WEBVTT 1 00:00:01.520 --> 00:00:05.599 Welcome to the quart Side Quantum Physics Podcast, an exploration 2 00:00:05.679 --> 00:00:10.919 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 00:00:27.519 --> 00:00:29.559 I want you to imagine, just for a second, stepping 6 00:00:29.559 --> 00:00:35.439 outside on a really crisp, clear night. You look up 7 00:00:35.560 --> 00:00:37.799 and you see the night sky in all its glory. 8 00:00:37.920 --> 00:00:39.560 Right, it's completely breathtaking here. 9 00:00:39.679 --> 00:00:43.039 Yeah, you see the stars twinkling, maybe the faint smudge 10 00:00:43.039 --> 00:00:46.439 of a distant galaxy, or the glowing dust of the 11 00:00:46.479 --> 00:00:50.159 Milky Way stretching right across the horizon. It feels incredibly vast, 12 00:00:50.280 --> 00:00:52.039 it really does. It feels like you are looking at 13 00:00:52.079 --> 00:00:56.640 the entire universe. Yeah, but here is the mind bending reality. 14 00:00:57.240 --> 00:01:00.520 Everything you can see, I mean everything emitting light, absorbing light, 15 00:01:00.640 --> 00:01:04.040 or reflecting light. It's just a tiny microscopic fraction of 16 00:01:04.079 --> 00:01:05.120 what is actually out there. 17 00:01:05.239 --> 00:01:08.560 Yeah, it's wild. The vast, overwhelming majority of our universe 18 00:01:08.640 --> 00:01:11.719 is completely invisible to our eyes and well to our 19 00:01:11.760 --> 00:01:15.400 telescopes too, completely invisible. Exactly. We only know this unseen 20 00:01:15.439 --> 00:01:19.120 matter exists because we can observe its gravity pulling on 21 00:01:19.159 --> 00:01:20.959 the luminous structures, we actually can. 22 00:01:20.840 --> 00:01:23.599 See, like, we can literally see its effects without seeing it. 23 00:01:24.000 --> 00:01:27.040 Right. We watch galaxies rotating at speeds that you know, 24 00:01:27.120 --> 00:01:30.599 frankly you should tear them apart, yet they hold together, 25 00:01:30.879 --> 00:01:35.519 basically bound by the immense weight of this invisible scaffolding. 26 00:01:35.680 --> 00:01:38.000 We are talking about dark matter, of course. It's the 27 00:01:38.120 --> 00:01:39.519 universe's ultimate. 28 00:01:39.200 --> 00:01:41.239 Ghost, the ultimate ghost, yeah, because it just. 29 00:01:41.239 --> 00:01:45.480 Doesn't interact with electromagnetism at all. It drifts right through everything, 30 00:01:46.159 --> 00:01:50.159 and for decades the physics community has been completely obsessed 31 00:01:50.159 --> 00:01:51.079 with trying to catch it. 32 00:01:51.200 --> 00:01:51.359 Oh. 33 00:01:51.359 --> 00:01:53.599 Absolutely, everyone wants to figure out what it is made of, 34 00:01:53.719 --> 00:01:58.159 and you know, to detect it directly right here on Earth, which. 35 00:01:57.959 --> 00:02:01.799 Is why we are currently living through this incredible boom 36 00:02:01.840 --> 00:02:05.680 in quantum technology. Like physicists are building these hyper sensitive, 37 00:02:05.719 --> 00:02:09.719 cutting edge quantum machines designed specifically to hunt for this 38 00:02:09.800 --> 00:02:10.840 ghostly matter. 39 00:02:10.759 --> 00:02:14.120 And that technological leap that's what sets the stage for 40 00:02:14.199 --> 00:02:18.400 a really fascinating paradise paradox. Yeah, because a groundbreaking new 41 00:02:18.439 --> 00:02:22.319 study analyzing how these detectors interact with dark matter has 42 00:02:22.400 --> 00:02:25.080 revealed this profound cosmic irony. 43 00:02:25.159 --> 00:02:26.840 Okay, I love a good cosmic irony. 44 00:02:27.080 --> 00:02:30.800 Well, the fundamental quantum nature of dark matter is completely 45 00:02:30.840 --> 00:02:32.599 fundamentally undetectable to us. 46 00:02:33.240 --> 00:02:34.680 Wait really, yeah. 47 00:02:34.520 --> 00:02:38.360 The universe is actively hiding its quantum mechanics from our machines. 48 00:02:38.800 --> 00:02:41.840 Wow. Okay, so here is where we are going today. 49 00:02:42.319 --> 00:02:45.360 We're going to explore the mechanics of why the universe 50 00:02:45.479 --> 00:02:50.840 is burying its quantum secrets, how this massive realization actually works, 51 00:02:51.360 --> 00:02:57.439 and why surprisingly this seemingly impassable wall is actually brilliant news. 52 00:02:57.759 --> 00:02:59.360 It really is great news for science. 