WEBVTT - What is a Quantum Dot? 0:00:08.640 --> 0:00:13.160 Hey, Daniel, I found another physics related scam recently. Oh 0:00:13.320 --> 0:00:16.360 did someone try to sell you quantum girl scott cookies? Again? 0:00:17.800 --> 0:00:20.279 Girls cut cookies do seem to quantum tunnel into my 0:00:20.360 --> 0:00:23.960 stomach pretty easily. I don't even have to eat him. 0:00:24.040 --> 0:00:26.319 So then, what's the scam? I saw an ad for 0:00:26.400 --> 0:00:31.480 a quantum television? Can you believe that? Nonsense? Actually? Wait, 0:00:31.640 --> 0:00:34.440 what do you mean? This is the real thing? What 0:00:34.520 --> 0:00:37.280 does the quantum TV do? Is it always fuzzy because 0:00:37.280 --> 0:00:40.040 of the uncertainty principle? Yeah, you know, the word quantum 0:00:40.040 --> 0:00:43.320 gets abused a lot, but this one time it's for real. 0:00:43.720 --> 0:00:47.600 It's not a scam. No, quantum televisions are a real thing, 0:00:47.720 --> 0:01:07.120 and they are extra crispy, just like a girl's Scout cookie. 0:01:08.040 --> 0:01:11.440 I am or Hammaye, cartoonists and the creator of PhD comics. Hi, 0:01:11.680 --> 0:01:14.200 I'm Daniel. I'm a particle of physicists, and I'm at 0:01:14.280 --> 0:01:18.640 least made out of girls Scout cookies. Oh wow, you're 0:01:18.680 --> 0:01:21.760 you're a big fan. It's for a good cause, you know, 0:01:21.800 --> 0:01:23.360 that's why I eat them. It's for a good cause. 0:01:24.600 --> 0:01:26.959 You know you can buy them and not eat them. 0:01:27.040 --> 0:01:29.720 What that would be offensive? You have to throw them 0:01:29.720 --> 0:01:31.880 in the trash, and you don't have to tell the 0:01:31.920 --> 0:01:35.360 girls cuts they would know. But welcome to our podcast. 0:01:35.440 --> 0:01:38.080 Daniel and Jorge Explain the Universe April, that kind of 0:01:38.120 --> 0:01:41.480 irt radio in which we take our cookie fueled brains 0:01:41.560 --> 0:01:45.640 and try to understand everything about the universe, not just 0:01:45.720 --> 0:01:49.160 the tiny quantum particles and the crazy stuff happening in 0:01:49.240 --> 0:01:53.200 the center of stars, but everything in between. We take 0:01:53.280 --> 0:01:55.760 that immense mental journey all the way out into the 0:01:55.840 --> 0:01:58.960 universe and back into the quantum particles and explain all 0:01:59.000 --> 0:02:01.160 of it to you. Yeah, do you have a favorite 0:02:01.160 --> 0:02:03.760 girl Scout cookies? Daniel? Oh, we're getting real here, huh. 0:02:03.840 --> 0:02:06.320 I'm not gonna endorse one particular Girls Scott Cookies. I 0:02:06.320 --> 0:02:08.720 gotta go. I think with the classic than mint. You know, 0:02:08.760 --> 0:02:11.000 It's just it's so easy for them to tunnel into 0:02:11.040 --> 0:02:15.320 your stomach. My spouse would be appalled at the mixing 0:02:15.360 --> 0:02:21.360 of mint and chocolate. Do this taste like toothpaste to her? Yeah? 0:02:21.720 --> 0:02:26.920 With chocolate. There's probably a reason there's no chocolate toothpaste flavor. 0:02:27.760 --> 0:02:30.120 But there are a lot of interesting and amazing things 0:02:30.160 --> 0:02:32.280 in this universe that we like to talk about in 0:02:32.320 --> 0:02:35.079 this podcast. Things that are out there in the vast 0:02:35.080 --> 0:02:37.720 reaches of space, and also things that are right here 0:02:37.720 --> 0:02:40.320 at home, and things that are maybe at the tip 0:02:40.480 --> 0:02:43.560 of your fingertip without even knowing. Yes, things that are 0:02:43.720 --> 0:02:47.760 harder to understand even then, the combination of herbs and chocolate, 0:02:47.960 --> 0:02:50.880 things that are weird, things that are quantum, things that 0:02:50.919 --> 0:02:54.919 make no sense but are actually real. Yeah, because physics 0:02:55.160 --> 0:02:58.160 reveals that the universe is a pretty weird place. It 0:02:58.200 --> 0:03:01.280 doesn't always work the same way that we grew up 0:03:01.320 --> 0:03:04.400 thinking that it worked. There's all kinds of strange things 0:03:04.440 --> 0:03:09.000 going on, especially at the microscopic and at the quantum level. Yeah, 0:03:09.080 --> 0:03:11.720 that's basically the job of physics is to figure