that direction and a fully indefinite spin in the Z direction "Afterwards", Bob could measure all his particles in the Z direction. If Alice did "a", he would get 1/3u, 2/3d. If she did "b" he would get 1/2u, 1/2d. In this way, Alice could transfer a bit of information to Bob faster than light by changing the probability of his measurements. My assumption is that such a system can't be constructed for some reason or that I've made some kind of a mistake while constructing it. sunita singh sunita singh 1 year ago I'm a layperson and I got u. U explain things so well! U r such a gift! 2 Anders Estes Jacobsen Anders Estes Jacobsen 1 year ago I've watched every single YouTube video with you Sean. But I don't understand the first thing about entanglement or the wave function. But I'm not giving up 👆 Keep the awsome content coming, much abliged KalynnDarcy KalynnDarcy 1 year ago Wow. The way you answered "what space is the wave function in" actually made me realise.. When you describe the wave function as a transformation on a vector space into another space, its easy to understand why the earliest attempt at formalising QM was called "Matrix Mechanics." If you described those spaces in a matrix, you're just doing some transformation on it. Joao Joao 1 year ago Hello doctor Sean! Thanks for the great video! It was awesome! =) Jay Fig Jay Fig 1 year ago Sean, I hope you’ve considered that when you see a different probable world (or particle), you’re also in a world that has a slightly different history ;) - time traveler :) 1 Kate Nicholls Kate Nicholls 1 year ago I am so gripped by this series I am unashamedly binge-watching. Started July 29 and already at the entanglement Q and A. The Q and A sections are SO helpful and as if by magic I am intuitively grasping maths that I would have predicted beyond me. Some significant air-punching going on :) What a great teacher. Thank you so much. Martin Polonski Martin Polonski 1 year ago great video! one comment: Stern-Gerlach experiment is experimentally really hard to do with electrons due to Lorentzforce. Elto Desukane Elto Desukane 1 year ago (edited) 34:40 Thanks for giving a clear and meaningful answer to this question. 37:54 So the Bohm pilot wave theory not working well in case of many particles. stridedeck stridedeck 1 year ago My understanding of the collapse wave function is that in the Many World Interpretation, this describes 100% outcome after the collapse with the entire system (branched); whereas, David Bohm Pilot Wave Theory is describing before the collapse there is hidden (from us) information what the actual outcome will be and thus we have this probability equation. 1 Jon Olsen Jon Olsen 1 year ago How great would it be to join a live stream with Sean 1 joshuad31 joshuad31 1 year ago I'm invested in figuring out the correct interpretation of QM, but with 95% certainty it's probably an Everettian model. yak yak 1 year ago There's something wonderful about how important it is to Sean that we don't kill the cat, even in a thought experiment. Loving these lectures. 19 zerooskul zerooskul 1 year ago (edited) Hey, SEAN! You know how I know you were in front of that camera while you were shooting this and I don't have to ask you or see a making-of video to verify it? Because classical systems are entangled. Without my own being there and without evidence of your actually doing anything I know you shot this, edited it, asked someone about their opinion about it and posted it to YouTube. Must be magic. I see a person and I know they are there and I can prove it without asking or measuring, or searching the whole rest of the universe to see if they might be elsewhere. You know why? BECAUSE CLASSICAL SYSTEMS ARE ENTANGLED. If we meet on the street, you know I am not in my house and you do not have to go check my house, and you know it faster than light because classical systems are entangled. QUIT KEEPING PEOPLE MISINFORMED ABOUT REALITY. C.J. McELEAVY C.J. McELEAVY 1 year ago Wonder what Seans view is on the possible existence of a"Higgs Force?" Yassine Elouafi Yassine Elouafi 1 year ago (edited) Thanks for those great vides!. I'm not sure that the many worlds is the most economical understanding of QM. My (naive) understanding is that we have 2 things: 1. What might happen and 2. What "really" happens. The MW formulation affirms that 1 & 2 are in fact the same thing. But it can be also seen from another POV that the Copenhagen formulation is the most economical in that only one thing happens instead of all of them. BTW this seems a