WEBVTT 1 00:00:01.480 --> 00:00:05.599 Welcome to the quart Side Quantum Physics podcast, an exploration 2 00:00:05.679 --> 00:00:10.880 of the fundamental structure of reality, where quantum laws govern matter, energy, 3 00:00:11.199 --> 00:00:16.239 and information. Here, uncertainty is a feature, not a flaw, 4 00:00:16.719 --> 00:00:19.239 and understanding begins at the smallest scales. 5 00:00:27.640 --> 00:00:31.879 If you really stop and think about the human condition, 6 00:00:32.119 --> 00:00:37.119 or maybe the scientific condition, it really all boils down 7 00:00:37.200 --> 00:00:42.600 to a refusal to be blind. We have this aggressive, 8 00:00:42.759 --> 00:00:45.960 almost stubborn curiosity. We just can't accept that something is 9 00:00:46.039 --> 00:00:46.679 hidden from us. 10 00:00:46.799 --> 00:00:48.560 Right, It's never enough, never, It's. 11 00:00:48.399 --> 00:00:50.000 Not enough to see the mountain range. We have to 12 00:00:50.000 --> 00:00:52.000 see the rocky. So enough to see the rock, we 13 00:00:52.000 --> 00:00:54.280 need to see the crystal lattice, then the molecule, then 14 00:00:54.320 --> 00:00:59.320 the atom. It's this insatiable need to just peel back 15 00:00:59.359 --> 00:01:01.679 the layers of reality until there's nothing left. 16 00:01:02.200 --> 00:01:04.640 And that drive is I mean, it's pretty much the 17 00:01:04.719 --> 00:01:07.519 engine of our entire technological history. You can draw a 18 00:01:07.519 --> 00:01:11.480 straight line of ambition from the very first clunky glass 19 00:01:11.560 --> 00:01:14.319 lenses back in the sixteen hundreds, which were basically just 20 00:01:14.359 --> 00:01:17.079 polished pebbles, all the way to the smartphone camera in 21 00:01:17.120 --> 00:01:20.040 your pocket, which has more computing power than the Apollo missions. 22 00:01:20.079 --> 00:01:21.599 Incredible when you think about it, that way. 23 00:01:21.680 --> 00:01:24.280 And you can extend that line even further out to 24 00:01:24.319 --> 00:01:27.239 the James Webb Space Telescope sitting out at lagrange point two. 25 00:01:27.280 --> 00:01:30.719 It's all the same impulse reveal the hidden structure. We 26 00:01:30.959 --> 00:01:31.879 just want to see more. 27 00:01:32.040 --> 00:01:36.439 It is. It's this universal desire for I guess higher resolution. 28 00:01:36.760 --> 00:01:37.200 Yeah. 29 00:01:37.359 --> 00:01:40.159 But here's the thing, and this is really the central 30 00:01:40.200 --> 00:01:43.159 conflict of what we're talking about today. For the longest time, 31 00:01:43.200 --> 00:01:45.319 we thought there was a hard stop, a wall, a 32 00:01:45.359 --> 00:01:48.799 physical do not enter sign put up by the universe itself. 33 00:01:49.319 --> 00:01:51.719 We assumed that as you try to look at smaller 34 00:01:51.760 --> 00:01:55.480 and smaller things, specifically when you're using light to do it, 35 00:01:56.079 --> 00:01:58.680 you eventually hit a fundamental boundary, a wall where the 36 00:01:58.719 --> 00:02:02.319 picture just goes and no amount of zooming in is 37 00:02:02.319 --> 00:02:02.920 going to fix it. 38 00:02:03.079 --> 00:02:05.480 That's exactly right, and for a long long time that 39 00:02:05.560 --> 00:02:09.159 boundary seemed absolute. It wasn't a failure of our engineering 40 00:02:09.240 --> 00:02:10.520 or not having enough budget. 41 00:02:10.680 --> 00:02:12.520 It wasn't a skill issue, no, not at all. 42 00:02:12.560 --> 00:02:15.840 It was a failure of the medium itself. The widely 43 00:02:15.919 --> 00:02:18.719 held belief in physics was that the very nature of 44 00:02:18.840 --> 00:02:21.400 light prevented us from seeing the building blocks of matter. 