out 0:03:11.800 --> 0:03:14.400 how does the world actually work, Not the way we 0:03:14.560 --> 0:03:16.480 thought it should work, or the way we might have 0:03:16.560 --> 0:03:19.919 imagined it worked from our experience with rivers and rocks 0:03:19.960 --> 0:03:23.680 and stuff, but the way fundamentally things actually happen. And 0:03:23.800 --> 0:03:27.320 sometimes that's just for our edification, just to know how 0:03:27.360 --> 0:03:31.680 the universe actually works. But sometimes it's actually useful and 0:03:31.760 --> 0:03:34.000 we can use it to build cool new stuff. Wait, 0:03:34.040 --> 0:03:38.280 what physics can be useful? Who told you that? Some 0:03:38.360 --> 0:03:44.520 physicists your parents, some physicist After he told me some cookies. 0:03:44.720 --> 0:03:48.760 Oh right, right, a limit or professional limit to being 0:03:48.800 --> 0:03:53.120 a girl scout. You've never had a physics scott cookie? 0:03:54.080 --> 0:03:56.760 Does it taste like particles? I hear the Higgs boson 0:03:56.880 --> 0:04:00.800 is pretty tasty. Everything tastes like particles, man, everything particles. 0:04:00.800 --> 0:04:04.600 Particles are also the only things doing any tasting. Yeah, 0:04:04.720 --> 0:04:08.000 you're saying that physics can be useful. Physics can be useful. Yes. 0:04:08.040 --> 0:04:10.720 In fact, you know, the Worldwide Web was invented at 0:04:10.720 --> 0:04:14.040 a particle physics laboratory, and all sorts of things come 0:04:14.040 --> 0:04:17.880 out of just like gaining knowledge about how the universe works, right, 0:04:18.000 --> 0:04:20.320 And we all know how useful the Worldwide Web is. 0:04:20.920 --> 0:04:25.880 That's right. It's contributed to a huge decrease in productivity worldwide. 0:04:26.480 --> 0:04:29.080 It's like an anti useful particle there, depends on your 0:04:29.160 --> 0:04:34.400 goals man of reducing work. But yeah, well I do 0:04:34.480 --> 0:04:37.640 admit this useful to know physics, for sure, and sometimes 0:04:37.720 --> 0:04:41.560 we can use that knowledge to build amazing and and 0:04:41.720 --> 0:04:44.120 cool things that we couldn't do before. And that includes 0:04:44.160 --> 0:04:47.640 maybe quantum mechanics, which is like the weirdest and most 0:04:47.680 --> 0:04:50.640 awesomest thing in the universe. It is, and our understanding 0:04:50.760 --> 0:04:54.520 quantum mechanics underlies most modern electronics. It's the reason that 0:04:54.600 --> 0:04:57.200 your phone works, it's the reason your computer boots up. 0:04:57.360 --> 0:05:00.080 It's also the reason your computer crashes. I guess no, 0:05:00.240 --> 0:05:02.719 that's the fault of the girls got cookie crumples that 0:05:02.760 --> 0:05:06.880 fell in my keywork. It's like a physical virus infecting 0:05:06.880 --> 0:05:11.560 your computer. Yeah, quantum mechanics helps us not just kind 0:05:11.600 --> 0:05:15.320 of understand what's happening with our electronics and everything around us, 0:05:15.320 --> 0:05:17.599 but you can actually use some of these weird quantum 0:05:17.600 --> 0:05:22.200 effects to do interesting things like microscopes, right, like electric microscopes. 0:05:22.240 --> 0:05:25.919 They work on quantum mechanical principles. Yeah. Basically, everything that 0:05:25.960 --> 0:05:29.000 works at the very small scale that uses one or 0:05:29.040 --> 0:05:32.839 two or small set of particles has to follow quantum rules. 0:05:33.000 --> 0:05:36.880 So anything that's been super miniaturized or uses particles to 0:05:36.960 --> 0:05:40.039 look at super tiny stuff has to follow quantum rules. 0:05:40.040 --> 0:05:42.960 And sometimes those quantum rules are different in a really 0:05:43.080 --> 0:05:46.680 useful way. Yeah. And usually this kind of technology is 0:05:46.760 --> 0:05:50.880 limited to physics labs and engineering labs and research centers. 0:05:50.920 --> 0:05:55.479 But soon quantum mechanics technology might be coming to your home. 0:05:55.760 --> 0:06:00.200 That's right, Get ready to buy quantum cookies, I mean 0:06:00.279 --> 0:06:04.760 quantum TVs you know, there is actually something quantized by cookies. 