little oddly similar to the domain of computation: there we have also 1. Programs and 2. Processes. Program is the source code which describes what "should happen" for each possible branche in the program. Processes are what "happens" when you actually run the program. Running the program to some point collapses some branches and chooses only one branch to continue evaluation. In fact there is what we call "lazy evaluation" where a piece of code is not actually evaluated until necessary (when we need the value to figure out which branch to take). What's more? Some branches are finite (testing a Boolean value) while other branches are infinite (like which branch to take based on the value provided by the user). *EDIT* One more thing is that in computation we distinguish between "pure computations" and "computations with side effects". Pure computations seem similar to the Laplacian view: in a closed program we can predict deterministically the outcome before running the program. With side effects however it's not possible. One kind of side effects is "non determinism" where evaluating an expression could return multiple answers (there is even one version with probabilities"). The point is maybe the interpretation of the wave function is simply that the universe is non deterministic in nature: that may sound crazy because it implies that elementary particles have free will. Well that's not crazier than human having it according to the free will theorem https://en.m.wikipedia.org/wiki/Free_will_theorem 4 Zeno Hamzi Zeno Hamzi 1 year ago Hello Sean, can you please explain what is the process that entangles particle, where why how. If particles get entangled at a point in time how do they get to the other side of the universe. I am looking for the applications of entanglement in the real world. Keep up the great work. Pete Brisbourne Pete Brisbourne 1 year ago Sean, I wish I could upvote your videos more than once. 6 munch hut munch hut 1 year ago Just asking.. let's say we replace the cat with an explosive that could go off at any time. Does observing it determine if it blows up or would it just blow up randomly? 3 Rajkumar Dhakad Rajkumar Dhakad 5 months ago This means, no one really understood how QM works. Everyone has their own interpretations, and each of them has certain limitations. 2 Paul Perkins Paul Perkins 1 year ago I think this got me one baby step closer to understanding what "probability" means in Many Worlds. And for me, if I ever get there, it will be a big deal. Cool. Tubluer Tubluer 1 year ago Are these the biggest ideas in the universe? It occurred to me that there are much larger ideas in mathematics, like the Enormous Theorem. But then, are they really in the universe? Dr10Jeeps Dr10Jeeps 1 year ago I could listen to Sean Carroll and Brian Greene for hours on end. Oh wait, I already do! 1 Grow-Nanny Inc Grow-Nanny Inc 1 year ago The question I have always wanted to ask is, in the next few hundred years with advances in Ai and computing, do you feel it may be possible to compute probabilities of macroscopic events such as, "should I take the job?" or "should I ask her to marry me?" My understanding of the 2 slit experiment and decoherence dictates that the only reason we see an interference pattern is we have not disturbed the waveform by entangling with it. I don't mean telling the future. I mean having a large enough database, fast enough computer and lot of supervised learning models. In this sense wouldn't we be in a sense reconnecting to another branch of the waveform? But on purpose. I feel like that's almost telling the future. Is this impossible and why? David Chung David Chung 1 year ago Based on what you said, the impression I get of the "measurement" is it signifies "entanglement." So, os the universe. from the perspective of a detector (i.e., observer) a collection of entangled objects and non-entangled wave functions, with respect to the detector? Jadyn Anczarski Jadyn Anczarski 1 year ago does the size of the system determine the amount of branches in the universe? If we take the universe as our system, is there only one branch? The wavefunction branches when two systems come into contact with each other? wafy Fahim wafy Fahim 1 year ago PLEASE Sean, answer me this question, please, Can quantum mechanics principles apply on biological systems? 