WEBVTT 1 00:00:01.480 --> 00:00:05.599 Welcome to the quark 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 00:00:27.600 --> 00:00:31.640 Okay, so let's start with a box. A box, Yeah, 6 00:00:31.679 --> 00:00:33.920 the box. I know you've heard the story a thousand times, 7 00:00:34.359 --> 00:00:37.119 but we have to start here. Right inside this box, 8 00:00:37.159 --> 00:00:37.520 there's a. 9 00:00:37.479 --> 00:00:40.399 Cat and a pretty grim little device. 10 00:00:40.479 --> 00:00:44.439 Oh it's diabolical, A single radioactive atom that might decay, 11 00:00:44.920 --> 00:00:47.960 a Geiger counter to detect it, and a hammer that, 12 00:00:48.159 --> 00:00:50.479 if triggered, smashes a vial of poison. 13 00:00:50.759 --> 00:00:53.200 It is probably the most famous and definitely the most 14 00:00:53.240 --> 00:00:56.280 morbid thought experiment in all of science exactly. 15 00:00:56.320 --> 00:00:58.640 And the punchline, the thing everyone kind of knows is 16 00:00:58.640 --> 00:01:01.679 that until you open that box, the atom is in 17 00:01:01.719 --> 00:01:05.439 this weird state of both decayed and not decayed, a superposition, 18 00:01:05.840 --> 00:01:08.159 so the poison is both released and not released. 19 00:01:08.280 --> 00:01:08.480 Yeah. 20 00:01:08.480 --> 00:01:12.040 And the cat, well, the cats somehow simultaneously alive and dead. 21 00:01:12.200 --> 00:01:15.920 Schrodinger's cat, that's the poster child for quantum mechanics. Is weird. 22 00:01:16.040 --> 00:01:18.000 It really is, and for decades, I mean That's all 23 00:01:18.040 --> 00:01:20.719 it was, wasn't It was like a philosophical party trick, 24 00:01:21.000 --> 00:01:23.480 something to highlight the absurdity of it all it was. 25 00:01:23.599 --> 00:01:25.519 It was a paradox, to show that the rules of 26 00:01:25.519 --> 00:01:28.599 the tiny quantum world made no sense when you scaled 27 00:01:28.640 --> 00:01:31.159 them up to our world, the cats and boxes. 28 00:01:31.519 --> 00:01:34.280 It felt like an abstraction, something for physicists to argue 29 00:01:34.280 --> 00:01:34.640 about on. 30 00:01:34.640 --> 00:01:37.159 A blackboard, right, not for the real world. 31 00:01:37.239 --> 00:01:39.239 But and this is the whole point of our conversation 32 00:01:39.280 --> 00:01:43.079 today on February second, twenty twenty six, that's not the 33 00:01:43.120 --> 00:01:46.319 story anymore. That idea that it's just a weird puzzle, 34 00:01:46.400 --> 00:01:47.200 it's outdated. 35 00:01:47.519 --> 00:01:50.879 It's completely changed. We've gone from the blackboard to well, 36 00:01:51.040 --> 00:01:51.719 the motherboard. 37 00:01:51.840 --> 00:01:54.680 Yeah, we're not talking about a hypothetical cat anymore. We 38 00:01:54.719 --> 00:01:58.560 are talking about the invisible engine powering I mean pretty 39 00:01:58.599 --> 00:02:02.640 much the entire modern world. The weirdness isn't a bug. 40 00:02:03.239 --> 00:02:05.239 It turns out it's the operating system. 41 00:02:05.280 --> 00:02:06.400 That's a perfect way to put it. 42 00:02:06.439 --> 00:02:08.719 And what's prompting This is a brand new piece that 43 00:02:08.800 --> 00:02:11.360 just came out in the journal Science. It's a perspective 44 00:02:11.400 --> 00:02:14.879 by doctor Marlin Scully and the title just says it all. 45 00:02:15.759 --> 00:02:18.800 Its started with a cat how one hundred years of 46 00:02:18.879 --> 00:02:21.039 quantum weirdness powers today's tech. 47 00:02:21.120 --> 00:02:23.840 And we should say doctor Scully is the perfect person 48 00:02:23.919 --> 00:02:26.400 to be writing this. He's not just a historian here. 49 00:02:26.680 --> 00:02:28.960 He's a major figure in the field. Who is He's 50 00:02:28.960 --> 00:02:31.280 a distinguished professor at Texas A and M. He's got 51 00:02:31.280 --> 00:02:35.759 an affiliation with Princeton. I mean, if you study quantum optics, 52 00:02:35.759 --> 00:02:38.360 you've probably read his textbook. He's one of the people 53 00:02:38.680 --> 00:02:42.840 who helped build the bridge from the old strange theory 54 00:02:43.280 --> 00:02:45.759 to the new practical applications. 