1 00:00:01,168 --> 00:00:04,670 ♪ ♪ 2 00:00:04,739 --> 00:00:06,372 NARRATOR: We live in a world 3 00:00:06,440 --> 00:00:09,408 where objects have permanence. 4 00:00:09,477 --> 00:00:13,379 And we see cause, then effect. 5 00:00:13,447 --> 00:00:16,448 But a startling phenomenon is revealing 6 00:00:16,517 --> 00:00:17,850 that this is not how the universe works 7 00:00:17,918 --> 00:00:21,653 at the smallest scales of atoms and tiny particles. 8 00:00:21,722 --> 00:00:23,622 ♪ ♪ 9 00:00:23,691 --> 00:00:27,793 Albert Einstein argued it couldn't possibly be real. 10 00:00:27,862 --> 00:00:30,462 DAVID KAISER: Einstein was like a jack-in-the-box; 11 00:00:30,531 --> 00:00:32,998 every day, he'd pop up with a new challenge. 12 00:00:33,067 --> 00:00:36,035 NARRATOR: But after a century of disputes and discoveries... 13 00:00:36,103 --> 00:00:38,203 ANTON ZEILINGER: The experiment is just beautiful. 14 00:00:38,272 --> 00:00:43,142 NARRATOR: ...we're using it to create revolutionary, new technologies. 15 00:00:43,210 --> 00:00:45,911 What we have here is a quantum playground. 16 00:00:45,980 --> 00:00:48,514 JIAN-WEI PAN: We want to push these technologies 17 00:00:48,582 --> 00:00:50,115 as far as possible. 18 00:00:50,184 --> 00:00:53,152 NARRATOR: It's perhaps the strangest concept in physics. 19 00:00:53,220 --> 00:00:56,088 SHOHINI GHOSE: We're left with conclusions that make no sense whatsoever. 20 00:00:56,157 --> 00:01:00,025 NARRATOR: Yet it could be what forms the very fabric of our cosmos. 21 00:01:00,094 --> 00:01:02,494 In the end, we just have this quantum mechanical world. 22 00:01:02,563 --> 00:01:03,896 There is no space anymore. 23 00:01:03,964 --> 00:01:06,231 GHOSE: It's like being in "Alice in Wonderland." 24 00:01:06,300 --> 00:01:07,900 Everything is possible. 25 00:01:07,968 --> 00:01:11,003 NARRATOR: Could it be real? 26 00:01:11,072 --> 00:01:14,339 It's "Einstein's Quantum Riddle," 27 00:01:14,408 --> 00:01:17,176 right now, on "NOVA." 28 00:01:17,244 --> 00:01:21,680 ♪ ♪ 29 00:01:29,256 --> 00:01:33,292 NARRATOR: Is reality an illusion? 30 00:01:33,360 --> 00:01:36,728 Could something here mysteriously affect 31 00:01:36,797 --> 00:01:39,465 something there? 32 00:01:39,533 --> 00:01:42,234 A century of discoveries in physics 33 00:01:42,303 --> 00:01:45,237 reveals a strange, counterintuitive micro-world 34 00:01:45,306 --> 00:01:47,506 of atoms and tiny particles 35 00:01:47,575 --> 00:01:50,242 that challenges our intuitive understanding 36 00:01:50,311 --> 00:01:53,045 of the world we see around us. 37 00:01:54,648 --> 00:01:59,084 It's known as quantum mechanics. 38 00:01:59,153 --> 00:02:00,686 This strange theory has enabled us to develop 39 00:02:00,754 --> 00:02:04,656 the remarkable technologies of our digital age. 40 00:02:04,725 --> 00:02:09,628 But it makes a very troubling prediction-- 41 00:02:09,697 --> 00:02:11,797 called quantum entanglement. 42 00:02:11,866 --> 00:02:15,667 ♪ ♪ 43 00:02:15,736 --> 00:02:17,436 GHOSE: Entanglement is 44 00:02:17,505 --> 00:02:20,139 this very powerful but strange connection 45 00:02:20,207 --> 00:02:23,342 that exists between pairs of particles. 46 00:02:23,410 --> 00:02:25,310 ROBBERT DIJKGRAAF: Even if they're very far apart, 47 00:02:25,379 --> 00:02:27,479 in a way, they're always coordinated. 48 00:02:27,548 --> 00:02:29,615 ♪ ♪ 49 00:02:29,683 --> 00:02:32,918 NARRATOR: Nature's fundamental building blocks could be connected 50 00:02:32,987 --> 00:02:35,587 and influence each other instantaneously, 51 00:02:35,656 --> 00:02:39,424 as if the space between them doesn't exist. 52 00:02:39,493 --> 00:02:42,794 As if two objects can mirror each other 53 00:02:42,863 --> 00:02:44,863 without any apparent connection. 54 00:02:44,932 --> 00:02:46,331 ♪ ♪ 55 00:02:46,400 --> 00:02:50,435 Einstein called it "spooky action at a distance." 56 00:02:50,504 --> 00:02:52,538 He rejected the idea 57 00:02:52,606 --> 00:02:54,907 and tried to prove it couldn't be real. 58 00:02:54,975 --> 00:02:56,275 GHOSE: You could have situations 59 00:02:56,343 --> 00:02:59,311 where the cause and the effect happen at the same time. 60 00:03:00,648 --> 00:03:03,649 NARRATOR: But if entanglement isn't real, 61 00:03:03,717 --> 00:03:06,084 cutting-edge technologies could be in jeopardy. 62 00:03:06,153 --> 00:03:08,654 KAISER: Quantum computers, quantum encryption-- 63 00:03:08,722 --> 00:03:11,890 they depend on entanglement being a fact in the world. 64 00:03:11,959 --> 00:03:13,392 ♪ ♪ 65 00:03:13,460 --> 00:03:14,660 NARRATOR: Underlying it all 66 00:03:14,728 --> 00:03:17,596 is a profound question: 67 00:03:17,665 --> 00:03:23,268 do we live in Einstein's universe of common-sense laws 68 00:03:23,337 --> 00:03:25,070 or a bizarre quantum reality 69 00:03:25,139 --> 00:03:29,041 that allows spooky connections across space and time? 70 00:03:29,109 --> 00:03:31,977 ♪ ♪ 71 00:03:41,055 --> 00:03:44,890 ♪ ♪ 72 00:03:49,897 --> 00:03:52,864 300 miles off the coast of West Africa, 73 00:03:52,933 --> 00:03:55,634 on one of the Canary Islands, 74 00:03:55,703 --> 00:03:59,104 a team of physicists is setting up a remarkable experiment 75 00:03:59,173 --> 00:04:03,308 that will use almost the entire breadth of the universe 76 00:04:03,377 --> 00:04:05,644 to settle the question, 77 00:04:05,713 --> 00:04:08,747 "Is the seemingly impossible phenomenon 78 00:04:08,816 --> 00:04:10,282 "of quantum entanglement 79 00:04:10,351 --> 00:04:11,850 "an illusion, 80 00:04:11,919 --> 00:04:14,753 or is it actually real?" 81 00:04:14,822 --> 00:04:18,924 Leading the team is Anton Zeilinger. 82 00:04:18,993 --> 00:04:25,097 ZEILINGER: So we're now going up the mountain 83 00:04:25,165 --> 00:04:27,866 towards the Roque de los Muchachos. 84 00:04:27,935 --> 00:04:30,969 So everything looks perfect today. 85 00:04:32,906 --> 00:04:34,473 NARRATOR: It's a precarious undertaking. 86 00:04:34,541 --> 00:04:36,775 They've got a short window 87 00:04:36,844 --> 00:04:40,345 on two of Europe's largest telescopes. 88 00:04:40,414 --> 00:04:44,716 Each one will simultaneously focus on a different quasar-- 89 00:04:44,785 --> 00:04:45,984 an extremely distant galaxy 90 00:04:46,053 --> 00:04:50,856 emitting huge amounts of light from its core. 91 00:04:50,924 --> 00:04:52,224 ♪ ♪ 92 00:04:52,293 --> 00:04:56,528 This light will be used to control precise equipment 93 00:04:56,597 --> 00:04:58,063 that must be perfectly aligned 94 00:04:58,132 --> 00:05:01,733 to make measurements on tiny subatomic particles. 95 00:05:02,369 --> 00:05:04,936 (speaking German): 96 00:05:05,005 --> 00:05:06,104 MAN (on radio): Okay. 97 00:05:06,173 --> 00:05:08,140 NARRATOR: And if that isn't tricky enough, 98 00:05:08,208 --> 00:05:12,711 the weather on the mountain is notoriously unpredictable. 99 00:05:12,780 --> 00:05:14,780 The team needs perfect conditions 100 00:05:14,848 --> 00:05:16,448 for the experiment to work. 101 00:05:16,517 --> 00:05:19,051 ♪ ♪ 102 00:05:19,119 --> 00:05:21,720 ZEILINGER: In the end it could be running smoothly 103 00:05:21,789 --> 00:05:26,425 or there need to be a couple of decisions made, 104 00:05:26,493 --> 00:05:30,295 you know, in an excited state in the last instant. 105 00:05:30,364 --> 00:05:33,999 ♪ ♪ 106 00:05:34,068 --> 00:05:37,436 NARRATOR: With the experiment finally set up, 107 00:05:37,504 --> 00:05:42,908 the team takes their positions. 108 00:05:42,976 --> 00:05:44,776 ♪ ♪ 109 00:05:46,347 --> 00:05:49,114 David Kaiser has worked on this experiment 110 00:05:49,183 --> 00:05:50,148 with his colleagues 111 00:05:50,217 --> 00:05:53,218 Jason Gallicchio and Andy Friedman 112 00:05:53,287 --> 00:05:55,187 for four years. 113 00:05:55,255 --> 00:05:59,157 Coordinating it all is Dominik Rauch. 114 00:05:59,226 --> 00:06:01,793 The experiment is his thesis project, 115 00:06:01,862 --> 00:06:03,628 and it's been years in the making. 116 00:06:03,697 --> 00:06:07,032 But as darkness falls, 117 00:06:07,101 --> 00:06:11,136 temperatures on the mountain begin to drop. 118 00:06:11,205 --> 00:06:15,607 MAN (speaking German, on radio): 119 00:06:16,243 --> 00:06:18,643 (speaking German) 120 00:06:18,712 --> 00:06:20,679 Okay, there's bad news. 121 00:06:20,748 --> 00:06:23,715 They have been told to leave the William Herschel 122 00:06:23,784 --> 00:06:25,217 because the road will be so dangerous, 123 00:06:25,285 --> 00:06:27,419 too dangerous, so they have to go down now. 124 00:06:27,488 --> 00:06:28,620 KAISER: Too icy? 125 00:06:28,689 --> 00:06:29,888 Yeah. That's okay. 126 00:06:29,957 --> 00:06:32,023 ♪ ♪ 127 00:06:34,895 --> 00:06:38,296 ♪ ♪ 128 00:06:45,572 --> 00:06:51,977 NARRATOR: The next day, the team prepares for another attempt. 