53 00:02:59.479 --> 00:03:03.039 But to really grasp why the quantum nature of dark 54 00:03:03.039 --> 00:03:06.919 matter is playing hide and seek with our most advanced technology, 55 00:03:07.080 --> 00:03:09.199 we need to talk about what physicists actually think this 56 00:03:09.240 --> 00:03:09.919 ghost is made of. 57 00:03:10.080 --> 00:03:11.960 Right, We have to start with the suspects. 58 00:03:11.520 --> 00:03:13.960 Exactly, because for a long time we've had a roster 59 00:03:14.080 --> 00:03:15.919 of theoretical candidates. 60 00:03:15.479 --> 00:03:18.479 We have because dark matter refuses to interact with normal 61 00:03:18.520 --> 00:03:21.159 matter in any meaningful way, you basically have to build 62 00:03:21.240 --> 00:03:25.560 theoretical models of particles that fit that extreme ghostly profile. 63 00:03:26.280 --> 00:03:29.080 And one of the leading theoretical candidates right now is 64 00:03:29.080 --> 00:03:30.479 a particle called the axion. 65 00:03:30.800 --> 00:03:33.240 The axion, Okay, I know this is a front runner, 66 00:03:33.560 --> 00:03:37.400 but how does it differ from the heavy bulky dark 67 00:03:37.439 --> 00:03:39.719 matter particles people used to theorize about. 68 00:03:39.960 --> 00:03:42.439 So the axion is what we call an ultra light particle. 69 00:03:42.800 --> 00:03:44.599 Ultra light How light is ultra light? 70 00:03:44.719 --> 00:03:46.879 Well, to give you a sense of scale, its mass 71 00:03:46.960 --> 00:03:51.639 is so vanishingly small that it might be a trillionth 72 00:03:51.639 --> 00:03:54.000 of a trillionth the mass of a single electron. 73 00:03:54.159 --> 00:03:56.479 A trillionth of a trillion that's I mean, that's barely 74 00:03:56.479 --> 00:03:57.599 even a thing exactly. 75 00:03:57.639 --> 00:04:01.479 Because each individual axion carries almost zero mass. The only 76 00:04:01.520 --> 00:04:04.280 way they could account for the immense gravitational weight of 77 00:04:04.360 --> 00:04:06.680 dark matter in our galaxy is if there is an 78 00:04:06.840 --> 00:04:09.360 unimaginably large number of them. 79 00:04:09.280 --> 00:04:11.120 Way a completely absurd amount, Right. 80 00:04:11.000 --> 00:04:14.000 We're talking about a density so high that they just 81 00:04:14.120 --> 00:04:16.839 permeate every single inch of the universe around us. 82 00:04:16.920 --> 00:04:21.240 Okay, let's unpack this. Yeah, because trying to visualize a 83 00:04:21.279 --> 00:04:25.480 swarm of invisible, almost weightless particles making up a quarter 84 00:04:25.519 --> 00:04:28.199 of the universe is honestly hurting my brain a bit. 85 00:04:28.279 --> 00:04:29.560 It's definitely not easy to picture. 86 00:04:29.759 --> 00:04:33.680 So I want to picture this correctly. When scientists model axions, 87 00:04:33.720 --> 00:04:37.600 they don't treat them like a hail storm of tiny 88 00:04:37.639 --> 00:04:40.879 individual bullets, do they. They treat them as a classical field. 89 00:04:40.720 --> 00:04:43.079 Right they do. Yeah, And it really comes down to 90 00:04:43.120 --> 00:04:46.639 a fundamental principle of quantum mechanics called the Dobroglei. 91 00:04:46.160 --> 00:04:48.279 Wavelength the de Brogli wavelength. Right. 92 00:04:48.439 --> 00:04:51.680 In quantum physics, every particle can also be described as 93 00:04:51.680 --> 00:04:56.000 a wave, and the lighter the particle, the longer its 94 00:04:56.079 --> 00:04:57.000 wave stretches out. 95 00:04:57.079 --> 00:04:59.279 Okay, that makes sense. The lighter equals longer. 96 00:04:59.120 --> 00:05:02.319 Exactly because because the axion is so incredibly light, it's 97 00:05:02.360 --> 00:05:06.920 quantum wavelength is just huge compared to standard sub atomic particles. 98 00:05:07.079 --> 00:05:09.519 So you have these massive, stretched out waves, and because 99 00:05:09.519 --> 00:05:12.439 you need trillions upon trillions of them packed into the 100 00:05:12.480 --> 00:05:14.519 exact same space just to make up a tiny bit 101 00:05:14.560 --> 00:05:18.120 of gravity, they all sort of crowd together. 