1 Christine LaBeach Christine LaBeach 1 year ago (edited) For a single electron, maybe it's more efficient or takes less energy for it to simply propagate as a wave and go through both slits in the double slit experiment. I think the electrons are behaving in such a way to simple obey the laws of conservation. Mikkel Mikkel 1 day ago (edited) Thanks Sean Carroll for this fantastic serie. This goes in better dept than many, and not too deep. Should I recommend something. Delete that cat, as you planned. Don't delete the double slit. But the cat is only confusing for layman. As layman you need to first understand superposition and entanglement by other examples, to understand that cat. Consider accepting Simulation Theory as a Quantum Mechanic Interpretation. The deep simulation of the simulation theories. normskis69 normskis69 1 year ago I'm a uni lecturer teaching the semester online due to Corona. Been making PPTs with video and some drawing using mousepad on the slides. I really like your style of going through what you're teaching using a pen and the pad you use. It's much more like what I do in the classroom, than the PPT audio-visual lecture. Thank you for explaining in the Ask Me Anything about the Eric Weinstein (et al) perspective. I can understand now. Perhaps you could encourage him in his approach. I think he's going nuts because he needs some grounding. Give the man a problem. He'll try to work it out xxxxxxxxxxxxxx 1 Javi Kroonenburg Javi Kroonenburg 1 year ago So in the first MWI probability example (two spins equal prob.), you'll end up with the upperbranch given amplitude = √1/2, and the other two branches with an amplitude √1/4....? Rajkumar Dhakad Rajkumar Dhakad 5 months ago (edited) When the electron is falling into gravitational field, its entangled gravitationally, that is why its falling i.e. behaving in a certain way rather than wandering randomly. Plss explain. John Bach John Bach 1 year ago I'll be reading 'Something Deeply Hidden' next week. I have many doubts about MWI, but between your book and this podcast (starting it now), I suspect they'll be alleviated. A Kumar A Kumar 1 year ago Top notch, plus like alot of other viewers, I too think you have a lovely speaking voice ♥ 24 Bailey Bartley Bailey Bartley 1 year ago (edited) What happens if Bz is rotated 90 degrees whilst measuring spin, say through a rotating cylinder ? Is our current form of measurement too discrete to get anything substantial? David Campos David Campos 1 year ago I have chosen to go a step farther from "Many Worlds" to a many blurred universes. A string universe, a probability universe and a many worlds universe are the first three. To be continued... crush537 crush537 1 year ago Customer : This cat is dead! Sean : It's only sleeping. 27 D L D L 1 year ago Thank you Sean 👍 Markus Wöhrenschimmel Markus Wöhrenschimmel 1 year ago In the awake/sleeping cat example, why for example (cat awake, seen sleeping) is not taken into account- isn‘t that just possible or do we as observer prejudge what makes sense or not - is there a hidden bias of the observer distracting the system (leading to decoherence) Patrick McHargue Patrick McHargue 1 year ago If you have two entangled particles, and one falls into a black hole, when you measure the (say) spin of the particle outside of the BH, do you now know the spin of the particle in the BH? Is there some other case when two entangled particles are outside of one another's light-cone, yet may effect a change upon the other? Robert Spiess Robert Spiess 1 year ago (edited) First it was stated if a particle is measured in Z to be spin up then you measure it again for Z it will always be spin up. So in the Alice and Bob scenario if Alice measures Z to be spin up we know Bob is spin up. Ok now say Bob measures X and gets spin right. Now we cannot say if Bob Z is spin up due to uncertainty. NOW ALICE PERFORMS A SECOND CONSECUTIVE Z MEASUREMENT. Will it be spin up, due to the first Z being spin up or 50/50 due to Bob making the Z direction uncertain ? 1 James Swift James Swift 1 year ago In another world, Sean can draw a good cat. markweitzman's wannabe a theoretical physicist school markweitzman's wannabe a theoretical physicist school 1 year ago I think the Born rule is circular, without using the L2 norm, you won't get the absolute square. There is no explanation why absolute value can't be the probability instead of absolute square. enotdetcelfer enotdetcelfer 1 year ago Wow... I now finally really get what the fuss is about with quantum mechanics. Hurray~ David Bonar David Bonar 1 year ago the universe... what a concept! :D Elnur Hacıyev Elnur Hacıyev 1 year ago Correct me if I am wrong: In the last part of the video, isn’t it cheating to represent the two