WEBVTT - Why can’t we see quantum effects in everyday objects? 0:00:08.720 --> 0:00:12.760 Hey, Daniel, can you pass through walls? No? Keep trying 0:00:12.840 --> 0:00:14.880 and just keep getting more bumps on my head? How 0:00:14.880 --> 0:00:17.160 about can you bean too pleased at the same time? 0:00:17.360 --> 0:00:19.560 Sometimes it feels like I'm supposed to be but I've 0:00:19.600 --> 0:00:21.720 never actually managed it. So I guess you're not a 0:00:22.000 --> 0:00:25.520 quantum object. No. Actually, I'm quite classical. But you're a 0:00:25.560 --> 0:00:28.520 particle physicists. Aren't you made of particles? And aren't those 0:00:28.560 --> 0:00:33.640 particles quantum mechanical? I study particles and I'm made of particles, 0:00:33.640 --> 0:00:37.839 but I follow the rules of classical physics. Classic. I 0:00:37.880 --> 0:00:56.880 mean you're classic, Daniel. I'm not new Coke Daniel. I 0:00:56.920 --> 0:00:59.960 am more hammad cartoonists and the creator of PhD comics. 0:01:00.320 --> 0:01:04.200 I'm Daniel. I'm a particle physicist, but I'm quite classical 0:01:04.400 --> 0:01:06.640 in my tastes. Are you a fan of classical music 0:01:06.680 --> 0:01:08.680 and it's better than quantum music? Let me tell you 0:01:09.520 --> 0:01:12.000 that's a new genre to mak a new category at 0:01:12.000 --> 0:01:14.039 the Grammy. Oh I wish it was a new genre, 0:01:14.080 --> 0:01:16.399 but I'm sure if we type it into Google we 0:01:16.480 --> 0:01:19.000 will find something for quantum music. I feel like that's 0:01:19.000 --> 0:01:22.200 all music these days. It's both good and bad. It's 0:01:22.280 --> 0:01:26.880 kind of incoherent. It's both original and stale. Welcome to 0:01:26.880 --> 0:01:29.840 our podcast, Daniel and Jorge Explain the Universe, a production 0:01:29.920 --> 0:01:32.640 of My Heart Radio in which we explore everything in 0:01:32.680 --> 0:01:35.200 the universe and try to make sense of it. We 0:01:35.280 --> 0:01:37.640 try to understand how things move in our world and 0:01:37.680 --> 0:01:40.960 how tiny particles move. We try to understand the rules 0:01:41.200 --> 0:01:44.600 of the universe, whether they govern supernovas and black holes 0:01:44.720 --> 0:01:47.720 or tiny little electrons, and we try to make sure 0:01:47.800 --> 0:01:50.520 that you understand them. Yeah, because we try to make 0:01:50.560 --> 0:01:55.280 this podcast a super position of both fun and real science, 0:01:56.240 --> 0:01:59.240 physics and banana jokes. You often think those two can't 0:01:59.240 --> 0:02:01.800 be in the same place. Said the same time, what 0:02:01.920 --> 0:02:04.520 makes you say that you haven't met any fun physicists. 0:02:04.560 --> 0:02:07.040 You mean the physicists is fun, or they know how 0:02:07.040 --> 0:02:09.840 to have fun, or just doing physics is fun. Why 0:02:09.919 --> 0:02:12.320 doesn't everybody see that? Come on, I think that's the 0:02:12.360 --> 0:02:15.639 problems and that's the problem. But yeah, it's a weird 0:02:15.840 --> 0:02:18.640 and strange universe out there, and so we like to 0:02:18.680 --> 0:02:21.160 talk about all of the things and make it weird 0:02:21.200 --> 0:02:24.600 and strange. It's pretty unintuitive the universe it is, and 0:02:24.680 --> 0:02:27.600 physics has done a great job of building this edifice 0:02:27.639 --> 0:02:30.720 to help us understand the way the universe really is, 0:02:30.840 --> 0:02:33.040 not the way we think the universe should be or 0:02:33.160 --> 0:02:35.480 might be, or the way that makes sense to us 0:02:35.800 --> 0:02:38.760 based on our limited experience, but actually revealing to us 0:02:38.960 --> 0:02:42.160 the true nature of reality. But sometimes what we learn 0:02:42.320 --> 0:02:45.760 is pretty hard to swallow. Yeah, and specifically quantum mechanics. 