129 00:06:52,045 --> 00:06:55,046 ♪ ♪ 130 00:06:55,115 --> 00:07:00,252 They verify the equipment hasn't been affected by the weather. 131 00:07:02,055 --> 00:07:07,659 But now, the air is thick with clouds. 132 00:07:13,267 --> 00:07:15,801 ZEILINGER: Here's the humidity at the various telescopes, 133 00:07:15,869 --> 00:07:19,337 and you see the humidity is 100%. 134 00:07:19,406 --> 00:07:23,608 So as long as this lasts, 135 00:07:23,677 --> 00:07:25,610 we can't do much. 136 00:07:25,679 --> 00:07:29,214 (wind whistling) 137 00:07:29,283 --> 00:07:30,615 (phone ringing) 138 00:07:30,684 --> 00:07:34,619 NARRATOR: The teams at both telescopes wait. 139 00:07:37,024 --> 00:07:40,125 But the clouds don't clear. 140 00:07:40,194 --> 00:07:45,063 All the preparation has come to nothing. 141 00:07:45,132 --> 00:07:48,934 Time on these huge telescopes is precious, 142 00:07:49,002 --> 00:07:50,902 and theirs has run out. 143 00:07:50,971 --> 00:07:54,105 This ambitious test of quantum entanglement 144 00:07:54,174 --> 00:07:57,476 must wait. 145 00:07:57,544 --> 00:08:03,982 ♪ ♪ 146 00:08:04,051 --> 00:08:06,117 Why are physicists so determined 147 00:08:06,186 --> 00:08:08,687 to put this bizarre aspect of quantum mechanics 148 00:08:08,755 --> 00:08:11,056 to the ultimate test? 149 00:08:13,994 --> 00:08:15,594 To explore the beginning of the story, 150 00:08:15,662 --> 00:08:17,929 David Kaiser has come to Brussels, 151 00:08:17,998 --> 00:08:22,868 the city that Albert Einstein traveled to in 1927 152 00:08:22,936 --> 00:08:26,137 to attend a meeting about a new theory 153 00:08:26,206 --> 00:08:30,542 that described the micro-world of atoms and tiny particles-- 154 00:08:30,611 --> 00:08:34,179 quantum mechanics. 155 00:08:34,248 --> 00:08:35,680 Quantum mechanics is one 156 00:08:35,749 --> 00:08:38,216 of the most amazing intellectual achievements in human history. 157 00:08:38,285 --> 00:08:40,752 GHOSE: For the first time, 158 00:08:40,821 --> 00:08:45,857 scientists were able to probe a world that was, until then, 159 00:08:45,926 --> 00:08:47,125 quite invisible to us. 160 00:08:47,194 --> 00:08:50,729 Looking at the world at the scale of atoms, 161 00:08:50,797 --> 00:08:54,799 a million times smaller than the width of a human hair. 162 00:08:54,868 --> 00:08:56,334 One way to think about the scales 163 00:08:56,403 --> 00:08:58,570 is that if you take an everyday object, 164 00:08:58,639 --> 00:09:02,874 like a soccer ball... 165 00:09:02,943 --> 00:09:04,442 and you enlarge that soccer ball, 166 00:09:04,511 --> 00:09:08,246 so that actually you can see the individual atoms, 167 00:09:08,315 --> 00:09:12,951 you roughly have to make it the size of the Earth. 168 00:09:13,020 --> 00:09:16,488 And then move into the planet. 169 00:09:16,557 --> 00:09:21,526 Then you are in the world of atoms and particles. 170 00:09:21,595 --> 00:09:24,863 NARRATOR: It was the nature of fundamental particles, 171 00:09:24,932 --> 00:09:28,333 which make up the world we see around us, 172 00:09:28,402 --> 00:09:31,269 that Einstein had come to Brussels to discuss. 173 00:09:31,338 --> 00:09:34,539 And it was here that Einstein entered into a heated debate 174 00:09:34,608 --> 00:09:41,880 that would lead to the discovery of quantum entanglement-- 175 00:09:41,949 --> 00:09:44,849 a concept that would trouble him for the rest of his life. 176 00:09:44,918 --> 00:09:47,185 ♪ ♪ 177 00:09:47,254 --> 00:09:50,789 David Kaiser has come to the place where it all began. 178 00:09:50,857 --> 00:09:53,458 ♪ ♪ 179 00:09:53,527 --> 00:09:57,195 KAISER: This is the original Solvay Institute building. 180 00:09:57,264 --> 00:09:59,431 Beautiful grand building. 181 00:09:59,499 --> 00:10:00,832 And this is the place, 182 00:10:00,901 --> 00:10:04,235 back in October 1927, 183 00:10:04,304 --> 00:10:06,304 where the fifth Solvay Conference was held. 184 00:10:06,373 --> 00:10:10,475 This amazing, weeklong series of discussions 185 00:10:10,544 --> 00:10:11,876 on really what the world was made of, 186 00:10:11,945 --> 00:10:15,246 on the nature of matter and the new quantum theory. 187 00:10:15,315 --> 00:10:19,584 And these steps are the very steps 188 00:10:19,653 --> 00:10:23,388 on which this famous group photograph was taken. 189 00:10:23,457 --> 00:10:25,190 It's a collection 190 00:10:25,258 --> 00:10:28,393 of the some of the most brilliant people in the world. 191 00:10:28,462 --> 00:10:30,662 Here in the front row, we see Albert Einstein, 192 00:10:30,731 --> 00:10:33,231 and the great Marie Curie and Max Planck; 193 00:10:33,300 --> 00:10:36,768 in the back row, standing, the dapper Erwin Schrödinger. 194 00:10:36,837 --> 00:10:38,903 And these sort of brash 20-year-olds, or mid-20s, 195 00:10:38,972 --> 00:10:41,373 Werner Heisenberg and Wolfgang Pauli. 196 00:10:41,441 --> 00:10:46,411 NARRATOR: These scientists were the pioneers of quantum mechanics. 197 00:10:46,480 --> 00:10:49,247 KAISER: I had a huge version of this photograph 198 00:10:49,316 --> 00:10:50,315 up on the wall, 199 00:10:50,384 --> 00:10:51,716 it was a poster in my college dorm room. 200 00:10:51,785 --> 00:10:53,518 My roommates had their favorite bands, 201 00:10:53,587 --> 00:10:55,954 and I had the 1927 Solvay Conference, 202 00:10:56,023 --> 00:10:57,555 which says a lot. 203 00:10:57,624 --> 00:11:00,792 NARRATOR: This was one of the greatest meetings of minds 204 00:11:00,861 --> 00:11:02,927 in history. 205 00:11:02,996 --> 00:11:05,664 More than half were, or would become, 206 00:11:05,732 --> 00:11:08,667 Nobel Prize winners. 207 00:11:08,735 --> 00:11:13,271 Their experiments were showing that deep inside matter, 208 00:11:13,340 --> 00:11:17,208 tiny particles-- like atoms and their orbiting electrons-- 209 00:11:17,277 --> 00:11:20,512 were not solid little spheres. 210 00:11:20,580 --> 00:11:25,483 They seemed fuzzy and undefined. 211 00:11:25,552 --> 00:11:28,119 KAISER: So this, this group here, 212 00:11:28,188 --> 00:11:29,554 these, these were the folks 213 00:11:29,623 --> 00:11:34,092 who had just been plumbing deeper and deeper and deeper 214 00:11:34,161 --> 00:11:36,494 to find what they hoped would be a bedrock 215 00:11:36,563 --> 00:11:37,529 of what the world was made of, 216 00:11:37,597 --> 00:11:39,364 and to their surprise, 217 00:11:39,433 --> 00:11:42,200 they found things less and less solid as they dug in. 218 00:11:42,269 --> 00:11:44,135 This world was not tiny little bricks 219 00:11:44,204 --> 00:11:45,470 that got smaller and smaller. 220 00:11:45,539 --> 00:11:48,907 At some point, the bricks gave way to this mush, 221 00:11:48,975 --> 00:11:51,176 and what looked like solidity, solidness, 222 00:11:51,244 --> 00:11:53,178 in fact became very confusing 223 00:11:53,246 --> 00:11:56,281 and kind of a whole new way of thinking about nature. 224 00:11:56,349 --> 00:11:58,883 ♪ ♪ 225 00:12:01,321 --> 00:12:03,521 NARRATOR: The theory of quantum mechanics presented at the meeting 226 00:12:03,590 --> 00:12:06,891 was strange. 227 00:12:06,960 --> 00:12:10,528 It said that a particle, like an electron, 228 00:12:10,597 --> 00:12:15,066 isn't physically real until it's observed-- 229 00:12:15,135 --> 00:12:19,604 measured by an instrument that can detect it. 230 00:12:19,673 --> 00:12:21,840 Before it's detected, 231 00:12:21,908 --> 00:12:24,442 instead of being a solid particle, 232 00:12:24,511 --> 00:12:27,846 an electron is just a fuzzy wave-- 233 00:12:27,914 --> 00:12:31,616 a wave of probability. 234 00:12:31,685 --> 00:12:34,919 These objects, like electrons and atoms, 235 00:12:34,988 --> 00:12:37,622 when we describe mathematically their behavior, 236 00:12:37,691 --> 00:12:39,157 the only thing we can describe 237 00:12:39,226 --> 00:12:44,129 is the probability of being at one place or another. 238 00:12:44,197 --> 00:12:45,263 CARROLL: It's like a wave 239 00:12:45,332 --> 00:12:47,098 of all those different possibilities. 240 00:12:47,167 --> 00:12:50,201 It's not that the electron is in one place or the other, 241 00:12:50,270 --> 00:12:51,903 we just don't know, 242 00:12:51,972 --> 00:12:54,239 it's that the electron really is a combination 243 00:12:54,307 --> 00:12:56,975 of every possible place it could be 244 00:12:57,043 --> 00:12:58,409 until we look at it. 245 00:12:59,813 --> 00:13:03,014 NARRATOR: Quantum mechanics only tells us the probability 246 00:13:03,083 --> 00:13:04,849 of a particle's properties, 247 00:13:04,918 --> 00:13:07,085 like location. 