0:06:04.760 --> 0:06:06.479 You notice how you can't eat one and a half 0:06:06.480 --> 0:06:09.400 cookies or three in a quarters cookies. It's always like 0:06:09.440 --> 0:06:12.360 into your numbers of cookies. Oh my god, you just 0:06:12.400 --> 0:06:17.359 discovered the whites and quantum cookie principle. I did a 0:06:17.360 --> 0:06:20.400 lot of experiments. It's more of a social science principle though. Yeah, 0:06:20.400 --> 0:06:22.400 it's a bit of a soft science there. Cookies, I 0:06:22.400 --> 0:06:26.680 get the software my sciences and your stomach and your 0:06:26.720 --> 0:06:30.960 body exactly. Well. There there is now a proposed quantum 0:06:31.000 --> 0:06:34.599 television technology and it's based on kind of a and 0:06:34.800 --> 0:06:37.440 not a new technology, but a technology that's been around 0:06:37.560 --> 0:06:39.840 for a while in quantum mechanics. Yeah, this is really 0:06:39.880 --> 0:06:43.560 fascinating idea that lets us build something like artificial atoms 0:06:43.560 --> 0:06:46.280 and manipulate electron energy levels to get all sorts of 0:06:46.320 --> 0:06:49.720 fascinating properties that we could use for really a wide 0:06:49.839 --> 0:06:52.400 range of possible technologies. So to be on the program, 0:06:52.440 --> 0:07:01.240 we'll be talking about what are quantum dots? That does 0:07:01.279 --> 0:07:04.800 sound like a girl's got a very very small cookie, 0:07:04.839 --> 0:07:07.520 the quantum dot. You know, someone what is it? Thin 0:07:07.640 --> 0:07:12.080 min's and snickerdoodles and quantum dots? But how many quantum 0:07:12.080 --> 0:07:14.080 dots would be in one box of cookies, right, like 0:07:14.160 --> 0:07:18.400 ten to twenty six. That's a pretty good deal, mom, 0:07:18.400 --> 0:07:20.520 I only had ten of the twelve quantum dot cookies 0:07:20.520 --> 0:07:24.560 for dessert. That's your alignment for the rest of your life. 0:07:26.280 --> 0:07:28.920 So when you heard the phrase quantum dot, did you 0:07:28.960 --> 0:07:31.360 think it was another one of these ridiculous schemes. Yeah, 0:07:31.400 --> 0:07:34.320 I'd heard of him before. I just never knew what 0:07:34.360 --> 0:07:37.000 they are. I mean, I imagine they're just really small 0:07:37.160 --> 0:07:40.560 dots at the quantum level. But you know, is it 0:07:40.720 --> 0:07:43.120 like a dot of ink, dot of what? It's a 0:07:43.200 --> 0:07:47.440 dot of quantum? Right, pure quantum? All right? Well, as usual, 0:07:47.560 --> 0:07:49.679 Daniel went out there into the wild of the Internet 0:07:49.760 --> 0:07:53.080 to ask people if they knew what quantum dots are. 0:07:53.280 --> 0:07:56.200 So thank you to everyone who broke through their inhibitions 0:07:56.240 --> 0:07:59.880 and answered these random questions without any research. If you 0:08:00.040 --> 0:08:02.320 would like to participate in the future, please write to 0:08:02.360 --> 0:08:05.560 me at questions at Daniel and Jorge dot com. Yes, 0:08:05.640 --> 0:08:07.240 I think about it for a second. Is so, when 0:08:07.320 --> 0:08:10.360 asked you what a quantum dot is, what would you answer? 0:08:10.920 --> 0:08:13.840 Here's what people had to say. I think a quantum 0:08:13.960 --> 0:08:18.640 dot refers to a single particle such as an electron 0:08:19.080 --> 0:08:25.880 that is isolated by means of electromagnetic fields. The particle 0:08:26.720 --> 0:08:32.160 is confined to a small region in space, so it 0:08:32.240 --> 0:08:36.560 has a very high um kinetic energy. Okay, I think 0:08:36.640 --> 0:08:44.040 quantum dots are really small collections of atoms. Believe often 0:08:44.120 --> 0:08:48.520 it's um for gold atoms to lump together. Maybe if 0:08:48.559 --> 0:08:52.800 the idea that like the universe is pixelated, maybe quantum 0:08:52.840 --> 0:08:56.760 dots are there, the grid points that underly everything. If 0:08:56.800 --> 0:09:00.280 I had guess, I would say quantum dots are maybe 0:09:00.360 --> 0:09:04.160 something like string theory, where if we break things down 0:09:04.200 --> 0:09:07.160 as small as we can get, we're we're stuck with 0:09:07.200 --> 0:09:10.880 these quantum dots, and and they can be the building 0:09:10.920 --> 0:09:15.640 blocks for a lot of quantum things. I think, or 