45 00:02:21.680 --> 00:02:25.680 We are talking about Adams the assumption was you cannot 46 00:02:25.719 --> 00:02:26.439 see an atom with. 47 00:02:26.439 --> 00:02:29.719 Light period, which is such a depressing thought. Yeah, but 48 00:02:29.759 --> 00:02:32.400 as you and I both know, impossible is usually just 49 00:02:32.439 --> 00:02:34.919 a challenge waiting for the right group of researchers. Because 50 00:02:34.919 --> 00:02:38.080 today we're discussing a massive breakthrough, something that happened just 51 00:02:38.120 --> 00:02:41.719 a few days ago on January thirty, twenty twenty six. 52 00:02:42.000 --> 00:02:46.360 It's a really fascinating development. Researchers from the University of Regensburg, 53 00:02:46.879 --> 00:02:51.280 specifically their Center for Ultrafastinoscopy, and the University of Birmingham 54 00:02:51.639 --> 00:02:54.639 have well, they've effectively smashed right through that wall. 55 00:02:54.879 --> 00:02:57.840 They publish their findings in Nano letters and the headline is, 56 00:02:58.240 --> 00:03:01.319 I mean, it's essentially this, we can now see the unseeable. 57 00:03:01.680 --> 00:03:05.000 They've achieved optical measurements with atomic resolution. 58 00:03:04.960 --> 00:03:08.520 Which, just to be crystal clear, shouldn't be possible, not 59 00:03:08.639 --> 00:03:11.159 if you follow the classical rules of optics. If you 60 00:03:11.199 --> 00:03:14.039 open a textbook from say ten years ago, it would 61 00:03:14.080 --> 00:03:15.240 tell you this is forbidden. 62 00:03:15.560 --> 00:03:18.759 So today our mission is to explore exactly how they 63 00:03:18.759 --> 00:03:21.240 did it, how they managed to see the unseeable. We're 64 00:03:21.240 --> 00:03:23.800 going to look at that impossible barrier they broke the 65 00:03:23.840 --> 00:03:27.719 surprise discovery, and it involves quantum mechanics that acted as 66 00:03:27.759 --> 00:03:31.199 the key, and and why this changes material science forever. 67 00:03:31.400 --> 00:03:33.240 Yeah, we need to really get into the weeds of 68 00:03:33.280 --> 00:03:35.800 how they managed to turn a barrier into a bridge, 69 00:03:35.879 --> 00:03:38.599 because they didn't just break a rule here, they in 70 00:03:38.680 --> 00:03:41.159 a sense, rewrote the entire rule book. 71 00:03:41.199 --> 00:03:43.919 Okay, so let's start with the problem itself. I want 72 00:03:43.919 --> 00:03:46.879 to understand the enemy. Why can't I just take a 73 00:03:47.000 --> 00:03:50.599 really really strong microscope and zoom in until I see 74 00:03:50.639 --> 00:03:54.199 an atom? I mean, we have powerful lenses. We can 75 00:03:54.240 --> 00:03:57.479 see bacteria, we can see cells. What is physically stopping us. 76 00:03:58.039 --> 00:04:00.560 It's not the lens, that's the thing. It's the light. 77 00:04:00.840 --> 00:04:04.000 The light itself, the light itself. You see in our 78 00:04:04.080 --> 00:04:06.400 daily lives, we tend to think of light as a 79 00:04:06.400 --> 00:04:09.719 straight line, like a laser beam or you know, a 80 00:04:09.879 --> 00:04:11.639 rave sunlight coming through the window. 81 00:04:11.960 --> 00:04:12.120 Right. 82 00:04:12.199 --> 00:04:16.519 Yeah, But fundamentally, light behaves as a wave, and waves 83 00:04:16.519 --> 00:04:19.160 have a specific size a wavelength, right. 84 00:04:19.079 --> 00:04:21.720 Like ripples in a pond have a certain distance between 85 00:04:22.120 --> 00:04:23.920 the crests of each wave exactly. 86 00:04:24.399 --> 00:04:26.680 Now, let's stick with that pond analogy for a second. 87 00:04:27.079 --> 00:04:29.240 Imagine you're standing at the edge of a pond and 88 00:04:29.279 --> 00:04:31.639 you want to detect some hidden object in the water 89 00:04:32.040 --> 00:04:34.480 just by watching how the waves bounce off it. Okay, 90 00:04:34.560 --> 00:04:36.319 if you have a large rock in there and the 91 00:04:36.360 --> 00:04:39.399 waves hit it, they bounce back, they scatter. You can 92 00:04:39.439 --> 00:04:41.240 look at the pattern in the water and say, Aha, 93 00:04:41.279 --> 00:04:41.920 there's a rock there. 94 00:04:42.079 --> 00:04:44.839 Sure the wave hits the rock, it gets disturbed, and 95 00:04:44.879 --> 00:04:47.480 I can see that disturbance, simple enough. 96 00:04:47.600 --> 00:04:49.279 But now what if you're trying to find a tiny 97 00:04:49.319 --> 00:04:52.399 marble and the waves you're sending out are these big 98 00:04:52.680 --> 00:04:55.480 rolling swells. Let's say there're a meter between each crest. 99 00:04:56.000 --> 00:04:58.800 What happens when that big wave hits the tiny marble? 