248 00:13:07,154 --> 00:13:10,555 The laws of nature were no longer definite statements 249 00:13:10,624 --> 00:13:12,657 about what's going to happen next. 250 00:13:12,726 --> 00:13:15,460 They were just statements about probabilities. 251 00:13:15,529 --> 00:13:18,062 And Einstein felt, "Well, that's defeat. 252 00:13:18,131 --> 00:13:21,766 "You're giving up on the heart of what physics has been, 253 00:13:21,835 --> 00:13:25,136 namely, to give a complete description of reality." 254 00:13:25,205 --> 00:13:28,139 ♪ ♪ 255 00:13:28,208 --> 00:13:30,175 NARRATOR: For Einstein, 256 00:13:30,243 --> 00:13:33,511 the idea that particles only pop into existence 257 00:13:33,580 --> 00:13:35,413 when they're observed 258 00:13:35,482 --> 00:13:39,450 is akin to magic. 259 00:13:39,519 --> 00:13:41,186 It's said he asked, 260 00:13:41,254 --> 00:13:43,888 "Do you really believe the moon is not there 261 00:13:43,957 --> 00:13:47,959 when you are not looking at it?" 262 00:13:48,028 --> 00:13:49,327 ♪ ♪ 263 00:13:49,396 --> 00:13:52,530 Outside of the formal setting of the conference... 264 00:13:52,599 --> 00:13:54,265 KAISER: Bonsoir. 265 00:13:54,334 --> 00:13:57,001 NARRATOR: ...he challenged the most vocal supporter of these ideas: 266 00:13:57,070 --> 00:14:02,240 the great Danish physicist Niels Bohr. 267 00:14:02,309 --> 00:14:04,943 KAISER: Einstein would show up to breakfast at the hotel, 268 00:14:05,011 --> 00:14:06,544 and Niels Bohr would be there, 269 00:14:06,613 --> 00:14:08,880 and Einstein would present his latest challenge. 270 00:14:08,949 --> 00:14:11,516 Niels Bohr would sort of mumble and wonder 271 00:14:11,585 --> 00:14:13,384 and confer with his younger colleagues. 272 00:14:13,453 --> 00:14:16,588 They'd head off to the formal meeting at the institute, 273 00:14:16,656 --> 00:14:19,657 and somehow, every night by suppertime, 274 00:14:19,726 --> 00:14:21,226 Bohr would have an answer. 275 00:14:21,294 --> 00:14:22,927 One of the observers said 276 00:14:22,996 --> 00:14:24,529 that Einstein was like a jack-in-the-box; 277 00:14:24,598 --> 00:14:26,431 every day, he'd pop up with a new challenge. 278 00:14:26,499 --> 00:14:28,733 And Bohr would flip this way and that, 279 00:14:28,802 --> 00:14:31,169 and in the end, by supper, have crushed that one, 280 00:14:31,238 --> 00:14:32,604 and it would start all over again. 281 00:14:34,774 --> 00:14:36,774 NARRATOR: To Bohr and his colleagues, 282 00:14:36,843 --> 00:14:41,012 quantum mechanics not only explained experimental results, 283 00:14:41,081 --> 00:14:45,083 its mathematics were elegant and beautiful. 284 00:14:45,151 --> 00:14:49,153 And since Einstein hadn't found flaws in their equations, 285 00:14:49,222 --> 00:14:53,291 they left the Solvay meeting feeling more confident than ever 286 00:14:53,360 --> 00:14:55,126 in their ideas. 287 00:14:55,195 --> 00:14:58,329 But Einstein didn't give up his conviction 288 00:14:58,398 --> 00:15:02,033 that quantum mechanics was flawed. 289 00:15:02,102 --> 00:15:03,635 And in his refusal to accept 290 00:15:03,703 --> 00:15:06,237 the weird implications of the theory, 291 00:15:06,306 --> 00:15:10,909 he would wind up uncovering something even weirder. 292 00:15:10,977 --> 00:15:12,410 ♪ ♪ 293 00:15:12,479 --> 00:15:17,482 In 1933, with the Nazi Party in power in Germany, 294 00:15:17,550 --> 00:15:20,018 Einstein chose to settle in America 295 00:15:20,086 --> 00:15:22,820 and took a position at the Institute for Advanced Study 296 00:15:22,889 --> 00:15:24,889 in Princeton, New Jersey. 297 00:15:24,958 --> 00:15:27,625 ♪ ♪ 298 00:15:27,694 --> 00:15:30,795 He recruited two physicists to help him, 299 00:15:30,864 --> 00:15:35,266 Nathan Rosen and Boris Podolsky. 300 00:15:35,335 --> 00:15:38,202 And in 1935, at afternoon tea, 301 00:15:38,271 --> 00:15:41,906 the three men spotted a possible flaw in quantum mechanics 302 00:15:41,975 --> 00:15:45,043 that would shake the very foundations of the theory. 303 00:15:46,980 --> 00:15:49,814 They noticed that the mathematics of quantum mechanics 304 00:15:49,883 --> 00:15:54,886 led to a seemingly impossible situation. 305 00:15:54,955 --> 00:15:59,490 Today, Robbert Dijkgraaf is the director of the institute. 306 00:15:59,559 --> 00:16:00,992 DIJKGRAAF: Apparently Podolsky would say, 307 00:16:01,061 --> 00:16:02,927 "Well, Professor Einstein, 308 00:16:02,996 --> 00:16:05,496 "this is very important in your arguments 309 00:16:05,565 --> 00:16:08,566 showing that quantum theory is incomplete." 310 00:16:08,635 --> 00:16:11,736 So they got this very animated discussion 311 00:16:11,805 --> 00:16:13,638 and what can happen still is, 312 00:16:13,707 --> 00:16:16,240 now you have a bunch of scientists discussing, 313 00:16:16,309 --> 00:16:19,877 and at some point, someone says, "Let's write a paper together." 314 00:16:19,946 --> 00:16:20,878 So they did. 315 00:16:20,947 --> 00:16:23,448 ♪ ♪ 316 00:16:23,516 --> 00:16:26,985 NARRATOR: Their paper, known today as EPR, 317 00:16:27,053 --> 00:16:31,856 argued that the equations of quantum mechanics 318 00:16:31,925 --> 00:16:35,360 predicted an impossible connection between particles-- 319 00:16:35,428 --> 00:16:37,695 a seemingly magical effect. 320 00:16:39,265 --> 00:16:42,834 It would be like having two particles, 321 00:16:42,902 --> 00:16:44,969 each hidden under a cup. 322 00:16:47,407 --> 00:16:49,674 Looking at one 323 00:16:49,743 --> 00:16:54,245 mysteriously causes the other to reveal itself, too, 324 00:16:54,314 --> 00:16:58,016 with matching properties. 325 00:16:59,019 --> 00:17:00,752 Quantum theory suggested 326 00:17:00,820 --> 00:17:04,555 this effect could happen in the real world, 327 00:17:04,624 --> 00:17:08,826 for example, with particles of light-- photons. 328 00:17:10,330 --> 00:17:13,398 The equations implied that a source of photons 329 00:17:13,466 --> 00:17:16,667 could create pairs in such a way 330 00:17:16,736 --> 00:17:18,936 that when we measure one, 331 00:17:19,005 --> 00:17:21,539 causing it to snap out of its fuzzy state, 332 00:17:21,608 --> 00:17:26,277 the other mysteriously snaps out of its fuzzy state 333 00:17:26,346 --> 00:17:28,112 at the same instant, 334 00:17:28,181 --> 00:17:30,615 with correlated properties. 335 00:17:36,156 --> 00:17:39,824 The 1935 paper that described this effect 336 00:17:39,893 --> 00:17:44,729 has become Einstein's most referenced work of all. 337 00:17:44,798 --> 00:17:48,833 It has captivated generations of physicists, 338 00:17:48,902 --> 00:17:52,537 including Anton Zeilinger. 339 00:17:52,605 --> 00:17:56,974 ZEILINGER: The Einstein-Podolsky-Rosen paper fascinated me. 340 00:17:57,043 --> 00:18:00,511 And I had to read it at least five or six times 341 00:18:00,580 --> 00:18:03,181 until I finally understood what goes on. 342 00:18:03,249 --> 00:18:06,184 And then it didn't let me go again. 343 00:18:06,252 --> 00:18:09,687 NARRATOR: Another way to think of the paired particles 344 00:18:09,756 --> 00:18:14,258 is to imagine a game of chance that's somehow rigged. 345 00:18:14,327 --> 00:18:19,130 Suppose I had a pair of quantum dice. 346 00:18:19,199 --> 00:18:24,569 I put these two quantum dice in my little cup, 347 00:18:24,637 --> 00:18:28,005 throw them. 348 00:18:28,074 --> 00:18:31,876 I look at them, they show the same number-- six. 349 00:18:31,945 --> 00:18:34,245 I put them again in the cup, 350 00:18:34,314 --> 00:18:36,848 throw them again. 351 00:18:36,916 --> 00:18:39,784 Now they both show three. 352 00:18:39,853 --> 00:18:44,255 I put them in again, throw again, 353 00:18:44,324 --> 00:18:46,858 now they both show one. 354 00:18:46,926 --> 00:18:50,394 Point now being, what I see here is, 355 00:18:50,463 --> 00:18:53,531 I see two random processes-- 356 00:18:53,600 --> 00:18:56,000 namely, each die showing some number-- 357 00:18:56,069 --> 00:19:02,106 but these two random processes do the same. 358 00:19:02,175 --> 00:19:03,708 It's really mind-boggling. 359 00:19:03,776 --> 00:19:05,276 ♪ ♪ 360 00:19:05,345 --> 00:19:08,513 NARRATOR: How could two particles act in unison, 361 00:19:08,581 --> 00:19:11,282 even when they're separated from each other? 362 00:19:13,786 --> 00:19:15,586 Essential to the EPR argument 363 00:19:15,655 --> 00:19:18,089 is that these particles can be, can be separated 364 00:19:18,158 --> 00:19:19,357 at an arbitrary distance. 