0:09:15.720 --> 0:09:18.040 he said it once. The word quantum just goes in 0:09:18.040 --> 0:09:20.839 front of anything these days. It seems like I don't 0:09:21.080 --> 0:09:23.920 know for sure, but I think it might refer to 0:09:24.160 --> 0:09:29.840 the mathematical concept of a um particle that doesn't have 0:09:29.880 --> 0:09:32.880 a volume, so it only has coordinates, but not volume 0:09:32.880 --> 0:09:37.200 in space or zero volume. Quantum it's something small and 0:09:37.280 --> 0:09:44.439 a dot. It's something small also, so quantum dot. Probably 0:09:44.800 --> 0:09:50.160 you'll find it in at the end of a quantum sentence, 0:09:51.679 --> 0:09:54.200 how about it. So, I've never actually heard the phrase 0:09:54.400 --> 0:09:58.840 quantum dots before. My guess is that it has to 0:09:58.880 --> 0:10:03.880 do with the idea of that space itself is quantized, 0:10:04.640 --> 0:10:07.920 and that if you were able to zoom in far enough, 0:10:08.800 --> 0:10:13.720 there would be a smallest possible point. I've never ever 0:10:13.840 --> 0:10:17.160 heard of a quantum dotum afraid. I'm guessing they have 0:10:17.280 --> 0:10:19.839 something to do with the idea that space is quantized, 0:10:19.880 --> 0:10:23.160 so like pixels on a display. All right, not a 0:10:23.160 --> 0:10:25.480 lot of people know what a quantum dot is, apparently no. 0:10:25.600 --> 0:10:28.360 But there are some really nice speculations here, like the 0:10:28.400 --> 0:10:31.560 math concept of a particle with no volume. That's definitely 0:10:31.600 --> 0:10:35.360 something we've talked about in the podcast. I guess everything 0:10:35.440 --> 0:10:39.640 is a quantum dot technically, right, like all particles are 0:10:39.679 --> 0:10:41.960 just the point particles. Was the difference between a dot 0:10:41.960 --> 0:10:45.960 and a point, Daniel get philosophical? One of them has 0:10:46.040 --> 0:10:47.640 mint in it, I guess, and the other one doesn't. 0:10:49.280 --> 0:10:52.080 I have no idea. I have no idea when it's round, 0:10:52.360 --> 0:10:55.599 maybe the other one is pointing. Maybe yeah, I don't know. 0:10:55.640 --> 0:10:59.360 A point, technically speaking, is a single value in space, 0:10:59.360 --> 0:11:02.480 whereas I guess a dot could have some width to it. 0:11:03.520 --> 0:11:07.160 You have a good point that dot. All right, let's 0:11:07.200 --> 0:11:09.720 jump into it. Daniel, what is the quantum dot? Settle 0:11:09.800 --> 0:11:12.640 this for us? Yeah, quantum dot is really fascinating. It's 0:11:12.679 --> 0:11:15.600 basically just a piece of semi conductor, but a very 0:11:15.679 --> 0:11:19.680 very very small piece, so you get interesting quantum effects 0:11:19.760 --> 0:11:23.400 because semiconductors are sort of very flexible electrically and can 0:11:23.440 --> 0:11:26.200 be manipulated by doping and adding different kinds of materials. 0:11:26.240 --> 0:11:29.440 You can essentially construct any kind of energy levels you 0:11:29.480 --> 0:11:32.440 want for your electron, which is really what determines the 0:11:32.480 --> 0:11:36.079 sort of like bulk properties of a material. So it's 0:11:36.120 --> 0:11:39.200 just a really really tiny piece of anything, right, doesn't 0:11:39.200 --> 0:11:41.280 have you a semiconductor. It can be any material that 0:11:41.320 --> 0:11:43.400 you can call it a quantum dot. Yeah, it could 0:11:43.400 --> 0:11:46.360 be any material, but we typically use semiconductors because of 0:11:46.360 --> 0:11:49.679 their interesting electrical properties. And so take some piece of 0:11:49.720 --> 0:11:51.800 material and make a really really small version of it, 0:11:51.840 --> 0:11:55.200 and then quantum effects take over. Things like the electron, 0:11:55.240 --> 0:11:58.079 for example, gets trapped in your quantum dot, and then 0:11:58.120 --> 0:12:00.080 the width of it is now important to how of 0:12:00.080 --> 0:12:02.680 that electron behaves. It changes like the energy levels the 0:12:02.720 --> 0:12:05.439 electron can have, which changes like how it absorbs light 0:12:05.520 --> 0:12:08.400 or a midst light or conducts electricity. How big are 0:12:08.440 --> 0:12:10.280 we talking about or how small are we talking about? 