102 00:05:18.319 --> 00:05:21.560 And when they crowd together, those elongated quantum waves overlap, 103 00:05:21.639 --> 00:05:22.360 they sync. 104 00:05:22.240 --> 00:05:23.360 Up, they sink up. 105 00:05:23.519 --> 00:05:26.439 Yeah. Instead of acting like a bunch of erratic individual 106 00:05:26.439 --> 00:05:29.720 particles bouncing around, they behave collectively, they just wash over 107 00:05:29.759 --> 00:05:32.800 the Earth as a single macroscopic. 108 00:05:32.120 --> 00:05:34.959 Wave, oscillating it as specific frequency. 109 00:05:34.519 --> 00:05:40.000 Precisely, that smooth, continuous sloshing that is the classical field model. 110 00:05:40.240 --> 00:05:42.879 I think I've got it. It's like the difference between 111 00:05:42.920 --> 00:05:46.439 looking at dark matter as a massive invisible ocean current, 112 00:05:47.040 --> 00:05:51.240 that macroscopic classical field versus you know, focusing on the 113 00:05:51.279 --> 00:05:54.519 individual microscopic drops of water that make up the current. 114 00:05:54.600 --> 00:05:56.120 That is a perfect way to look at it. 115 00:05:56.240 --> 00:05:59.480 So currently we're just constantly swimming in this smooth ocean 116 00:05:59.519 --> 00:06:00.639 current of dark matter. 117 00:06:00.839 --> 00:06:04.519 Yeah, that ocean current analogy perfectly captures the classical view, 118 00:06:05.000 --> 00:06:08.680 and it works flawlessly for predicting how galaxies form and 119 00:06:08.680 --> 00:06:12.279 how gravity behaves on a large cosmological scale. 120 00:06:12.360 --> 00:06:16.199 Here's where it gets really interesting, though, because if axioans 121 00:06:16.279 --> 00:06:20.000 are technically sub atomic particles, you know, these tiny drops 122 00:06:20.000 --> 00:06:23.360 of water, shouldn't they behave by the bizarre rules of 123 00:06:23.439 --> 00:06:25.480 quantum mechanics. When we look closely. 124 00:06:25.240 --> 00:06:26.199 Enough, you would think so. 125 00:06:26.319 --> 00:06:28.560 Yes. If you zoom in on anything with a powerful 126 00:06:28.639 --> 00:06:31.759 enough microscope, the smooth illusion usually breaks down, right and 127 00:06:31.839 --> 00:06:34.040 you see the discrete quantum pieces. 128 00:06:34.360 --> 00:06:37.879 And that logical leap is the exact foundation of the 129 00:06:37.959 --> 00:06:41.360 current push to build highly sensitive dark matter detectors. 130 00:06:41.399 --> 00:06:43.240 Okay, so that's what we're trying to do, right. 131 00:06:43.480 --> 00:06:47.360 Physicists have developed these instruments called haloscopes taloscopes. Yeah, they 132 00:06:47.439 --> 00:06:54.240 use incredibly powerful magnetic fields and superconducting quantum sensors. They 133 00:06:54.279 --> 00:06:58.040 are attempting to coax a single axion to interact with 134 00:06:58.079 --> 00:07:02.439 the magnetic field and basically canvert into a detectable microwave photon. 135 00:07:02.639 --> 00:07:05.199 So we're trying to build machines that can detect the 136 00:07:05.519 --> 00:07:09.839 absolute faintest whispers of energy, the absolute faintest. Yes, we 137 00:07:09.879 --> 00:07:12.839 basically want the machine to go click when a single 138 00:07:12.920 --> 00:07:15.240 drop of water from that dark matter ocean hits it. 139 00:07:15.360 --> 00:07:19.360 Exactly. The scientific community assumed that by utilizing detectors that 140 00:07:19.439 --> 00:07:23.120 operate on strict quantum principles, we would naturally be able 141 00:07:23.160 --> 00:07:26.879 to detect the underline, discrete quantum nature of the dark 142 00:07:26.920 --> 00:07:27.600 matter itself. 143 00:07:27.759 --> 00:07:29.680 We just expected it to happen, right. 144 00:07:30.040 --> 00:07:34.199 We anticipated seeing the erratic particle like behavior, those individual 145 00:07:34.279 --> 00:07:36.279 clicks of quantum interactions you just mentioned. 146 00:07:36.639 --> 00:07:39.160 And this is where a team of physicists Lion Tao 147 00:07:39.240 --> 00:07:41.959 Wang and his colleagues from the University of Chicago, Lawrence 148 00:07:42.000 --> 00:07:45.959 Berkeley National Lab, and UC Berkeley stepped in and realized 149 00:07:47.120 --> 00:07:49.759 a major piece of the puzzle was simply missing. 150 00:07:50.079 --> 00:07:51.000 A huge piece. 