100 00:04:59.319 --> 00:05:02.160 Probably nothing, just rolls right over it. The marble isn't 101 00:05:02.199 --> 00:05:05.839 big enough to disturb the wave at all. It's it's 102 00:05:05.879 --> 00:05:07.560 basically invisible to the wave. 103 00:05:07.720 --> 00:05:11.560 Precisely the wave effectively ignores it. And this is what 104 00:05:11.600 --> 00:05:14.560 we call the diffraction limit. Because light is a wave, 105 00:05:14.759 --> 00:05:18.240 you can't focus it purely down to a single geometric point. 106 00:05:18.240 --> 00:05:20.600 It always spreads out a little bit. You just can't 107 00:05:20.639 --> 00:05:22.319 focus it arbitrarily sharply. 108 00:05:22.600 --> 00:05:24.839 So there's a minimum size to the spot you can 109 00:05:24.879 --> 00:05:25.560 make with light. 110 00:05:25.800 --> 00:05:30.160 Yes, And the consequence of that is that conventional optical microscopes, 111 00:05:30.319 --> 00:05:32.680 the kind you might remember from high school biology or 112 00:05:32.759 --> 00:05:35.759 even the really expensive ones in medical labs. They cannot 113 00:05:35.800 --> 00:05:39.240 resolve structures that are smaller than roughly half the wavelength 114 00:05:39.240 --> 00:05:40.160 of the light they're using. 115 00:05:40.240 --> 00:05:42.000 Okay, so let's put some numbers on this to make 116 00:05:42.040 --> 00:05:45.319 it real. Visible light has a wavelength of what somewhere 117 00:05:45.319 --> 00:05:48.399 between four hundred and seven hundred animeters roughly. Yeah, that's 118 00:05:48.399 --> 00:05:52.160 the range, which means the absolute best resolution you can 119 00:05:52.240 --> 00:05:57.639 possibly get with visible light is maybe two hundred animeters. 120 00:05:57.199 --> 00:06:00.439 Best case scenario. Yes, and an atom is atom is 121 00:06:00.439 --> 00:06:04.079 typically in the range of point one two point three nanometers. 122 00:06:04.240 --> 00:06:07.480 Okay, so the scale is completely off. It's not even close. 123 00:06:07.600 --> 00:06:10.360 We are trying to pick up a single sesame seed 124 00:06:10.759 --> 00:06:14.639 with a bulldozer. The lightweights are literally thousands of times 125 00:06:14.680 --> 00:06:16.439 too fat to feel the atom. 126 00:06:16.800 --> 00:06:19.720 That is the perfect way to visualize it. And that's why, 127 00:06:19.759 --> 00:06:22.639 for the longest time, the very building blocks of matter, 128 00:06:22.720 --> 00:06:26.199 the atoms themselves, were simply beyond direct optical observation. We 129 00:06:26.279 --> 00:06:27.879 literally could not see them with light. 130 00:06:28.079 --> 00:06:29.600 Now, I know what some of our listeners are probably 131 00:06:29.600 --> 00:06:33.000 thinking right now, Who cares about light? We have electron microscopes. 132 00:06:33.040 --> 00:06:35.560 I've seen those black and like pictures of atoms from 133 00:06:35.600 --> 00:06:39.319 electron microscopes. So why is this specific breakthrough with light 134 00:06:39.439 --> 00:06:40.120 so important? 135 00:06:40.319 --> 00:06:42.879 That is a really critical distinction. And yes, you're right. 136 00:06:42.920 --> 00:06:46.319 We do have electron microscopes and scanning tunneling microscopes that 137 00:06:46.399 --> 00:06:50.120 use physical probes, and those are amazing, amazing. 138 00:06:49.639 --> 00:06:51.879 Tool, but they have limitations. 139 00:06:51.519 --> 00:06:55.959 Severe limitations. Electron microscopes, for example, often require a high 140 00:06:56.040 --> 00:06:59.160 vacuum that means you can't look at anything that's wet 141 00:06:59.240 --> 00:07:03.279 or alive volatile, so no biology, really not living biology. No, 142 00:07:03.759 --> 00:07:07.360 And the high energy electrons you use can actually damage 143 00:07:07.399 --> 00:07:10.079 or destroy the very sample you're trying to look at. 144 00:07:10.319 --> 00:07:12.759 So you get the picture, but you might kill the 145 00:07:12.759 --> 00:07:14.360 patient in the process often. 