I think it is important to clarify that it is not "observing" a quantum system that makes it resolve itself into a specific outcome, but rather the object interacting with something other than itself that forces it to resolve its state. The object is not conscious and it happens independently of human observation. It's important to consider the language we use so as to not give the quantum systems, nor ourselves supernatural qualities.
@@pluto9000 In the context, yes. But most people don't have that background. It's important to make that distinction clear. To "observe" something you have to interact with it. You must change it by affecting it.
This distinction disappears the moment one realizes that "conscious matter" is not any different than "ordinary matter". Existence observes itself with or without the awareness of the observation/interaction/interdependence
The particle knows where it is at all times. It knows this because it knows where it isn't, by subtracting where it is, from where it isn't, or where it isn't, from where it is, whichever is greater, it obtains a difference, or deviation. /s
It therefore follows that the particle has no knowledge about it's momentum. It doesn't know its momentum because it doesn't know what its momentum isn't. There is no sensible way to subtract the momentum it has from the momentum it hasn't, nor the momentum it hasn't from the momentum it has, nor is it possible to define a rigorous notion of whichever is greater...
There may be more than one force at work in the particle of light. One electric, which only has a velocity, and the other magnetic, which is only stable in one place! The light is moving unless it has a reason to stall, such as a relationship outside of itself- the measurement is one. Fun!
like honestly your explanations are very clear and to the point and they are comprehensive, i really appreciate :) its not usual to be able to tackle subjects as difficult as the ones you explain as easily as this channel allows to. thanks :)
@@ppmico Thanks! I'm always worried that I complicate things too much and I'm also always worried that I simplify things too much, so I'm glad you're getting something from it!
@@physicsforthebirds I really like your niche/small channel style, when channels go big they usually go towards a more mainstream style which feels like a TV show rather than a genuine random idea fuelled by fun and curiosity. I also like things coming completely out of left field sprinkled with sarcasm and existential crisis. So I really like you overall.
@@physicsforthebirds i assure you, i'm pretty dumb, and i find these videos both insightful and feeding a level of curiosity that makes my brain real happy
I wonder when the scientists are going to realize that they can just entangle particles with just some string and a pair of tiny baby hands without having to resort to jellyfish and olive garden
I’m so glad I found this channel, thank you so much for creating such unique and inspiring content; I love the way you often explore topics at a scientifically deeper level than many channels, but still keep everything accessible and clear :) I’m looking forward to all of your future content and growth!
Found out your channel about a week ago, through the popcorn video and was surprised about how well your videos are made, truly an awesome work. If you keep like that, in no time you’ll get lot of subs and view, rlly appreciate the efforts you put on the animations, talking and even the sources on the description. Hope we see you thrive soon, good work!
Do you not understand how soul crushing this video is??? My soul, my everything was dedicated to creating a quantum computer that uses olive oil. Every day I toil in the mines creating olive oil and growing the silicone to create the supercomputer. What will do now?
Cute cartoon of a dilution refrigerator at 11:34! N.B. 3:49 is accurate but a little imprecise. It’s possible to have linearly or circularly polarized light in a superposition of horizontally and vertically polarized states too (per choice of HV basis). Linear polarization and circular polarization are special cases of elliptical polarization that can correspond to the 50/50 HV probabilities you show at 4:07. N.B. 3:58 and 4:08 are inaccurate, and you need to be careful regarding what parts of this quantum “system” you’re talking about. If you’re talking about the quantum state of the smaller system “photon after polarizer,” the photon already “decided” its polarization (and pass/no-pass) when it encountered the polarizer and was projected onto the vertical state, before it encounters your eyeball. Your eye is not required to modify the photon’s state in this perspective, nor is your eyeball projecting passing photons onto the vertical state. If you’re thinking about the quantum state of a larger system of “photons before and after polarizer,” the polarizer is actually part of the system too. After a photon encounters the polarizer but before encountering your eye, the whole system (photon and polarizer together) is described by a mixed state of “vertical polarized, passing photon” and “messy whatever happens when the photon is absorbed by the polarizer and decoherence kicks in.” If you’re skeptical, consider this: the inner product of the state of any quantum system with itself MUST be 1 (i.e. the system has 100% probability of being in some quantum state). The state corresponding to “50% vertical probability and nothing else” isn’t possible without using mixed states.
Idk if it was your explanation being extremely well done and simplified, or if it's just bad, but I think I've come to the realization that Quantum Mechanics is a stupid semantics game. Entanglement sounds like you broke a cookie in half and tossed them in the air, and then said "You don't know which side is the up or down until they land! And they're going to fit together mysteriously!" Yeah, of course they're going to be opposites of each other, you just broke them in half. They fit together. Why is this a surprise? It's all semantics and sophistry.
This channel is amazing, the way you explained quantum mechanics was great. I am doing a school project( I am in 8th grade) about quantum internet. and the information you explained helped my project so much. Your explanation on SPDC is great! Because of you I learned so many new things! My project is 10 times better because of your video! Thank you for your amazing videos!
@@physicsforthebirds Yes I will, I will present it on may 9th (my birthday)! I REALLY want to send you the link to it (it is a google site) but I also don't want the entire comments to get the link to my website. If I knew being a bird meant getting these types of videos about physics before, I would have became a bird earlier! Also I have put you in the citations and in the special thanks!
Always excited for a new video from this channel :). Taking a quantum computing course this quarter but it's more focused on the theoretical foundations for qubits and gates. Love to hear these musings on more practical problems when it comes to the physics of obtaining an entangled state :) (and it certainly doesn't hurt that they're accompanied by such cute drawings)
love your stuff. finishing my BSc in physics and these jus kinda scratch my brain the right way. idk why the mood you set while talking about familiar topics just kinda soothes me. thanks
I think of it more like when the entangled photons are emitted, they each have opposite polarizations, and are both already in whichever state that they are in when one gets measured (and then let's you know the other is opposite). They 'know' exactly which state they should be in ever since they were emitted. we just have no way to determine which state they're in until measuring them. so they're in a superposition only as far as our knowledge of them is concerned. in actuality they've always been in the 'collapsed' waveform state the entire time. there is no need for instantaneous information transfer upon viewing one to determine the other like, imagine two sisters were going to an event and wanted to wear different color dresses... you know that they coordinated before leaving that one would be wearing red, the other blue. what you don't know is exactly which sister is wearing red and which will be wearing blue, you just know that those are the options. (the sisters are in a superposition of either wearing red or blue). when you arrive at the event, you say hi to one of the sisters, noticing that she is wearing red (the superposition waveform has collapsed) so you can intuit that the other must be wearing blue, and sure enough you see her later and see that she did wear blue. this doesn't mean that the sisters were each "maybe wearing red, maybe wearing blue" No, they decided before going out who would wear which color, they just didn't tell you about it. so to your perspective, you had no clue until you finally saw one of them later. sister 1 was always going to be wearing the red, and sister 2 always the blue. you just had no way of knowing until you saw for yourself. if information was transmitted upon 'measuring', then that would mean that when you saw the first sister in red at the event, she turns around and calls the second sister to tell her to change into her blue dress right then and there. that wouldn't make any sense.
oh my goodness! i had just identified a picture on inaturalist the other day of that jellyfish which apparently only lives here in the pnw. and now i learn it's where that glow protein comes from in this video! that's so cool, and weird, it's not like i'm regularly thinking about jellyfish, that was the only one recently. i'm finding the world works in mysterious ways. quantum mechanics in general is also kind of scary and weird and cool, thanks for explaining some! i knew particles could be entangled but didn't know specific ways it actually could happen.
this channel is gold, I'm glad to see you upload these amazing videos every time >:) I hope you will grow to become the next big physics channel you deserve it!
The information that determines which state the system assumes upon observation(the term for interaction), is not encoded upon observation(interaction), but is encoded at the moment of entanglement. :D The information doesnt actually have to travel between the particles, it was already encoded in the past. This misunderstanding is very common... and it makes it seem like "magic"... but there is nothing magical happening xD So i must point it put to everyone >:3 (I'm looking at you, New Age Hippies!!!)
I like thouse Videos and i always Watch them. Today i was learning quantum mechanics in german for my Uni and had some Problems. To procastinate i started to Watch some TH-cam. And this Video is the second I Watch. Well now i understand them a Bit More.
For the polarized glasses example, wouldnt it make more sense to say that the photon that was blocked does "know" when its measured by the glasses but the one that isnt doesnt until it reaches your eyeball ?