151 00:07:51.199 --> 00:07:53.800 Yeah, because we were using all this advanced quantum math 152 00:07:54.120 --> 00:07:58.680 to engineer the inner workings of the detectors, but researchers 153 00:07:58.720 --> 00:08:02.319 hadn't actually applied strict quantum mechanics to describe the dark 154 00:08:02.360 --> 00:08:05.959 matter itself at the exact moment it interacts with the machine. 155 00:08:05.639 --> 00:08:10.720 Which reveals a really fascinating blind spot in the theoretical framework. 156 00:08:10.279 --> 00:08:11.279 A huge blind spot. 157 00:08:11.399 --> 00:08:15.879 Yeah, the models dictating how the detector operates were entirely quantum, 158 00:08:16.240 --> 00:08:18.680 but the input in a dark matter expected to hit 159 00:08:18.680 --> 00:08:21.319 the detector was still largely being fed in as a 160 00:08:21.360 --> 00:08:22.959 smooth classical wave. 161 00:08:23.279 --> 00:08:25.240 Okay, I really have to push back on the logic 162 00:08:25.279 --> 00:08:26.600 of the scientific community here. 163 00:08:26.639 --> 00:08:27.600 Oh, fair enough, go ahead. 164 00:08:27.639 --> 00:08:31.399 Why would physicists spend decades at like millions of dollars 165 00:08:31.759 --> 00:08:35.879 building highly sensitive quantum heloscopes without first checking the fundamental 166 00:08:35.919 --> 00:08:38.320 math to see if the dark matter they are looking 167 00:08:38.320 --> 00:08:41.039 for actually acts like a quantum particle when it strikes 168 00:08:41.080 --> 00:08:43.440 the sensor. I know, I know. It feels like building 169 00:08:43.480 --> 00:08:46.720 an ultra sensitive microphone to record a bat's echo location 170 00:08:47.440 --> 00:08:50.519 without I don't know, checking if bats actually make noise 171 00:08:50.559 --> 00:08:51.399 in that frequency. 172 00:08:51.559 --> 00:08:53.759 It really seems like a massive oversight when you frame 173 00:08:53.799 --> 00:08:57.120 it that way, but it stems from how theoretical physics 174 00:08:57.120 --> 00:09:00.879 practically evolves. You mean, well, the classical field model that 175 00:09:01.039 --> 00:09:05.120 smooth ocean current. It explained all the gravitational effects we 176 00:09:05.120 --> 00:09:06.159 could observe perfectly. 177 00:09:06.320 --> 00:09:07.600 Okay, so it worked right. 178 00:09:08.159 --> 00:09:12.919 So when experimentalists began designing quantum level detectors, they relied 179 00:09:13.080 --> 00:09:17.000 on a standard assumption. It is incredibly common in physics 180 00:09:17.039 --> 00:09:19.919 to assume that if you push your magnification deep enough 181 00:09:20.000 --> 00:09:24.440 into the microscopic realm, the classical limits will naturally break down. 182 00:09:24.399 --> 00:09:26.840 And the quantum stuff will just sort of pop out exactly. 183 00:09:27.399 --> 00:09:31.039 They assumed the discrete quantum signatures would just emerge. They 184 00:09:31.039 --> 00:09:34.559 didn't rigorously calculate the dark matter's quantum state during detection 185 00:09:34.720 --> 00:09:38.879 because honestly, that assumption just felt mathematically safe. 186 00:09:38.639 --> 00:09:42.519 Safe, until Wang and his team decided it was time 187 00:09:42.559 --> 00:09:46.200 to stop assuming and actually run the numbers exactly. 188 00:09:46.279 --> 00:09:49.200 They wanted to see what a quantum axion would mathematically 189 00:09:49.240 --> 00:09:51.480 look like to a modern quantum detector. 190 00:09:51.759 --> 00:09:52.519 So what did they do. 191 00:09:53.159 --> 00:09:57.440 They built a brand new, entirely quantum mechanical framework from 192 00:09:57.480 --> 00:10:01.039 the ground up, modeling both the detector and the dark 193 00:10:01.080 --> 00:10:03.679 matter as interacting quantum entities. 194 00:10:03.879 --> 00:10:06.240 They put the whole system into the quantum math. 195 00:10:06.519 --> 00:10:10.320 Right. They set out to mathematically prove whether an experiment 196 00:10:10.399 --> 00:10:14.720 could distinguish the hidden quantum states, those discrete particle like 197 00:10:14.840 --> 00:10:19.720 clicks from the continuous, smooth, classical wave state we've always modeled. 198 00:10:20.159 --> 00:10:23.159 And the findings they publish, which are incredible by the way, 199 00:10:23.159 --> 00:10:26.600 they found that the intrinsically quantum effects of axions are 200 00:10:26.799 --> 00:10:29.720 completely fundamentally undetectable. 201 00:10:29.840 --> 00:10:30.559 Undetectable. 