146 00:07:14.480 --> 00:07:17.800 Yes, And those physical probes, the scanning ones, are very 147 00:07:17.920 --> 00:07:20.720 very slow. They literally drag a needle across a surface 148 00:07:20.839 --> 00:07:22.120 line by line. 149 00:07:21.759 --> 00:07:24.120 Like an old dot matrix printer, a very. 150 00:07:24.000 --> 00:07:24.720 Very slow one. 151 00:07:24.800 --> 00:07:25.079 Yes. 152 00:07:25.399 --> 00:07:28.800 Light, on the other hand, is fast, it's generally non destructive, 153 00:07:29.199 --> 00:07:32.800 and most importantly, light interacts with materials in unique ways 154 00:07:32.800 --> 00:07:35.879 that tell us about their chemical and electronic properties. If 155 00:07:35.879 --> 00:07:38.000 we could just see atoms with light, we could learn 156 00:07:38.040 --> 00:07:40.639 things that electron microscopes simply cannot tell us. 157 00:07:41.079 --> 00:07:43.399 So the goal has always been this kind of holy grail. 158 00:07:44.040 --> 00:07:46.920 Can we get the resolution of an electron microscope but 159 00:07:47.040 --> 00:07:48.920 with the versatility and the speed of light. 160 00:07:49.120 --> 00:07:51.600 That has been the dream, and that is exactly what 161 00:07:51.720 --> 00:07:54.480 this team from Regensburg and Birmingham went hunting for. 162 00:07:54.839 --> 00:07:57.399 So let's talk about their setup. They knew they couldn't 163 00:07:57.399 --> 00:07:59.720 just use a normal lens because of that diffraction limit 164 00:07:59.720 --> 00:08:03.160 we just talked about. So how did they try to 165 00:08:03.240 --> 00:08:05.040 cheat the system? What was the work around? 166 00:08:05.279 --> 00:08:08.600 Their approach falls under a category of science called near 167 00:08:08.639 --> 00:08:12.639 field optics. The basic idea is, if the problem is 168 00:08:12.639 --> 00:08:14.959 that lightweights are too big when they're traveling through free 169 00:08:15.000 --> 00:08:18.000 space what we call the far field, right, the solution 170 00:08:18.199 --> 00:08:20.800 is to manipulate the light right up against the object 171 00:08:20.839 --> 00:08:21.319 you want. 172 00:08:21.120 --> 00:08:23.639 To look at, so get up close and personal. You 173 00:08:23.759 --> 00:08:26.920 eliminate the travel distance where it can spread out extremely close. 174 00:08:27.000 --> 00:08:30.519 They used a setup that involves a very sharp metal tip. 175 00:08:30.800 --> 00:08:32.759 Now when I say sharp, I don't mean like a 176 00:08:32.840 --> 00:08:35.360 needle you'd sew with. I mean atomically sharp. 177 00:08:35.399 --> 00:08:38.240 Atomically sharp. What does that even mean? In practice? 178 00:08:38.320 --> 00:08:41.320 It means the radius of curvature at the very apex 179 00:08:41.360 --> 00:08:45.279 of this tip is typically about ten nanometers ten animeters. 180 00:08:45.360 --> 00:08:48.919 Okay, for context, a human hair is roughly eighty thousand 181 00:08:48.919 --> 00:08:51.840 to one hundred thousand nanometers wide, So this tip is 182 00:08:52.519 --> 00:08:54.519 thousands of times sharper than a single hair. 183 00:08:54.799 --> 00:08:58.360 It is, and the technique involves bringing this tip extraordinarily 184 00:08:58.399 --> 00:09:01.159 close to the surface of the material they want to study, 185 00:09:01.600 --> 00:09:02.639 hovering just above it. 186 00:09:02.919 --> 00:09:06.360 So they have this nanometer sharp needle floating over a sample. Yeah, 187 00:09:06.759 --> 00:09:09.000 then what do they just shine a light on it 188 00:09:09.039 --> 00:09:09.919 and hope for the best. 189 00:09:10.240 --> 00:09:13.720 Yes, but with a clever twist, they use a continuous 190 00:09:13.759 --> 00:09:17.559 wave laser to illuminate the whole system. Now, normally that 191 00:09:17.679 --> 00:09:19.679 light would just hit the surface and bounce off, and 192 00:09:19.720 --> 00:09:20.840 you'd be stuck with the same. 193 00:09:20.720 --> 00:09:23.679 Old diffraction limit, the bulldozer problem again exactly. 194 00:09:24.120 --> 00:09:27.399 But because that sharp metal tip is there, something really 195 00:09:27.519 --> 00:09:32.840 interesting happens. The system squeezes the infrared light into the 196 00:09:32.879 --> 00:09:34.519 tiny gap between the tip and. 197 00:09:34.440 --> 00:09:38.879 The sample, squeezing light. I love that image. It sounds 198 00:09:38.879 --> 00:09:41.679 like they are physically forcing the light to be smaller 199 00:09:41.759 --> 00:09:44.039 than it wants to be, like putting a corset on 200 00:09:44.080 --> 00:09:44.519 a photon. 