One issue Ive always had with quantum physics is if we have to entangled photons people use language like "if we observe the spin of one the spin of another is forced to change." How do we know its being forced to change? How do we know it wasnt always in that spin position before observing and really by observing it we're taking a coin flip and saying it landed on heads after the reveal? NO ONE ever explains that its just taken for a fact of 'the quirks of quantum science'
1. Q: The entangled particles decides its spin right after it gets split, not at measurement!!! It's just that the spin is unknown. Short Answer: The above statement is MISLEADING at best and might even be WRONG. 2. Q: What is a measurement, really? Isn't it just when an interaction occurs with an external particle or force? Does it have anything to do with consciousness. Short Answer: Physicists don't know what a measurement really is. And no, an interaction is not the same thing as a measurement. A measurement probably doesn't need a concious being. 3. Q: Isn't this just an overly complicated version of when we have a ball hidden underneath 2 cups and we don't know which cup it's under until we "measure" by lifting one of the cups? Short Answer: No. 4. Does it really matter whether the particle gets its spin right after entanglement or if it gets its spin only after measuring? Isn't this just bad philosophy by physicists to make things seem more complex or a matter of annoying semantics? Short answer: Yes! It matters. They are fundamentally different things! It's not just physicists trying to seem smart or being pedantic. LONG ANSWER: Physicists don't fully understands what a wave collapse is or what a measurement is! That being said, there are a few good and not so good perspectives and ways to interpret QM (Quantum Mechanics): 1. Realist (aka Local Hidden Variable Theory): The quantum system is just like a ball underneath some cups. The ball already has a determined cup its under. We just don't know it until we measure it. There must be a hidden state or a hidden variable that somehow describes what state the ball is in since the realists think the ball is already under a determined cup. QM must be incomplete since this hidden variable isn't anywhere in modern QM. 2. Orthodox (aka Copenhagen Interpretation): The quantum system is not like a ball under a cup. We don't know what spin the particle is in until we measure it. No one in the universe knows what cup the ball is under until we measure. God doesn't know what cup the ball is under. The ball doesn't know what cup its under. [Insert omniscient personification here] doesn't know what cup the ball is under until there is a measurement. We say the measurement causes the particle's wave function to collapse. The act of measuring "creates" the spin of the particle or forces the ball to be under one of the cups, but not before. 3. Agnostic: Bury your head in the sand and don't think about it cause it doesn't matter when the particle gets its spin, since after all either way we don't know until we measure. The difference between the realist and orthodox perspective is just semantics. 4. Other: More advanced or modern ways to explain measurements and wave function collapse. Examples might include non-local hidden variable or everett (many worlds) interpretations. Let me start by saying that any serious physicist will only consider the "Orthodox" or one of the "Other" interpretations. This video considers the Orthodox position, since this is the oldest (so it's stood the test of time and hasn't been proven wrong by experiments), it's what most students are taught, and it's also more conceptually simple compared to the "Other" interpretations. The Realist and Agnostic interpretations are unlikely to be true because of a something called Bell's Inequality. Bell's Inequality is a mathematical statement that is implied by realism. Physicists showed that if realism is true then that means Bell's Inequality is true. But the surprising result is that if Bell's Inequality is true, then quantum mechanics is not just incomplete, but completely wrong. Many experiments have been performed and have shown that quantum mechanics is extremely accurate and have shown that bell's inequality is false, which basically means that realism is very unlikely to be true (in fact the most recent 2022 Nobel Prize was awarded to physicists who showed that Bell Inequality was violated or false). Since realism is probably wrong, then that means that there actually is a difference between orthodox and realism. So there really is a difference between the particle having a definite spin before measurement versus the particle having the definite spin only after measurement. Thus the agnostic position is wrong. There are real physical differences that can be found through experiments. So you can't bury your head in the sand like an agnostic believer. What is a measurement, really? Isn't it just when an interaction occurs with an external particle or force? A measurement is not just an external interaction. A particle that interacts with an external particle doesn't necessarily have to result in a measurement. In fact, Quantum computers work by manipulating particles in superposition using external fields/particles, but this doesn't result in any collapse in the wavefunction (so it's not a measurement). The particles in the quantum computer still retain a state which is a superposition. So not all external interactions are measurements. So you might ask what kind of interactions are measurements (i.e. causes the wave function to collapse). Again this is an unsolved problem in physics (google the measurement problem). But again there are a few good and some bad interpretations of what a measurement is: 1. A measurement is made when a macroscopic (classical) system interacts with a quantum particle/system or what a scientist does in a lab using classical tools like a ruler, stopwatch, spectrometer, etc. (Bohr) This is probably the simplest way to imagine what a measurement is and works pretty well for intro level QM. This is what the video defines a measurement as. 2. A measurement is when an irreversible process occurs, aka increase in entropy. 3. A measurement is made when a conscious being observes something (Wigner) 4. A measurement is made when a permanent record is made (Heisenberg) I think 1 and 2 are probably the best ways to think about what a measurement is. Most physicists don't think 3 is right since all known physical laws don't really care whether humans exist. All these perspectives have problems of course. Like for 1, what differentiates a macroscopic and quantum system? When does the transition occur. And for 4, what does "permanent" mean? * Footnote: Bell's Inequality only holds if particles affect each other slower than the speed of light. Some newer theories with hidden variables can work if the particles can influence each other at faster than light speeds (called non-local hidden variable theory). D.J. Griffiths and D.F. Schroeter, Introduction to Quantum Mechanics, 3rd ed. (Cambridge University Press, Cambridge, 2018). ^ for those with more math background, check out the proof of bell's inequality.
I love this channel, always waiting for a new upload.
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As a side note, that maybe you will find interesting, a while ago I read that "you shouldn't put your titles as questions" because most probably, the answer is "no", if not, you would probably set the title as "Making a Quantum Computer out of Olive Oil", meaning that you would have make your title positive, instead of hiding it with a question.
@@physicsforthebirds its great stuff! your video on jazz and entropy has been super informative for my composition work, the overlap between music and physics is super interesting :)
Fun medical facts: in a dark room, you actually CAN see a source emitting 100 photons per second. The cells in your eyes only need one photon to activate, though your brain requires more to make sure the cells aren't discharging by accident (which they do, though stunningly rarely)! research.physics.illinois.edu/QI/Photonics/pdf/PWDec16Holmes.pdf
So why can't it be that when you split a photon, their state is already deterministic, we just can't know until we measure it. The explanation of superposition always confuses me. It's like saying I don't know what my roommate is doing in the other room, so he is doing everything at the same time until I see him, then he resolves into doing one thing.
the use of the word "observing" tends to confuse people, we're not special, it's not because a person "looked at" a superposed object that it's state became known. "Observing" just means "interaction with a system that's strong enough to entangle it with the environment" basically once the particles observed state becomes part of a system that locks it into that state. It's the same kind of thing he explains about his table not disappearing when he leaves his room, all of the particles of the table are "observing" each other and entangled in a state that overall, means it's a table (well that its fibers that make up wood etc etc)
"deterministic" would mean that we knew the state before the measurement, based on the initial conditions. "we don't know until we measure" is precisely the meaning of indeterministic. I think you meant "determined but we don't know how" which are hidden variable theories, most of which have been disproven
1. Q: The entangled particles decides its spin right after it gets split, not at measurement!!! It's just that the spin is unknown. Short Answer: The above statement is MISLEADING at best and might even be WRONG. 2. Q: What is a measurement, really? Isn't it just when an interaction occurs with an external particle or force? Does it have anything to do with consciousness. Short Answer: Physicists don't know what a measurement really is. And no, an interaction is not the same thing as a measurement. A measurement probably doesn't need a concious being. 3. Q: Isn't this just an overly complicated version of when we have a ball hidden underneath 2 cups and we don't know which cup it's under until we "measure" by lifting one of the cups? Short Answer: No. 4. Does it really matter whether the particle gets its spin right after entanglement or if it gets its spin only after measuring? Isn't this just bad philosophy by physicists to make things seem more complex or a matter of annoying semantics? Short answer: Yes! It matters. They are fundamentally different things! It's not just physicists trying to seem smart or being pedantic. LONG ANSWER: Physicists don't fully understands what a wave collapse is or what a measurement is! That being said, there are a few good and not so good perspectives and ways to interpret QM (Quantum Mechanics): 1. Realist (aka Local Hidden Variable Theory): The quantum system is just like a ball underneath some cups. The ball already has a determined cup its under. We just don't know it until we measure it. There must be a hidden state or a hidden variable that somehow describes what state the ball is in since the realists think the ball is already under a determined cup. QM must be incomplete since this hidden variable isn't anywhere in modern QM. 2. Orthodox (aka Copenhagen Interpretation): The quantum system is not like a ball under a cup. We don't know what spin the particle is in until we measure it. No one in the universe knows what cup the ball is under until we measure. God doesn't know what cup the ball is under. The ball doesn't know what cup its under. [Insert omniscient personification here] doesn't know what cup the ball is under until there is a measurement. We say the measurement causes the particle's wave function to collapse. The act of measuring "creates" the spin of the particle or forces the ball to be under one of the cups, but not before. 3. Agnostic: Bury your head in the sand and don't think about it cause it doesn't matter when the particle gets its spin, since after all either way we don't know until we measure. The difference between the realist and orthodox perspective is just semantics. 4. Other: More advanced or modern ways to explain measurements and wave function collapse. Examples might include non-local hidden variable or everett (many worlds) interpretations. Let me start by saying that any serious physicist will only consider the "Orthodox" or one of the "Other" interpretations. This video considers the Orthodox position, since this is the oldest (so it's stood the test of time and hasn't been proven wrong by experiments), it's what most students are taught, and it's also more conceptually simple compared to the "Other" interpretations. The Realist and Agnostic interpretations are unlikely to be true because of a something called Bell's Inequality. Bell's Inequality is a mathematical statement that is implied by realism. Physicists showed that if realism is true then that means Bell's Inequality is true. But the surprising result is that if Bell's Inequality is true, then quantum mechanics is not just incomplete, but completely wrong. Many experiments have been performed and have shown that quantum mechanics is extremely accurate and have shown that bell's inequality is false, which basically means that realism is very unlikely to be true (in fact the most recent 2022 Nobel Prize was awarded to physicists who showed that Bell Inequality was violated or false). Since realism is probably wrong, then that means that there actually is a difference between orthodox and realism. So there really is a difference between the particle having a definite spin before measurement versus the particle having the definite spin only after measurement. Thus the agnostic position is wrong. There are real physical differences that can be found through experiments. So you can't bury your head in the sand like an agnostic believer. What is a measurement, really? Isn't it just when an interaction occurs with an external particle or force? A measurement is not just an external interaction. A particle that interacts with an external particle doesn't necessarily have to result in a measurement. In fact, Quantum computers work by manipulating particles in superposition using external fields/particles, but this doesn't result in any collapse in the wavefunction (so it's not a measurement). The particles in the quantum computer still retain a state which is a superposition. So not all external interactions are measurements. So you might ask what kind of interactions are measurements (i.e. causes the wave function to collapse). Again this is an unsolved problem in physics (google the measurement problem). But again there are a few good and some bad interpretations of what a measurement is: 1. A measurement is made when a macroscopic (classical) system interacts with a quantum particle/system or what a scientist does in a lab using classical tools like a ruler, stopwatch, spectrometer, etc. (Bohr) This is probably the simplest way to imagine what a measurement is and works pretty well for intro level QM. This is what the video defines a measurement as. 2. A measurement is when an irreversible process occurs, aka increase in entropy. 3. A measurement is made when a conscious being observes something (Wigner) 4. A measurement is made when a permanent record is made (Heisenberg) I think 1 and 2 are probably the best ways to think about what a measurement is. Most physicists don't think 3 is right since all known physical laws don't really care whether humans exist. All these perspectives have problems of course. Like for 1, what differentiates a macroscopic and quantum system? When does the transition occur. And for 4, what does "permanent" mean? * Footnote: Bell's Inequality only holds if particles affect each other slower than the speed of light. Some newer theories with hidden variables can work if the particles can influence each other at faster than light speeds (called non-local hidden variable theory). D.J. Griffiths and D.F. Schroeter, Introduction to Quantum Mechanics, 3rd ed. (Cambridge University Press, Cambridge, 2018). ^ for those with more math background, check out the proof of bell's inequality.