55 00:02:45.840 --> 00:02:47.960 So he's seen the whole transition. 56 00:02:47.639 --> 00:02:49.599 He's lived it, he's helped cause it. 57 00:02:50.080 --> 00:02:53.120 Okay, so our mission today is to trace that journey. 58 00:02:53.319 --> 00:02:56.039 We're going to go back one hundred years to when 59 00:02:56.439 --> 00:02:58.240 the smartest people on the planet. 60 00:02:57.960 --> 00:03:00.319 Were just baffled, completely baffled. 61 00:03:00.000 --> 00:03:02.759 And bring it forward to today where we use that 62 00:03:02.879 --> 00:03:06.800 bafflement to build things that honestly feel a lot like magic. 63 00:03:06.919 --> 00:03:08.080 And we're going to break it down. We're not just 64 00:03:08.159 --> 00:03:09.680 going to list a bunch of gadgets. We want to 65 00:03:09.719 --> 00:03:13.000 get into the why. We'll talk about a concept called coherence, 66 00:03:13.039 --> 00:03:16.080 which is the secret behind every laser. Okay, we'll dive 67 00:03:16.120 --> 00:03:20.520 into entanglement, the spooky connection that Einstein hated, but that 68 00:03:20.639 --> 00:03:22.120 now protects your bank account. 69 00:03:22.159 --> 00:03:24.520 And you mentioned it even gets into what breaking the 70 00:03:24.560 --> 00:03:25.800 rules of engines. 71 00:03:25.639 --> 00:03:28.439 Breaking the classical rules. Yeah, we'll look at how quantum 72 00:03:28.479 --> 00:03:31.759 mechanics is pushing the limits of energy efficiency, and then 73 00:03:31.800 --> 00:03:33.879 we'll get into some really unexpected. 74 00:03:33.319 --> 00:03:37.319 Places like biology and weather forecasting. I saw that on 75 00:03:37.360 --> 00:03:39.439 the outline and it just seemed out of left field. 76 00:03:39.520 --> 00:03:42.919 It is, But that's how deep this goes. Now. It's everywhere. 77 00:03:42.960 --> 00:03:44.759 So if you want to understand the phone in your hand, 78 00:03:44.879 --> 00:03:47.199 the Internet, even the future of medicine, you kind of 79 00:03:47.199 --> 00:03:48.120 have to understand the cat. 80 00:03:48.599 --> 00:03:49.479 You have to start with the cat. 81 00:03:49.520 --> 00:03:51.479 All right, let's do it. Rewind the clock for us, 82 00:03:51.960 --> 00:03:54.479 take us back to the nineteen twenties. What did the 83 00:03:54.479 --> 00:03:56.199 world of physics feel like then. 84 00:03:56.960 --> 00:04:01.560 In a word, chaos, complete intellectual crisis. 85 00:04:01.680 --> 00:04:05.400 Really, I always pictured these confident guys in tweed jackets. 86 00:04:05.439 --> 00:04:08.120 Well, maybe in nineteen hundred they were confident. At the 87 00:04:08.120 --> 00:04:10.360 turn of the century, there was this feeling that physics 88 00:04:10.439 --> 00:04:12.120 was basically done. 89 00:04:12.240 --> 00:04:14.319 The end of science idea exactly. 90 00:04:14.360 --> 00:04:17.519 You had Newton's laws for gravity and motion, you had 91 00:04:17.800 --> 00:04:22.920 Maxwell's equations for light and electricity. You had thermodynamics. Lord 92 00:04:23.000 --> 00:04:25.879 Kelvin famously said there was nothing new left to discover, 93 00:04:26.079 --> 00:04:27.800 just more and more precise measurements. 94 00:04:27.879 --> 00:04:28.879 Wow was he wrong. 95 00:04:29.160 --> 00:04:33.000 He was spectacularly wrong, because as soon as they started 96 00:04:33.040 --> 00:04:36.079 probing the atom, the whole thing fell apart. All those 97 00:04:36.120 --> 00:04:38.800 beautiful classical rules just broke. 98 00:04:39.079 --> 00:04:41.360 Give me an example, what's the first big crack that 99 00:04:41.439 --> 00:04:42.720 appears the electron? 100 00:04:43.240 --> 00:04:45.160 Okay, so we know an atom has a nucleus in 101 00:04:45.199 --> 00:04:48.439 the middle and electrons buzzing around it. The simple picture 102 00:04:48.680 --> 00:04:49.959 is a tiny solar. 