subsequent experiments with separate wave functions, especially if we are talking in the context of the Many Worlds Theory? The moment we are putting a condition for doing the second experiment based on the outcome of the first one, needn’t the two to be treated entangled with each other within a single wave function? I think of it as prooving 1=2 from a mathematical equation by ignoring the initial assumptions or some fundamental rules. I am probably missing some point in this particular thought experiment, so I am looking for an explanation of why the above-mentioned assumptions do not apply here. I would be happy if you had time to bring a clarification. Onbored Onbored 1 year ago The first rule of entanglement is we do not talk about entanglement. 23 Steven Lang Steven Lang 1 year ago How big is a "world" when it branches? Is it just a local branching which then propagates from there (at the speed of light)? Or is it the size of the entire "parent" universe from the beginning? Neither? 1 David Thomas David Thomas 1 year ago The probability problem was the thing I had the most trouble with regarding Many Worlds when I read Something Deeply Hidden. I don't understand how it explains that I could use statistics to predict, say, how many spin up vs spin down outcomes I'd get from repeating a prepared experiment, and get the distribution I expect. I guess the problem is that questions like "Which future branch of the wave function will I find myself on?" seem like they aren't really well defined questions at all, since I will find myself on all of them. It's more like, "after I do the experiment but before I learn the result, what credence will make sense at that point to assign to the different possibilities of self-location?" So confusing. Boris Petrov Boris Petrov 1 year ago How any two things -- particles, photons, other -- become entangled? The process that creates entanglement... Reiner Wilhelms-Tricarico Reiner Wilhelms-Tricarico 1 month ago Found a nice, somewhat more geeky, lecture explaining the mathematical details of the spin 1/2 operators. See the 4th lecture by Prof Barton Zwiebach on Spin One-half, Bras, Kets, and Operators, MIT 8.05 Quantum Physics II, Fall 2013 https://www.youtube.com/watch?v=BWM0RXg-uvI fubarbazqux fubarbazqux 1 year ago Does the problem with locality arise if you take the frequentist view of probabilities? Say, Alice measured up and left, so Bob is "forced" to measure down and right. But why isn't he allowed to measure "right", given psi = (right/sqrt(2) + left/sqrt(2))? That equation does not prevent this particular measurement from going any particular way. And if we take a series of experiments, Bob's frequencies are determined by Alice's frequencies, which will comply with amplitudes of outcomes. Allan Zed Allan Zed 1 year ago So if Bob measures his spin first he knows x light years before Alice what her spin is. Could you say that Bob can tell the future wrt to Alice? And what if we were once all entangled our lives might be playing out in a fatalistic way that was already known at the big bang? Somebody or something (call it the Universe) might already know our destiny- now that's spooky. And if our brains are quantum measuring devices we might be able to 'sense' things not immediately in front of us? Christine LaBeach Christine LaBeach 1 year ago I'm assuming that the spin of a photon is related to it's polarization? Brian Cannard Brian Cannard 1 year ago @Sean try this format of videos so it will be much less distractive in terms of speaking/writing context switching. You might enjoy the result! https://youtu.be/GuiIyYbI0HM Jainal Abdin Jainal Abdin 1 year ago How does the conservation of energy work with Many Worlds? Everytime we get a branch from the wavefunction, we get a new universe spanning off this branch? Where is this energy coming from? Doesn't make sense. Also, probabilities don't make sense in Many Worlds. For example, in the double slit experiment, you'll find a world where the interference pattern doesn't show up because it's extremely unlikely to happen but it is still going to happen due to the non-zero probability from the wavefunction. Adrian Cockburn Adrian Cockburn 1 year ago How can an electron be a little bit entangled? Surely its either entangled or not entangled? 