0:02:45.760 --> 0:02:49.000 I feel like that really trips people up. It trips 0:02:49.040 --> 0:02:50.640 me up, for sure, And it's kind of hard to 0:02:50.680 --> 0:02:53.799 wrap your head around all of the weird, kind of 0:02:54.040 --> 0:02:57.800 unintuitive phenomenon that happens at the quantum level. Yeah, it 0:02:57.880 --> 0:03:01.079 is pretty weird because quantum particles seem to be following 0:03:01.160 --> 0:03:03.919 different rules. They seem to be able to break rules 0:03:03.960 --> 0:03:06.840 that are hard and fast for things like baseballs and 0:03:06.960 --> 0:03:09.959 basketballs and scoops of ice cream. And that's a hard 0:03:09.960 --> 0:03:12.600 thing to understand because it's weird and it's new. It's 0:03:12.639 --> 0:03:15.519 also hard to understand, like why are there different rules? 0:03:15.520 --> 0:03:18.240 And you know, what's the difference between an electron and 0:03:18.320 --> 0:03:20.720 a baseball? You know, where is the sort of threshold 0:03:20.800 --> 0:03:23.320 between those two where the quantum rules take over or 0:03:23.320 --> 0:03:25.600 the classical rules take over. Yeah, it is kind of 0:03:25.600 --> 0:03:28.120 weird that, you know, things are so weird at that level, 0:03:28.400 --> 0:03:31.360 at the microscopic level, but then once you scale up, 0:03:31.560 --> 0:03:37.600 things feel more gosh normal, more solid, less uncertain, or 0:03:37.640 --> 0:03:40.800 at least more familiar. Right. Science is all about delving 0:03:40.840 --> 0:03:43.760 into the unknown, and typically we try to explain the 0:03:43.840 --> 0:03:47.400 unknown in terms of the known, but that fails if 0:03:47.440 --> 0:03:50.839 the unknown is something really new, something different, something that's 0:03:51.000 --> 0:03:54.600 fundamentally can't be described by what we already know. We've 0:03:54.600 --> 0:03:57.320 often talked about how physics is like exploring the universe, 0:03:57.440 --> 0:03:59.800 but it's just been studying the tail of the elephant, 0:04:00.120 --> 0:04:01.600 and when you look at the rest of the elephant, 0:04:01.600 --> 0:04:03.920 it's not always true that what you learn from the 0:04:03.960 --> 0:04:06.280 tail can help you understand the rest of the elephant. 0:04:06.440 --> 0:04:09.640 Sometimes you really do discover something weird and different. Yeah, 0:04:09.720 --> 0:04:13.560 but is that elephant quantum mechanical, Daniel, Is it really 0:04:13.600 --> 0:04:17.719 there or not there? It's a theoretical thought experiment elephant. 0:04:17.760 --> 0:04:21.000 So it's just totally not there. That's classically non existent. 0:04:21.560 --> 0:04:25.000 Al Right. Well, that connection between the quantum world and 0:04:25.080 --> 0:04:28.960 our regular, everyday world is what we'll be exploring today 0:04:29.040 --> 0:04:31.599 on this episode to be on the podcast. We'll be 0:04:31.640 --> 0:04:41.719 asking the question what is quantum decoherence? That's hopefully a 0:04:41.800 --> 0:04:46.440 coherent question, yes, and quantum decoherence is the key concept 0:04:46.720 --> 0:04:50.919 to understanding the answer to this question. Why do big 0:04:50.960 --> 0:04:54.599 objects not seem to follow quantum rules? What is the 0:04:54.640 --> 0:04:58.640 difference between quantum objects and big objects? Where is the threshold? 0:04:58.640 --> 0:05:01.160 Why do we seem to have two sets of rules 0:05:01.360 --> 0:05:02.960 or is it just that one set of rules sort 0:05:02.960 --> 0:05:06.000 of morpse into the other. Right, it's an important concept, 0:05:06.080 --> 0:05:08.840 and it seems to be sort of related to this 0:05:09.040 --> 0:05:13.200 idea of quantum measurements. I think maybe that's something that 0:05:13.240 --> 0:05:15.840 if you've heard of quantum mechanics or have talked about 0:05:15.880 --> 0:05:18.760 it or seen any videos about it or read about it, 0:05:18.760 --> 0:05:20.880 it's something that seems to be important that you know 0:05:21.040 --> 0:05:23.719 things are quantum, but then when you poke at them 0:05:23.880 --> 0:05:26.719 or measure them or try to look at them, things 0:05:26.800 --> 0:05:29.240 collapse for some reason. Yeah, this is a big and 0:05:29.320 --> 0:05:33.920 still totally unsolved problem in quantum mechanics. Quantum mechanical things 0:05:33.960 --> 0:05:38.120 can have like multiple possibilities, but we don't observe multiple possibilities. 