202 00:10:30.639 --> 00:10:32.360 Yes, when the detector looks at the dark matter, it 203 00:10:32.399 --> 00:10:34.159 basically only sees the classical. 204 00:10:33.840 --> 00:10:36.480 Wave, right, The discrete quantum nature just vanishes. 205 00:10:36.679 --> 00:10:39.200 But why why does a fundamental particle just lose its 206 00:10:39.279 --> 00:10:40.440 quantum identity like that? 207 00:10:41.039 --> 00:10:43.679 The disappearance of the quantum nature basically comes down to 208 00:10:43.720 --> 00:10:46.039 the relationship between the mean and the variance of the 209 00:10:46.080 --> 00:10:47.440 signal mean invariance. 210 00:10:47.480 --> 00:10:48.879 Okay, let's break that down. 211 00:10:49.120 --> 00:10:52.879 So when a detector measures the axion field, it is 212 00:10:52.960 --> 00:10:56.200 measuring the average strength of the wave over time. That 213 00:10:56.360 --> 00:10:56.840 is the mean. 214 00:10:57.039 --> 00:10:58.519 Got it. The average is the mean. 215 00:10:58.679 --> 00:11:01.919 But the quantum quarks, the individual particle interactions we are 216 00:11:01.960 --> 00:11:04.960 actually looking for, they live in the variance. 217 00:11:05.080 --> 00:11:05.600 The variants. 218 00:11:05.679 --> 00:11:08.879 Yeah, the tiny statistical fluctuations away from that average. 219 00:11:08.960 --> 00:11:11.360 Okay, so the fluctuations are the discrete. 220 00:11:11.200 --> 00:11:15.759 Clicks precisely, And there are two major physical factors working 221 00:11:15.759 --> 00:11:18.600 in tandem here to completely suppress those fluctuations. 222 00:11:18.679 --> 00:11:19.480 What's the first one? 223 00:11:19.639 --> 00:11:24.039 First, the sheer weakness of the interaction heavily penalizes our 224 00:11:24.080 --> 00:11:27.200 ability to see anything other than the massive. 225 00:11:26.840 --> 00:11:28.559 Average because it's a ghost. 226 00:11:28.600 --> 00:11:32.360 Right, Because the axion interacts so faintly with the magnetic 227 00:11:32.360 --> 00:11:35.039 fields in our haloscopes to begin with, the overall signal 228 00:11:35.080 --> 00:11:39.360 strength is incredibly low. It's super quiet, exactly so to 229 00:11:39.440 --> 00:11:44.200 see tiny variances inside an already microscopic signal requires just 230 00:11:44.240 --> 00:11:46.000 an impossible level of precision. 231 00:11:46.159 --> 00:11:49.279 Wait, earlier we established that there are trillions upon trillions 232 00:11:49.279 --> 00:11:53.120 of these axions permeating everything, Right, doesn't the sheer volume 233 00:11:53.200 --> 00:11:56.440 of particles make up for the weak interaction, Like, if 234 00:11:56.519 --> 00:11:59.320 enough of them are flowing through the detector, shouldn't the 235 00:11:59.360 --> 00:12:02.399 sheer quantity amplify those little quantum fluctuations. 236 00:12:02.559 --> 00:12:06.360 See, that is the intuitive assumption, but statistically the exact 237 00:12:06.399 --> 00:12:07.200 opposite happens. 238 00:12:07.240 --> 00:12:07.759 The opposite. 239 00:12:07.919 --> 00:12:10.840 Yeah, the immense density of the axions is actually the 240 00:12:10.879 --> 00:12:13.320 primary mechanism hiding their quantum nature. 241 00:12:13.440 --> 00:12:15.000 You're kidding, No, It is an. 242 00:12:14.919 --> 00:12:19.200 Extreme example of the central limit theorem in statistics. 243 00:12:18.639 --> 00:12:21.399 The central limit theorem. Okay, let's try to visualize this. 244 00:12:22.039 --> 00:12:26.399 Imagine you are standing in the middle of a massive stadium, Okay, 245 00:12:26.440 --> 00:12:29.639 a stadium, and there are one hundred thousand people in 246 00:12:29.679 --> 00:12:33.000 the stands, and they are all humming the exact same 247 00:12:33.679 --> 00:12:34.679 continuous note. 248 00:12:34.799 --> 00:12:39.480 Okay, so the humming represents the mean the macroscopic classical 249 00:12:39.559 --> 00:12:41.519 dark matter wave rolling over the Earth. 250 00:12:41.639 --> 00:12:45.720 Right now. In the quantum world, things are a little unpredictable. 251 00:12:45.720 --> 00:12:48.080 So maybe one person over in section one oh four 252 00:12:48.159 --> 00:12:50.639 has their voice cracked for a split second. Okay, that 253 00:12:50.840 --> 00:12:54.440 tiny vocal fluctuation, that little anomaly, That is your quantum variance. 