1 Stephen McConnel Stephen McConnel 8 months ago Where did you get that 1 over the square root of 2? viewer viewer 1 year ago Slightly off topic but maybe somebody can explain this please. The Centre of the Earth is younger (as time goes slower there ) than the Surface. So if the Earth is created from the centre to the outside then if you could go back in time, then the outside of the Earth would be older that the centre. Is this a Paradox. Even allowing for the matter changing, the space in the centre would have had to be created before something that is older than it ! Can you explain this ?If I created instantly(or close to, hypothetically) my own sphere/earth of uniform material from the centre to the outside. Would the same question exist. How could the older outside be built up on a younger centre ? Thanks. Steven MqCueen Steven MqCueen 1 year ago If Schrodinger’s cat is no longer alive or dead but is rather awake or sleeping, then it’s not in a box — it’s in a safe space. bmoneybby bmoneybby 1 year ago (edited) Sean is starting to look like me in this quarantine. .. hungover. Lol Alex Tritt Alex Tritt 1 year ago “ ‘in’ is not a technical term” LaTeX is starting to look nervous 3 Tubluer Tubluer 1 year ago It was bad enough when all these half-existent dead cats started showing up all over the apartment, but now there is spectral copy of Sean Carroll observing each one of them and half of those are demanding tea and biscuits. The other half want coffee and croissants. I can't afford this quantum mechanics stuff. Help! bondmode bondmode 1 year ago that lapsus at the end is gold KHALIL ULLAH KHALIL ULLAH 1 year ago Sir explain the concept of time dilition Travis Cook Travis Cook 1 year ago Is a superposition an interaction necessarily? that is; is it a physical event or just a state? (can a state not be a physical event, even?) I know that not ALL interactions are superpositions, but are ALL superpositions interactions? lplt lplt 1 year ago when everything makes sense except the entanglement vs correlation Christine LaBeach Christine LaBeach 1 year ago Could reference frames be entangled at the quantum level? Steen Eugen Poulsen Steen Eugen Poulsen 1 year ago The non bolsmann copy of me seems problematic as you need a copy of the "infinite" universe, to create a copy of me. You are either going to need a radically different universe, where you can't spit without hitting life, that every solar system has life and a large potion of it has some intelligence, because you need to create an infinite number of not me's in order to create one me. Even an infinite universe can't just have ME, Me2 and nothing else, it must have an infinite number of not me's, in order to have a chance of creating just one ME and an even higher number in order to create a ME2. Anthony Pazana Anthony Pazana 1 year ago Who is there at the other end of the universe to confirm that there is "entanglement" 1 Travis Cook Travis Cook 1 year ago He's really careful not to kill these fictional cats isn't he? 1 Jainal Abdin Jainal Abdin 1 year ago I liked this video and agreed with you in this universe, and in the other universe, my other self disliked this video and disagreed with you regarding Many Worlds. Soul DFS Soul DFS 1 year ago Awesome and sad 76ers point in the video. No one in the world would have thought there would not be a 2020 championship series. Maybe we will see a no fan playoff bracket. Then you’ll still be right. artyom Diogtev artyom Diogtev 1 year ago I love Sean’s t-shirt 🤟 1 mountainhobo mountainhobo 1 year ago "444 likes, 4 dislikes" -- Looks like 4 got entangled. 5 MyOther Soul MyOther Soul 1 year ago I don't understand what the branch probabilities mean in many worlds. As Sean points out it's not the credence meaning of probability. And it can't be the frequency meaning because all branches happen with the same probability (p=1). What meaning is left? It seems for many worlds to work it needs to make some extra postulate about probability even if such isn't called a postulate. Paul C. Paul C. 1 year ago Dear Prof. Carroll, what is the best way to send you a question please ? (I do not have a twitter account.) Thanks. All the best from West Wales (UK), Paul C. Tobias Wahl Tobias Wahl 1 year ago Isn't ↑ = ½ → + ½ ← (no square roots)? Praetor2000 Praetor2000 1 year ago Entanglement isn't the same thing as classical correlation because entanglement isn't the same thing as classical correlation. Ahhh. NOW it makes sense. Go Mezant Go Mezant 1 year ago If "many worlds" exist, are they entangled? Stormbringer_777 Stormbringer_777 1 year ago Do live streams!