0:05:38.120 --> 0:05:40.520 When you poke an electron, as you say, it picks 0:05:40.560 --> 0:05:43.280 one of them, and we don't really understand how that happens, 0:05:43.320 --> 0:05:45.720 how one of them gets picked, and actually when that 0:05:45.760 --> 0:05:48.479 picking happens, you know, Does it happen when your finger 0:05:48.600 --> 0:05:50.600 touches the electron? Does it happen when you look at 0:05:50.600 --> 0:05:53.839 the results? That happens somewhere in between. That's a really 0:05:53.880 --> 0:05:57.840 interesting and hard problem, and it's related to quantum decoherence, 0:05:57.880 --> 0:06:00.480 but they're not quite the same thing. To today, we'll 0:06:00.480 --> 0:06:03.159 try to explain what quantum decoherence is, how it helps 0:06:03.200 --> 0:06:06.200 us understand the difference between quantum and classical objects. But 0:06:06.240 --> 0:06:08.520 it's important to understand that it doesn't actually solve this 0:06:08.600 --> 0:06:11.720 problem of the quantum measurement. Is that what happens when 0:06:11.720 --> 0:06:14.560 you pull on the tail of the elephant, things get 0:06:14.600 --> 0:06:18.320 real real quick. You get quantum stomped. It makes quantum 0:06:18.400 --> 0:06:20.240 music out of you. All right, Well, this is an 0:06:20.240 --> 0:06:23.200 interesting question what is quantum decoherence? And so as usual 0:06:23.240 --> 0:06:25.440 we were wondering how many people out there in the 0:06:25.600 --> 0:06:28.599 real world know what it means. So as usual, Daniel 0:06:28.640 --> 0:06:30.799 went other into the wilds of the internet to ask 0:06:31.520 --> 0:06:34.680 what is quantum decoherence? So thank you very much to 0:06:34.760 --> 0:06:38.320 everybody who will volunteered your speculation for the podcast. If 0:06:38.400 --> 0:06:40.960 you would like to volunteer for a future podcast, please 0:06:41.040 --> 0:06:44.000 write to us. Two questions at Daniel and Jorge dot com. 0:06:44.160 --> 0:06:46.039 Think about it for a second, soone ask you what 0:06:46.279 --> 0:06:50.400 quantum decoherence is. What would you say it is, or 0:06:50.440 --> 0:06:53.680 at least guess it is. Here's what people had to say. 0:06:53.880 --> 0:06:57.000 I'm not sure if I recognized this right, but I 0:06:57.040 --> 0:07:00.760 think decoherence is about how the quantum and the normal 0:07:00.839 --> 0:07:05.799 little few collide, so how we can map quantum effects 0:07:05.839 --> 0:07:10.520 into all reality. Since coherent means to make sense, I'm 0:07:10.560 --> 0:07:16.280 thinking quantum decoherence is when quantum particles can't logically follow 0:07:16.840 --> 0:07:19.160 the rules of the universe, of the constants of the universe, 0:07:19.320 --> 0:07:22.280 or something of the nature. I'm not sure what quantum 0:07:22.320 --> 0:07:27.240 decoherence is, but I think it might be wave function collapse, 0:07:27.360 --> 0:07:32.080 which is how the wave function of a quantity and 0:07:32.120 --> 0:07:36.120 a quantum system collapses when you measure that quantity. I 0:07:36.160 --> 0:07:40.720 don't know what quantum decoherence is, but my guess would 0:07:40.800 --> 0:07:45.679 be that it is the occurrence of something totally inconsistent 0:07:46.600 --> 0:07:50.400 that disrupts the quantum realm. It's got me thinking of 0:07:50.600 --> 0:07:53.160 something to do with quantum entanglement. All right, Some pre 0:07:53.760 --> 0:07:57.000 coherent answers for the most part, or at least coherent 0:07:57.040 --> 0:08:01.200 in there not knowing what it is. Nobody actually quite 0:08:01.280 --> 0:08:03.240 nailed it. But you know, people are in the vicinity, 0:08:03.360 --> 0:08:06.680 and they seem to understand that there's a concept of coherence, 0:08:06.720 --> 0:08:09.480 at least in quantum mechanics. Somebody said that it is 0:08:09.520 --> 0:08:13.400 sort of where the real world and the normal world collide. 