254 00:12:54.440 --> 00:12:56.399 That's the discrete particle click we want to hear. 255 00:12:56.639 --> 00:12:59.320 But here's the problem. If you are standing in the 256 00:12:59.320 --> 00:13:02.320 center of the field holding a microphone, you aren't just 257 00:13:02.399 --> 00:13:04.639 recording that one person in section one o four. 258 00:13:04.919 --> 00:13:08.679 You're recording the other ninety nine hundred ninety nine people 259 00:13:09.039 --> 00:13:14.039 constantly humming that perfect, overwhelming note exactly. The sheer volume 260 00:13:14.080 --> 00:13:17.440 of the massive crowd completely drowns out the anomaly. The 261 00:13:17.480 --> 00:13:20.919 massive number of axions hitting the detector means those tiny 262 00:13:21.000 --> 00:13:25.120 quantum variances just average out into the smooth, continuous roar 263 00:13:25.240 --> 00:13:26.200 of the classical wave. 264 00:13:26.440 --> 00:13:29.279 It is physically impossible to hear the voice crack wow 265 00:13:29.480 --> 00:13:32.960 because the detector is absorbing energy from so many overlapping 266 00:13:33.000 --> 00:13:38.200 axion waves simultaneously. The quantum fluctuations just smooth themselves over. 267 00:13:38.320 --> 00:13:39.720 They just blur together, right. 268 00:13:39.919 --> 00:13:43.279 The mathematics of the wangpaper prove that these quantum signatures 269 00:13:43.279 --> 00:13:46.759 would only manifest as extremely slight changes to what statisticians 270 00:13:46.799 --> 00:13:48.279 call higher order statistics. 271 00:13:48.399 --> 00:13:52.440 Higher order statistics, So we are talking about analyzing the 272 00:13:52.480 --> 00:13:53.919 shape of the data curve itself. 273 00:13:54.039 --> 00:13:56.600 Yes, you're looking at things like the skewness of the 274 00:13:56.639 --> 00:13:59.399 signal or the variance of the variants. You are basically 275 00:13:59.480 --> 00:14:01.879 trying to find correlations in the noise. 276 00:14:01.519 --> 00:14:03.440 Of the data, which sounds impossible. 277 00:14:03.639 --> 00:14:06.639 It essentially is because as the number of particles in 278 00:14:06.639 --> 00:14:10.080 the field approaches the astronomical numbers required for dark matter, 279 00:14:10.799 --> 00:14:14.159 the central limit theorem dictates that the variance grows much 280 00:14:14.279 --> 00:14:15.440 much slower than. 281 00:14:15.279 --> 00:14:17.720 The mean, So the signal just disappears. 282 00:14:18.679 --> 00:14:21.759 The quantum signal essentially gets pushed to zero relative to 283 00:14:21.799 --> 00:14:22.679 the classical wave. 284 00:14:22.840 --> 00:14:25.320 It becomes a statistical whisper lost in a hurricane. 285 00:14:25.360 --> 00:14:27.480 That's a great way to put it. And it leads 286 00:14:27.519 --> 00:14:32.399 to the most staggering calculation in their entire paper. With that, well, 287 00:14:32.639 --> 00:14:35.360 the researchers wanted to know the absolute limit. They assumed 288 00:14:35.399 --> 00:14:40.919 an optimally designed, theoretically perfect experiment utilizing the absolute pinnacle 289 00:14:41.039 --> 00:14:45.879 of quantum technology, running without any background noise whatsoever. 290 00:14:45.480 --> 00:14:48.919 A perfect machine, and to find those higher order statistics, 291 00:14:49.200 --> 00:14:51.120 you know, to hear that single voice crack in a 292 00:14:51.159 --> 00:14:54.200 stadium of trillions, How long would this perfect machine need 293 00:14:54.240 --> 00:14:54.600 to run? 294 00:14:55.080 --> 00:14:57.879 The experiment would have to run for significantly longer than 295 00:14:57.919 --> 00:14:59.360 the age of the universe. 