😂 Bits at a time🤔🙌 4 NUKE NUKE 1 year ago Mr Carroll I have a question, not related to this video necessarily, I'm only asking here anyway cuz I can't find any answer anywhere else on the internet about it... My question has to do with how all those things look like, are they real? Quarks, atoms, protons neutrons etc? Or are they just mathematical models, nothing more than mathematics? For example, if we were to blow up an atom to the size of say... a basketball, ... what would it look like? Would it have like colors or even a surface? Would it have anything that we could see? (assuming we could see the entire spectrum of light and not just visible light). Could we touch it and if yes how would that even feel like? Or would it be invisible? Like a force sphere that you just can't see or feel in any way, but if you tried to pass through it - it would be standing in your way blocking it from you? Blade Runner6997 Blade Runner6997 1 year ago I have a hypothesis. Sean decided to do these videos because he is in love with this new writing gadget he's using ! 10 John Baker John Baker 1 year ago I love these talks. Most of it is too complicated for me, but the little bit I do follow is fascinating. 5 AndyBeans AndyBeans 1 year ago The last lecture kind of lost me, will have to try watch it again Sergey Novikov Sergey Novikov 1 year ago (edited) )) it's a real BS here at 27:10 -- neither a 'cat' nor its 'environment' can be strictly determined as a quantum system to which we can prescribe certain quantum states.. it's nonsence to speak about a cat in a box as about a well defined local quantum system)) btw, a laborant will permanently feel the state of a cat in a box through gravity, for instance. it's impossible to separate a laborant from a cat, firmly speaking.. Rajen Shah Rajen Shah 1 year ago It sounds like people say 'superposition' just because we don't understand how to measure things accurately Moshe Callen Moshe Callen 1 year ago I prefer to look at QM via propagating degrees of freedom. A measurement is then just any localized interaction which fixes a physical degree of freedom. Tom Lakosh Tom Lakosh 1 year ago Time/distance/acceleration and entanglement are mutually exclusive as superposition requires instantaneous response over any distance, thus precluding acceleration and the time function in that realm. That's why, in my humble amateur opinion, we need a component of matter that still exists in a realm without a time dimension. My TOE posits a dual membrane electromagnetic field with an antimatter half that doesn't have a time function, (i.e. a 3-brane). The EMF when properly stimulated, produces circular string pairs of 4-brane matter and 3-brane antimatter to form 1 to 3 aspect ratio tori that we call gravitons that are the building blocks of all subsequent more complex matter. The circuit or conduction tensor formed in the torus keeps these strings from annihilating as does the conduction tensor holding graviton clusters together, (looks like a barbell). Time just renders these antimatter strings to a recessive manifestation in the graviton and in the subsequently more complex structures unless an annihilation event is created with counter rotating structures that force a matter-antimatter collision. Some of the less complex structures can synchronize wave functions such that when they reach zero, allow transport of all or part of the particle through the antimatter 3-brane but information can always flow between the superposed antimatter components. Gravity is just the electromagnetic and fluid dynamics processes applied to the flow of graviton and graviton clusters around and through Standard Model particles when time applies on our 4-brane. The clusters are actually gluons that were formed en mass during the GUT Epoch and are continually formed in SM particle cores. These gluons/clusters act like a dipole gas subject to condensation via Feshbach resonance and BCS field effect, and this condensate is formed in the electromagnetic field of galaxies as dark matter that is scattered by cosmic rays immediately after formation of a droplet that is detected as point source gravity in a halo around galaxies. The dipole gas is spin and charge coupled on the surface of leptons and baryons to form the Higgs field via fluid dynamics to operate as an electromagnetic rectenna generating space-time viscosity as it captures the momentum of gravitons and clusters flying through the field, (https://www.youtube.com/watch?v=EVbdbVhzcM4&feature=youtu.be&t=288 , the secondary torus represents the Higgs boson terminating/reversing Higgs field flow). The gas is also the working fluid for a gravitational propulsion system operating as an “ion thruster” through the core of the