103 00:04:49.639 --> 00:04:51.560 System, right, planets orbiting the Sun. 104 00:04:51.920 --> 00:04:56.680 But an electron is a charged particle, and classical physics 105 00:04:57.360 --> 00:05:01.319 Maxwell's equations are very clear about this. A charged particle 106 00:05:01.480 --> 00:05:04.560 moving in a circle has to radiate energy, it has 107 00:05:04.560 --> 00:05:07.720 to give off light. Okay, so if it's constantly losing energy, 108 00:05:07.920 --> 00:05:10.920 it should slow down, its orbit should decay, and in 109 00:05:10.959 --> 00:05:14.319 a fraction of a second, every electron should spiral into 110 00:05:14.319 --> 00:05:16.959 the nucleus, which would mean every atom in the universe 111 00:05:16.959 --> 00:05:21.000 should instantly collapse. Matters shouldn't exist. You meet this table, 112 00:05:21.160 --> 00:05:24.519 none of it. So clearly something was deeply wrong with 113 00:05:24.560 --> 00:05:25.240 the old rules. 114 00:05:25.319 --> 00:05:27.800 The theory predicted. We shouldn't be here to discuss the theory. 115 00:05:27.920 --> 00:05:29.560 Pretty much bit of a problem. 116 00:05:29.639 --> 00:05:31.800 So who rides to the rescue first. This is where 117 00:05:31.839 --> 00:05:33.319 Neil's Bore comes in, right. 118 00:05:33.360 --> 00:05:39.720 Yes, Neil's Bore from Denmark. He comes along and proposes this. Well, 119 00:05:39.759 --> 00:05:41.920 it was a radical idea. He basically just said the 120 00:05:41.959 --> 00:05:42.920 old rules don't apply. 121 00:05:43.079 --> 00:05:44.040 He just declared it. 122 00:05:44.120 --> 00:05:47.199 He did. He proposed his model, the one we all 123 00:05:47.279 --> 00:05:50.199 drew in high school chemistry, the little solar system with 124 00:05:50.240 --> 00:05:50.959 fixed rings. 125 00:05:51.240 --> 00:05:54.720 Yeah, the nucleus and then shells for the electrons, right, and. 126 00:05:54.680 --> 00:05:57.360 He said electrons can only exist in these specific shells, 127 00:05:57.399 --> 00:06:00.319 these allowed orbits. They can't be in between. They can 128 00:06:00.519 --> 00:06:02.759 jump from one shell to another, but they can't spiral 129 00:06:02.800 --> 00:06:05.040 in Why not? He didn't really have a deep why. 130 00:06:05.519 --> 00:06:08.959 His answer was basically, because if they did, Adams wouldn't exist, 131 00:06:08.959 --> 00:06:11.560 and they clearly do. It was a brilliant patch. It 132 00:06:11.639 --> 00:06:13.879 was a band aid that stopped the bleeding, and it 133 00:06:13.920 --> 00:06:17.600 worked remarkably well for explaining why Adams emit light in 134 00:06:17.759 --> 00:06:18.879 very specific colors. 135 00:06:19.000 --> 00:06:21.160 So it was a good description, but not a fundamental 136 00:06:21.199 --> 00:06:22.240 explanation exactly. 137 00:06:22.240 --> 00:06:25.040 It's set the stage, but the next step, the search 138 00:06:25.079 --> 00:06:27.879 for the real why is where the drama really kicks in. 139 00:06:28.040 --> 00:06:29.959 This is the big clash of the nineteen twenties. 140 00:06:30.040 --> 00:06:32.600 This is Schrodinger versus Heisenberg. 141 00:06:32.160 --> 00:06:36.279 The ultimate physics showdown. And they had completely different approaches 142 00:06:36.319 --> 00:06:38.680 to the problem. I mean fundamentally different philosophies. 143 00:06:38.720 --> 00:06:40.600 Okay, lay it out. Who's in the first corner. 144 00:06:41.040 --> 00:06:43.759 In the first corner, you have the let's say, the 145 00:06:43.800 --> 00:06:48.600 more traditional intuitive thinker, Erwin Schrodinger, the cat guy himself, 146 00:06:48.759 --> 00:06:52.040 the very same. He looked at the electron and said, look, 147 00:06:52.519 --> 00:06:55.240 maybe this whole kind of little ball idea is wrong. 148 00:06:56.040 --> 00:06:58.959 What if the electron isn't a particle at all? What 149 00:06:59.000 --> 00:07:02.319 if it's a wave, a wave of a wave of probability, 150 00:07:02.519 --> 00:07:05.560 a kind of smear of existence. He came up with 151 00:07:05.560 --> 00:07:09.600 the famous shrewding your equation, which describes the electron perfectly 152 00:07:10.160 --> 00:07:13.879 as a wave function. And a lot of physicists love this. 153 00:07:14.199 --> 00:07:16.759 Why because we can picture waves. You can imagine a 154 00:07:16.839 --> 00:07:19.680 ripple on a pond. It felt comfortable, it felt like 155 00:07:19.720 --> 00:07:20.879 something you could visualize. 