201 00:09:44.679 --> 00:09:47.039 That's a fair way to visualize it. It's a phenomenon 202 00:09:47.080 --> 00:09:51.120 called plasmonic nanofocusing. The presence of the metal tip acts 203 00:09:51.120 --> 00:09:54.240 like a lightning rod or an antenna, and it concentrates 204 00:09:54.240 --> 00:09:56.000 the light field right at its apex. 205 00:09:56.159 --> 00:09:56.919 So it's a funnel. 206 00:09:57.080 --> 00:10:00.120 It's a perfect funnel for light. It confines the energy 207 00:10:00.600 --> 00:10:03.720 and by doing this they completely bypass the diffraction limit 208 00:10:03.840 --> 00:10:06.879 because the light isn't traveling freely anymore. It's trapped in 209 00:10:06.960 --> 00:10:08.679 this tiny, tiny cavity. 210 00:10:08.879 --> 00:10:10.799 So by confining the light to the very end of 211 00:10:10.799 --> 00:10:13.919 the tip, the resolution of the picture you take is 212 00:10:14.000 --> 00:10:16.679 no longer determined by the wavelength of the light, but 213 00:10:16.759 --> 00:10:18.480 by the size of the tip exactly. 214 00:10:18.559 --> 00:10:21.639 The resolution becomes roughly the size of the tip's apex. 215 00:10:22.080 --> 00:10:25.360 In this case that's about ten nanometers, which is huge. 216 00:10:25.080 --> 00:10:27.200 Right, I mean, going from two hundred nanometers down to 217 00:10:27.240 --> 00:10:29.039 ten ananimeters is a massive jump. 218 00:10:29.080 --> 00:10:32.559 Oh, it's a dramatic improvement. This technique, in its early 219 00:10:32.600 --> 00:10:36.960 stages is called near field optical tunneling emission, and getting 220 00:10:36.960 --> 00:10:40.639 down to ten nanometers is a massive victory for optical microscopy. 221 00:10:41.080 --> 00:10:43.759 It allows you to see things like large molecules, proteins, 222 00:10:43.799 --> 00:10:44.360 that kind of thing. 223 00:10:44.720 --> 00:10:47.320 But and there is always a butt in these stories, 224 00:10:47.320 --> 00:10:50.559 isn't there always ten nanometers is still not an atom correct? 225 00:10:50.720 --> 00:10:53.480 As we establish, atoms are generally in that zero point 226 00:10:53.519 --> 00:10:57.279 one two point three nanometer range. So while ten nanometers 227 00:10:57.399 --> 00:10:59.919 is incredibly small, it's still about a factor of three 228 00:11:00.000 --> 00:11:02.360 alreaty two coarse to see an individual atom. 229 00:11:02.600 --> 00:11:04.879 It's like trying to type on a smartphone keyboard while 230 00:11:04.879 --> 00:11:08.000 you're wearing boxing gloves. You know the keys are there, 231 00:11:08.200 --> 00:11:11.080 but your finger, or in this case, the tip is 232 00:11:11.159 --> 00:11:12.559 just too wide to hit one at a time. 233 00:11:12.639 --> 00:11:15.480 That is a perfect analogy. If you scan a grid 234 00:11:15.480 --> 00:11:18.720 of atoms with a ten nanimeter wide tip, you are 235 00:11:18.759 --> 00:11:22.720 effectively averaging the signal from dozens, maybe hundreds of atoms, 236 00:11:22.759 --> 00:11:25.000 all at once. The image you get just looks like 237 00:11:25.039 --> 00:11:28.240 a smooth surface. You can't see the individual bumps, you 238 00:11:28.240 --> 00:11:29.720 can't see the lattice structure. 239 00:11:29.960 --> 00:11:33.559 So up until January thirtieth of this year, the consensus 240 00:11:33.639 --> 00:11:36.120 was essentially this is as good as it gets. You 241 00:11:36.120 --> 00:11:38.159 can squeeze light down to the size of your tip, 242 00:11:38.399 --> 00:11:40.480 but you can't really make the tip smaller than about 243 00:11:40.519 --> 00:11:44.519 ten nanimeters because well, metal isn't infinitely strong. You run 244 00:11:44.519 --> 00:11:45.960 into physical limits, right. 245 00:11:45.840 --> 00:11:48.759 You run into structural limits of the material itself. So 246 00:11:48.799 --> 00:11:51.200 they had a great microftote had an amazing microscope, but 247 00:11:51.240 --> 00:11:52.960 it wasn't an atomic microscope. 248 00:11:53.279 --> 00:11:56.200 And this is where the story gets really good because 249 00:11:56.240 --> 00:11:59.080 typically in science, when you hit a physical limit, like 250 00:11:59.120 --> 00:12:01.399 the size of your tool, you sort of accept it 251 00:12:01.440 --> 00:12:04.879 and work around it. But this team, led by the 252 00:12:04.919 --> 00:12:08.879 researchers at the Regensburg Center for Ultra Fastinoscopy, they were 253 00:12:08.919 --> 00:12:10.840 determined to find the absolute limit. 