leptons and baryons. Dark energy is just the increase in quantum friction of the propulsion system in barren space where the Higgs field drags the particle backwards toward even less dense space because the propulsion system no longer counteracts the Higgs field generated momentum captured from the low density gravity flux emanating from the center of the universe. The gluons also form the structure of the SM particles when fused together in rings under activation energy with four graviton clusters forming leptons, six graviton gluons forming nucleus shells and eight graviton clusters forming nucleon shells with each modular element absorbing the strings from the distal gravitons into the linear conduction tensor forming the core of the structural ring. Neutrinos are one of the rings from a lepton that can oscillate because of the triple density string structure in the ring core. Aaron Cunningham Aaron Cunningham 1 year ago Bra + Ket = Bracket..... I'm an engineer; that shouldn't have blown my mind >.< Go Mezant Go Mezant 1 year ago If the big bang is true, then everything is entangled with everything else and entangled again and again all the way down to turtles. 1 august putrinsh august putrinsh 1 year ago https://www.youtube.com/watch?v=IB50S4J4c8k&t=25m when Alise measures "right", we know, what Bob would measure. If now Alica measures "up", we instantly lose knowledge about Bob's "right", right? Barry Kort Barry Kort 1 year ago One model that explains the results of the Stern-Gerlach experiment posits that the spin of an electron is analogous the spin axis of a top that is precessing at a 45° angle, sweeping out a 45° cone. The time-averaged direction of spin could be fixed along the z-axis, but the instantaneous direction is precessing around the z-axis , which would explains why a second measurement along the x-axis would nevertheless be 50-50. ironic legacy ironic legacy 1 year ago (edited) Could the bertlemann’s sock example be improved by saying not only does bertlemann always wear different colored socks but he only puts on a second sock when someone sees his first sock and also bertlemann is blind? nathanisbored nathanisbored 1 year ago holy shit i think i legit heard a lightbulb go off in my head at 49:32 august putrinsh august putrinsh 1 year ago https://www.youtube.com/watch?v=IB50S4J4c8k&t=30m how come two particles are entangled after collision but not before? this asymmetry gives me uneasy feeling. Andrea Paolini Andrea Paolini 1 year ago (edited) Planet-A is many l.y. away from Planet-B; Bob will misure speen-Z every 20 seconds so Alice can send istantant-fast message to Bob; how? spin-z-up=1 and spin-z-down=0; A want to send a 1 to Bob, A mesures spin-Z=down=0 (wrong), so A mesure spin-X and ignores the result, then re-mesures spin-Z=down=0=wrong, then she re-mesures spin-x (just to "reset" the superposition of the Z-spin) and she re-mesures spin-Z and so on until she mesures the spin-Z=up=1=ok! (hopefully in 20 seconds, or you can add an error code). !?!?!?!? What's wrong? Spencer Delallo Spencer Delallo 1 year ago Your shirt is amazing 🤣🤣 Randy Arvello Randy Arvello 1 year ago Is being a little entangled like being a little pregnant? Travis Fitzwater Travis Fitzwater 8 months ago That's 52 minutes I could have sworn you said now let's try a little bit bitter example then I thought about it I realized you said better I know he said let's try a slightly better example and I thought he said hey let's try a slightly I don't know he said okay now let's try a slightly bitter example it's that funny? Benjamin Kruger Benjamin Kruger 1 year ago I'm just watching to see when Dr. Carroll gives up and cuts his hair. Hargey _ Hargey _ 1 year ago When the alert sound went off I wasted a minute trying to find the tab that made it... 7 Andre Amorim Andre Amorim 1 year ago (edited) Very important to crypto keys exchange and distribution 🗝️🔓🔒 x-y-Zed x spectrum Smoogems Smoogems 1 year ago I drink and I watch things 7 Nathan Van Pelt Nathan Van Pelt 1 year ago is sean married? if so, what a lucky lady. 1 apburner1 apburner1 1 year ago Ya fugged up on the Alice and Bob thing. Every laymen pop-sci nerd on the planet knows nothing but one is up so the other is down. Confusing it with "they are related" and making the spins the same just makes it confusing for everyday J means that particles far apart somehow share information and follow the evolution of their Hamiltonian. It would seem to obviate the need for a virtual particle to exchange energy or other information between them.