156 00:07:20.920 --> 00:07:23.360 It's intuitive. Okay, it's not a hard little dot, it's 157 00:07:23.360 --> 00:07:24.199 a fuzzy cloud. 158 00:07:24.360 --> 00:07:26.120 I think that. But in the other corner you have 159 00:07:26.160 --> 00:07:29.959 the young radical Werner. Heisenberg, the abstract guy, the completely 160 00:07:30.000 --> 00:07:33.079 abstract guy. He looked at the data, which were these 161 00:07:33.120 --> 00:07:36.959 tables of numbers about how atoms absorbed in emitted light, 162 00:07:37.360 --> 00:07:40.079 and he basically said, I don't care about your pictures. 163 00:07:40.279 --> 00:07:43.399 I don't care about your intuitive waves. All that matters 164 00:07:43.519 --> 00:07:46.079 is the math that predicts the experimental results. 165 00:07:46.319 --> 00:07:48.360 So you just focused on the numbers. 166 00:07:48.199 --> 00:07:51.120 Only the numbers. He developed something called matrix mechanics, which was, 167 00:07:51.360 --> 00:07:55.480 I mean, it's just pure abstract linear algebra. Tables, numbers 168 00:07:55.519 --> 00:07:59.240 going in, tables, numbers coming out, no orbits, no waves, 169 00:07:59.279 --> 00:08:00.519 nothing to picture in your head. 170 00:08:00.560 --> 00:08:02.759 And I'm guessing these two cams did not get along. 171 00:08:02.879 --> 00:08:06.600 They hated each other's theories, I mean truly. Schrodinger called 172 00:08:06.600 --> 00:08:13.279 Heisenberg's math repulsive and monstrous. Wow. And Heisenberg thought Schrodinger's 173 00:08:13.319 --> 00:08:17.000 wave idea was I think the quote is sentimental trash. 174 00:08:17.279 --> 00:08:19.399 He thought it was a cowardly attempt to stuff the 175 00:08:19.439 --> 00:08:22.680 weird new quantum reality back into an old classical box. 176 00:08:22.759 --> 00:08:24.720 It sounds like an argument between an artist and an 177 00:08:24.759 --> 00:08:27.000 accountant over how to describe a painting. 178 00:08:27.079 --> 00:08:29.519 That's a fantastic analogy. One is talking about the feeling 179 00:08:29.560 --> 00:08:32.559 in the form the others talking about the pigment codes 180 00:08:32.559 --> 00:08:33.720 and the canvas dimensions. 181 00:08:34.039 --> 00:08:34.759 So who won? 182 00:08:35.000 --> 00:08:38.360 That's the amazing part. They both did. It was eventually 183 00:08:38.399 --> 00:08:44.960 proven that their two different mathematical formalisms were actually identical. 184 00:08:45.000 --> 00:08:47.600 There were just two different languages describing the exact same. 185 00:08:47.440 --> 00:08:51.600 Thing precisely, and the merger of those ideas that's what 186 00:08:51.639 --> 00:08:55.039 gave us modern quantum field theory, the single most successful, 187 00:08:55.240 --> 00:08:58.799 most precisely tested theory in the entire history of science. 188 00:08:59.200 --> 00:09:02.039 But in this is the key point from doctor Scully's article. 189 00:09:02.679 --> 00:09:04.879 For a long long time, this was all just about 190 00:09:04.919 --> 00:09:08.519 describing things. It was about explaining why the atom doesn't collapse. 191 00:09:08.759 --> 00:09:11.759 Yes, it was passive. We were observers. We were looking 192 00:09:11.759 --> 00:09:14.360 at the quantum world and saying, wow, isn't that weird. 193 00:09:14.679 --> 00:09:16.399 Let's write down the math for the weirdness. 194 00:09:16.639 --> 00:09:19.440 But the big shift, the centennial we're sort of celebrating here, 195 00:09:19.600 --> 00:09:24.200 is moving from observation to what application utilization. 196 00:09:24.360 --> 00:09:26.240 We stopped just looking at the electron and we started 197 00:09:26.279 --> 00:09:28.559 putting it to work. As Kelly says in his piece, 198 00:09:28.799 --> 00:09:31.360 it started as a way to explain tiny particles, but 199 00:09:31.480 --> 00:09:34.120 now it's driving innovations that were just I mean, they 200 00:09:34.120 --> 00:09:36.000 were unimaginable the generation to go. 201 00:09:36.200 --> 00:09:38.200 So we took the weirdness, the stuff that made them 202 00:09:38.200 --> 00:09:40.799 all argue, the paradoxes, all of it. 203 00:09:40.840 --> 00:09:44.000 The uncertainty, the superposition, the spookiness. 