00:41 wait, there are 2 options and you check one. isn't this just process of elimination? 3:07 so a wave function is a list of possible parts in a particle and their rarity? 3:48 what if each particle had multiple predetermined parts before it was "observed" and the glasses are just straining it? 6:04 "collapsing the wave function" seems to be an accounting of expected parts. am i tripping or does this boil down to which cup is the ball under? if someone could enlighten me i would appreciate it.
you're right. this video made an awful job trying to explain quantum physics. each entangled photon gets the state immediately and when we measure one it just shows the state it doesn't magically transfer information to the other photon, the information was there all along
@@NuclearLama I wouldn't say the video is awful. And saying that each entangled photon immediately gets its state is misleading and might even be wrong. The truth is physicists don't know if the state is determined after or before measurement. It's still an unsolved problem called the measurement problem (physicists don't even know what counts as a measurement!). But most physicists believe that the state of the particle is only determined at measurement*. This is what is taught the most and what the video assumes and what I'll assume for the rest of your questions: 00:41: Yeah there are only 2 options. But we don't know which particle is up or down until we measure. Before we measure one of the particles, no one knows. Not god, not the particle, not the universe, not anyone. It's not that the case that the particle determined its state after being split and that it's just unknown. It determines only after measuring. So you're correct that after measurement, it's pretty simple and we can just use elimination. But what makes QM interesting is that the particle doesn't decide its state until measurement. 3:07: Yeah basically correct. Although if you want to be more technically correct, the parts of the wave function squared gives you the probability. 6:04: Collapsing the wavefunction picks one of the possible parts. But the interesting thing is that the particle doesn't pick the part until a measurement is made. I wouldn't say its like picking a ball under a cup. In this analogy, the ball is already under one of the cups. The measurement doesn't change that fact. Even though we might not know which cup its under, the ball still is under just one and only one cup, even before measurement. Even if you don't know where the ball is, God, the ball, the universe, [insert your choice of omniscent personification here] knows which cup the ball is under. That's not what the quantum particle does. The particle isn't in one cup before measurement. The particle doesn't know what cup it's under. God doesn't know what cup it's under. The universe doesn't know what cup it's under. Only when you measure it, does the particle/God/universe/you know. * So you might be asking why most physicists think that the particle doesn't choose its state until measurement. Why don't physicists think that the particle gets its state immediately but its just unknown until measurement (called a hidden variable). The answer is that we don't know which of these two contrasting viewpoints is correct for certain. But there's a theorem called Bell's Inequality which says that if the particle gets its state immediately, then Quantum Mechanics is completely wrong. Physicists have rigorously tested lots of predictions from quantum mechanics and have not found anything contradicting the theory, so most physicists and so that seems to imply that hidden variables don't exist. If hidden variables don't exist, then that means the particle only gets its state after measurement. Now you might ask what is a measurement. This again is an unsolved problem and this comment is already too long, so just Google the measurement problem. Hope that helped!
I'm still curious what the meaningful distinction is between quantum superpositions and merely unknown positions. I "understand" (and by 'understand' I mean the cliffnotes version, I read and understood the wikipedia page) the technical definition, don't get me wrong. But if you throw a photon at some particle, that then splits that photon into two oppositely polarized photons of lesser energy, it doesn't seem intuitively obvious to me how you'd prove they're entangled and of indeterminate polarity until measured as opposed to simply unknown until measured. Say you measure photon a and learn its polarity, this then locks in the polarity of photon b, but this does not seem to, intuitively, result from the measurement of the photon -- rather we'd find the same to be true as well in the case where the photons had a fixed polarity at time of emission, and us learning the polarity of photon a lets us deduce the polarity of photon b since it is opposite. I suppose then that my specific question ought to be dictated as such: "How do we experimentally prove that two particles are entangled such that their properties are truly indeterminate until observed as opposed to already having said properties at time of emission, it would appear that quantum entangled particles would otherwise transmit information at a speed far greater than C which, as we understand it, ought not be possible. It seems impossible to me to collapse the wavefunction by observing the particle, and to then uncollapse it and re-observe it, so it seems like an, at best, fancy way of saying "the polarity is random and we don't know which", this however still means it had a definite state at time of emission irrespective of observation or not. That is to say, it seems to me the particles were always in a fixed but unknown state until time of observation, as opposed to the state being decided upon such a time and retroactively cascading to entangled particles irrespective of distance."
Great video! Also, we live nearby each other haha! Kind of neat, I wish I knew more people that were into physics nearby. Oh well, glad to know there are others haha.
Its hard for me to remember exactly why measurement/observation/interaction *has* to be the thing that causes collapse at a specific moment and it couldnt have just already been thay way. Doesnt the theory work just as well if it was already that way, and we couldn't have seen the difference?
That's a great observation. The reason this does not seem to be the case is the Bell inequalities and the corresponding experiments. In short summary: What they show is that if there was any additional kind of information the particle posessed (e.g. what its ACTUAL state is), this would lead to a behaviour which is inconsistent with what we see in experiments. To me, all of this gets less spooky by knowing that there is a quantity which you can clearly put numbers on: The wave function. It is the thing that describes the particles state completely and you're able to make all kinds of experimental predictions from that.
@@bengoodwin2141 Yes, you are right about that! Bell's inequalities only rule out "local hidden variable theories". Local theories are (loosely speaking) theories in which particles have no influence that propagates immediatley to a place far from them. In fact, there are working non-local hidden variable theories (a prominent one is Bohmian mechanics), which predict the same experimental results, but every particle has a definite location and velocity at all times. It's just that we won't be able measure them to full accuracy without altering them. Imho there is no good answer on how to interpret quantum mechanics correctly. I find the Copenhagen interpretation (which is often presented as "that's how it is") highly questionable as it simply doesn't make any sense as a physical theory. But I don't have a really good answer either
@@asdf56790 I was more thinking that interactions that happened in the past, but not faster than light, could influence the outcome of any given interaction and weight it to what we see, or something like that. That sounds like between local and global, I think.
This is spooky you mean that the light of the photon have half the energy of the other photo «even when they are separated by great distances» ??? this is so unusual because in classical physic thing behave so differently «even when [things] are separated by great distances»
Decides, knows, decide decide decide. The photon decides. The elementary particle knows. TIL wave function collapse is due to a conscious choice of the quantum particle
@@physicsforthebirds on one hand it sucks that I can’t listen to the full song on Spotify, on the other hand that’s so cool that you custom make all the music for these videos. The bit from 1:38 sounded so unique and cool
How can you say what the particle "knows" or does not "know" when a particle has no concept of "knowing" to begin with? It's like saying a chair knows it's in my room. It doesn't know anything because it's a chair. We know that when two particles come out that are entangled, we don't know what they each are until we measure one of them. We also know that both particles will be opposites of each other. It's really confusing saying that an inanimate physical thing can "know" something when you're trying to describe physics to beginners
I don't understand the part where the particle itself doesn't know its state. Surely there's an objective truth and measuring it just means we find out what that state is?