254 00:12:11.000 --> 00:12:13.919 They wanted to know what happens if you just keep pushing, So. 255 00:12:13.840 --> 00:12:16.320 They started moving the tip closer and closer to the 256 00:12:16.399 --> 00:12:19.600 surface just to see what would happen to that confined 257 00:12:19.679 --> 00:12:22.480 light as the gap got smaller and smaller. 258 00:12:22.679 --> 00:12:26.000 Yeah, and we are talking about closing the gap down 259 00:12:26.039 --> 00:12:30.799 to atomic dimensions. Here they are hovering a sharp metal spike, 260 00:12:31.200 --> 00:12:33.919 maybe a single atom's width away from the surface. 261 00:12:34.080 --> 00:12:36.919 That sounds incredibly risky. Yeah, And what happens if you 262 00:12:37.000 --> 00:12:39.480 touch the surface? Do you just crash the machine? 263 00:12:39.519 --> 00:12:42.080 You absolutely crash the tip, you blunt it, you ruin 264 00:12:42.159 --> 00:12:44.840 the sample. The experiments over. It's like trying to fly 265 00:12:44.960 --> 00:12:47.639 a helicopter six inches off the ground in the middle 266 00:12:47.639 --> 00:12:50.639 of a hurricane. It requires an immense amount of stability 267 00:12:50.679 --> 00:12:51.679 and precision, but. 268 00:12:51.679 --> 00:12:54.720 They did it. They kept reducing the distance between the 269 00:12:54.720 --> 00:12:57.440 tip and the sample until it was comparable to the 270 00:12:57.480 --> 00:12:59.519 spacing between individual atoms. 271 00:13:00.120 --> 00:13:03.440 This is where the AHA moment happens. I was reading 272 00:13:03.480 --> 00:13:06.480 the account from Felix Shiell, one of the lead authors 273 00:13:06.480 --> 00:13:09.440 from the University of Regensburg. He described it almost like 274 00:13:09.480 --> 00:13:09.919 a shock. 275 00:13:10.279 --> 00:13:13.399 Yeah. He noted that at these very very small distances, 276 00:13:13.919 --> 00:13:16.559 the signal, the light that was coming back from that 277 00:13:16.679 --> 00:13:20.279 tiny gap, it just shot up dramatically. It wasn't a 278 00:13:20.320 --> 00:13:22.600 gradual increase, it was a massive spike. 279 00:13:22.679 --> 00:13:24.879 And he said, and this is the quote, we didn't 280 00:13:24.919 --> 00:13:28.000 immediately understand what was happening. That is the most exciting 281 00:13:28.080 --> 00:13:30.759 sentence in all of science. It's never eureka, it's. 282 00:13:30.840 --> 00:13:34.360 Huh, that's weird. That's weird. Usually proceeds either a Nobel 283 00:13:34.399 --> 00:13:37.879 prize or a laboratory fire, in this case, hopefully the former. 284 00:13:38.000 --> 00:13:41.919 Hopefully they realized that when that signal spiked, the resolution 285 00:13:42.039 --> 00:13:44.879 of their image suddenly sharpened. I mean drastically. 286 00:13:44.960 --> 00:13:47.320 You weren't seeing those ten nanimeter blobs anymore. 287 00:13:47.399 --> 00:13:52.000 No, they were suddenly resolving features down to point one nanimeters. 288 00:13:51.519 --> 00:13:54.320 Zero point one nanometers, that is the atomic scale. They 289 00:13:54.320 --> 00:13:56.720 were suddenly seeing the atoms they were. 290 00:13:56.879 --> 00:14:00.639 They had inadvertently accidentally broken the barrier. But the question, 291 00:14:00.720 --> 00:14:04.639 of course, was how their tip was still ten nanometers wide. 292 00:14:05.039 --> 00:14:07.840 How could a ten nanometer tip possibly take a zero 293 00:14:07.960 --> 00:14:09.440 point one nanometer picture? 294 00:14:09.759 --> 00:14:09.960 Right? 295 00:14:10.000 --> 00:14:12.320 I mean, let's go back to our boxing glove analogy. Yeah, 296 00:14:12.360 --> 00:14:14.559 how did the boxing gloves suddenly turn into a needle. 297 00:14:14.759 --> 00:14:15.679 The glove didn't. 298 00:14:15.519 --> 00:14:18.399 Change size, the glove didn't change, but the physics of 299 00:14:18.440 --> 00:14:21.360 the interaction changed. And this is why we're here today. 300 00:14:21.919 --> 00:14:24.120 The answer lies in quantum mechanics. 301 00:14:24.200 --> 00:14:26.159 Okay, let's unpack this. This is where we need to 302 00:14:26.159 --> 00:14:29.519 be really careful, because quantum mechanics is usually where our 303 00:14:29.559 --> 00:14:32.919 everyday intuition goes to die. How does a quantum effect 304 00:14:32.919 --> 00:14:36.159 turn a ten nanometer flashlight into an atomic spotlight? 