365 00:19:19,425 --> 00:19:20,791 One could be here at Princeton, 366 00:19:20,860 --> 00:19:22,593 one could be in the Andromeda Galaxy. 367 00:19:22,662 --> 00:19:25,396 And yet, according to quantum mechanics, 368 00:19:25,465 --> 00:19:27,298 a choice to measure something here 369 00:19:27,367 --> 00:19:30,034 is somehow instantaneously affecting 370 00:19:30,103 --> 00:19:32,503 what could be said about this other particle. 371 00:19:32,572 --> 00:19:34,939 You can't go from Princeton to Andromeda instantly, 372 00:19:35,008 --> 00:19:36,440 and yet that, they argued, 373 00:19:36,509 --> 00:19:38,643 is what the equations of quantum mechanics seemed to imply, 374 00:19:38,711 --> 00:19:39,844 and that, they said, 375 00:19:39,913 --> 00:19:41,279 so much the worse for quantum mechanics. 376 00:19:41,347 --> 00:19:43,748 The world simply can't operate that way. 377 00:19:45,418 --> 00:19:49,153 NARRATOR: For Einstein, this strange effect conflicted 378 00:19:49,222 --> 00:19:53,391 with the most basic concept we use to describe reality-- 379 00:19:53,459 --> 00:19:55,092 space. 380 00:19:55,161 --> 00:20:00,264 For him, objects, particles, everything that exists 381 00:20:00,333 --> 00:20:04,368 is located in space. 382 00:20:04,437 --> 00:20:07,138 Space, together with time, 383 00:20:07,207 --> 00:20:10,374 was the key ingredient in his theory of special relativity, 384 00:20:10,443 --> 00:20:17,615 with its famous equation, E = MC squared. 385 00:20:17,684 --> 00:20:21,886 CARROLL: Einstein, of course, was the master of space-time. 386 00:20:21,955 --> 00:20:24,255 He thought that if something happened here, 387 00:20:24,324 --> 00:20:27,058 that shouldn't immediately and instantaneously 388 00:20:27,126 --> 00:20:28,960 change something that is going on over there-- 389 00:20:29,028 --> 00:20:31,829 the principle of locality, as we currently call it. 390 00:20:33,533 --> 00:20:36,434 NARRATOR: For Einstein, it's simply common sense 391 00:20:36,502 --> 00:20:39,704 that if objects are separated in space, 392 00:20:39,772 --> 00:20:41,906 for one to affect the other, 393 00:20:41,975 --> 00:20:45,977 something must travel between them. 394 00:20:46,045 --> 00:20:50,281 ♪ ♪ 395 00:20:50,350 --> 00:20:52,083 And that traveling takes time. 396 00:20:56,189 --> 00:20:59,757 Quantum particles acting in unison could be explained 397 00:20:59,826 --> 00:21:03,194 if they were communicating-- 398 00:21:03,263 --> 00:21:06,998 one particle instantly sending a signal to the other, 399 00:21:07,066 --> 00:21:10,935 telling it what properties it should have. 400 00:21:11,004 --> 00:21:12,837 But that would require a signal 401 00:21:12,905 --> 00:21:15,573 traveling faster than the speed of light, 402 00:21:15,642 --> 00:21:18,209 something Einstein's theory of special relativity 403 00:21:18,278 --> 00:21:22,747 had proven impossible. 404 00:21:22,815 --> 00:21:28,085 And it would mean the particles were fuzzy and undefined 405 00:21:28,154 --> 00:21:33,791 until the moment they were observed. 406 00:21:33,860 --> 00:21:35,760 Instead, 407 00:21:35,828 --> 00:21:39,430 Einstein thought the particles should be real all along. 408 00:21:39,499 --> 00:21:43,534 They must carry with them a hidden layer of deeper physics 409 00:21:43,603 --> 00:21:48,105 that determines their properties from the start. 410 00:21:48,174 --> 00:21:50,574 Almost the way that magic tricks, 411 00:21:50,643 --> 00:21:56,480 while appearing mysterious, have a hidden explanation. 412 00:21:56,549 --> 00:22:00,551 But this hidden physics was missing from quantum theory. 413 00:22:00,620 --> 00:22:05,022 So Einstein, Podolsky, and Rosen argued that quantum mechanics 414 00:22:05,091 --> 00:22:07,124 was incomplete. 415 00:22:07,193 --> 00:22:09,493 ♪ ♪ 416 00:22:09,562 --> 00:22:12,596 DIJKGRAAF: Podolsky was very enthusiastic about this project. 417 00:22:12,665 --> 00:22:14,365 In fact, he was so enthusiastic 418 00:22:14,434 --> 00:22:17,368 that he ran to the "New York Times" 419 00:22:17,437 --> 00:22:18,602 and told them the news. 420 00:22:18,671 --> 00:22:21,639 So Einstein was really upset with Podolsky, 421 00:22:21,708 --> 00:22:24,275 and apparently, he didn't speak to him anymore. 422 00:22:24,344 --> 00:22:25,876 ♪ ♪ 423 00:22:25,945 --> 00:22:28,779 NARRATOR: When Niels Bohr heard of Einstein's paper, 424 00:22:28,848 --> 00:22:32,149 he wrote an obscure response, 425 00:22:32,218 --> 00:22:35,252 arguing that one particle could somehow 426 00:22:35,321 --> 00:22:38,522 mysteriously influence the other. 427 00:22:38,591 --> 00:22:40,591 This seemingly impossible phenomenon 428 00:22:40,660 --> 00:22:45,296 became known as quantum entanglement. 429 00:22:47,367 --> 00:22:52,670 But Einstein dismissed it as "spooky actions at a distance." 430 00:22:54,374 --> 00:22:56,707 No one could think of an experiment to test 431 00:22:56,776 --> 00:23:01,746 whether Einstein or Bohr was correct. 432 00:23:01,814 --> 00:23:04,682 But that didn't stop physicists and engineers 433 00:23:04,751 --> 00:23:06,384 from making use of quantum mechanics 434 00:23:06,452 --> 00:23:09,520 to do new things. 435 00:23:09,589 --> 00:23:11,689 GHOSE: In the '30s and '40s, 436 00:23:11,758 --> 00:23:15,426 the debate around the EPR paper sort of dies down. 437 00:23:15,495 --> 00:23:17,328 But, quantum theory actually takes off. 438 00:23:17,397 --> 00:23:19,730 ♪ ♪ 439 00:23:19,799 --> 00:23:23,734 The mathematics leads to all kinds of amazing developments. 440 00:23:23,803 --> 00:23:26,370 NARRATOR: Entanglement aside, 441 00:23:26,439 --> 00:23:27,838 the equations of quantum mechanics 442 00:23:27,907 --> 00:23:31,175 enabled the scientists of the Manhattan Project 443 00:23:31,244 --> 00:23:33,911 to develop the atomic bomb. 444 00:23:33,980 --> 00:23:36,347 And in the years after the Second World War, 445 00:23:36,416 --> 00:23:39,083 researchers at Bell Labs New Jersey 446 00:23:39,152 --> 00:23:42,286 used quantum theory to develop one of the first lasers... 447 00:23:42,355 --> 00:23:43,621 MAN (in film): In our laboratories, 448 00:23:43,689 --> 00:23:45,356 men experiment with a light 449 00:23:45,425 --> 00:23:48,292 once undreamed-of in the natural world. 450 00:23:48,361 --> 00:23:49,760 NARRATOR: ...and build small devices 451 00:23:49,829 --> 00:23:52,430 that could control the flow of electricity-- 452 00:23:52,498 --> 00:23:54,398 transistors. 453 00:23:54,467 --> 00:23:57,468 MAN 2 (on film): It's destined to play a vital role in your future, 454 00:23:57,537 --> 00:23:59,637 your electronic future. 455 00:23:59,705 --> 00:24:02,640 NARRATOR: Transistors became the building blocks 456 00:24:02,708 --> 00:24:05,276 of the burgeoning field of electronics. 457 00:24:05,344 --> 00:24:06,677 Computers, disc drives-- 458 00:24:06,746 --> 00:24:10,414 the entire digital revolution soon followed, 459 00:24:10,483 --> 00:24:11,449 all made possible 460 00:24:11,517 --> 00:24:14,785 by the equations of quantum theory. 461 00:24:15,855 --> 00:24:19,557 Yet Einstein's questions about entanglement 462 00:24:19,625 --> 00:24:20,758 and what it implied 463 00:24:20,827 --> 00:24:22,726 about the incompleteness of quantum mechanics 464 00:24:22,795 --> 00:24:27,398 remained unanswered until the 1960s, 465 00:24:27,467 --> 00:24:30,634 when a physicist from Northern Ireland 466 00:24:30,703 --> 00:24:32,970 made a remarkable breakthrough-- 467 00:24:33,039 --> 00:24:35,372 John Bell. 468 00:24:35,441 --> 00:24:38,075 KAISER: Bell was a very talented young physics student, 469 00:24:38,144 --> 00:24:40,811 but he quickly grew dissatisfied with what he considered almost, 470 00:24:40,880 --> 00:24:43,047 almost a kind of dishonesty among his teachers. 471 00:24:43,115 --> 00:24:44,448 (talking in background) 472 00:24:44,517 --> 00:24:45,783 NARRATOR: Bell insisted 473 00:24:45,852 --> 00:24:48,586 that Einstein's questions about quantum mechanics 474 00:24:48,654 --> 00:24:50,221 had not been addressed. 475 00:24:50,289 --> 00:24:52,990 KAISER: He got into shouting matches with his professors. 476 00:24:53,059 --> 00:24:55,292 "Don't tell us that Bohr solved all the problems. 477 00:24:55,361 --> 00:24:58,028 This really deserves further thought." 478 00:24:58,097 --> 00:25:01,765 BELL: Quantum mechanics has been fantastically successful. 479 00:25:01,834 --> 00:25:04,969 So it is a very intriguing situation 480 00:25:05,037 --> 00:25:07,705 that at the, at the foundation 481 00:25:07,773 --> 00:25:10,908 of all that impressive success, 482 00:25:10,977 --> 00:25:12,443 there are these great doubts. 