He didn’t explain why, but: no, it can’t be explained by local variables. Bell's theorem shows some limits on the kinds of correlations that can happen under “local realism” , and the Bell Tests have measured correlations that violate that. An important detail is that there is more than one way to make the measurement, and the correlation between the observations of the two particles in the pair depend on what measurement is made on each end. For polarization you can measure “was it polarized vertically, or horizontally?”, OR you can measure “was is polarized along this one diagonal direction, or the direction perpendicular to that?”. (You can measure this kind of question for any choice of angle, and there are always 2 possible outcomes of a successful measurement.) If you measure “is it vertical or horizontal?” and the other person measures their as to whether “main diagonal or opposite of main diagonal” then there will be no correlation between the results, but if you measure at the same pair of angles they will be completely correlated, and it varies smoothly between these two options depending on the difference in angles that the two of you measure at. (So, if you measure close to 45 degrees off from how they measure, will be close to uncorrelated but not entirely uncorrelated, and if close to same angle, or close to 90 degrees apart, then close to entirely correlated.)
How long after you measure something does it take before it gets fuzzy again? Is there a formula, like a half-life that controls what the likelihood of a measured electron becoming a superposition again after a certain amount of time?
Once the wave function collapses into one of the states which comprised the superposition, the state of the system does not return to the prior superposition. Once an electron is confronted with deciding wither it'll be up or down on observation, it cannot revert back to being a carefree combination of the two possibilities as it was before.
@@willparker9874 No it defintiely will because as soon as you stop looking, it'll start getting hit by virtual particles and running feynman diagrams and possibly emitting photons or tunneling so after a while it MUST be fuzzy again i just want to know the timescale like is it nanoseconds or milliseconds, or what?
Nice video, but trying to talk about "measurement" is a snake pit one should avoid. For contrary to what a lot of physics-TH-cam appears to think, a measurement unsatisfyingly is merely the fact that (in some admittedly vague sense) the *classical* state (observable eigenstate) is clear. The notion is inseperably linked to the concept of a lab and an experimentor who "thinks in classical states" for lack of a better description. The whole "collisions measure" thing is highly misleading, because the colliding particles are actually in superpositions of various classical states before and in an entangled *combined state* after the collision - no measuring at any point there!
I am quite obsessed (and frustrated) that my conversation with ChatGPT the third and a half is leading nowhere... he is convinced that taking one photon and splinting it in half (in two) such that both photons have a correlation to one an other... is something unusual because it will have non-local correlations... (I think it was pretty localized when the 2 photons have be created inside a molecule... « However, it is also true that the probabilistic nature and non-local correlations of quantum entanglement are not directly observable in our everyday experiences and can be difficult to fully comprehend without a background in quantum mechanics» AI which have vectors in more than one million dimensions space is way more impressive and counter intuitive an fascinating... than 2 particules having a correlation «even when they are separated by great distances» ... I am really not impressed by that AI (and by myself for wasting 70 minutes arguing with an AI)... but yea I have to live my live in a sigle dimension space in only a sigle direction in time and in 3 dimensions in space... So how can I understand a thing that thinks in a million dimension in vector space... I think I will need to do a nap before I can watch the video... but since I watched all your other videos... I am not worried that I will catch up soon...
4:54 isn't this like saying: "this is why it's called ztrumpz physics: the energy is ztrumpzed". It's not an explanation! you are using the same word root twice. wouldn't it be better to say that it comes from latin ("how much")?
The Bird explains what quantized means for 2 minutes before 4:54. Your ztrumpz analogy wasn't meant to explain quantized (since the bird already explained quantized for 2 minutes before). Instead the whole "it's called ztrumpz physics because it's ztrumpzed" is to point out how the name of the field of physics came about (the etymology). The bird did go a bit fast when explaining quantized, but basically it just means discrete. In math, discrete means variables can only go up or down in steps. Continuous means a variables can go up and down smoothly (think of a smooth graph). An analogy might be a that continuous is a smooth light dimmer that can be set to any value between off and full brightness. While a discrete light dimmer is a light dimmer that can only be set to 3 values. Off, Full Brightness, and Medium brightness. For a more real life example, let's consider speed instead of energy. Normally in our everyday macroscopic world, speed is continuous. For a car, this means it can be any value from 0 to 120 mph (an infinite amount of values). A car can be at 1 mph. It can be 2 mph. It can be 3.99999 mph. It can be theoretically be at pi mph. It can be at 100.38494949 mph. But when dealing with certain types of molecules, light, particles, systems, etc. the speed can only be discrete values. So for example, let's say for an imaginary particle, the speed of the particle can only be multiples of 69. So my imaginary particle can be at 69 m/s, 138 m/s, 207 m/s, 276 m/s. For a real world example, light at a fixed frequency can only have energies that are multiples of (planck's constant * frequency). So for red light: wavelength of 650 nm or a frequency of (c/650) nm^-1 Planck's constant=1239 eV*nm/c So red light's energy is multiples of 1239/650 = 1.9 eV So a red light energy can only be 1.9 eV, 3.8 eV, 5.7 eV, 7.6 eV, and so on Put another way, when I adjust the energy of light coming from a light bulb, I can only lower the energy in increments of 1.9 eV. 1.9 eV is a puny amount of energy, which is why our human eyes can't perceive the jagged jumps between energy levels whenever we use a smooth light dimmer (it would take 10^23 1.9 eV photons to make up 1 Food Calorie).
What if both observers were somehow on synchronized timers, and one observer had a decent guess at the time which the other observer collapsed the waveform? I know time dilation could seriously screw this up and that clocks can drift, but what if the observers, once initially synchronized, periodically synchronize their clocks to prevent the observers from getting their waveform collapsing operations screwed up due to miniscule amounts of time dilation or clock drift? On a side note, it would be cool to have a sci-fi series where genetically engineered organisms act as quantum communication platforms.
The question is still how to actually get information out of that system. Even if you know for certain that you're scheduled to measure it before or after the other party, the only knowledge you gained is which result the other scientist will see(the opposite of yours). So it seems that it could perhaps be used for long distance coordination maybe with a clever scheme pre-prepared ahead of time(do X after 3 days in a row of identical results), but not long distance communication. For sci-fi though go wild!
I think it is important to clarify that it is not "observing" a quantum system that makes it resolve itself into a specific outcome, but rather the object interacting with something other than itself that forces it to resolve its state. The object is not conscious and it happens independently of human observation. It's important to consider the language we use so as to not give the quantum systems, nor ourselves supernatural qualities.
Interaction is observation
- Chris Fields
@@pluto9000 In the context, yes. But most people don't have that background. It's important to make that distinction clear. To "observe" something you have to interact with it. You must change it by affecting it.
This distinction disappears the moment one realizes that "conscious matter" is not any different than "ordinary matter". Existence observes itself with or without the awareness of the observation/interaction/interdependence
@@0FAS1 But that isn't common knowledge and not making that clear can build an inaccurate understanding of concepts in science.
@@0FAS1 the problem is, not everyone is a materialist and quantum "observation" had been repeatedly misunderstood and used to "prove" the soul.
The particle knows where it is at all times. It knows this because it knows where it isn't, by subtracting where it is, from where it isn't, or where it isn't, from where it is, whichever is greater, it obtains a difference, or deviation. /s
Haha, I saw your comment right after posting mine, also with that reference
This difference is called Error
It therefore follows that the particle has no knowledge about it's momentum. It doesn't know its momentum because it doesn't know what its momentum isn't. There is no sensible way to subtract the momentum it has from the momentum it hasn't, nor the momentum it hasn't from the momentum it has, nor is it possible to define a rigorous notion of whichever is greater...
There may be more than one force at work in the particle of light. One electric, which only has a velocity, and the other magnetic, which is only stable in one place! The light is moving unless it has a reason to stall, such as a relationship outside of itself- the measurement is one. Fun!
Rockwell Automation has shills for that Turbo Encabulator everywhere.
i honestly think this channel is underrated. really excited to see you grow as u deserve
like honestly your explanations are very clear and to the point and they are comprehensive, i really appreciate :) its not usual to be able to tackle subjects as difficult as the ones you explain as easily as this channel allows to. thanks :)
@@ppmico Thanks! I'm always worried that I complicate things too much and I'm also always worried that I simplify things too much, so I'm glad you're getting something from it!
@@physicsforthebirds I really like your niche/small channel style, when channels go big they usually go towards a more mainstream style which feels like a TV show rather than a genuine random idea fuelled by fun and curiosity.
I also like things coming completely out of left field sprinkled with sarcasm and existential crisis. So I really like you overall.