204 00:09:43.360 --> 00:09:46.159 And we realized they weren't problems, they were features. 205 00:09:46.200 --> 00:09:49.399 They were tools, the best tools nature ever gave us. 206 00:09:49.519 --> 00:09:52.360 Okay, so let's get into those tools. Doctor Scully breaks 207 00:09:52.360 --> 00:09:54.480 it down into three big concepts. Let's start with the 208 00:09:54.480 --> 00:09:57.840 first one. Coherence. I have to admit when I hear 209 00:09:57.879 --> 00:09:59.759 that word, I just think of an argument that makes sense. 210 00:10:00.039 --> 00:10:00.919 I don't think physics. 211 00:10:01.080 --> 00:10:04.639 It's a fair point. Yeah, But in physics, coherence is 212 00:10:04.679 --> 00:10:09.480 really about synchronization harmony. 213 00:10:09.759 --> 00:10:10.039 Okay. 214 00:10:10.279 --> 00:10:13.519 To get it, you have to first picture what normal 215 00:10:13.759 --> 00:10:17.159 everyday light is like. Think about a regular old incandescent 216 00:10:17.240 --> 00:10:17.679 light bulb. 217 00:10:17.759 --> 00:10:19.679 Okay, got it. It's on, it's giving off light. 218 00:10:19.799 --> 00:10:23.639 But at the atomic level, inside that filament, it's absolute chaos. 219 00:10:23.720 --> 00:10:26.679 The atoms are hot, they're jiggling around randomly. One atom 220 00:10:26.720 --> 00:10:29.720 spits out a photon, a particle of light going left. 221 00:10:29.720 --> 00:10:32.240 A nanosecond later, another one spits when out going right, 222 00:10:32.320 --> 00:10:32.799 and they're. 223 00:10:32.600 --> 00:10:35.039 All different colors, lightly exactly. 224 00:10:34.679 --> 00:10:38.159 Different phases, different directions, different frequencies. The light waves are 225 00:10:38.159 --> 00:10:40.480 all jumbled up and out of sink. It's noise. 226 00:10:40.639 --> 00:10:42.960 It's like a huge crowd of people all talking at once. 227 00:10:43.399 --> 00:10:48.159 That's the perfect analogy. It's a noisy, disorganized crowd that 228 00:10:48.279 --> 00:10:49.600 is incoherent light. 229 00:10:49.759 --> 00:10:50.960 So what's coherent light? 230 00:10:51.600 --> 00:10:54.559 Coherent light is when you somehow manage to grab every 231 00:10:54.600 --> 00:10:57.360 single one of those atoms and force them to do 232 00:10:57.399 --> 00:10:59.679 the exact same thing at the exact same time. 233 00:11:00.000 --> 00:11:01.480 Turn the crowd into a choir. 234 00:11:01.559 --> 00:11:06.120 A perfectly disciplined, perfectly synchronized choir. Every single light wave 235 00:11:06.200 --> 00:11:09.919 is marching in lockstep, same frequency, same phase, same direction. 236 00:11:10.320 --> 00:11:12.399 The peaks of the waves lineup, the troughs of the 237 00:11:12.399 --> 00:11:13.120 waves lineup. 238 00:11:13.159 --> 00:11:14.559 And when you do that, what do you get. 239 00:11:14.720 --> 00:11:16.320 You don't get a light bulb, You get a laser. 240 00:11:16.559 --> 00:11:19.240 The laser. It's funny it lasers feel so normal now 241 00:11:19.279 --> 00:11:22.080 they're in barcode scanners. My cat chase is a laser pointer. 242 00:11:22.159 --> 00:11:23.279 It feels like old tech. 243 00:11:23.440 --> 00:11:26.159 It's totally ubiquitous. Yeah, but we can't lease sight of 244 00:11:26.200 --> 00:11:29.360 how completely impossible it seemed. I mean, when the idea 245 00:11:29.440 --> 00:11:32.879 was first proposed based on an insight from Einstein, a 246 00:11:32.879 --> 00:11:35.679 lot of top physicists said it was practically impossible. 247 00:11:35.879 --> 00:11:37.120 Why what was the barrier? 248 00:11:37.840 --> 00:11:41.799 They just thought that nature's tendency towards disorder, towards chaos, 249 00:11:42.080 --> 00:11:45.639 towards that noisy crowd would always win. They didn't think 250 00:11:45.639 --> 00:11:47.639 you could ever impose that much quantum order on a 251 00:11:47.679 --> 00:11:48.559 real world system. 