0:12:10.360 --> 0:12:13.280 These quantum dots being like how many nanometers we're talking 0:12:13.320 --> 0:12:17.400 about like one to ten nanometers in size. These are 0:12:17.520 --> 0:12:19.960 really tiny, Like you could line up a million of 0:12:20.000 --> 0:12:23.560 these things across your finger. They're super duper small, and 0:12:23.600 --> 0:12:25.520 they have to be small in order to get to 0:12:25.559 --> 0:12:27.640 the quantum effects, right, they have to be basically on 0:12:27.720 --> 0:12:32.120 the quantum scale, the Antman scale, so one to ten nanometers. 0:12:32.160 --> 0:12:34.480 And how does that compare it to like the you know, 0:12:34.559 --> 0:12:37.520 the quote unquote with of an atom. It's about ten 0:12:37.760 --> 0:12:41.679 or fifteen times wider than like the hydrogen atom is 0:12:41.720 --> 0:12:44.080 defined by like you know, the cloud of electrons around 0:12:44.120 --> 0:12:46.720 the nucleus. So you're definitely getting down to that scale. 0:12:47.240 --> 0:12:49.480 And I think that's sort of the key idea is 0:12:49.520 --> 0:12:51.679 that you know, when you get electrons down to this 0:12:51.880 --> 0:12:54.439 really small scale, like the size of a hydrogen atom 0:12:54.520 --> 0:12:57.040 or what happens in atoms, they start to exhibit these 0:12:57.080 --> 0:13:01.160 quantum properties, like having very specific energy levels that only 0:13:01.240 --> 0:13:05.079 happens when you can strain an electron m all right, 0:13:05.120 --> 0:13:08.360 So you know it's like maybe ten atoms wide these dots, 0:13:08.640 --> 0:13:11.520 and are they actually like dots? Are they like cubes? 0:13:11.559 --> 0:13:14.439 Are they like little balls? Do we have pictures of them? 0:13:14.559 --> 0:13:17.240 We do have pictures of them. Usually they're little crystals. 0:13:17.280 --> 0:13:19.480 And it depends a little bit on how they are 0:13:19.520 --> 0:13:21.920 built and how their fabricatum. And we'll get into it 0:13:21.960 --> 0:13:23.600 in a minute about how you make these things. And 0:13:23.640 --> 0:13:25.520 you can make them in almost any shape. You can 0:13:25.559 --> 0:13:28.920 make cubes, you can make pyramids, you can make you know, 0:13:29.360 --> 0:13:32.000 diamond shapes, whatever you like. And the shape of the 0:13:32.080 --> 0:13:35.760 nanocrystals changes how the electron is sort of capture it 0:13:35.800 --> 0:13:38.160 in it and can change its behavior. So depending on 0:13:38.520 --> 0:13:41.040 what you want for its electrical properties, you might design 0:13:41.080 --> 0:13:43.960 a different shape. M M. All right, So it's almost 0:13:44.000 --> 0:13:47.040 like you're kind of making an atom, almost. Yeah. The 0:13:47.120 --> 0:13:48.920 key idea here is that when you look at the 0:13:48.920 --> 0:13:51.400 periodic table, you see lots of different elements, and those 0:13:51.440 --> 0:13:54.000 elements all have really different properties, right, Some of them 0:13:54.000 --> 0:13:56.920 conduct a lot of electricity, some of them are really interactive, 0:13:56.920 --> 0:13:59.119 and some of them are not. All of those properties 0:13:59.160 --> 0:14:02.600 come from behavior of the electrons and their energy levels, 0:14:02.600 --> 0:14:06.160 like are those electron orbitals filled? And how big are they? Etcetera, etcetera. 0:14:06.200 --> 0:14:08.720 But we're sort of limited to the atoms that we 0:14:08.800 --> 0:14:10.760 have in nature. You know, if you want an atom 0:14:10.800 --> 0:14:13.360 that does a specific kind of thing that emits light 0:14:13.400 --> 0:14:16.480 of a certain frequency or absorbs light of a certain frequency, 0:14:16.600 --> 0:14:18.280 you sort of have to pick from the menu that 0:14:18.320 --> 0:14:21.560 we have until now. Because quantum dots allow you to 0:14:21.600 --> 0:14:25.680 basically engineer electron energy levels to say, I'd like electron 0:14:25.760 --> 0:14:27.720 energy levels that look like this, so you can have 0:14:27.800 --> 0:14:31.520 whatever whatever property. That's why they're sometimes called artificial atoms. 