@@physicsforthebirds i assure you, i'm pretty dumb, and i find these videos both insightful and feeding a level of curiosity that makes my brain real happy
@@physicsforthebirds I think you do a fantastic job of neither over or under explaining
Using quantum mechanics to understand Olive Oil was not on my Life Bingo Card
I wonder when the scientists are going to realize that they can just entangle particles with just some string and a pair of tiny baby hands without having to resort to jellyfish and olive garden
I’m so glad I found this channel, thank you so much for creating such unique and inspiring content; I love the way you often explore topics at a scientifically deeper level than many channels, but still keep everything accessible and clear :) I’m looking forward to all of your future content and growth!
Found out your channel about a week ago, through the popcorn video and was surprised about how well your videos are made, truly an awesome work. If you keep like that, in no time you’ll get lot of subs and view, rlly appreciate the efforts you put on the animations, talking and even the sources on the description. Hope we see you thrive soon, good work!
Do you not understand how soul crushing this video is???
My soul, my everything was dedicated to creating a quantum computer that uses olive oil. Every day I toil in the mines creating olive oil and growing the silicone to create the supercomputer. What will do now?
I appreciate you saying "no" right away. You earned that like in that exact moment. Great content
Cute cartoon of a dilution refrigerator at 11:34!
N.B. 3:49 is accurate but a little imprecise. It’s possible to have linearly or circularly polarized light in a superposition of horizontally and vertically polarized states too (per choice of HV basis). Linear polarization and circular polarization are special cases of elliptical polarization that can correspond to the 50/50 HV probabilities you show at 4:07.
N.B. 3:58 and 4:08 are inaccurate, and you need to be careful regarding what parts of this quantum “system” you’re talking about. If you’re talking about the quantum state of the smaller system “photon after polarizer,” the photon already “decided” its polarization (and pass/no-pass) when it encountered the polarizer and was projected onto the vertical state, before it encounters your eyeball. Your eye is not required to modify the photon’s state in this perspective, nor is your eyeball projecting passing photons onto the vertical state. If you’re thinking about the quantum state of a larger system of “photons before and after polarizer,” the polarizer is actually part of the system too. After a photon encounters the polarizer but before encountering your eye, the whole system (photon and polarizer together) is described by a mixed state of “vertical polarized, passing photon” and “messy whatever happens when the photon is absorbed by the polarizer and decoherence kicks in.” If you’re skeptical, consider this: the inner product of the state of any quantum system with itself MUST be 1 (i.e. the system has 100% probability of being in some quantum state). The state corresponding to “50% vertical probability and nothing else” isn’t possible without using mixed states.
Idk if it was your explanation being extremely well done and simplified, or if it's just bad, but I think I've come to the realization that Quantum Mechanics is a stupid semantics game.
Entanglement sounds like you broke a cookie in half and tossed them in the air, and then said "You don't know which side is the up or down until they land! And they're going to fit together mysteriously!"
Yeah, of course they're going to be opposites of each other, you just broke them in half. They fit together. Why is this a surprise?
It's all semantics and sophistry.
I wish these effects applies to large scale objects too, that would make the daily life more interesting
This channel is amazing, the way you explained quantum mechanics was great. I am doing a school project( I am in 8th grade) about quantum internet. and the information you explained helped my project so much. Your explanation on SPDC is great! Because of you I learned so many new things! My project is 10 times better because of your video! Thank you for your amazing videos!
Awesome! Let me know how the project goes!
@@physicsforthebirds Yes I will, I will present it on may 9th (my birthday)! I REALLY want to send you the link to it (it is a google site) but I also don't want the entire comments to get the link to my website. If I knew being a bird meant getting these types of videos about physics before, I would have became a bird earlier!
Also I have put you in the citations and in the special thanks!
@@GirusBetterThanVirusHow did it go? :D
@@aileenyxit went great
This man just explained quantum computers to me in less time than it takes to take a shit and I respect that
Probably shit faster without the phone
Always excited for a new video from this channel :).
Taking a quantum computing course this quarter but it's more focused on the theoretical foundations for qubits and gates. Love to hear these musings on more practical problems when it comes to the physics of obtaining an entangled state :) (and it certainly doesn't hurt that they're accompanied by such cute drawings)
This was a great video and I really love your story-telling and animations! :)
love your stuff. finishing my BSc in physics and these jus kinda scratch my brain the right way. idk why the mood you set while talking about familiar topics just kinda soothes me. thanks
I think of it more like when the entangled photons are emitted, they each have opposite polarizations, and are both already in whichever state that they are in when one gets measured (and then let's you know the other is opposite). They 'know' exactly which state they should be in ever since they were emitted. we just have no way to determine which state they're in until measuring them. so they're in a superposition only as far as our knowledge of them is concerned. in actuality they've always been in the 'collapsed' waveform state the entire time. there is no need for instantaneous information transfer upon viewing one to determine the other
like, imagine two sisters were going to an event and wanted to wear different color dresses... you know that they coordinated before leaving that one would be wearing red, the other blue. what you don't know is exactly which sister is wearing red and which will be wearing blue, you just know that those are the options. (the sisters are in a superposition of either wearing red or blue). when you arrive at the event, you say hi to one of the sisters, noticing that she is wearing red (the superposition waveform has collapsed) so you can intuit that the other must be wearing blue, and sure enough you see her later and see that she did wear blue. this doesn't mean that the sisters were each "maybe wearing red, maybe wearing blue" No, they decided before going out who would wear which color, they just didn't tell you about it. so to your perspective, you had no clue until you finally saw one of them later. sister 1 was always going to be wearing the red, and sister 2 always the blue. you just had no way of knowing until you saw for yourself.
if information was transmitted upon 'measuring', then that would mean that when you saw the first sister in red at the event, she turns around and calls the second sister to tell her to change into her blue dress right then and there. that wouldn't make any sense.
Look up bell's theorem. You are postulating a hidden variable theory, which is impossible if you also want the theory to be local.
your videos are great, my eyes will appreciate a dark theme.
oh my goodness! i had just identified a picture on inaturalist the other day of that jellyfish which apparently only lives here in the pnw. and now i learn it's where that glow protein comes from in this video!
that's so cool, and weird, it's not like i'm regularly thinking about jellyfish, that was the only one recently. i'm finding the world works in mysterious ways.
quantum mechanics in general is also kind of scary and weird and cool, thanks for explaining some! i knew particles could be entangled but didn't know specific ways it actually could happen.
The worlds first quantum computer video to feature the materials used to create entangled pairs
Saw an upload, I click.
omg i love ichthyology and quantum mechanics this video is perfect
I am physics teacher in high school and i often show your videos to my students, you are doing great :)
Keep it up!
Well, technically,,,,, the probability (±density) function is actually the absolute value of the wavefunction squared :)
this channel is gold, I'm glad to see you upload these amazing videos every time >:) I hope you will grow to become the next big physics channel you deserve it!
What if I drink the genetically modified quantum olive oil
This video is the perfect example of molecular bioengineering. I am going to use it now when people ask me what it is.
The information that determines which state the system assumes upon observation(the term for interaction), is not encoded upon observation(interaction), but is encoded at the moment of entanglement.
:D
The information doesnt actually have to travel between the particles, it was already encoded in the past.
This misunderstanding is very common... and it makes it seem like "magic"... but there is nothing magical happening xD
So i must point it put to everyone >:3 (I'm looking at you, New Age Hippies!!!)
exactly, this video is so wrong in so many ways
The level of this channel is insane.
It’s time like this that I’m glad to have read the Rascal does not Dream series for its tackling of quantum mechanics
I like thouse Videos and i always Watch them. Today i was learning quantum mechanics in german for my Uni and had some Problems. To procastinate i started to Watch some TH-cam. And this Video is the second I Watch. Well now i understand them a Bit More.
For the polarized glasses example, wouldnt it make more sense to say that the photon that was blocked does "know" when its measured by the glasses but the one that isnt doesnt until it reaches your eyeball ?
New vid from this channel feels like christmas, thanks for the vids & keep up the quality!
One issue Ive always had with quantum physics is if we have to entangled photons people use language like "if we observe the spin of one the spin of another is forced to change." How do we know its being forced to change? How do we know it wasnt always in that spin position before observing and really by observing it we're taking a coin flip and saying it landed on heads after the reveal?
NO ONE ever explains that its just taken for a fact of 'the quirks of quantum science'
Yes there is literature dealing with that specific stuff.
You have to read:-
Bell's inequality
EPR paradox.
1. Q: The entangled particles decides its spin right after it gets split, not at measurement!!! It's just that the spin is unknown.
Short Answer: The above statement is MISLEADING at best and might even be WRONG.
2. Q: What is a measurement, really? Isn't it just when an interaction occurs with an external particle or force? Does it have anything to do with consciousness.
Short Answer: Physicists don't know what a measurement really is. And no, an interaction is not the same thing as a measurement. A measurement probably doesn't need a concious being.
3. Q: Isn't this just an overly complicated version of when we have a ball hidden underneath 2 cups and we don't know which cup it's under until we "measure" by lifting one of the cups?
Short Answer: No.
4. Does it really matter whether the particle gets its spin right after entanglement or if it gets its spin only after measuring? Isn't this just bad philosophy by physicists to make things seem more complex or a matter of annoying semantics?
Short answer: Yes! It matters. They are fundamentally different things! It's not just physicists trying to seem smart or being pedantic.
LONG ANSWER:
Physicists don't fully understands what a wave collapse is or what a measurement is!