305 00:14:36.480 --> 00:14:39.000 It all has to do with what happens in that tiny, 306 00:14:39.080 --> 00:14:41.759 tiny gap between the tip and the sample. Now, in 307 00:14:41.799 --> 00:14:44.799 the classical world, the world of baseballs and planets, if 308 00:14:44.799 --> 00:14:46.519 you hold a ball close to a wall, but you 309 00:14:46.559 --> 00:14:49.000 don't touch it, the ball stays in your hand, there 310 00:14:49.080 --> 00:14:50.639 is a gap. Nothing closses it. 311 00:14:50.799 --> 00:14:54.039 Right, almost touching is still not touching, the circuit is open, 312 00:14:54.279 --> 00:14:55.480 no electricity flows. 313 00:14:55.679 --> 00:14:59.399 But in the quantum world, things are well, they're fuzzier. 314 00:15:00.240 --> 00:15:03.799 Electrons Specifically, they have a probability of being in different 315 00:15:03.799 --> 00:15:06.919 places at once. They aren't just hard little marbles. They 316 00:15:06.919 --> 00:15:09.919 are more like probability clouds. Okay, And if you bring 317 00:15:10.080 --> 00:15:13.159 two conductive materials close enough together, like the metal tip 318 00:15:13.159 --> 00:15:16.360 and the sample surface, the edge of the electron cloud 319 00:15:16.440 --> 00:15:19.080 in the tip starts to actually overlap with the sample. 320 00:15:19.240 --> 00:15:23.120 So even though there is still empty space between them, physically, 321 00:15:23.600 --> 00:15:26.519 the electron can sort of bridge that gap. 322 00:15:26.799 --> 00:15:30.240 Exactly, there is a non zero probability that an electron 323 00:15:30.279 --> 00:15:33.399 can simply appear on the other side. It doesn't travel 324 00:15:33.399 --> 00:15:36.679 through the space, It tunnels through the barrier of empty space. 325 00:15:36.720 --> 00:15:38.159 It's a purely quantum effect. 326 00:15:38.200 --> 00:15:40.879 Okay, so we have electrons tunneling. I've heard of scanning 327 00:15:40.960 --> 00:15:44.440 tunneling microscopes, so that part makes sense. But tunneling usually 328 00:15:44.480 --> 00:15:47.120 just creates an electrical current. How does that create light? 329 00:15:47.480 --> 00:15:51.120 And more importantly, how does it create this super resolution light. 330 00:15:51.480 --> 00:15:53.799 This is where the laser comes back into play. Remember 331 00:15:53.840 --> 00:15:56.720 they are constantly shining that infrared laser on the whole system. 332 00:15:56.960 --> 00:15:59.840 Light is an electromagnetic wave. That means it consists of 333 00:15:59.840 --> 00:16:03.799 an an oscillating electric field. It pushes and it pulls 334 00:16:03.799 --> 00:16:05.759 on charged particles like electrons. 335 00:16:06.039 --> 00:16:09.799 So the light is providing this rhythmic push pull push pull. 336 00:16:09.919 --> 00:16:15.000 Correct, This infrared light creates a continuously oscillating electric field 337 00:16:15.159 --> 00:16:18.000 right in that tiny gap, and it acts as a driver. 338 00:16:18.480 --> 00:16:21.559 This field forces the electrons to leap back and forth 339 00:16:21.600 --> 00:16:24.000 between the apex atom of the tip and the sample. 340 00:16:24.279 --> 00:16:26.519 So the light is like a pump or maybe a 341 00:16:26.519 --> 00:16:28.639 conductor's baton, setting the rhythm it. 342 00:16:28.639 --> 00:16:30.679 Conductor's baton is a great way to think of it. 343 00:16:30.679 --> 00:16:33.360 It drives the rhythm. The electrons are tunneling back and forth, 344 00:16:33.399 --> 00:16:35.919 but they're doing it in perfect time with the frequency 345 00:16:35.919 --> 00:16:36.679 of the laser light. 346 00:16:36.840 --> 00:16:39.559 Okay, so we have electrons jumping back and forth across 347 00:16:39.559 --> 00:16:42.360 this gap in time with the laser. I'm still missing 348 00:16:42.360 --> 00:16:44.720 the last step. How does that help us see anything. 349 00:16:45.039 --> 00:16:46.879 This is where the antenna analogy they use in the 350 00:16:46.879 --> 00:16:49.519 paper comes in, and it's perfect. Think about how a 351 00:16:49.559 --> 00:16:52.840 simple radio antenna works. You drive electrons up and down 352 00:16:52.879 --> 00:16:55.720 a metal rod with an electrical signal, and that acceleration 353 00:16:55.799 --> 00:16:59.960 of electrons generates radio waves, it generates an electromagnetic signal. 