0:14:32.280 --> 0:14:34.520 They don't have a nucleus and electrons around them, but 0:14:34.560 --> 0:14:36.960 they have that sort of property of an atom that 0:14:36.960 --> 0:14:40.360 they're controlled by their electron energy levels. Interesting, they're like 0:14:40.440 --> 0:14:45.480 designer atoms, yes, exactly, designer atoms like made to order. Yeah, 0:14:45.560 --> 0:14:48.000 And so if we want a material that does something 0:14:48.000 --> 0:14:51.120 that no natural material does, then we can maybe build 0:14:51.120 --> 0:14:53.560 it out of quantum dots or design quantum dots that 0:14:53.640 --> 0:14:57.120 have that specific ability. What kinds of abilities are we 0:14:57.200 --> 0:15:01.200 talking about, like reflecting light or like conduct or how 0:15:01.240 --> 0:15:04.360 easy they give off an electron or or how they taste. 0:15:05.400 --> 0:15:07.920 I would not recommend eating any of these quantum dots. 0:15:08.040 --> 0:15:10.560 Almost all of them are totally toxic. But yeah, they 0:15:10.600 --> 0:15:13.400 have interesting optical properties, like they can absorb light at 0:15:13.400 --> 0:15:16.040 whatever frequency you want, you know, and they can give 0:15:16.080 --> 0:15:18.920 off light at whatever frequencies you want, which is very 0:15:18.960 --> 0:15:22.040 helpful for example and making a very crisp display for 0:15:22.160 --> 0:15:25.400 your television, and other kinds of things like absorbing power 0:15:25.480 --> 0:15:28.040 for solar cells. And there's another aspect to it, which 0:15:28.040 --> 0:15:31.160 is maybe less practical but more fascinating, which is that 0:15:31.240 --> 0:15:34.800 you can sort of design quantum behaviors. Previously, when people 0:15:34.800 --> 0:15:37.480 wanted to do quantum experiments, it was hard because you 0:15:37.520 --> 0:15:40.600 had to use like actual atoms that we find in nature, 0:15:40.840 --> 0:15:43.000 and those atoms going to be difficult to deal with. 0:15:43.080 --> 0:15:45.720 You have to like have a vacuum system and lasers 0:15:45.720 --> 0:15:49.040 to capture it. Remember we talked about Bose Einstein contensate. 0:15:49.360 --> 0:15:51.960 It's a difficult thing to do because it has to 0:15:51.960 --> 0:15:55.000 be done with atoms and all these complex systems. Yeah, 0:15:55.040 --> 0:15:59.480 I lose my atoms all the time. They're slippery, they 0:15:59.520 --> 0:16:01.840 are slip bury and it's a pain and it's expensive. 0:16:02.280 --> 0:16:04.400 But if you could do it with quantum dots, they're 0:16:04.480 --> 0:16:06.880 much easier to manufacture. You might even be able to 0:16:06.880 --> 0:16:09.760 print them on chips for example, So you could do 0:16:09.840 --> 0:16:14.640 all sorts of fascinating quantum experiments without all the expensive machinery. 0:16:15.040 --> 0:16:19.040 Could you print like a quantum computer out of quantum dots? Yes, exactly, 0:16:19.120 --> 0:16:22.200 that's one direction. People are going trying to build cubits 0:16:22.280 --> 0:16:25.600 out of quantum dots. But doesn't the quantum no iss 0:16:25.600 --> 0:16:28.720 of something always decrease the more atoms you get, Like 0:16:28.760 --> 0:16:31.560 if you have ten atoms, that's usually sort of like 0:16:31.720 --> 0:16:34.240 less quantumy than one atom. Right, you can worry about 0:16:34.280 --> 0:16:37.760 like decoherence effects. As it interacts with its environment, it 0:16:37.840 --> 0:16:41.280 loses some of those quantum effects because the wave functions decohere. 0:16:41.440 --> 0:16:43.600 And that's something that's really difficult to do with atoms 0:16:43.600 --> 0:16:46.280 because it's hard to isolate them from the system. Right, 0:16:46.400 --> 0:16:49.320 The key is isolation. You could have a really large 0:16:49.400 --> 0:16:52.240 system that doesn't deco here as long as it remains 0:16:52.240 --> 0:16:54.760 isolated from the environment. That's hard to do with atoms 0:16:54.800 --> 0:16:57.120 because you know, they bounce around and they jiggle and stuff. 