That being said, there are a few good and not so good perspectives and ways to interpret QM (Quantum Mechanics):
1. Realist (aka Local Hidden Variable Theory): The quantum system is just like a ball underneath some cups. The ball already has a determined cup its under. We just don't know it until we measure it. There must be a hidden state or a hidden variable that somehow describes what state the ball is in since the realists think the ball is already under a determined cup. QM must be incomplete since this hidden variable isn't anywhere in modern QM.
2. Orthodox (aka Copenhagen Interpretation): The quantum system is not like a ball under a cup. We don't know what spin the particle is in until we measure it. No one in the universe knows what cup the ball is under until we measure. God doesn't know what cup the ball is under. The ball doesn't know what cup its under. [Insert omniscient personification here] doesn't know what cup the ball is under until there is a measurement. We say the measurement causes the particle's wave function to collapse. The act of measuring "creates" the spin of the particle or forces the ball to be under one of the cups, but not before.
3. Agnostic: Bury your head in the sand and don't think about it cause it doesn't matter when the particle gets its spin, since after all either way we don't know until we measure. The difference between the realist and orthodox perspective is just semantics.
4. Other: More advanced or modern ways to explain measurements and wave function collapse. Examples might include non-local hidden variable or everett (many worlds) interpretations.
Let me start by saying that any serious physicist will only consider the "Orthodox" or one of the "Other" interpretations. This video considers the Orthodox position, since this is the oldest (so it's stood the test of time and hasn't been proven wrong by experiments), it's what most students are taught, and it's also more conceptually simple compared to the "Other" interpretations.
The Realist and Agnostic interpretations are unlikely to be true because of a something called Bell's Inequality.
Bell's Inequality is a mathematical statement that is implied by realism. Physicists showed that if realism is true then that means Bell's Inequality is true. But the surprising result is that if Bell's Inequality is true, then quantum mechanics is not just incomplete, but completely wrong.
Many experiments have been performed and have shown that quantum mechanics is extremely accurate and have shown that bell's inequality is false, which basically means that realism is very unlikely to be true (in fact the most recent 2022 Nobel Prize was awarded to physicists who showed that Bell Inequality was violated or false).
Since realism is probably wrong, then that means that there actually is a difference between orthodox and realism. So there really is a difference between the particle having a definite spin before measurement versus the particle having the definite spin only after measurement. Thus the agnostic position is wrong. There are real physical differences that can be found through experiments. So you can't bury your head in the sand like an agnostic believer.
What is a measurement, really? Isn't it just when an interaction occurs with an external particle or force?
A measurement is not just an external interaction. A particle that interacts with an external particle doesn't necessarily have to result in a measurement. In fact, Quantum computers work by manipulating particles in superposition using external fields/particles, but this doesn't result in any collapse in the wavefunction (so it's not a measurement). The particles in the quantum computer still retain a state which is a superposition. So not all external interactions are measurements.
So you might ask what kind of interactions are measurements (i.e. causes the wave function to collapse). Again this is an unsolved problem in physics (google the measurement problem). But again there are a few good and some bad interpretations of what a measurement is:
1. A measurement is made when a macroscopic (classical) system interacts with a quantum particle/system or what a scientist does in a lab using classical tools like a ruler, stopwatch, spectrometer, etc. (Bohr)
This is probably the simplest way to imagine what a measurement is and works pretty well for intro level QM. This is what the video defines a measurement as.
2. A measurement is when an irreversible process occurs, aka increase in entropy.
3. A measurement is made when a conscious being observes something (Wigner)
4. A measurement is made when a permanent record is made (Heisenberg)
I think 1 and 2 are probably the best ways to think about what a measurement is. Most physicists don't think 3 is right since all known physical laws don't really care whether humans exist. All these perspectives have problems of course. Like for 1, what differentiates a macroscopic and quantum system? When does the transition occur. And for 4, what does "permanent" mean?
* Footnote: Bell's Inequality only holds if particles affect each other slower than the speed of light. Some newer theories with hidden variables can work if the particles can influence each other at faster than light speeds (called non-local hidden variable theory).
D.J. Griffiths and D.F. Schroeter, Introduction to Quantum Mechanics, 3rd ed. (Cambridge University Press, Cambridge, 2018).
^ for those with more math background, check out the proof of bell's inequality.
10:12 "or does it?"
Vsauce music
Amazing video! I am having a related course in uni and I am amazed by the amount of research you put in your videos 😳
Can't get enough of these videos, I'm learning so much. Thank you!
I love this channel, always waiting for a new upload.
As a side note, that maybe you will find interesting, a while ago I read that "you shouldn't put your titles as questions" because most probably, the answer is "no", if not, you would probably set the title as "Making a Quantum Computer out of Olive Oil", meaning that you would have make your title positive, instead of hiding it with a question.
great video! do you know the name of the music in the background during the intro?
All of the music I use is mine, made for the videos. I might release it all on its own at some point!
@@physicsforthebirds its great stuff! your video on jazz and entropy has been super informative for my composition work, the overlap between music and physics is super interesting :)
The way you explain the material and relate it to physical phenomena is effective and truelly delightfull!
Keep it up!
If you see this, may i ask what your background is?
This is a really interesting concept! But, your audio seems very quiet. I'm not sure if it's just me but it would be something to look into.
Great work again, this is becoming my favorite science youtube channel
Really good explanation and graphics. Thanks!!
Fun medical facts: in a dark room, you actually CAN see a source emitting 100 photons per second. The cells in your eyes only need one photon to activate, though your brain requires more to make sure the cells aren't discharging by accident (which they do, though stunningly rarely)!
research.physics.illinois.edu/QI/Photonics/pdf/PWDec16Holmes.pdf
So why can't it be that when you split a photon, their state is already deterministic, we just can't know until we measure it. The explanation of superposition always confuses me. It's like saying I don't know what my roommate is doing in the other room, so he is doing everything at the same time until I see him, then he resolves into doing one thing.
the use of the word "observing" tends to confuse people, we're not special, it's not because a person "looked at" a superposed object that it's state became known. "Observing" just means "interaction with a system that's strong enough to entangle it with the environment" basically once the particles observed state becomes part of a system that locks it into that state.
It's the same kind of thing he explains about his table not disappearing when he leaves his room, all of the particles of the table are "observing" each other and entangled in a state that overall, means it's a table (well that its fibers that make up wood etc etc)
"deterministic" would mean that we knew the state before the measurement, based on the initial conditions. "we don't know until we measure" is precisely the meaning of indeterministic. I think you meant "determined but we don't know how" which are hidden variable theories, most of which have been disproven
1. Q: The entangled particles decides its spin right after it gets split, not at measurement!!! It's just that the spin is unknown.
Short Answer: The above statement is MISLEADING at best and might even be WRONG.
2. Q: What is a measurement, really? Isn't it just when an interaction occurs with an external particle or force? Does it have anything to do with consciousness.
Short Answer: Physicists don't know what a measurement really is. And no, an interaction is not the same thing as a measurement. A measurement probably doesn't need a concious being.
3. Q: Isn't this just an overly complicated version of when we have a ball hidden underneath 2 cups and we don't know which cup it's under until we "measure" by lifting one of the cups?
Short Answer: No.
4. Does it really matter whether the particle gets its spin right after entanglement or if it gets its spin only after measuring? Isn't this just bad philosophy by physicists to make things seem more complex or a matter of annoying semantics?
Short answer: Yes! It matters. They are fundamentally different things! It's not just physicists trying to seem smart or being pedantic.
LONG ANSWER:
Physicists don't fully understands what a wave collapse is or what a measurement is!
That being said, there are a few good and not so good perspectives and ways to interpret QM (Quantum Mechanics):
1. Realist (aka Local Hidden Variable Theory): The quantum system is just like a ball underneath some cups. The ball already has a determined cup its under. We just don't know it until we measure it. There must be a hidden state or a hidden variable that somehow describes what state the ball is in since the realists think the ball is already under a determined cup. QM must be incomplete since this hidden variable isn't anywhere in modern QM.
2. Orthodox (aka Copenhagen Interpretation): The quantum system is not like a ball under a cup. We don't know what spin the particle is in until we measure it. No one in the universe knows what cup the ball is under until we measure. God doesn't know what cup the ball is under. The ball doesn't know what cup its under. [Insert omniscient personification here] doesn't know what cup the ball is under until there is a measurement. We say the measurement causes the particle's wave function to collapse. The act of measuring "creates" the spin of the particle or forces the ball to be under one of the cups, but not before.
3. Agnostic: Bury your head in the sand and don't think about it cause it doesn't matter when the particle gets its spin, since after all either way we don't know until we measure. The difference between the realist and orthodox perspective is just semantics.
4. Other: More advanced or modern ways to explain measurements and wave function collapse. Examples might include non-local hidden variable or everett (many worlds) interpretations.
Let me start by saying that any serious physicist will only consider the "Orthodox" or one of the "Other" interpretations. This video considers the Orthodox position, since this is the oldest (so it's stood the test of time and hasn't been proven wrong by experiments), it's what most students are taught, and it's also more conceptually simple compared to the "Other" interpretations.