483 00:25:12,512 --> 00:25:15,279 ♪ ♪ 484 00:25:15,348 --> 00:25:18,349 CARROLL: It's a very strange thing that ever since the 1930s, 485 00:25:18,417 --> 00:25:20,551 the idea of sitting and thinking hard 486 00:25:20,620 --> 00:25:22,319 about the foundations of quantum mechanics 487 00:25:22,388 --> 00:25:25,389 has been disreputable among professional physicists. 488 00:25:25,458 --> 00:25:27,057 When people tried to do that, 489 00:25:27,126 --> 00:25:29,393 they were kicked out of physics departments. 490 00:25:29,462 --> 00:25:31,228 And so, for someone like Bell, 491 00:25:31,297 --> 00:25:34,965 he needed to have a day job doing ordinary particle physics, 492 00:25:35,034 --> 00:25:36,800 but at night, you know, hidden away, 493 00:25:36,869 --> 00:25:38,002 he could do work 494 00:25:38,070 --> 00:25:39,503 on the foundations of quantum mechanics. 495 00:25:39,572 --> 00:25:42,740 NARRATOR: Bell became a leading particle physicist 496 00:25:42,808 --> 00:25:44,608 at CERN, in Geneva. 497 00:25:44,677 --> 00:25:46,844 But he continued to explore the debate 498 00:25:46,913 --> 00:25:50,047 between Einstein and Bohr. 499 00:25:50,116 --> 00:25:54,752 And in 1964, he published an astonishing paper. 500 00:25:56,522 --> 00:25:58,656 Bell proved 501 00:25:58,724 --> 00:26:02,860 that Bohr's and Einstein's ideas made different predictions. 502 00:26:02,929 --> 00:26:07,197 If you could randomly perform one of two possible measurements 503 00:26:07,266 --> 00:26:08,666 on each particle, 504 00:26:08,734 --> 00:26:13,370 and check how often the results lined up, 505 00:26:13,439 --> 00:26:16,173 the answer would reveal whether we lived in Einstein's world-- 506 00:26:16,242 --> 00:26:20,044 a world that followed common-sense laws-- 507 00:26:20,112 --> 00:26:23,514 or Bohr's-- 508 00:26:23,583 --> 00:26:25,816 a world that was deeply strange 509 00:26:25,885 --> 00:26:28,919 and allowed spooky quantum connections. 510 00:26:28,988 --> 00:26:30,187 We now know with hindsight 511 00:26:30,256 --> 00:26:32,523 this was one of the most significant articles 512 00:26:32,592 --> 00:26:33,757 in the history of physics-- 513 00:26:33,826 --> 00:26:35,559 not just the history of 20th-century physics, 514 00:26:35,628 --> 00:26:38,128 in the history of, of the field as a whole. 515 00:26:40,266 --> 00:26:42,866 But Bell's article appears in this, you know, 516 00:26:42,935 --> 00:26:44,201 sort of out-of-the-way journal-- 517 00:26:44,270 --> 00:26:46,503 in fact, the journal itself folds a few years later. 518 00:26:46,572 --> 00:26:49,006 This is not central to the physics community. 519 00:26:49,075 --> 00:26:51,875 It's sort of dutifully filed on library shelves 520 00:26:51,944 --> 00:26:53,077 and then forgotten. 521 00:26:53,145 --> 00:26:55,512 It literally collects dust on the shelf. 522 00:26:55,581 --> 00:27:00,584 NARRATOR: A few years later, completely by chance, 523 00:27:00,653 --> 00:27:02,252 a brilliant experimental physicist 524 00:27:02,321 --> 00:27:05,389 stumbled upon Bell's article. 525 00:27:05,458 --> 00:27:08,525 JOHN CLAUSER: I thought this is one of the most amazing papers 526 00:27:08,594 --> 00:27:11,662 I had ever read in my whole life. 527 00:27:11,731 --> 00:27:15,332 And I kept wondering, "Well, gee, this is wonderful, 528 00:27:15,401 --> 00:27:18,135 but where's the experimental evidence?" 529 00:27:18,204 --> 00:27:20,704 NARRATOR: John worked on Bell's theory 530 00:27:20,773 --> 00:27:22,539 with fellow physicist Abner Shimony, 531 00:27:22,608 --> 00:27:25,709 and at the University of California, Berkeley, 532 00:27:25,778 --> 00:27:28,812 started work on an experiment to test it. 533 00:27:28,881 --> 00:27:32,683 He had a talent for tinkering in the lab 534 00:27:32,752 --> 00:27:34,118 and building the parts he needed. 535 00:27:34,186 --> 00:27:35,586 CLAUSER: I used to rummage around here 536 00:27:35,655 --> 00:27:38,489 and scavenge and dumpster-dive for old equipment. 537 00:27:38,557 --> 00:27:42,793 NARRATOR: He knew where to find hidden storage rooms, like this, 538 00:27:42,862 --> 00:27:45,863 which he could raid to salvage spare parts 539 00:27:45,931 --> 00:27:48,165 for his experiments. 540 00:27:48,234 --> 00:27:50,968 (grunts) 541 00:27:51,037 --> 00:27:55,873 CLAUSER: This was a power supply for diode lasers. 542 00:27:55,941 --> 00:27:58,008 That looks like something I built. 543 00:27:58,077 --> 00:28:01,278 ♪ ♪ 544 00:28:01,347 --> 00:28:03,881 Here is a picture of the experiment I did. 545 00:28:03,949 --> 00:28:07,751 (chuckling): I had more hair in those days. 546 00:28:07,820 --> 00:28:09,286 Here's another picture. 547 00:28:09,355 --> 00:28:10,954 This is of Stu Freedman, 548 00:28:11,023 --> 00:28:13,223 who worked on it with me. 549 00:28:13,292 --> 00:28:18,162 NARRATOR: Piece by piece, John Clauser and Stuart Freedman 550 00:28:18,230 --> 00:28:21,498 constructed the world's first Bell test experiment. 551 00:28:21,567 --> 00:28:25,636 They focused a laser onto calcium atoms, 552 00:28:25,705 --> 00:28:28,672 causing them to emit pairs of photons 553 00:28:28,741 --> 00:28:31,608 that the equations of quantum theory suggested 554 00:28:31,677 --> 00:28:34,611 should be entangled. 555 00:28:34,680 --> 00:28:37,347 They recorded whether or not the photons passed 556 00:28:37,416 --> 00:28:40,284 through filters on each side 557 00:28:40,352 --> 00:28:44,822 and checked how often the answers agreed. 558 00:28:44,890 --> 00:28:47,491 After hundreds of thousands of measurements, 559 00:28:47,560 --> 00:28:49,259 if the pairs were more correlated 560 00:28:49,328 --> 00:28:51,929 than Einstein's physics predicted, 561 00:28:51,997 --> 00:28:57,201 they must be spookily entangled. 562 00:28:57,269 --> 00:28:59,103 We saw the stronger correlation 563 00:28:59,171 --> 00:29:00,771 characteristic of quantum mechanics. 564 00:29:00,840 --> 00:29:04,708 We measured it, and that is what we got. 565 00:29:04,777 --> 00:29:06,477 ♪ ♪ 566 00:29:06,545 --> 00:29:07,678 NARRATOR: The outcome was exactly 567 00:29:07,747 --> 00:29:11,181 what Bohr's quantum mechanics predicted. 568 00:29:11,250 --> 00:29:14,151 The experiment appeared to show 569 00:29:14,220 --> 00:29:16,954 that the spooky connections of quantum entanglement 570 00:29:17,022 --> 00:29:20,090 did exist in the natural world. 571 00:29:20,159 --> 00:29:27,531 Could it be that the great Albert Einstein was wrong? 572 00:29:27,600 --> 00:29:29,333 Remarkably, 573 00:29:29,401 --> 00:29:33,604 the first people to react to this extraordinary result 574 00:29:33,672 --> 00:29:36,707 were not the world's leading physicists. 575 00:29:36,776 --> 00:29:40,277 ♪ ♪ 576 00:29:40,346 --> 00:29:43,313 CLAUSER: Ronald Reagan's definition of a hippie 577 00:29:43,382 --> 00:29:47,217 was someone who dresses like Tarzan, 578 00:29:47,286 --> 00:29:48,452 has hair like Jane, 579 00:29:48,521 --> 00:29:50,721 and smells like Cheeta. 580 00:29:50,790 --> 00:29:51,388 (laughs) 581 00:29:51,457 --> 00:29:54,625 ♪ ♪ 582 00:29:54,693 --> 00:29:57,694 NARRATOR: A small group of free-thinking physicists 583 00:29:57,763 --> 00:30:01,198 at the heart of San Francisco's New Age scene 584 00:30:01,267 --> 00:30:04,001 got in touch with John. 585 00:30:04,069 --> 00:30:07,070 KAISER: They called themselves the Fundamental Fysiks Group. 586 00:30:07,139 --> 00:30:08,972 They spelled physics with an F. 587 00:30:09,041 --> 00:30:12,075 Some members would experiment with psychedelic drugs. 588 00:30:12,144 --> 00:30:14,077 I mean, they were, they were kind of in the flow 589 00:30:14,146 --> 00:30:15,412 of the kind of hippie scene. 590 00:30:15,481 --> 00:30:17,815 And that group was just mesmerized 591 00:30:17,883 --> 00:30:19,016 by the question of entanglement. 592 00:30:19,084 --> 00:30:21,885 ♪ ♪ 593 00:30:21,954 --> 00:30:24,855 CLAUSER: The idea was just to discuss fringe subjects 594 00:30:24,924 --> 00:30:26,023 with an open mind. 595 00:30:26,091 --> 00:30:27,357 And I thought, "Oh, sure! 596 00:30:27,426 --> 00:30:29,459 Uh, that's kind of what I do." 597 00:30:29,528 --> 00:30:31,495 ♪ ♪ 598 00:30:31,564 --> 00:30:36,200 They were doing their best to link Eastern mysticism 599 00:30:36,268 --> 00:30:38,769 with quantum entanglement. 600 00:30:38,838 --> 00:30:41,338 They sold a lot of popular textbooks. 601 00:30:41,407 --> 00:30:43,640 There were a lot of followers. 602 00:30:43,709 --> 00:30:46,076 NARRATOR: Their books became bestsellers, 603 00:30:46,145 --> 00:30:50,214 like "The Tao of Physics," which highlighted 604 00:30:50,282 --> 00:30:52,082 that Eastern philosophy and quantum entanglement 605 00:30:52,151 --> 00:30:55,052 both described a deep connectedness 606 00:30:55,120 --> 00:30:57,621 of things in the universe. 