0:08:14.240 --> 0:08:16.360 I guess they do, maybe think it has something to 0:08:16.400 --> 0:08:19.560 do with the connection between the quantum world and our 0:08:19.600 --> 0:08:21.920 everyday experience. Yeah, and that one is the closest I 0:08:21.960 --> 0:08:23.880 think to the right answer, to the right way of 0:08:23.880 --> 0:08:27.000 thinking about it. Quantum to coherence, in brief is the 0:08:27.080 --> 0:08:31.000 idea that explains how quantum objects look like classical objects 0:08:31.000 --> 0:08:33.040 when they get really big and messy. All right, well, 0:08:33.120 --> 0:08:35.839 let's jump into a Daniel and I guess let's start 0:08:35.960 --> 0:08:39.360 with just a quick recap of quantum of a small 0:08:39.400 --> 0:08:43.160 subject called quantum physics. You know, what is it that 0:08:43.320 --> 0:08:46.600 we actually call quantum and how can we kind of 0:08:46.640 --> 0:08:49.720 describe those effects? So the thing to understand is that 0:08:49.760 --> 0:08:53.439 when you look at really small objects, things like electrons 0:08:53.600 --> 0:08:57.240 or photons or individuals tiny particles, they seem to be 0:08:57.280 --> 0:09:01.839 following rules that don't apply to bigger objects like baseballs 0:09:01.880 --> 0:09:06.640 and Basketball's right, and the key concept to understand when 0:09:06.640 --> 0:09:10.160 thinking about these tiny particles is that they're not just particles. 0:09:10.160 --> 0:09:13.240 They're not like tiny versions of a baseball. They're not 0:09:13.320 --> 0:09:17.120 just like miniaturize little blobs of stuff flying through space. 0:09:17.400 --> 0:09:20.120 Right when people were first thinking about the atom, for example, 0:09:20.160 --> 0:09:22.920 they were thinking about the electron like orbiting the nucleus 0:09:23.000 --> 0:09:25.720 like a tiny planet around the star. But we pretty 0:09:25.800 --> 0:09:29.160 quickly figured out that was impossible because if an electron 0:09:29.280 --> 0:09:32.079 orbits and nucleus, then it's going to give off radiation 0:09:32.160 --> 0:09:35.400 because it's accelerating, it's giving off radiation. And they did 0:09:35.400 --> 0:09:37.960 the calculation and discovered, well, that would collapse in like 0:09:38.120 --> 0:09:40.480 a hundred billions of a second because they would lose 0:09:40.520 --> 0:09:42.960 all of his energy. And so instead they had to 0:09:42.960 --> 0:09:46.320 have a new idea for what controls and electron, what 0:09:46.440 --> 0:09:49.840 defines what an electron does and how it interacts, and 0:09:49.840 --> 0:09:52.680 so instead they try to use like wave like properties 0:09:52.679 --> 0:09:55.319 to describe it. So you've probably heard this phrase called 0:09:55.480 --> 0:09:58.840 the wave function. The wave function is just a mathematical 0:09:58.880 --> 0:10:01.719 tool that helps us under and what an electron is 0:10:01.800 --> 0:10:04.520 likely to do. And the key concept is that the 0:10:04.559 --> 0:10:07.720 wave function tells you where a particle is likely to 0:10:07.760 --> 0:10:10.560 be and where it's not likely to be. Sean Carroll 0:10:10.600 --> 0:10:13.439 says that the wave function is the dope ist name 0:10:13.480 --> 0:10:15.880 in the world for one of the most profound things 0:10:15.960 --> 0:10:18.720 in the universe, which really made me laugh. Well, dope 0:10:18.840 --> 0:10:21.680 and profound go hand in hand. I think like physics 0:10:21.679 --> 0:10:24.280 and fun, right, Yeah, well, yeah, I think that is 0:10:24.320 --> 0:10:28.360 maybe the hardest thing to grasp about quantum mechanics and physics. 0:10:28.400 --> 0:10:31.040 You know, I think everyone sort of grows up at 0:10:31.120 --> 0:10:34.480 Leaston's early in school and definitely in popular culture. You know, 0:10:34.559 --> 0:10:37.320 the depiction, like pictures of an atom always look like 0:10:37.520 --> 0:10:39.800 little planetary systems, you know, like a bunch of little 0:10:39.800 --> 0:10:43.679 balls in the middle cluster together, and then other little 0:10:43.679 --> 0:10:47.360 balls kind of swinging around in large orbits and rings 0:10:47.400 --> 0:10:50.080 around that. And that's the picture that we have about 0:10:50.120 --> 0:10:52.720 the atom. But you're saying, at some point we figured 0:10:52.760 --> 0:10:57.800 out that's not possible, like that that doesn't make sense. Yeah, exactly. 