The Realist and Agnostic interpretations are unlikely to be true because of a something called Bell's Inequality.
Bell's Inequality is a mathematical statement that is implied by realism. Physicists showed that if realism is true then that means Bell's Inequality is true. But the surprising result is that if Bell's Inequality is true, then quantum mechanics is not just incomplete, but completely wrong.
Many experiments have been performed and have shown that quantum mechanics is extremely accurate and have shown that bell's inequality is false, which basically means that realism is very unlikely to be true (in fact the most recent 2022 Nobel Prize was awarded to physicists who showed that Bell Inequality was violated or false).
Since realism is probably wrong, then that means that there actually is a difference between orthodox and realism. So there really is a difference between the particle having a definite spin before measurement versus the particle having the definite spin only after measurement. Thus the agnostic position is wrong. There are real physical differences that can be found through experiments. So you can't bury your head in the sand like an agnostic believer.
What is a measurement, really? Isn't it just when an interaction occurs with an external particle or force?
A measurement is not just an external interaction. A particle that interacts with an external particle doesn't necessarily have to result in a measurement. In fact, Quantum computers work by manipulating particles in superposition using external fields/particles, but this doesn't result in any collapse in the wavefunction (so it's not a measurement). The particles in the quantum computer still retain a state which is a superposition. So not all external interactions are measurements.
So you might ask what kind of interactions are measurements (i.e. causes the wave function to collapse). Again this is an unsolved problem in physics (google the measurement problem). But again there are a few good and some bad interpretations of what a measurement is:
1. A measurement is made when a macroscopic (classical) system interacts with a quantum particle/system or what a scientist does in a lab using classical tools like a ruler, stopwatch, spectrometer, etc. (Bohr)
This is probably the simplest way to imagine what a measurement is and works pretty well for intro level QM. This is what the video defines a measurement as.
2. A measurement is when an irreversible process occurs, aka increase in entropy.
3. A measurement is made when a conscious being observes something (Wigner)
4. A measurement is made when a permanent record is made (Heisenberg)
I think 1 and 2 are probably the best ways to think about what a measurement is. Most physicists don't think 3 is right since all known physical laws don't really care whether humans exist. All these perspectives have problems of course. Like for 1, what differentiates a macroscopic and quantum system? When does the transition occur. And for 4, what does "permanent" mean?
* Footnote: Bell's Inequality only holds if particles affect each other slower than the speed of light. Some newer theories with hidden variables can work if the particles can influence each other at faster than light speeds (called non-local hidden variable theory).
D.J. Griffiths and D.F. Schroeter, Introduction to Quantum Mechanics, 3rd ed. (Cambridge University Press, Cambridge, 2018).
^ for those with more math background, check out the proof of bell's inequality.
Upvoted for not leading us on until the end of the vid.
00:41 wait, there are 2 options and you check one. isn't this just process of elimination? 3:07 so a wave function is a list of possible parts in a particle and their rarity? 3:48 what if each particle had multiple predetermined parts before it was "observed" and the glasses are just straining it? 6:04 "collapsing the wave function" seems to be an accounting of expected parts. am i tripping or does this boil down to which cup is the ball under? if someone could enlighten me i would appreciate it.
you're right. this video made an awful job trying to explain quantum physics.
each entangled photon gets the state immediately and when we measure one it just shows the state it doesn't magically transfer information to the other photon, the information was there all along
@@Oscar4u69 thanks. but if that's how it works doesn't it makes Schrodinger's cat really dumb?
@@NuclearLama Schrodinger's cat was Schrodinger showing how "stupid" and counterintuitive the idea was.
@@NuclearLama I wouldn't say the video is awful. And saying that each entangled photon immediately gets its state is misleading and might even be wrong. The truth is physicists don't know if the state is determined after or before measurement. It's still an unsolved problem called the measurement problem (physicists don't even know what counts as a measurement!).
But most physicists believe that the state of the particle is only determined at measurement*. This is what is taught the most and what the video assumes and what I'll assume for the rest of your questions:
00:41: Yeah there are only 2 options. But we don't know which particle is up or down until we measure. Before we measure one of the particles, no one knows. Not god, not the particle, not the universe, not anyone. It's not that the case that the particle determined its state after being split and that it's just unknown. It determines only after measuring.
So you're correct that after measurement, it's pretty simple and we can just use elimination. But what makes QM interesting is that the particle doesn't decide its state until measurement.
3:07: Yeah basically correct. Although if you want to be more technically correct, the parts of the wave function squared gives you the probability.
6:04: Collapsing the wavefunction picks one of the possible parts. But the interesting thing is that the particle doesn't pick the part until a measurement is made.
I wouldn't say its like picking a ball under a cup. In this analogy, the ball is already under one of the cups. The measurement doesn't change that fact. Even though we might not know which cup its under, the ball still is under just one and only one cup, even before measurement. Even if you don't know where the ball is, God, the ball, the universe, [insert your choice of omniscent personification here] knows which cup the ball is under.
That's not what the quantum particle does. The particle isn't in one cup before measurement. The particle doesn't know what cup it's under. God doesn't know what cup it's under. The universe doesn't know what cup it's under. Only when you measure it, does the particle/God/universe/you know.
* So you might be asking why most physicists think that the particle doesn't choose its state until measurement. Why don't physicists think that the particle gets its state immediately but its just unknown until measurement (called a hidden variable). The answer is that we don't know which of these two contrasting viewpoints is correct for certain. But there's a theorem called Bell's Inequality which says that if the particle gets its state immediately, then Quantum Mechanics is completely wrong.
Physicists have rigorously tested lots of predictions from quantum mechanics and have not found anything contradicting the theory, so most physicists and so that seems to imply that hidden variables don't exist. If hidden variables don't exist, then that means the particle only gets its state after measurement.
Now you might ask what is a measurement. This again is an unsolved problem and this comment is already too long, so just Google the measurement problem.
Hope that helped!
Every video is a treat
Good job with this one, i liked it a lot
The narrator in the beginning said “No” it can’t be done but I’ll say it’s as likely as building a nuclear bomb from bananas. 😁 have a pleasant day.
I'm still curious what the meaningful distinction is between quantum superpositions and merely unknown positions. I "understand" (and by 'understand' I mean the cliffnotes version, I read and understood the wikipedia page) the technical definition, don't get me wrong.
But if you throw a photon at some particle, that then splits that photon into two oppositely polarized photons of lesser energy, it doesn't seem intuitively obvious to me how you'd prove they're entangled and of indeterminate polarity until measured as opposed to simply unknown until measured.
Say you measure photon a and learn its polarity, this then locks in the polarity of photon b, but this does not seem to, intuitively, result from the measurement of the photon -- rather we'd find the same to be true as well in the case where the photons had a fixed polarity at time of emission, and us learning the polarity of photon a lets us deduce the polarity of photon b since it is opposite.
I suppose then that my specific question ought to be dictated as such: "How do we experimentally prove that two particles are entangled such that their properties are truly indeterminate until observed as opposed to already having said properties at time of emission, it would appear that quantum entangled particles would otherwise transmit information at a speed far greater than C which, as we understand it, ought not be possible. It seems impossible to me to collapse the wavefunction by observing the particle, and to then uncollapse it and re-observe it, so it seems like an, at best, fancy way of saying "the polarity is random and we don't know which", this however still means it had a definite state at time of emission irrespective of observation or not. That is to say, it seems to me the particles were always in a fixed but unknown state until time of observation, as opposed to the state being decided upon such a time and retroactively cascading to entangled particles irrespective of distance."
Some fungi fluoresce green and orange in the presence of ultraviolet light, could this be quantum entanglement?
1st time optics felt attractive
Outer wilds players already functionally knowing the basics of quantum mechanics from a game: 😎
Great Chanel! But Music way too loud!
Great video! Also, we live nearby each other haha! Kind of neat, I wish I knew more people that were into physics nearby. Oh well, glad to know there are others haha.
Love this channel
Someone should send this video to DougDoug
Another wonderful video!
So what you saying is I can have a glowing cat.
HERE! Take all the money 💰
Good stuff!
Excellent video, this channel is awesome
amazing video
Its hard for me to remember exactly why measurement/observation/interaction *has* to be the thing that causes collapse at a specific moment and it couldnt have just already been thay way. Doesnt the theory work just as well if it was already that way, and we couldn't have seen the difference?
That's a great observation.
The reason this does not seem to be the case is the Bell inequalities and the corresponding experiments.
In short summary: What they show is that if there was any additional kind of information the particle posessed (e.g. what its ACTUAL state is), this would lead to a behaviour which is inconsistent with what we see in experiments.
To me, all of this gets less spooky by knowing that there is a quantity which you can clearly put numbers on: The wave function. It is the thing that describes the particles state completely and you're able to make all kinds of experimental predictions from that.
@@asdf56790 right, I remember about that now, thanks. I still feel like there might be able to be some other way similar to this? But I get the idea.
@@bengoodwin2141 Yes, you are right about that! Bell's inequalities only rule out "local hidden variable theories". Local theories are (loosely speaking) theories in which particles have no influence that propagates immediatley to a place far from them.