296 00:14:59.000 --> 00:15:02.399 Significantly longer than the thirteen point eight billion years our 297 00:15:02.519 --> 00:15:06.519 universe has even existed, just to catch a single statistical 298 00:15:06.559 --> 00:15:10.600 glimpse of a quantum axion doing something quantum that is, 299 00:15:11.080 --> 00:15:13.720 I mean, that is the universe firmly closing a door. 300 00:15:13.799 --> 00:15:16.159 It's a hard physical limit, it really is. 301 00:15:16.399 --> 00:15:18.919 It forces us to confront a profound boundary on what 302 00:15:19.000 --> 00:15:22.440 is observable in our reality. Yeah, the sheer density required 303 00:15:22.440 --> 00:15:25.360 for the axion to be dark matter makes us underlying 304 00:15:25.440 --> 00:15:28.120 quantum mechanics eternally inaccessible to us. 305 00:15:28.240 --> 00:15:31.240 So what does this all mean? Because learning that an 306 00:15:31.240 --> 00:15:35.279 experiment would take fourteen billion years sounds like a massive 307 00:15:35.480 --> 00:15:39.559 crushing failure for physics. If the quantum effects are totally invisible, 308 00:15:39.639 --> 00:15:42.720 doesn't that render all our highly sensitive quantum heloscopes and 309 00:15:42.759 --> 00:15:44.799 sensors completely useless. 310 00:15:44.960 --> 00:15:47.320 It's so crucial to make the distinction between the quantum 311 00:15:47.399 --> 00:15:50.080 nature of the dark matter and the quantum sensitivity of the. 312 00:15:50.039 --> 00:15:52.000 Detector, because they aren't the same thing. 313 00:15:52.000 --> 00:15:55.120 Exactly, because the immediate reaction is often disappointment, like you said, 314 00:15:55.440 --> 00:15:58.879 But the detectors we are building are not useless at all. 315 00:15:58.960 --> 00:15:59.399 They aren't. 316 00:15:59.639 --> 00:16:03.799 No. In fact, establishing this physical limit is a massive victory. 317 00:16:03.879 --> 00:16:07.639 It clears a dense fog of uncertainty for experimental physicists. 318 00:16:08.200 --> 00:16:12.240 Okay, how does hitting a fourteen billion year wall help 319 00:16:12.320 --> 00:16:13.799 the people building the machines? 320 00:16:14.080 --> 00:16:17.279 It resolves a massive amount of theoretical anxiety. 321 00:16:16.759 --> 00:16:19.200 In the field, anxiety about what Well. 322 00:16:19.159 --> 00:16:22.639 Returning to your ocean analogy, our quantum detectors are absolutely 323 00:16:22.679 --> 00:16:25.639 phenomenal at feeling the push of the massive ocean current. 324 00:16:26.399 --> 00:16:29.519 The high sensitivity is still required because the classical wave 325 00:16:29.559 --> 00:16:32.879 itself interacts so weakly with standard matter. Oh, I see, 326 00:16:33.000 --> 00:16:36.799 we need quantum level precision just to detect the macroscopic wave. 327 00:16:37.240 --> 00:16:41.039 Ah, so we need the ultrasensitive quantum microphone just to 328 00:16:41.039 --> 00:16:42.879 hear the crowd humming in the first place. 329 00:16:43.039 --> 00:16:46.360 Yes, what the study definitively proves is simply that we 330 00:16:46.399 --> 00:16:49.120 don't need to worry about trying to calibrate our machines 331 00:16:49.159 --> 00:16:50.960 to isolate the individual drops. 332 00:16:50.720 --> 00:16:52.519 Of water, because we literally can't. 333 00:16:52.720 --> 00:16:56.679 Right. Prior to this mathematical proof, physicists were actively debating 334 00:16:56.720 --> 00:17:00.279 whether intrinsic quantum fluctuations in the dark matter field might 335 00:17:00.320 --> 00:17:04.880 be skewing our data or creating strange interferences that were 336 00:17:04.920 --> 00:17:06.839 causing us to miss the signal entirely. 337 00:17:07.240 --> 00:17:10.359 So people were actually stressing out that the quantum quirks 338 00:17:10.359 --> 00:17:13.519 of the axions were throwing off the calibration of the. 339 00:17:13.480 --> 00:17:18.319 Traps exactly, and Wang and his team rigorously demonstrated that 340 00:17:18.319 --> 00:17:20.720 we can completely ignore those quantum. 341 00:17:20.400 --> 00:17:22.160 Effects because they average out to zero. 342 00:17:22.559 --> 00:17:26.359 Because they average out to zero, they will not interfere 343 00:17:26.400 --> 00:17:30.960 with the classical detection. This validates our historical models so easy. 344 00:17:31.160 --> 00:17:34.319 It proves that treating axion dark matter as a classical 345 00:17:34.440 --> 00:17:39.160 macroscopic wavefield works flawlessly on an experimental level, even when 346 00:17:39.240 --> 00:17:43.240 using quantum instruments. We can trust the classical models when 347 00:17:43.279 --> 00:17:45.240 we are hunting for the dark matter signal. 