0:10:57.840 --> 0:11:01.240 It's not like the electron has a trajectory, has a 0:11:01.280 --> 0:11:04.320 path and we just don't know it. It doesn't actually 0:11:04.440 --> 0:11:07.319 have a path that doesn't have like a position at 0:11:07.360 --> 0:11:10.560 every moment in time. Instead, what it has is this 0:11:10.640 --> 0:11:13.600 quantum wave that the quantum wave behaves all sorts of 0:11:13.840 --> 0:11:16.719 normal wave like rules. But what it does is tell 0:11:16.800 --> 0:11:19.600 us where the electron is likely to be, and so 0:11:19.640 --> 0:11:22.000 the electron is likely to be here and it's likely 0:11:22.040 --> 0:11:24.400 to be there now. Sometimes people say that means that 0:11:24.440 --> 0:11:27.719 the electron is in two places at once, but that's 0:11:27.760 --> 0:11:30.360 not actually correct. It means it has the probability to 0:11:30.400 --> 0:11:34.319 be here or there, and those in both probabilities can 0:11:34.440 --> 0:11:36.840 exist at the same time. It doesn't mean it's actually 0:11:36.960 --> 0:11:39.920 in both places at once. If you ask the electron 0:11:40.000 --> 0:11:43.000 where are you, then it collapses as we talked about earlier, 0:11:43.080 --> 0:11:45.600 It picks one place or the other. But the wave 0:11:45.679 --> 0:11:48.719 function describes what's likely to happen. Well, I guess you 0:11:48.960 --> 0:11:51.760 mentioned before that it has a dopey name. Why do 0:11:51.800 --> 0:11:53.760 you think it's a bad name, And what would you 0:11:53.760 --> 0:11:56.400 have called it if not the wave function? And why 0:11:56.480 --> 0:11:59.480 is it called the wave fund? Well, wave, I suppose 0:11:59.600 --> 0:12:03.199 because it follows a wave equation. Shorting's equation is very 0:12:03.280 --> 0:12:06.360 much like equations for other waves that we've seen before, 0:12:06.400 --> 0:12:10.200 that electromagnetism, and it just waves in water. Right, there's 0:12:10.200 --> 0:12:13.320 a certain differential equation which just looks like a wave equation, 0:12:13.400 --> 0:12:16.160 like a wiggle like a like a like a rippling wiggle. Yeah, 0:12:16.160 --> 0:12:18.240 it's like a rippling wiggle, but you know, it's not 0:12:18.320 --> 0:12:22.120 a rippling wiggle in anything physical, right, Like sound waves 0:12:22.160 --> 0:12:25.079 are a wiggle in air, like air pressure. Right yeah, 0:12:25.280 --> 0:12:28.480 light waves are a wiggle in the electromagnetic field, which, 0:12:28.760 --> 0:12:30.920 even if it's hard to imagine, is a physical thing. 0:12:31.280 --> 0:12:35.240 The wave function is complex. It's imaginary values. It's like 0:12:35.240 --> 0:12:38.160 you know, one plus three I and so it's not 0:12:38.280 --> 0:12:42.000 a wiggle in a physical thing itself. So it's it's 0:12:42.000 --> 0:12:45.000 hard to understand because it's like this sort of abstract 0:12:45.400 --> 0:12:48.439 literally complex things in the sense that it exists in 0:12:48.480 --> 0:12:51.719 the imaginary plane, but it controls something real. So I 0:12:51.760 --> 0:12:54.240 wouldn't have called it the wave function, you know, I 0:12:54.320 --> 0:12:56.600 like the word wave, but function to me is sort 0:12:56.640 --> 0:13:00.839 of confusing. Which you have called it the imaginary function? Well, 0:13:00.880 --> 0:13:04.680 I feel like alluding to the imaginary complex plane that 0:13:04.720 --> 0:13:07.480 is not helping me here, I guess, And you just 0:13:07.520 --> 0:13:09.720 brought up maybe a source of confusion, which is that 0:13:09.840 --> 0:13:12.160 you know, you just said the light or a photon 0:13:12.400 --> 0:13:16.360 is like a ripple in the electromagnetic field, right, It's 0:13:16.360 --> 0:13:19.320 a ripple like kind of like a sound waving that 0:13:19.400 --> 0:13:22.240 it's like, it's more intense here in this intense here 0:13:22.640 --> 0:13:25.679 are you saying that? There's also like a photon would 0:13:25.720 --> 0:13:30.920 also have another kind of waving, nous, which is imaginary. Absolutely, 0:13:31.200 --> 0:13:34.360 the photon also has a wave function, right, and that 0:13:34.400 --> 0:13:37.640 wave function determines where the photon is likely to go, 0:13:37.920 --> 0:13:41.440 like which parts of the electromagnetic field are likely to ripple, 0:13:41.880 --> 0:13:44.400 you know, for example, you know, the classical situation is, 0:13:44.440 --> 0:13:47.640 imagine you shoot a photon at two slits in a screen. 