In fact, there are working non-local hidden variable theories (a prominent one is Bohmian mechanics), which predict the same experimental results, but every particle has a definite location and velocity at all times. It's just that we won't be able measure them to full accuracy without altering them.
Imho there is no good answer on how to interpret quantum mechanics correctly. I find the Copenhagen interpretation (which is often presented as "that's how it is") highly questionable as it simply doesn't make any sense as a physical theory. But I don't have a really good answer either
@@asdf56790 I was more thinking that interactions that happened in the past, but not faster than light, could influence the outcome of any given interaction and weight it to what we see, or something like that. That sounds like between local and global, I think.
Shoutout to Orem
This is spooky you mean that the light of the photon have half the energy of the other photo «even when they are separated by great distances» ??? this is so unusual because in classical physic thing behave so differently «even when [things] are separated by great distances»
Decides, knows, decide decide decide. The photon decides. The elementary particle knows.
TIL wave function collapse is due to a conscious choice of the quantum particle
10:13 VSauce Vibes hahahahahha
Flourescence is nice but I think phosphorescence is another league. Anyways very nice video
I love your videos :)
Great news, I can use bioinformatics to make a quantum protein so that I can make a quantum computer and do more bioinformatics
The intro music gets a bit too loud for the volume of your voice.
Guys PLEASE I’d be so grateful if somebody told me the name of the song that starts at 1:38 and goes on until 2:00
All of the music I use is mine, made for the videos. I might release it all on its own at some point!
@@physicsforthebirds on one hand it sucks that I can’t listen to the full song on Spotify, on the other hand that’s so cool that you custom make all the music for these videos. The bit from 1:38 sounded so unique and cool
Yayyyyy new video 🎉
They made the glow-in-the-dark fishes for real ? I thought that was just a joke in The big bang theory series
How can you say what the particle "knows" or does not "know" when a particle has no concept of "knowing" to begin with? It's like saying a chair knows it's in my room. It doesn't know anything because it's a chair.
We know that when two particles come out that are entangled, we don't know what they each are until we measure one of them. We also know that both particles will be opposites of each other.
It's really confusing saying that an inanimate physical thing can "know" something when you're trying to describe physics to beginners
PJ never Disappoint.
Another banger
I don't understand the part where the particle itself doesn't know its state. Surely there's an objective truth and measuring it just means we find out what that state is?
He didn’t explain why, but: no, it can’t be explained by local variables. Bell's theorem shows some limits on the kinds of correlations that can happen under “local realism” , and the Bell Tests have measured correlations that violate that.
An important detail is that there is more than one way to make the measurement, and the correlation between the observations of the two particles in the pair depend on what measurement is made on each end.
For polarization you can measure “was it polarized vertically, or horizontally?”, OR you can measure “was is polarized along this one diagonal direction, or the direction perpendicular to that?”. (You can measure this kind of question for any choice of angle, and there are always 2 possible outcomes of a successful measurement.)
If you measure “is it vertical or horizontal?” and the other person measures their as to whether “main diagonal or opposite of main diagonal” then there will be no correlation between the results, but if you measure at the same pair of angles they will be completely correlated, and it varies smoothly between these two options depending on the difference in angles that the two of you measure at. (So, if you measure close to 45 degrees off from how they measure, will be close to uncorrelated but not entirely uncorrelated, and if close to same angle, or close to 90 degrees apart, then close to entirely correlated.)
pls reply with ending track name
All of the music I use is mine, I made it for my videos. I've been promising people I'll release it someday!
How long after you measure something does it take before it gets fuzzy again? Is there a formula, like a half-life that controls what the likelihood of a measured electron becoming a superposition again after a certain amount of time?
Once the wave function collapses into one of the states which comprised the superposition, the state of the system does not return to the prior superposition. Once an electron is confronted with deciding wither it'll be up or down on observation, it cannot revert back to being a carefree combination of the two possibilities as it was before.
@@willparker9874 Then why isn't every electron in the universe a classical particle since it's bound to have been measured
@@willparker9874 No it defintiely will because as soon as you stop looking, it'll start getting hit by virtual particles and running feynman diagrams and possibly emitting photons or tunneling so after a while it MUST be fuzzy again i just want to know the timescale like is it nanoseconds or milliseconds, or what?
Nice video, but trying to talk about "measurement" is a snake pit one should avoid. For contrary to what a lot of physics-TH-cam appears to think, a measurement unsatisfyingly is merely the fact that (in some admittedly vague sense) the *classical* state (observable eigenstate) is clear. The notion is inseperably linked to the concept of a lab and an experimentor who "thinks in classical states" for lack of a better description. The whole "collisions measure" thing is highly misleading, because the colliding particles are actually in superpositions of various classical states before and in an entangled *combined state* after the collision - no measuring at any point there!
How do we know it doesn't know 🤔
"Add a little bit of olive oil"
Biopunk is the way guy's
I love watching his vids and acting like I know what he’s talking about
The chlorophyll supplement is to make your body odor and downstairs smell and taste better
Nice
I am quite obsessed (and frustrated) that my conversation with ChatGPT the third and a half is leading nowhere... he is convinced that taking one photon and splinting it in half (in two) such that both photons have a correlation to one an other... is something unusual because it will have non-local correlations... (I think it was pretty localized when the 2 photons have be created inside a molecule... « However, it is also true that the probabilistic nature and non-local correlations of quantum entanglement are not directly observable in our everyday experiences and can be difficult to fully comprehend without a background in quantum mechanics» AI which have vectors in more than one million dimensions space is way more impressive and counter intuitive an fascinating... than 2 particules having a correlation «even when they are separated by great distances» ... I am really not impressed by that AI (and by myself for wasting 70 minutes arguing with an AI)... but yea I have to live my live in a sigle dimension space in only a sigle direction in time and in 3 dimensions in space... So how can I understand a thing that thinks in a million dimension in vector space... I think I will need to do a nap before I can watch the video... but since I watched all your other videos... I am not worried that I will catch up soon...
banger vid babes
Hold on a minute, we’ve made glow in the dark cats and dogs?!
Our race is weak ill be the one to conquer and succesfully harvest the power of the mighty olive oil
i have come to the understanding that i am not smart enough to understand this
4:54 isn't this like saying: "this is why it's called ztrumpz physics: the energy is ztrumpzed". It's not an explanation! you are using the same word root twice. wouldn't it be better to say that it comes from latin ("how much")?
The Bird explains what quantized means for 2 minutes before 4:54. Your ztrumpz analogy wasn't meant to explain quantized (since the bird already explained quantized for 2 minutes before). Instead the whole "it's called ztrumpz physics because it's ztrumpzed" is to point out how the name of the field of physics came about (the etymology).
The bird did go a bit fast when explaining quantized, but basically it just means discrete.
In math, discrete means variables can only go up or down in steps. Continuous means a variables can go up and down smoothly (think of a smooth graph). An analogy might be a that continuous is a smooth light dimmer that can be set to any value between off and full brightness. While a discrete light dimmer is a light dimmer that can only be set to 3 values. Off, Full Brightness, and Medium brightness.
For a more real life example, let's consider speed instead of energy. Normally in our everyday macroscopic world, speed is continuous. For a car, this means it can be any value from 0 to 120 mph (an infinite amount of values). A car can be at 1 mph. It can be 2 mph. It can be 3.99999 mph. It can be theoretically be at pi mph. It can be at 100.38494949 mph.
But when dealing with certain types of molecules, light, particles, systems, etc. the speed can only be discrete values. So for example, let's say for an imaginary particle, the speed of the particle can only be multiples of 69. So my imaginary particle can be at 69 m/s, 138 m/s, 207 m/s, 276 m/s.
For a real world example, light at a fixed frequency can only have energies that are multiples of (planck's constant * frequency).
So for red light: wavelength of 650 nm or a frequency of (c/650) nm^-1
Planck's constant=1239 eV*nm/c
So red light's energy is multiples of 1239/650 = 1.9 eV
So a red light energy can only be 1.9 eV, 3.8 eV, 5.7 eV, 7.6 eV, and so on
Put another way, when I adjust the energy of light coming from a light bulb, I can only lower the energy in increments of 1.9 eV.
1.9 eV is a puny amount of energy, which is why our human eyes can't perceive the jagged jumps between energy levels whenever we use a smooth light dimmer (it would take 10^23 1.9 eV photons to make up 1 Food Calorie).
🐦
What if both observers were somehow on synchronized timers, and one observer had a decent guess at the time which the other observer collapsed the waveform?
I know time dilation could seriously screw this up and that clocks can drift, but what if the observers, once initially synchronized, periodically synchronize their clocks to prevent the observers from getting their waveform collapsing operations screwed up due to miniscule amounts of time dilation or clock drift?
On a side note, it would be cool to have a sci-fi series where genetically engineered organisms act as quantum communication platforms.
The question is still how to actually get information out of that system. Even if you know for certain that you're scheduled to measure it before or after the other party, the only knowledge you gained is which result the other scientist will see(the opposite of yours). So it seems that it could perhaps be used for long distance coordination maybe with a clever scheme pre-prepared ahead of time(do X after 3 days in a row of identical results), but not long distance communication.
For sci-fi though go wild!
50k+ are birds
you are my vtuber oshi