607 00:30:57,690 --> 00:30:59,756 It was the great cosmic oneness. 608 00:30:59,825 --> 00:31:05,696 NARRATOR: The group held meetings at the iconic Esalen Institute. 609 00:31:05,764 --> 00:31:08,565 CLAUSER: It was a marvelous, beautiful place 610 00:31:08,634 --> 00:31:10,601 where they would discuss all of these ideas. 611 00:31:10,669 --> 00:31:13,670 It was right on the Pacific Coast 612 00:31:13,739 --> 00:31:15,606 with the overflow from the hot tubs 613 00:31:15,674 --> 00:31:18,942 cascading down the cliffs into the Pacific Ocean. 614 00:31:19,011 --> 00:31:21,945 To my knowledge, 615 00:31:22,014 --> 00:31:25,582 no useful connections to Eastern mysticism 616 00:31:25,651 --> 00:31:27,351 were ever discovered by the group. 617 00:31:27,419 --> 00:31:29,953 ♪ ♪ 618 00:31:30,022 --> 00:31:31,822 (chuckles): But it was fun. 619 00:31:33,359 --> 00:31:35,058 NARRATOR: The Fundamental Fysiks Group 620 00:31:35,127 --> 00:31:38,929 may not have uncovered the secrets of "cosmic oneness," 621 00:31:38,998 --> 00:31:42,900 but in seeing entanglement as central to physics, 622 00:31:42,968 --> 00:31:48,972 they were decades ahead of their time. 623 00:31:49,041 --> 00:31:53,310 ♪ ♪ 624 00:31:53,379 --> 00:31:55,145 40 years later, 625 00:31:55,214 --> 00:31:57,514 cutting-edge labs around the world 626 00:31:57,583 --> 00:32:00,584 are now racing to harness quantum entanglement 627 00:32:00,653 --> 00:32:04,488 to create revolutionary new technologies... 628 00:32:04,556 --> 00:32:07,190 ♪ ♪ 629 00:32:07,259 --> 00:32:10,627 ...like quantum computers. 630 00:32:10,696 --> 00:32:12,930 ♪ ♪ 631 00:32:12,998 --> 00:32:14,298 GHOSE: In our everyday computers, 632 00:32:14,366 --> 00:32:17,701 the fundamental unit of computing is a bit, 633 00:32:17,770 --> 00:32:19,770 a binary digit-- zero or one. 634 00:32:19,838 --> 00:32:22,506 And inside the computer, there's all these transistors, 635 00:32:22,574 --> 00:32:24,241 which are turning on and off currents. 636 00:32:24,310 --> 00:32:26,476 On is one, off is zero, 637 00:32:26,545 --> 00:32:30,180 and these combinations lead to universal computing. 638 00:32:30,249 --> 00:32:31,715 With a quantum computer, 639 00:32:31,784 --> 00:32:33,050 you start with a fundamental unit 640 00:32:33,118 --> 00:32:35,719 that's not a bit, but a quantum bit, 641 00:32:35,788 --> 00:32:38,288 which is not really a zero or a one, 642 00:32:38,357 --> 00:32:39,323 but it can be fluid. 643 00:32:39,391 --> 00:32:41,425 ♪ ♪ 644 00:32:41,493 --> 00:32:46,430 NARRATOR: A quantum bit makes use of the fuzziness of the quantum world. 645 00:32:46,498 --> 00:32:47,965 A qubit, as it's known, 646 00:32:48,033 --> 00:32:53,270 can be zero or one, or a combination of both. 647 00:32:53,339 --> 00:32:55,906 A particle or tiny quantum system 648 00:32:55,975 --> 00:32:58,075 can be made into a qubit. 649 00:32:58,143 --> 00:33:00,310 And today, it's not just pairs of particles 650 00:33:00,379 --> 00:33:02,512 that can be entangled. 651 00:33:02,581 --> 00:33:05,849 Groups of qubits can be linked with entanglement 652 00:33:05,918 --> 00:33:08,352 to create a quantum computer. 653 00:33:08,420 --> 00:33:10,454 ♪ ♪ 654 00:33:10,522 --> 00:33:14,124 The more qubits, the greater the processing power. 655 00:33:14,193 --> 00:33:16,426 ♪ ♪ 656 00:33:16,495 --> 00:33:20,464 At Google's quantum computing laboratory in Santa Barbara, 657 00:33:20,532 --> 00:33:23,834 the team has recently succeeded in creating a tiny chip 658 00:33:23,902 --> 00:33:27,738 that holds an array of 72 qubits. 659 00:33:27,806 --> 00:33:30,307 ♪ ♪ 660 00:33:30,376 --> 00:33:32,442 The task for researcher Marissa Giustina 661 00:33:32,511 --> 00:33:33,744 and her colleagues 662 00:33:33,812 --> 00:33:38,448 is to send signals to these microscopic qubits 663 00:33:38,517 --> 00:33:42,786 to control and entangle them. 664 00:33:42,855 --> 00:33:45,522 GIUSTINA: Mounted on the underside of this plate, 665 00:33:45,591 --> 00:33:47,457 we have the quantum processing chip itself, 666 00:33:47,526 --> 00:33:49,893 in essence, a quantum playground, 667 00:33:49,962 --> 00:33:50,894 you could say. 668 00:33:50,963 --> 00:33:54,164 Each qubit is a quantum object 669 00:33:54,233 --> 00:33:57,801 that we should be able to control at will. 670 00:33:57,870 --> 00:34:00,437 Thinking about it as... 671 00:34:00,506 --> 00:34:03,707 "the faster version of that PC over there" 672 00:34:03,776 --> 00:34:06,710 would be a great slight to this. 673 00:34:06,779 --> 00:34:08,345 It can be much more than that. 674 00:34:10,349 --> 00:34:12,849 NARRATOR: By using entangled qubits, 675 00:34:12,918 --> 00:34:15,786 quantum computers could tackle real-world problems 676 00:34:15,854 --> 00:34:19,589 that traditional computers simply can't cope with. 677 00:34:21,393 --> 00:34:22,826 For example, 678 00:34:22,895 --> 00:34:25,295 a salesman has to travel to several cities 679 00:34:25,364 --> 00:34:28,765 and wants to find the shortest route. 680 00:34:28,834 --> 00:34:31,935 Sounds easy. 681 00:34:32,004 --> 00:34:33,804 But with just 30 cities, 682 00:34:33,872 --> 00:34:36,273 there are so many possible routes 683 00:34:36,341 --> 00:34:38,341 that it would take an ordinary computer, 684 00:34:38,410 --> 00:34:39,843 even a powerful one, 685 00:34:39,912 --> 00:34:43,213 hundreds of years to try each one 686 00:34:43,282 --> 00:34:45,882 and find the shortest. 687 00:34:45,951 --> 00:34:48,385 But with a handful of entangled qubits, 688 00:34:48,454 --> 00:34:51,721 a quantum computer could resolve the optimal path 689 00:34:51,790 --> 00:34:55,092 in a fraction of the number of steps. 690 00:34:57,396 --> 00:35:00,897 There's another reason teams like Marissa's are racing 691 00:35:00,966 --> 00:35:03,200 to create a powerful quantum computer-- 692 00:35:03,268 --> 00:35:07,270 cracking secret codes. 693 00:35:07,339 --> 00:35:09,706 In today's world, everything from online shopping 694 00:35:09,775 --> 00:35:13,009 to covert military communications 695 00:35:13,078 --> 00:35:17,314 is protected from hackers using secure digital codes, 696 00:35:17,382 --> 00:35:22,652 a process called encryption. 697 00:35:22,721 --> 00:35:26,356 But what if hackers could get hold 698 00:35:26,425 --> 00:35:28,458 of quantum computers? 699 00:35:28,527 --> 00:35:29,793 GHOSE: A quantum computer 700 00:35:29,862 --> 00:35:32,462 could crack our best encryption protocols 701 00:35:32,531 --> 00:35:33,697 in minutes, 702 00:35:33,765 --> 00:35:35,031 whereas a regular computer, 703 00:35:35,100 --> 00:35:37,134 or even a super-computing network today, 704 00:35:37,202 --> 00:35:39,569 couldn't do it, you know, given months of time. 705 00:35:41,039 --> 00:35:43,507 NARRATOR: But while quantum entanglement may be a threat 706 00:35:43,575 --> 00:35:45,408 to traditional encryption, 707 00:35:45,477 --> 00:35:50,046 it also offers an even more secure alternative-- 708 00:35:50,115 --> 00:35:54,651 a communication system that the very laws of physics 709 00:35:54,720 --> 00:35:57,120 protect from secret hacking. 710 00:35:57,189 --> 00:35:59,923 ♪ ♪ 711 00:36:01,460 --> 00:36:05,762 Researchers in China are leading the way. 712 00:36:05,831 --> 00:36:08,165 Here in Shanghai, 713 00:36:08,233 --> 00:36:11,968 at the University of Science and Technology, 714 00:36:12,037 --> 00:36:18,108 Jian-Wei Pan runs a leading quantum research center. 715 00:36:18,177 --> 00:36:19,676 His teams are working to harness 716 00:36:19,745 --> 00:36:23,747 the properties of the quantum world. 717 00:36:23,815 --> 00:36:28,585 They can send secret messages using a stream of photons 718 00:36:28,654 --> 00:36:31,154 in a system that instantly detects 719 00:36:31,223 --> 00:36:34,391 any attempt to eavesdrop. 720 00:36:35,561 --> 00:36:37,294 Jian-Wei's team 721 00:36:37,362 --> 00:36:40,063 has created a network of optical fibers 722 00:36:40,132 --> 00:36:41,965 more than a thousand miles long 723 00:36:42,034 --> 00:36:44,501 that can carry secure information 724 00:36:44,570 --> 00:36:47,437 from Beijing to Shanghai. 725 00:36:47,506 --> 00:36:51,741 It is used by banks and data companies. 726 00:36:51,810 --> 00:36:56,246 But there's a limit to how far quantum signals can be sent 727 00:36:56,315 --> 00:36:59,382 through optical fibers. 