0:13:48.080 --> 0:13:49.600 You know which one is it going to go through. 0:13:49.679 --> 0:13:51.320 It has a probability to go through one and a 0:13:51.320 --> 0:13:54.239 probability to go through the other. The wave function controls 0:13:54.440 --> 0:13:57.800 what those probabilities are, right, And if it collapses and 0:13:57.800 --> 0:13:59.480 picks the one on the left, then you get an 0:13:59.480 --> 0:14:03.120 electro magnetic wave through the one on the left. So 0:14:03.200 --> 0:14:05.720 the probability wave and the electromagnetic wave are sort of 0:14:05.720 --> 0:14:08.160 two different things to keep in your mind, and they 0:14:08.280 --> 0:14:11.800 both spread differently. Like why did they call them waves 0:14:11.800 --> 0:14:14.880 in the first place, Like do these like probabilities ripple 0:14:14.960 --> 0:14:18.480 out into space also, or or do they just look 0:14:18.520 --> 0:14:21.080 like a ripple that moves around. They do ripple, and 0:14:21.080 --> 0:14:23.440 they do follow wave mechanics, and that's why they call 0:14:23.480 --> 0:14:25.560 it a wave, and that's why they can do really 0:14:25.600 --> 0:14:29.880 amazing and fascinating things. Because the location of electron is 0:14:30.000 --> 0:14:32.960 controlled by something which is fundamentally a wave, it can 0:14:33.000 --> 0:14:36.640 do things that waves can do. Like it can interfere, Right, 0:14:36.680 --> 0:14:40.720 you can have probabilities interfering with themselves, probably being here 0:14:40.840 --> 0:14:44.120 and there, can interfere with each other and create probabilities 0:14:44.160 --> 0:14:47.560 in other places, just like actual waves can. Right, you 0:14:47.640 --> 0:14:49.640 put two hands in a lake or in a bathtub 0:14:49.840 --> 0:14:52.240 and you make two sources of waves. Those waves can 0:14:52.280 --> 0:14:54.640 interfere with each other, meaning just that they can add 0:14:54.720 --> 0:14:56.960 up or cancel out. So, for example, if I have 0:14:57.120 --> 0:15:00.560 like an electron here, it has like a ripple of 0:15:00.680 --> 0:15:04.520 probability kind of emanating from it, or is that kind 0:15:04.520 --> 0:15:07.280 of static if the electron is static. Well, electrons can't 0:15:07.360 --> 0:15:10.520 actually be totally static, right, because their quantum objects. So 0:15:10.560 --> 0:15:13.000 you can't just like say, electron is here and it's 0:15:13.000 --> 0:15:15.760 not moving. That would violate the Heisenberger in certainty principle, 0:15:15.840 --> 0:15:19.080 would effectively be an electron at absolute zero. But if 0:15:19.080 --> 0:15:20.560 you have an electron, you shoot it out of like 0:15:20.600 --> 0:15:23.640 an electron gun or something, and you want to describe 0:15:23.880 --> 0:15:26.240 what's it likely to do, where is it likely to go? 0:15:26.800 --> 0:15:30.160 Then you have a probability for all those various outcomes, right, 0:15:30.160 --> 0:15:32.160 And the key thing to understand is like, there's not 0:15:32.400 --> 0:15:35.480 a real history that's happening between when you shoot the 0:15:35.520 --> 0:15:38.080 electron and when it hits the wall, and you're just 0:15:38.200 --> 0:15:42.840 learning about it. It's uncertain, right. It has both possibilities 0:15:42.960 --> 0:15:47.320 existing simultaneously until you measure it. And that's the key 0:15:47.320 --> 0:15:49.440 thing that's hard to understand about quantum mechanics is like 0:15:49.640 --> 0:15:53.440 how this measurement changes it from like having two possibilities 0:15:53.600 --> 0:15:57.280 to actually existing in one place, but doesn't exist between 0:15:57.320 --> 0:16:00.240 the places you measure. It only exists where you measure 0:16:00.360 --> 0:16:03.160 in between. They're just probabilities, all right. So you're saying 0:16:03.200 --> 0:16:06.320 that maybe, like an electron is like a little tiny baseball, 0:16:06.920 --> 0:16:09.280 but we just don't know where it is, and where 0:16:09.280 --> 0:16:13.080 it is is determined by this ripple in probability. Yeah, 