252 00:11:48.759 --> 00:11:49.320 But we did. 253 00:11:49.480 --> 00:11:52.639 We did in nineteen sixty. And that coherence, that order 254 00:11:53.039 --> 00:11:56.159 is what gives a laser. It's almost magical properties because 255 00:11:56.159 --> 00:11:59.960 all the waves are working together. The beam is incredibly intense, 256 00:12:00.480 --> 00:12:03.120 and it doesn't spread out like light from a flashlight. 257 00:12:03.200 --> 00:12:05.200 It stays in a tight straight line. 258 00:12:04.919 --> 00:12:08.159 A phenomenally tight line. I mean, we literally bounce lasers 259 00:12:08.159 --> 00:12:10.879 off of reflectors that the Apollo astronauts left on the 260 00:12:10.919 --> 00:12:13.799 Moon to measure the Earth Moon distance down to the millimeter. 261 00:12:14.000 --> 00:12:15.240 You can't do that with a flashlight. 262 00:12:15.399 --> 00:12:19.559 Okay, that's impressive, But what about the everyday stuff. Scully mentions, Well, the. 263 00:12:19.519 --> 00:12:23.360 Barcode scanner is the most famous, simple one, but think bigger. 264 00:12:23.639 --> 00:12:27.639 Think about medicine, a lis I searcher. Exactly, we are 265 00:12:27.759 --> 00:12:31.360 using a blade made of pure coherent light to reshape 266 00:12:31.399 --> 00:12:35.840 the human cornea, to vaporize tissue with microscopic precision that 267 00:12:35.919 --> 00:12:37.879 is only possible because of quantum coherence. 268 00:12:38.000 --> 00:12:40.279 Or what about the Internet itself? The whole thing runs 269 00:12:40.279 --> 00:12:41.519 on fiber optic. 270 00:12:41.399 --> 00:12:44.600 Billions of miles of glass fiber with pulses of coherent 271 00:12:44.639 --> 00:12:48.600 laser light flashing through them. Well, carrying this conversation right now, 272 00:12:48.679 --> 00:12:51.759 all of human knowledge flying around the globe is ordered photons. 273 00:12:52.080 --> 00:12:54.919 It's mind boggling that the solution to that nineteen twenties 274 00:12:55.000 --> 00:12:58.120 argument about waves and particles is the reason I can 275 00:12:58.159 --> 00:12:59.000 stream a movie. 276 00:12:59.120 --> 00:13:01.960 That's pillar number one one. We learned how to tame 277 00:13:02.159 --> 00:13:03.000 the quantum wave. 278 00:13:03.200 --> 00:13:07.440 Okay, pillar one, coherence gives us the laser. Let's move 279 00:13:07.440 --> 00:13:10.799 to pillar two. And this is the one that it's weird. 280 00:13:10.759 --> 00:13:13.440 Entanglement, spooky action at a distance. 281 00:13:13.639 --> 00:13:16.879 I love that Einstein said that it sounds so unscientific. 282 00:13:16.960 --> 00:13:18.200 He just called it spooky. 283 00:13:18.440 --> 00:13:20.600 It shows you how much it bothered him. I mean, 284 00:13:20.639 --> 00:13:23.960 Einstein was a firm believer in what's called locality mean 285 00:13:24.279 --> 00:13:26.279 meaning that if you want to affect something over there, 286 00:13:26.320 --> 00:13:27.879 you have to go over there and touch it, or 287 00:13:27.919 --> 00:13:30.399 you have to send something a baseball, a sound wave, 288 00:13:30.440 --> 00:13:34.399 a beam of light to interact with it, and nothing, nothing, 289 00:13:34.600 --> 00:13:35.799 can travel faster than. 290 00:13:35.759 --> 00:13:37.759 Light, the cosmic speed limit. 291 00:13:37.559 --> 00:13:40.320 The absolute speed limit. But quantum mechanics predicted something that 292 00:13:40.360 --> 00:13:43.360 seemed to violate this. It predicted that you could create 293 00:13:43.360 --> 00:13:47.879 two particles, say two photons, in a special linked state, 294 00:13:48.519 --> 00:13:49.639 an entangled state. 295 00:13:49.720 --> 00:13:50.639 What does that mean linked? 296 00:13:50.919 --> 00:13:54.399 It means they no longer have separate identities. They were 297 00:13:54.399 --> 00:13:59.039 described by a single shared wave function, a single mathematical reality, 298 00:13:59.519 --> 00:14:01.120 even if they're physically separated. 299 00:14:01.240 --> 00:14:03.159 So they're like one object in two different places. 300 00:14:03.200 --> 00:14:05.440 That's a good way to think about it. Their properties 301 00:14:05.440 --> 00:14:08.720 are correlated in a way that classical physics just forbids. 