0:16:57.120 --> 0:16:59.480 But quantum dots are sort of easier to localize. And 0:16:59.520 --> 0:17:02.520 if we're easier to isolate, is the idea, Oh man, 0:17:02.600 --> 0:17:04.920 are we going to go back to dot matrix printers, 0:17:05.000 --> 0:17:09.680 but this time there will be quantum dot matrix printers. Yeah, 0:17:09.680 --> 0:17:14.280 exactly is that? What is that our featured again, and 0:17:14.320 --> 0:17:20.359 then we'll go back to quantum motives too, but it 0:17:20.400 --> 0:17:22.520 will be the quantum version of those sounds. It would 0:17:22.520 --> 0:17:26.199 be much spookier, sound cooler, which is by definition. And 0:17:26.320 --> 0:17:28.720 something that's really fascinating about these things is that they're 0:17:28.720 --> 0:17:34.160 offering referred to as zero dimensional objects, of course, because 0:17:34.200 --> 0:17:37.800 that's not confusing, and that was really confusing for me 0:17:37.840 --> 0:17:39.639 when I first was reading about that, because you know, 0:17:39.800 --> 0:17:43.159 I'm three dimensional, there's forward, backwards, side to side, and 0:17:43.240 --> 0:17:45.919 up and down. I'm defined by three different dimensions, and 0:17:45.960 --> 0:17:47.840 you can imagine, you know, a sheet of paper is 0:17:47.840 --> 0:17:50.560 almost two dimensional, and like a thin piece of string 0:17:50.680 --> 0:17:54.320 is like almost one dimensional. What's a zero dimensional object? 0:17:54.760 --> 0:17:57.520 And it's really something where it can't go anywhere, So 0:17:57.600 --> 0:18:00.399 it's really like a point in space us. There are 0:18:00.400 --> 0:18:02.879 electrons in there, and yes, technically they can move a 0:18:02.920 --> 0:18:05.960 little bit sideways, but really they're constrained and the only 0:18:05.960 --> 0:18:07.639 way they can move is sort of up and down 0:18:07.680 --> 0:18:11.840 in energy. Oh interesting, almost like a perfect box for electrons. Yeah, 0:18:11.920 --> 0:18:14.199 it's a perfect little box for electrons. And you know, 0:18:14.240 --> 0:18:18.240 quantum mechanically, the way the electron behaves is completely defined 0:18:18.320 --> 0:18:20.840 by the shape of the box. Like an electron just 0:18:20.880 --> 0:18:24.120 floating through space is not actually quantized like you could 0:18:24.119 --> 0:18:27.200 have any energy level. Free electrons are not quantized at all. 0:18:27.280 --> 0:18:29.800 The quantization only happens when you constrain it, when you 0:18:29.840 --> 0:18:32.159 say you gotta live in this little box or whizz 0:18:32.160 --> 0:18:35.439 around this nucleus of the atom. That's where the quantization 0:18:35.480 --> 0:18:38.359 comes from. And so here, by constructing your own box, 0:18:38.440 --> 0:18:41.160 you define your own energy levels for the electron, which 0:18:41.200 --> 0:18:44.639 I think is pretty cool. So we're like quantum designers. Wow, 0:18:45.200 --> 0:18:47.399 And this is an idea from the eighties. It was 0:18:47.440 --> 0:18:49.960 made a long time ago, but only now maybe we're 0:18:49.960 --> 0:18:53.560 getting into how to actually use these thoughts. Yeah, exactly. 0:18:53.560 --> 0:18:56.280 The idea has been around for a few decades, and 0:18:56.320 --> 0:18:58.720 the proof of principle was done in the eighties. But 0:18:58.840 --> 0:19:01.280 with lots of things, it's only really useful if you 0:19:01.320 --> 0:19:02.679 can make a lot of them, and if you can 0:19:02.720 --> 0:19:06.200 make them at less than like a billion dollars per dot. Right, 0:19:06.200 --> 0:19:08.280 All right, well, let's get into how you actually make 0:19:08.320 --> 0:19:11.040 a quantum dot and what can you do with them. 0:19:11.040 --> 0:19:24.760 But first let's take a quick break. All right, we're 0:19:24.760 --> 0:19:28.760 talking about quantum dots, which are not girls cout cookies, 0:19:29.000 --> 0:19:33.760 but possibly TVs in the future, yes, TVs, maybe even 0:19:33.800 --> 0:19:37.400 in your present. They might end up on our phones. Yeah, 0:19:37.480 --> 0:19:40.040 you could have a quantum dots screen. They could create 0:19:40.040 --> 0:19:41.760 screens that are like really flexible. You can like a 0:19:41.840 --> 0:19:44.320 roll up in the stuff in your pocket. Just don't 0:19:44.320 --> 0:19:49.040 eat them. Do not eat quantum screens, all right. Quantum 0:19:49.040 --> 0:19:52.200 dot is a little tiny piece of semiconductor, maybe one 0:19:52.280 --> 0:19:56.560 to ten nanometers wide, which is about like ten atoms 0:19:56.560 --> 0:20:00.800 in with and they can act like little niner atoms. 