0:16:13.120 --> 0:16:15.240 I'm saying an electron is like a little tiny baseball, 0:16:15.280 --> 0:16:17.560 but it doesn't have a place where it is. It's 0:16:17.600 --> 0:16:20.680 not like it is someplace and we don't know its 0:16:20.720 --> 0:16:23.320 place is not determined the probability of it being in 0:16:23.360 --> 0:16:26.240 one place or another is determined by the way functions 0:16:26.320 --> 0:16:30.440 like probably to be there seventy one probability be here 0:16:30.760 --> 0:16:32.760 or whatever, so they add up to one. But the 0:16:32.760 --> 0:16:35.840 probabilities are determined by the way function but doesn't actually 0:16:35.920 --> 0:16:39.400 have a location. It just has those probabilities again until 0:16:39.440 --> 0:16:41.560 you measure it, which is the weird bit, and then 0:16:41.560 --> 0:16:43.440 when you measure it then it then it feels like 0:16:43.480 --> 0:16:46.240 you're hit by a baseball. It certainly does. And that's 0:16:46.240 --> 0:16:48.720 why we see these weird quantum effects because these particles 0:16:48.960 --> 0:16:51.960 like electrons can do things that waves can do, like 0:16:52.000 --> 0:16:54.080 if you have two sources of them, you get these 0:16:54.120 --> 0:16:57.880 interference effects, or they can like tunnel through walls. These 0:16:57.880 --> 0:17:00.360 are things that waves can do. Probability waves can do, 0:17:00.720 --> 0:17:03.440 and you get effects because you have these wave like 0:17:03.600 --> 0:17:07.639 properties of the electrons wave function. These probabilities can go 0:17:07.760 --> 0:17:10.320 through walls like the wall doesn't affect it, like it 0:17:10.400 --> 0:17:12.199 just goes through them. The wall does affect that. We 0:17:12.200 --> 0:17:16.000 have a whole fun podcast on quantum tunneling. And it's 0:17:16.040 --> 0:17:18.919 possible to go through walls right because you can have 0:17:18.960 --> 0:17:20.720 a probability to be on one side of the wall 0:17:20.880 --> 0:17:22.680 and then a probability to be on the other side 0:17:22.680 --> 0:17:24.720 of the wall, and you can do that without going 0:17:24.880 --> 0:17:28.280 through the wall. The probability can leak through the wall, 0:17:28.560 --> 0:17:30.600 giving you a chance to be on the other side 0:17:30.600 --> 0:17:33.119 of the wall, even if you're never actually in the wall, 0:17:34.160 --> 0:17:36.639 all right, And so that means that the baseball would 0:17:36.640 --> 0:17:38.760 just appear on the other side, or that that it's 0:17:38.760 --> 0:17:40.920 found a way through the wall. It just appears on 0:17:40.960 --> 0:17:44.119 the other side. Remember that quantum particles don't have to 0:17:44.160 --> 0:17:47.000 have paths between where you've seen them. You see it 0:17:47.040 --> 0:17:49.200 at A and you see it at B doesn't mean 0:17:49.200 --> 0:17:52.120 it went from A to B. Doesn't have like a 0:17:52.160 --> 0:17:55.159 secret history how it got from A to B. It 0:17:55.240 --> 0:17:57.520 was a A and then it was at B. Remember 0:17:57.520 --> 0:18:00.560 they follow fundamentally different rules. It was A, then it 0:18:00.640 --> 0:18:03.000 had lots of probabilities from maybe how it got to 0:18:03.040 --> 0:18:05.159 be not like one of them is true and we 0:18:05.240 --> 0:18:08.760 just don't know it. There are those probabilities. It's undetermined. 0:18:08.920 --> 0:18:12.280 It's not unknown, it's undetermined, and then later it's aid B. 0:18:12.680 --> 0:18:14.800 So it doesn't have to go from A to B 0:18:15.040 --> 0:18:16.960 in order to be at A and then be at B. 0:18:17.240 --> 0:18:19.800 And this is highlighted by the quantum tunneling experiment because 0:18:19.840 --> 0:18:22.040 you can't go from A to B. There's a barrier there. 