302 00:14:09.240 --> 00:14:11.720 So let's do the classic example. You create a pair 303 00:14:11.799 --> 00:14:14.960 of entangled photons. You send one to Alice in New York. 304 00:14:15.000 --> 00:14:16.320 And the other to Bob on Mars. 305 00:14:16.399 --> 00:14:19.360 Let's go with Mars. Sure, Alice and Bob. So while 306 00:14:19.399 --> 00:14:23.600 these photons are in flight, their properties are undefined. Let's 307 00:14:23.600 --> 00:14:26.759 talk about their polarization, like the orientation of the light wave. 308 00:14:27.480 --> 00:14:31.399 It's not horizontal or vertical. It's in a superposition of both, 309 00:14:31.799 --> 00:14:33.080 a cloud of possibility. 310 00:14:33.159 --> 00:14:35.480 Okay, so it's undecided, right. 311 00:14:35.919 --> 00:14:38.879 But the instant, and I mean the absolute instant that 312 00:14:38.960 --> 00:14:41.679 Alice in New York measures her photon and her detectors 313 00:14:41.679 --> 00:14:46.000 as vertical. She knows with one hundred percent certainty that 314 00:14:46.080 --> 00:14:49.840 Bob's photon on Mars, millions of miles away, has instantly 315 00:14:49.879 --> 00:14:51.759 resolved itself into the horizontal state. 316 00:14:51.960 --> 00:14:54.039 Instantly, not in the time it would take for a 317 00:14:54.120 --> 00:14:56.120 light signal to travel from here to Mars. 318 00:14:56.519 --> 00:15:01.360 Faster than that, infinitely faster, it seems. The collapse of 319 00:15:01.399 --> 00:15:05.039 the wave function appears to be instantaneous across any distance. 320 00:15:05.320 --> 00:15:07.360 I can see why Einstein called that spooky. 321 00:15:07.600 --> 00:15:10.120 He hated it. He thought it meant the theory had 322 00:15:10.120 --> 00:15:13.559 to be incomplete. He argued, there must be some hidden variables, 323 00:15:13.639 --> 00:15:16.519 like secret instructions the particles were carrying with them from 324 00:15:16.519 --> 00:15:17.440 the start. 325 00:15:17.080 --> 00:15:19.799 Like they flipped a coin before they left, and agreed, okay, 326 00:15:19.799 --> 00:15:23.039 if she asks your vertical, and I'm horizontal exactly. 327 00:15:23.440 --> 00:15:25.759 He thought it was a conspiracy, not a real connection. 328 00:15:26.519 --> 00:15:31.360 But here's the amazing thing. We've done the experiments. Yeah, 329 00:15:31.639 --> 00:15:34.360 over and over, and Einstein was wrong. 330 00:15:34.879 --> 00:15:36.440 There are no secret instructions. 331 00:15:36.519 --> 00:15:40.759 Nope, the spooky connection is real. The universe is non local. 332 00:15:41.080 --> 00:15:41.879 It's just a fact. 333 00:15:42.200 --> 00:15:45.159 Okay, So the universe is weirder than Einstein was comfortable with. 334 00:15:45.240 --> 00:15:47.519 We've established that, but how do we use this? What's 335 00:15:47.519 --> 00:15:48.200 the application? 336 00:15:48.360 --> 00:15:52.120 The number one application right now is cryptography keeping secrets safe? 337 00:15:52.360 --> 00:15:53.679 Okay, so digital security. 338 00:15:53.960 --> 00:15:57.759 Think about it. Our entire global economy, our military secrets 339 00:15:57.799 --> 00:16:02.320 are personal data. It's all part by encryption, and that 340 00:16:02.519 --> 00:16:06.000 encryption is based on math problems that are really really 341 00:16:06.080 --> 00:16:06.919 hard to solve. 342 00:16:06.799 --> 00:16:08.200 Like factoring huge numbers. 343 00:16:08.320 --> 00:16:12.679 Right, but really hard isn't the same as impossible. A 344 00:16:12.840 --> 00:16:17.519 powerful enough computer, say a future quantum computer, could potentially 345 00:16:17.519 --> 00:16:19.639 crack our current encryption methods. 346 00:16:19.399 --> 00:16:22.120 So all our secrets would be out in the open potentially. 347 00:16:22.200 --> 00:16:26.039 Yes, it's a huge concern. But entanglement offers a way out. 348 00:16:26.399 --> 00:16:28.480 It allows you to create an encryption key that isn't 349 00:16:28.519 --> 00:16:32.279 just mathematically hard to break, it's physically impossible to copy 350 00:16:32.440 --> 00:16:34.759 or even listen to without being detected. 