354 00:17:00.559 --> 00:17:03.799 Moving electrons create electromagnetic waves. That's physics, one. 355 00:17:03.759 --> 00:17:07.400 On one right exactly now, in this experiment, the electrons 356 00:17:07.440 --> 00:17:09.920 that are tunneling back and forth between the tip and 357 00:17:09.960 --> 00:17:13.400 the sample, they're doing the exact same thing. They are 358 00:17:13.440 --> 00:17:18.079 acting like a tiny, single atom sized antenna, and their 359 00:17:18.119 --> 00:17:22.079 motion produces its own faint electromagnetic signal, a little pulse 360 00:17:22.119 --> 00:17:22.440 of light. 361 00:17:22.599 --> 00:17:24.640 Essentially, wait a second, stop, this is the part that 362 00:17:24.680 --> 00:17:27.319 I want to make absolutely sure I'm getting the light 363 00:17:27.359 --> 00:17:30.519 that they are detecting. It isn't the laser light bouncing 364 00:17:30.559 --> 00:17:31.079 off the atom. 365 00:17:31.279 --> 00:17:35.000 No, and that is the absolute critical distinction. The light 366 00:17:35.079 --> 00:17:38.039 they detect is what they call the near field optical 367 00:17:38.119 --> 00:17:41.039 tunneling emission. It is light that is generated by the 368 00:17:41.039 --> 00:17:43.400 electrons motion as it tunnels back and forth. 369 00:17:43.480 --> 00:17:46.079 That is mind blowing. So the laser isn't the illumination 370 00:17:46.559 --> 00:17:49.559 the lasers the engine. The electron itself is the light bulb. 371 00:17:49.640 --> 00:17:51.559 That is a beautiful way to put it. The laser 372 00:17:51.640 --> 00:17:54.720 drives the electron, and the electron then broadcasts its own 373 00:17:54.720 --> 00:17:56.119 position by emitting light. 374 00:17:56.359 --> 00:17:59.960 Okay, okay, but why does this solve the fat finger problem? 375 00:18:00.079 --> 00:18:04.759 The boxing glove problem. Why is the resolution so unbelievably. 376 00:18:04.119 --> 00:18:08.279 Good Because quantum tunneling is incredibly sensitive to distance, I 377 00:18:08.319 --> 00:18:11.680 mean exponentially sensitive. If you move the tip just a 378 00:18:11.759 --> 00:18:14.759 tiny tiny bit further away, even just half an atom's 379 00:18:14.759 --> 00:18:18.519 with the probability of an electron tunneling drops to almost zero. 380 00:18:18.720 --> 00:18:19.559 It just stops. 381 00:18:19.759 --> 00:18:22.839 So the tunneling only happens at the absolute closest point 382 00:18:22.839 --> 00:18:24.000 between a tip and the sample. 383 00:18:24.160 --> 00:18:27.680 Yes, think about the geometry of the tip. It's a curve, right, Yeah, 384 00:18:27.799 --> 00:18:30.880 even though the metal tip is ten nanimeters wide. Overall, 385 00:18:31.279 --> 00:18:33.559 the only place that is close enough to the sample 386 00:18:33.640 --> 00:18:36.400 to allow tunneling is the single atom at the very 387 00:18:36.519 --> 00:18:39.440 very apex of that curve. The atoms right next to 388 00:18:39.480 --> 00:18:41.759 it on the tip are just slightly further away, and 389 00:18:41.839 --> 00:18:43.839 for tunneling, slightly is everything. 390 00:18:44.000 --> 00:18:46.519 So the active part of the sensor effectively shrinks from 391 00:18:46.519 --> 00:18:49.400 the whole ten nanimeter tip down to just that one 392 00:18:49.480 --> 00:18:50.359 final atom. 393 00:18:50.079 --> 00:18:53.160 At the point precisely. The rest of the tip is silent, 394 00:18:53.240 --> 00:18:56.319 it's too far away. Only that one single atom is 395 00:18:56.359 --> 00:18:59.359 broadcasting the signal. Yeah, that is how they get point 396 00:18:59.359 --> 00:19:01.759 one nimes resolution from a ten nanimeter object. 397 00:19:01.799 --> 00:19:04.960 That is just it's incredibly clever. You're using the geometry 398 00:19:04.960 --> 00:19:08.119 and the rules of quantum probability to filter out everything 399 00:19:08.240 --> 00:19:09.880 except the signal from a single point. 400 00:19:10.200 --> 00:19:13.440 It creates a virtual probe that is much much smaller 401 00:19:13.480 --> 00:19:15.039