0:18:22.320 --> 0:18:26.360 All right, Well, let's get into quantum coherence and how 0:18:26.400 --> 0:18:29.479 that relates or how that ties this uncertainty and this 0:18:29.520 --> 0:18:33.760 way function to real things like baseball. But first let's 0:18:33.760 --> 0:18:49.240 take a quick break. All right, we're talking about quantum decoherence, 0:18:49.359 --> 0:18:53.400 and hopefully Daniel will we're not. We're not breaking down 0:18:53.400 --> 0:18:57.200 into de coherence, talking about is. But okay, So particles 0:18:57.200 --> 0:19:00.320 have a way function which tells you it's like a 0:19:00.400 --> 0:19:05.160 ripple in the imaginary space, that tells you the probability 0:19:05.320 --> 0:19:08.879 where that little tiny baseball where you will find it. 0:19:09.040 --> 0:19:11.080 Maybe you weren't to poke in, Yes, exactly right. So 0:19:11.119 --> 0:19:14.560 then what does coherence and decoherence means? So quantum coherence 0:19:14.880 --> 0:19:17.919 is when you have two possible outcomes for what's going 0:19:17.960 --> 0:19:21.000 to happen to your particle, and those possibilities sort of 0:19:21.040 --> 0:19:24.600 line up like the wave functions for those two possibilities 0:19:24.880 --> 0:19:28.280 line up. Now, any solution to the wave equation, any 0:19:28.480 --> 0:19:31.080 like quantum state, you can take it and added to 0:19:31.119 --> 0:19:33.480 another quantum state to get a third quantum state, which 0:19:33.520 --> 0:19:35.840 is a mixture of the two. So you can mix 0:19:36.080 --> 0:19:38.520 two possible wave functions like if you have when it 0:19:38.520 --> 0:19:40.879 says the electron is gonna arrive at point A, and 0:19:40.880 --> 0:19:42.760 you have another one that says the electron's gonna arrive 0:19:42.760 --> 0:19:44.919 at point B. You can have a mixture that like 0:19:45.040 --> 0:19:48.400 mixes A and B with fifty fifty odds. So that's 0:19:48.400 --> 0:19:51.720 a coherent combination. It just says you have two possibilities 0:19:51.840 --> 0:19:55.320 and you've added them together, and they're coherent because their 0:19:55.359 --> 0:19:57.600 wave functions are sort of syncd up. They start in 0:19:57.640 --> 0:19:59.920 the same place and they sort of wiggle in time 0:20:00.000 --> 0:20:02.199 aim together, right, but they don't end up in the 0:20:02.240 --> 0:20:05.199 same place. Isn't there some kind of cancelation or some 0:20:05.320 --> 0:20:07.920 kind of or are you saying coherence is when they 0:20:07.920 --> 0:20:10.280 don't cancel. They can cancel, right. The fact that they 0:20:10.280 --> 0:20:13.320 can cancel is because they are coherent. You only get 0:20:13.400 --> 0:20:17.240 interference effects from coherence sources of waves. Like go back 0:20:17.240 --> 0:20:20.320 to the example of like bathtubs. Right, so you put 0:20:20.400 --> 0:20:22.199 your hand in the water and you slap it, You 0:20:22.240 --> 0:20:24.320 make a rhythm, and you get waves in the water. 0:20:24.640 --> 0:20:27.080 You do the same thing with your other hand if 0:20:27.080 --> 0:20:29.280 you're doing it in the same way, right, if you're 0:20:29.320 --> 0:20:32.040 like slapping the water in time, then you get these 0:20:32.040 --> 0:20:35.760 waves which either add up or cancel out coherently. If 0:20:35.800 --> 0:20:37.720 your second hand instead it's just like a random just 0:20:37.760 --> 0:20:39.960 like randomly slapping it, then they're not going to add 0:20:40.040 --> 0:20:41.880 up nicely. It's just going to be a big emotion. 0:20:41.880 --> 0:20:44.560 It's going to spread out to nothing. So you only 0:20:44.600 --> 0:20:48.439 get these interference effects when the quantum waves are in sync. 0:20:48.720 --> 0:20:52.199 That's quantum coherence, and that's what allows quantum things to 0:20:52.200 --> 0:20:56.119 be sort of quantumy, meaning that they're in sync in time. 0:20:56.440 --> 0:20:58.600 So what you're saying or in time and space, Yeah, 0:20:58.640 --> 0:21:01.760 they're in sync in time, and so at every point 0:21:01.880 --> 0:21:05.399 in space they can interfere. At one point in space, 0:21:05.400 --> 0:21:09.080 you might get cancelation because they're waving in opposite directions, 0:21:09.560 --> 0:21:12.400 and at another point in space they might support each 0:21:12.400 --> 0:21:15.280 other because they're waving in the same direction. But they 0:21:15.320 --> 0:21:18.919 can only do that consistently if they're in sync in time. 0:21:19.080 --> 0:21:22.080 So it sounds like, you know, particles have these wave 0:21:22.119 --> 0:21:25.280