351 00:16:34.919 --> 00:16:35.679 How does that work? 352 00:16:35.799 --> 00:16:38.120 Okay, So imagine Alice wants to send a secret key 353 00:16:38.120 --> 00:16:40.879 to Bob. Instead of sending a string of ones and zeros, 354 00:16:41.200 --> 00:16:45.000 she sends as free of entangled photons. Now, an evesdropper 355 00:16:45.039 --> 00:16:47.440 we'll call her Eve tries to intercept the message. 356 00:16:47.480 --> 00:16:49.519 She taps the fiber optic cable, right. 357 00:16:50.000 --> 00:16:51.840 But to find out the state of the photon. What 358 00:16:51.879 --> 00:16:52.799 does Eve have to do. 359 00:16:53.000 --> 00:16:53.919 She has to measure it. 360 00:16:54.200 --> 00:16:56.559 She has to measure it. And in quantum mechanics, the 361 00:16:56.600 --> 00:17:01.000 active measurement isn't passive. It changes the system. The moment 362 00:17:01.080 --> 00:17:04.960 ease detector interacts with that photon, it collapses the wave function, 363 00:17:05.480 --> 00:17:10.400 it breaks the entanglements. Sees the fingerprint a giant unmissible fingerprint. 364 00:17:10.960 --> 00:17:13.400 Alice and Bob can then sacrifice a small part of 365 00:17:13.400 --> 00:17:16.599 their key, compare notes over a public channel, and if 366 00:17:16.640 --> 00:17:18.640 they see a bunch of errors that shouldn't. 367 00:17:18.240 --> 00:17:19.720 Be there, they know Eve was listening. 368 00:17:19.839 --> 00:17:22.559 They know instantly they throw away the compromise key and 369 00:17:22.599 --> 00:17:26.079 start over. It's like a security system that's guaranteed by 370 00:17:26.079 --> 00:17:27.559 the fundamental laws of physics. 371 00:17:27.680 --> 00:17:30.240 It's like a message written in invisible ink that bursts 372 00:17:30.319 --> 00:17:33.279 into flame if anyone but the intended reader tries to 373 00:17:33.279 --> 00:17:33.759 look at it. 374 00:17:33.839 --> 00:17:35.319 That's a perfect way to put it. And this is 375 00:17:35.359 --> 00:17:39.559 in science fiction. Governments are building quantum communication networks. There's 376 00:17:39.599 --> 00:17:42.240 a Chinese satellite called Mishis that does this from space. 377 00:17:42.759 --> 00:17:45.519 We are building the foundations of a quantum internet. 378 00:17:45.640 --> 00:17:49.680 That's wild, but the source mentions another use for entanglement 379 00:17:49.720 --> 00:17:51.880 that's bigger. LEGO. 380 00:17:52.079 --> 00:17:55.319 Yes, the Laser Interferometer Gravitational Wave Observatory. 381 00:17:55.559 --> 00:17:59.200 These are the giant detectors that discovered gravitational waves, the 382 00:17:59.279 --> 00:18:01.839 ripples in SIE spacetime from colliding black holes. 383 00:18:01.920 --> 00:18:04.400 That's the one. And what they're trying to measure is 384 00:18:04.440 --> 00:18:10.039 almost impossibly small. A gravitational wave passing through Earth stretches 385 00:18:10.079 --> 00:18:13.440 and squeezes everything by a distant smaller than the width 386 00:18:13.440 --> 00:18:13.960 of a proton. 387 00:18:14.160 --> 00:18:17.440 How can you possibly measure that a truck driving by 388 00:18:17.559 --> 00:18:20.640 a mile away must shake the ground more than that it. 389 00:18:20.559 --> 00:18:24.119 Does, which is why the detectors are so isolated. But 390 00:18:24.279 --> 00:18:28.039 even with perfect isolation, there's a fundamental limit. It's called 391 00:18:28.119 --> 00:18:30.039 quantum noise or shot noise. 392 00:18:30.200 --> 00:18:30.599 What's that. 393 00:18:30.799 --> 00:18:33.440 It's the fact that a laser beam, even a perfect one, 394 00:18:33.599 --> 00:18:36.920 isn't a smooth, continuous river of light. It's made of 395 00:18:36.960 --> 00:18:39.960 individual photons. It's like rain on a roof. There's a 396 00:18:40.039 --> 00:18:43.759 natural randomness, a statistical jitter to when the photons arrive 397 00:18:43.799 --> 00:18:44.440 with the detector. 398 00:18:44.559 --> 00:18:47.440 So the laser beam itself is noisy at the quantum. 399 00:18:47.119 --> 00:18:50.000 Level exactly, and that noise can be bigger than the 400 00:18:50.079 --> 00:18:52.559 tiny signal from the gravitational wave you're trying to hear. 401 00:18:52.680 --> 00:18:54.839