728 00:36:59,451 --> 00:37:00,717 To send signals further, 729 00:37:00,786 --> 00:37:02,986 Jian-Wei's team launched 730 00:37:03,055 --> 00:37:07,257 the world's first quantum communication satellite. 731 00:37:09,761 --> 00:37:14,197 Above Earth's atmosphere, there are fewer obstacles, 732 00:37:14,266 --> 00:37:18,401 and quantum particles can travel much further. 733 00:37:18,470 --> 00:37:21,805 ♪ ♪ 734 00:37:21,873 --> 00:37:26,142 Each night, teams on the ground prepare to track the satellite 735 00:37:26,211 --> 00:37:28,078 across the sky. 736 00:37:28,146 --> 00:37:31,815 ♪ ♪ 737 00:37:31,883 --> 00:37:34,417 Laser guidance equipment locks on 738 00:37:34,486 --> 00:37:38,388 and allows signals to be sent and received. 739 00:37:38,457 --> 00:37:41,458 The team aims to use this equipment 740 00:37:41,526 --> 00:37:44,761 to create a new, secure communication system 741 00:37:44,830 --> 00:37:47,564 using quantum entanglement. 742 00:37:50,369 --> 00:37:52,535 The satellite sends entangled photons 743 00:37:52,604 --> 00:37:54,237 to two users. 744 00:37:54,306 --> 00:37:58,508 An eavesdropper could intercept one of the entangled photons, 745 00:37:58,577 --> 00:38:03,747 measure it, and send on a replacement photon. 746 00:38:03,815 --> 00:38:06,583 But it wouldn't be an entangled photon-- 747 00:38:06,652 --> 00:38:08,785 its properties wouldn't match. 748 00:38:08,854 --> 00:38:13,390 It would be clear an eavesdropper was on the line. 749 00:38:13,458 --> 00:38:15,225 In theory, this technique could be used 750 00:38:15,294 --> 00:38:19,162 to create a totally secure global communication network. 751 00:38:19,231 --> 00:38:20,897 PAN: So the next step is, 752 00:38:20,966 --> 00:38:23,900 we will have ground station, for example, in Canada, 753 00:38:23,969 --> 00:38:26,970 and also in Africa and many countries. 754 00:38:27,039 --> 00:38:29,239 So, we will use our satellite 755 00:38:29,308 --> 00:38:31,641 for the global quantum communication. 756 00:38:31,710 --> 00:38:35,345 We want to push this technology as far as possible. 757 00:38:36,682 --> 00:38:38,148 NARRATOR: These are the first steps 758 00:38:38,216 --> 00:38:41,318 in creating a completely unhackable quantum internet 759 00:38:41,386 --> 00:38:42,652 of the future-- 760 00:38:42,721 --> 00:38:47,424 made possible by quantum entanglement. 761 00:38:47,492 --> 00:38:49,626 But there's a problem. 762 00:38:49,695 --> 00:38:52,495 What if quantum entanglement-- 763 00:38:52,564 --> 00:38:55,365 "spooky action at a distance"-- 764 00:38:55,434 --> 00:38:57,200 isn't real after all? 765 00:38:59,237 --> 00:39:01,571 It could mean entangled photons are not the path 766 00:39:01,640 --> 00:39:04,874 to complete security. 767 00:39:04,943 --> 00:39:06,209 The question goes back 768 00:39:06,278 --> 00:39:10,347 to Clauser and Freedman's Bell test experiment. 769 00:39:10,415 --> 00:39:12,182 ♪ ♪ 770 00:39:12,250 --> 00:39:14,818 In the years after their pioneering work, 771 00:39:14,886 --> 00:39:17,721 physicists began to test possible loopholes 772 00:39:17,789 --> 00:39:21,024 in their experiment-- 773 00:39:21,093 --> 00:39:23,460 ways in which the illusion of entanglement 774 00:39:23,528 --> 00:39:25,929 might be created, 775 00:39:25,997 --> 00:39:29,966 so the effect might not be so spooky after all. 776 00:39:30,035 --> 00:39:34,371 One loophole is especially hard to rule out. 777 00:39:35,807 --> 00:39:39,943 In modern Bell test experiments, devices at each side test 778 00:39:40,011 --> 00:39:43,413 whether the photons can pass through one of two filters 779 00:39:43,482 --> 00:39:45,782 that are randomly chosen, 780 00:39:45,851 --> 00:39:48,651 effectively asking one of two questions 781 00:39:48,720 --> 00:39:52,655 and checking how often the answers agree. 782 00:39:52,724 --> 00:39:54,824 After thousands of photons, 783 00:39:54,893 --> 00:39:56,993 if the results show more agreement 784 00:39:57,062 --> 00:39:59,429 than Einstein's physics predicts, 785 00:39:59,498 --> 00:40:05,034 the particles must be spookily entangled. 786 00:40:05,103 --> 00:40:06,269 But what if something 787 00:40:06,338 --> 00:40:09,105 had mysteriously influenced the equipment 788 00:40:09,174 --> 00:40:11,908 so that the choices of the filters 789 00:40:11,977 --> 00:40:15,111 were not truly random? 790 00:40:15,180 --> 00:40:17,247 KAISER: Is there any common cause, 791 00:40:17,315 --> 00:40:20,784 deep in the past, before you even turn on your device, 792 00:40:20,852 --> 00:40:23,153 that could have nudged the questions to be asked 793 00:40:23,221 --> 00:40:24,921 and the types of particles to be emitted? 794 00:40:24,990 --> 00:40:26,990 Maybe some strange particle, 795 00:40:27,058 --> 00:40:29,826 maybe some force that had not been taken into account, 796 00:40:29,895 --> 00:40:31,327 so that what looks like entanglement 797 00:40:31,396 --> 00:40:33,730 might indeed be an accident, an illusion. 798 00:40:33,799 --> 00:40:36,900 Maybe the world still acts like Einstein thought. 799 00:40:36,968 --> 00:40:40,837 ♪ ♪ 800 00:40:40,906 --> 00:40:42,138 NARRATOR: It is this loophole 801 00:40:42,207 --> 00:40:44,908 that the team at the high-altitude observatory 802 00:40:44,976 --> 00:40:46,042 in the Canary Islands 803 00:40:46,111 --> 00:40:48,978 is working to tackle. 804 00:40:49,047 --> 00:40:52,916 ♪ ♪ 805 00:40:52,984 --> 00:40:57,320 With quantum mechanics now more established than ever, 806 00:40:57,389 --> 00:40:59,856 they're determined to put entanglement 807 00:40:59,925 --> 00:41:01,391 to the ultimate test, 808 00:41:01,460 --> 00:41:03,993 and finally settle the Einstein-Bohr debate 809 00:41:04,062 --> 00:41:05,662 beyond all reasonable doubt. 810 00:41:05,730 --> 00:41:09,666 The team is creating a giant version 811 00:41:09,734 --> 00:41:11,768 of Clauser and Freedman's Bell test, 812 00:41:11,837 --> 00:41:15,538 with the entire universe as their lab bench. 813 00:41:17,876 --> 00:41:21,911 In this "cosmic Bell test," 814 00:41:21,980 --> 00:41:24,814 the source of the entangled particles 815 00:41:24,883 --> 00:41:29,252 is about a third of a mile from each of the detectors. 816 00:41:29,321 --> 00:41:32,755 The team must send perfectly timed pairs of photons 817 00:41:32,824 --> 00:41:35,592 through the air to each side. 818 00:41:35,660 --> 00:41:38,795 At the same time, the telescopes will collect light 819 00:41:38,864 --> 00:41:42,832 from two extremely far-off, extremely bright galaxies 820 00:41:42,901 --> 00:41:44,868 called quasars. 821 00:41:44,936 --> 00:41:47,904 These are among the brightest objects in the sky, 822 00:41:47,973 --> 00:41:51,508 emitting light in powerful jets. 823 00:41:51,576 --> 00:41:53,977 Random variations in this light 824 00:41:54,045 --> 00:41:55,845 will control which filters are used 825 00:41:55,914 --> 00:41:58,548 to measure the photon pairs. 826 00:41:58,617 --> 00:42:01,684 And since the quasars are so far away-- 827 00:42:01,753 --> 00:42:04,354 the light has been traveling for billions of years 828 00:42:04,422 --> 00:42:06,356 to reach Earth-- 829 00:42:06,424 --> 00:42:08,191 it makes it incredibly unlikely 830 00:42:08,260 --> 00:42:10,927 that anything could be influencing the random nature 831 00:42:10,996 --> 00:42:13,763 of the test. 832 00:42:15,600 --> 00:42:17,667 If the experiment is successful, 833 00:42:17,736 --> 00:42:19,269 the team will have tackled the loophole 834 00:42:19,337 --> 00:42:21,905 and shown that quantum entanglement 835 00:42:21,973 --> 00:42:24,674 is as spooky as Bohr always claimed. 836 00:42:24,743 --> 00:42:28,878 Dominik and Jason are at one telescope. 837 00:42:28,947 --> 00:42:30,179 Hello, Anton. 838 00:42:30,248 --> 00:42:33,983 NARRATOR: Anton is at the other. 839 00:42:34,052 --> 00:42:37,320 (speaking German): 840 00:42:37,389 --> 00:42:39,756 ZEILINGER (speaking German on phone): 841 00:42:39,824 --> 00:42:42,191 RAUCH (speaking German): 842 00:42:42,894 --> 00:42:45,895 (both speaking German) 843 00:42:45,964 --> 00:42:51,367 ♪ ♪ 844 00:42:51,436 --> 00:42:54,604 NARRATOR: With clear skies finally overhead, 845 00:42:54,673 --> 00:42:57,473 the huge telescopes awaken... 846 00:42:57,542 --> 00:43:00,243 ♪ ♪ 847 00:43:03,915 --> 00:43:06,616 ...poised to collect light from distant quasars. 848 00:43:06,685 --> 00:43:10,853 ♪ ♪ 849 00:43:10,922 --> 00:43:11,921 Moving. 850 00:43:11,990 --> 00:43:14,157 MAN (speaking German on radio): 851 00:43:14,225 --> 00:43:15,158 MAN 2: All right. 852 00:43:15,226 --> 00:43:16,326 Dark count level. 853 00:43:16,394 --> 00:43:17,894 MAN (on radio): Okay, this is good. 854 00:43:17,963 --> 00:43:19,896 RAUCH: So we're doing everything... 