0:20:00.800 --> 0:20:03.640 They can trap electrons and you can make them sit 0:20:03.800 --> 0:20:06.439 at whatever energy levels you want. Yeah, you can make 0:20:06.480 --> 0:20:09.800 the particles dance whatever dance you tell them to. All right, 0:20:09.840 --> 0:20:11.560 So I guess the question is how do you make them? 0:20:11.640 --> 0:20:13.560 How do you make a quantum dot? Do you just 0:20:13.600 --> 0:20:16.400 like spray some quantumness and they form in the air. 0:20:16.520 --> 0:20:19.440 What's the formative? Yeah, it's one teaspoon of quantumness to 0:20:19.560 --> 0:20:22.480 teaspoons of dot and then just mix. There you go. 0:20:22.920 --> 0:20:25.200 It's hard, right, and this is one of the challenges. 0:20:25.520 --> 0:20:27.840 And so there are a lot of different approaches to 0:20:28.000 --> 0:20:30.480 making these quantum dots, and we'll see which one sort 0:20:30.480 --> 0:20:34.240 of takes off for various applications. There's basically three totally 0:20:34.280 --> 0:20:38.199 different approaches. One is chemical, so basically just try to 0:20:38.240 --> 0:20:40.639 mix these things like we were just joking about, but 0:20:40.760 --> 0:20:44.280 for real. And the idea is that these things are crystals, 0:20:44.320 --> 0:20:47.280 which means that in some sense they should self assemble, 0:20:47.440 --> 0:20:50.199 you know, the way like crystals will form themselves. If 0:20:50.280 --> 0:20:53.000 you put salt into solution and you shake it, the 0:20:53.040 --> 0:20:55.880 salt should come out of the solution, you know, make 0:20:56.000 --> 0:20:58.600 these crystals. And so you do the same thing with 0:20:58.640 --> 0:21:01.320 the kind of quantum dot you want to make. Whatever 0:21:01.359 --> 0:21:03.760 it is you're trying to build, maybe it's mostly silicon, 0:21:03.800 --> 0:21:05.719 maybe it has other stuff in it. You put all 0:21:05.720 --> 0:21:08.760 those ingredients into some solution, you heat it up so 0:21:08.760 --> 0:21:11.119 it all like breaks up into a big soup, and 0:21:11.119 --> 0:21:14.400 then you hope that nanocrystals get nucleated and then sort 0:21:14.400 --> 0:21:18.480 of build on themselves. But then they would be floating 0:21:18.520 --> 0:21:21.440 around or they would kind of form on your surface. No, 0:21:21.560 --> 0:21:24.040 then they would be floating around exactly, and then you 0:21:24.160 --> 0:21:26.880 need to do something to like pull them out and 0:21:27.320 --> 0:21:30.880 you know, make them useful somehow. But often you want 0:21:30.920 --> 0:21:33.520 them in solution, like maybe you want them suspended in 0:21:33.600 --> 0:21:35.919 water so they can glow a certain temperature where you 0:21:35.920 --> 0:21:40.199 can inject them into your experiment or whatever. Sounds kind 0:21:40.240 --> 0:21:42.480 of tricky. It's pretty tricky, and also it's tricky to 0:21:42.560 --> 0:21:44.960 filter them, right. You want only quantum dots that have 0:21:45.080 --> 0:21:47.879 formed well, and so this process isn't always going to 0:21:48.000 --> 0:21:51.320 form you high quality quantum dots every single time, and 0:21:51.359 --> 0:21:53.520 so it's tricky to get exactly the right ones out. 0:21:53.640 --> 0:21:55.879 And so people have tried all sorts of variations on 0:21:55.920 --> 0:21:59.680 this approach, like using molecular seating, you know, starting with 0:22:00.040 --> 0:22:01.960 something that has sort of like the right shape to 0:22:02.080 --> 0:22:04.879 nucleate those crystals and encourage things to form just the 0:22:04.960 --> 0:22:07.440 right way. It's really complex, sort of like as a 0:22:07.560 --> 0:22:09.800 chemistry problem. You know, how do you get all these 0:22:09.840 --> 0:22:12.760 molecules bouncing around in solution to come together and like 0:22:13.000 --> 0:22:17.359 build themselves out of these mini legos? Right? Yeah, sounds tricky. 0:22:17.480 --> 0:22:19.320 What are other ways that you can make them? Another 0:22:19.359 --> 0:22:23.920 way is basically following the principles of semiconductor technologies, which 0:22:23.920 --> 0:22:27.760