348 00:17:45.359 --> 00:17:48.240 So it's basically the universe giving us permission to simplify 349 00:17:48.319 --> 00:17:51.079 our approach pretty much. We don't have to account for 350 00:17:51.119 --> 00:17:55.119 the unpredictable discrete quantum behavior on the dark matter side 351 00:17:55.200 --> 00:17:57.960 because the universe naturally smooths it out for us. We 352 00:17:58.079 --> 00:18:00.680 just focus our quantum detectors on catching the big wave. 353 00:18:01.000 --> 00:18:07.119 It's correctly what signal profile we are looking for. 354 00:18:07.200 --> 00:18:09.359 Now. That is a huge relief, it is. 355 00:18:09.759 --> 00:18:12.480 And what makes this realization even more impactful is that 356 00:18:12.559 --> 00:18:15.799 this averaging out phenomenon isn't restricted to just axions. 357 00:18:15.880 --> 00:18:17.839 Wait, this applies to other areas of physics. 358 00:18:18.240 --> 00:18:21.839 It does. The exact same quantum hiding logic applies to 359 00:18:21.880 --> 00:18:23.680 the detection of gravitational waves. 360 00:18:23.720 --> 00:18:27.119 Gravitational waves. Oh, that makes perfect sense, because we detect 361 00:18:27.119 --> 00:18:30.400 gravitational waves using massive interferometers like Lego. 362 00:18:30.680 --> 00:18:30.960 Right. 363 00:18:31.359 --> 00:18:37.440 And theoretically gravity is composed of subatomic quantum particles called gravitons. 364 00:18:36.880 --> 00:18:41.640 Exactly, But a gravitational wave generated by say two black 365 00:18:41.640 --> 00:18:46.200 holes colliding it contains such an astronomically immense number of 366 00:18:46.240 --> 00:18:50.160 gravitons that their individual quantum quirks average. 367 00:18:49.839 --> 00:18:51.799 Out entirely, just like the axions. 368 00:18:51.880 --> 00:18:55.440 Just like the axiom field, the variance vanishes, and our 369 00:18:55.480 --> 00:18:59.279 detectors only observe the smooth classical ripple in space time 370 00:19:00.039 --> 00:19:03.559 virtual limit theorem and forces classical physics on any ultra light, 371 00:19:03.759 --> 00:19:05.400 highly abundant particle field. 372 00:19:05.519 --> 00:19:07.279 The bigger the crowd, the smooth than noise. 373 00:19:07.279 --> 00:19:10.400 I perfectly said, and this mathematical framework provides a real 374 00:19:10.480 --> 00:19:12.119 launch pad for future engineering. 375 00:19:12.279 --> 00:19:13.079 How so well. 376 00:19:13.119 --> 00:19:15.880 The researchers noted that their ongoing work involves developing a 377 00:19:15.920 --> 00:19:20.319 complete end to end quantum mechanical description of the detection process. 378 00:19:20.359 --> 00:19:21.680 But I thought we just said we can't see the 379 00:19:21.720 --> 00:19:22.480 quantum stuff. 380 00:19:22.559 --> 00:19:25.079 We can't. They aren't doing this to look for the 381 00:19:25.119 --> 00:19:29.000 impossible quantum quirks of the axion. They are using that 382 00:19:29.160 --> 00:19:34.160 deep mathematical understanding to search for entirely new quantum techniques 383 00:19:34.480 --> 00:19:36.400 to build better traps for the classical wave. 384 00:19:36.480 --> 00:19:36.960 Oh wow. 385 00:19:37.200 --> 00:19:39.680 They are utilizing the hard limits of what we can't 386 00:19:39.720 --> 00:19:42.839 see to optimize how we search for what we can see. 387 00:19:42.880 --> 00:19:45.880 A closed door just forces you to engineer a better window. 388 00:19:45.920 --> 00:19:47.000 I love that exactly. 389 00:19:47.119 --> 00:19:50.680 So let's recap the journey here. We started with the 390 00:19:50.799 --> 00:19:54.799 universe's most delusive ghost, dark matter right. We zoomed in, 391 00:19:55.359 --> 00:19:59.279 assuming that our incredible new quantum technology would reveal the 392 00:19:59.359 --> 00:20:04.160 microscope discrete quantum secrets of the axion, But instead we 393 00:20:04.240 --> 00:20:08.599 found that it's overwhelming abundance moves out all its quantum fluctuations. 394 00:20:08.640 --> 00:20:09.759 It's all about the averages. 395 00:20:09.839 --> 00:20:13.160 The central limit theorem basically hides its discrete nature behind 396 00:20:13.200 --> 00:20:16.079 the roar of the crowd, leaving us with a continuous 397 00:20:16.319 --> 00:20:17.480 classical wave. 398 00:20:17.319 --> 00:20:20.079 A wave we are now better equipped to find, precisely 399 00:20:20.119 --> 00:20:22.160 because we are no longer distracted by the search for 400 00:20:22.200 --> 00:20:23.000 its quantum. 401 00:20:22.759 --> 00:20:25.559