855 00:43:19,965 --> 00:43:21,931 ...everything at once now. 856 00:43:22,000 --> 00:43:23,333 So the guys for the links 857 00:43:23,401 --> 00:43:25,969 are setting the state of the entangled photon pair. 858 00:43:26,037 --> 00:43:27,804 We're trying to acquire the quasar. 859 00:43:27,872 --> 00:43:30,907 We're just centering it 860 00:43:30,976 --> 00:43:32,976 and making the field of view as small as possible, 861 00:43:33,044 --> 00:43:35,244 to be sure that we only have the quasar. 862 00:43:35,313 --> 00:43:36,279 Okay. 863 00:43:36,348 --> 00:43:37,547 It's guiding now? Yes. 864 00:43:37,616 --> 00:43:38,581 Let's wait for one more image. 865 00:43:38,650 --> 00:43:40,016 Okay. Of this one. 866 00:43:40,085 --> 00:43:41,050 MAN: All right. 867 00:43:41,119 --> 00:43:43,987 Great, great, great, great, great. 868 00:43:44,055 --> 00:43:45,355 Yeah, that's good. 869 00:43:45,957 --> 00:43:47,357 Looks like, 90, 870 00:43:47,425 --> 00:43:50,326 let's say 91 to be conservative, of purity. 871 00:43:52,097 --> 00:43:54,263 NARRATOR: With the telescopes now locked on 872 00:43:54,332 --> 00:43:57,033 to two different quasars, 873 00:43:57,102 --> 00:43:59,168 the team begins to take readings. 874 00:43:59,237 --> 00:44:01,971 MAN (on radio): The red counts, 12,000. 875 00:44:02,040 --> 00:44:04,107 Blue counts, 7,000. 876 00:44:04,175 --> 00:44:07,010 ♪ ♪ 877 00:44:12,150 --> 00:44:15,485 We did a full, the full cosmic Bell test. 878 00:44:15,553 --> 00:44:16,953 MAN: What? 879 00:44:17,022 --> 00:44:18,655 Yeah, we're doing a full cosmic Bell test. 880 00:44:20,025 --> 00:44:21,557 NARRATOR: It's working. 881 00:44:21,626 --> 00:44:25,695 Light from the quasars is selecting which filters are used 882 00:44:25,764 --> 00:44:30,366 to measure the entangled photons. 883 00:44:30,435 --> 00:44:32,035 RAUCH: It is exciting. 884 00:44:32,103 --> 00:44:33,136 It is. 885 00:44:33,204 --> 00:44:34,504 Now we do have a test, 886 00:44:34,572 --> 00:44:37,907 but it's not clear what the outcome will be. 887 00:44:37,976 --> 00:44:40,610 ♪ ♪ 888 00:44:40,679 --> 00:44:41,744 MAN: Moving. 889 00:44:41,813 --> 00:44:45,314 (man talking indistinctly on radio) 890 00:44:45,383 --> 00:44:46,749 MAN: All right. 891 00:44:46,818 --> 00:44:50,653 Everything is exactly the same, beautiful, perfect, yeah. 892 00:44:50,722 --> 00:44:52,755 ♪ ♪ 893 00:45:05,670 --> 00:45:08,938 ♪ ♪ 894 00:45:09,007 --> 00:45:10,840 NARRATOR: Two months later, back in Vienna, 895 00:45:10,909 --> 00:45:14,644 the team analyzes the experimental data. 896 00:45:14,713 --> 00:45:18,014 RAUCH: This might take a second. 897 00:45:19,584 --> 00:45:21,684 The numbers look really great. 898 00:45:21,753 --> 00:45:23,753 And it is extremely pleasing to see 899 00:45:23,822 --> 00:45:26,155 that all this worked so nice. 900 00:45:26,224 --> 00:45:28,524 We clearly see correlations 901 00:45:28,593 --> 00:45:29,926 that correspond to quantum mechanics. 902 00:45:29,994 --> 00:45:33,329 NARRATOR: The results show entanglement. 903 00:45:33,398 --> 00:45:36,332 ♪ ♪ 904 00:45:36,401 --> 00:45:38,334 And since the light from the quasars 905 00:45:38,403 --> 00:45:39,502 controlling the test 906 00:45:39,571 --> 00:45:43,005 was nearly eight billion years old, 907 00:45:43,074 --> 00:45:44,407 it's extremely unlikely 908 00:45:44,476 --> 00:45:48,377 that anything could have affected its random nature. 909 00:45:48,446 --> 00:45:53,282 This remaining loophole seems to be closed. 910 00:45:53,351 --> 00:45:56,652 ZEILINGER: The experiment we did is just fantastic. 911 00:45:56,721 --> 00:45:58,755 The big cosmos comes down 912 00:45:58,823 --> 00:46:01,924 to control a small quantum experiment. 913 00:46:01,993 --> 00:46:05,561 That, that in itself is a, is, is beautiful. 914 00:46:05,630 --> 00:46:10,233 ♪ ♪ 915 00:46:10,301 --> 00:46:13,035 You know, honestly, I still, I still get chills. 916 00:46:13,104 --> 00:46:14,837 I mean... 917 00:46:14,906 --> 00:46:16,205 ...when I realize what our team was able to do, 918 00:46:16,274 --> 00:46:19,442 in this intellectual journey that stretches back 919 00:46:19,511 --> 00:46:21,844 to the early years of the 20th century. 920 00:46:21,913 --> 00:46:24,947 There's, there's hardly any room left 921 00:46:25,016 --> 00:46:29,752 for a kind of alternative, Einstein-like explanation. 922 00:46:29,821 --> 00:46:31,087 We haven't ruled it out, 923 00:46:31,156 --> 00:46:34,257 but we've shoved it into such a tiny corner of the cosmos 924 00:46:34,325 --> 00:46:37,593 as to make it even more implausible 925 00:46:37,662 --> 00:46:39,829 for anything other than entanglement 926 00:46:39,898 --> 00:46:41,097 to explain our results. 927 00:46:41,166 --> 00:46:44,500 ♪ ♪ 928 00:46:44,569 --> 00:46:46,669 NARRATOR: Accepting that entanglement is a part 929 00:46:46,738 --> 00:46:49,305 of the natural world around us 930 00:46:49,374 --> 00:46:52,809 has profound implications. 931 00:46:52,877 --> 00:46:55,111 It means we must accept that an action in one place 932 00:46:55,180 --> 00:46:58,681 can have an instant effect anywhere in the universe, 933 00:46:58,750 --> 00:47:02,051 as if there's no space between them. 934 00:47:02,120 --> 00:47:07,023 Or that particles only take on physical properties 935 00:47:07,091 --> 00:47:10,726 when we observe them. 936 00:47:10,795 --> 00:47:13,663 Or we must accept both. 937 00:47:13,731 --> 00:47:15,998 We're left with conclusions about the universe 938 00:47:16,067 --> 00:47:17,767 that make no sense whatsoever. 939 00:47:17,836 --> 00:47:20,937 Science is stepping outside of all of our boundaries 940 00:47:21,005 --> 00:47:23,072 of common sense. 941 00:47:23,141 --> 00:47:25,341 It's almost like being in "Alice in Wonderland," right? 942 00:47:25,410 --> 00:47:28,277 Where everything is possible. 943 00:47:32,016 --> 00:47:33,749 ♪ ♪ 944 00:47:33,818 --> 00:47:35,484 NARRATOR: It was first seen 945 00:47:35,553 --> 00:47:38,387 as an unwelcome but unavoidable consequence 946 00:47:38,456 --> 00:47:40,890 of quantum mechanics. 947 00:47:40,959 --> 00:47:45,161 Now, after nearly a century of disputes and discoveries, 948 00:47:45,230 --> 00:47:47,530 "spooky action at a distance" 949 00:47:47,599 --> 00:47:51,868 is finally at the heart of modern physics. 950 00:47:51,936 --> 00:47:55,104 At the Institute for Advanced Study, 951 00:47:55,173 --> 00:47:57,306 where the concept of entanglement 952 00:47:57,375 --> 00:47:59,475 was first described, 953 00:47:59,544 --> 00:48:02,211 researchers are now using it 954 00:48:02,280 --> 00:48:06,148 in their search for a single unified theory of the universe-- 955 00:48:06,217 --> 00:48:10,286 the holy grail of physics. 956 00:48:11,923 --> 00:48:15,791 Einstein's theories of special and general relativity 957 00:48:15,860 --> 00:48:19,262 perfectly describe space, time, and gravity 958 00:48:19,330 --> 00:48:22,031 at the largest scales of the universe, 959 00:48:22,100 --> 00:48:26,035 while quantum mechanics perfectly describes 960 00:48:26,104 --> 00:48:27,503 the tiniest scales. 961 00:48:27,572 --> 00:48:33,409 Yet these two theories have never been brought together. 962 00:48:33,478 --> 00:48:36,946 So far, we have not yet had a single complete theory 963 00:48:37,015 --> 00:48:39,048 that is both quantum mechanical 964 00:48:39,117 --> 00:48:40,516 and reproduces the prediction 965 00:48:40,585 --> 00:48:44,687 of Einstein's wonderful theory of general relativity. 966 00:48:44,756 --> 00:48:47,790 Maybe the secret is entanglement. 967 00:48:49,661 --> 00:48:52,361 NARRATOR: What if space itself is actually created 968 00:48:52,430 --> 00:48:55,798 by the tiny quantum world? 969 00:48:55,867 --> 00:48:59,502 Just like temperature, warm and cold, 970 00:48:59,570 --> 00:49:04,173 consists simply of the movement of atoms inside an object, 971 00:49:04,242 --> 00:49:07,076 perhaps space as we know it 972 00:49:07,145 --> 00:49:12,148 emerges from networks of entangled quantum particles. 973 00:49:12,216 --> 00:49:16,118 It's a mind-blowing idea. 974 00:49:16,187 --> 00:49:18,321 DIJKGRAAF: What we are learning these days 975 00:49:18,389 --> 00:49:22,491 is that we might have to give up that what Einstein holds sacred, 976 00:49:22,560 --> 00:49:23,893 namely, space and time. 977 00:49:23,962 --> 00:49:26,028 So, he was always thinking, 978 00:49:26,097 --> 00:49:27,430 "Well, we have little pieces of space and time, 979 00:49:27,498 --> 00:49:30,666 and out of this, we build the whole universe." 980 00:49:30,735 --> 00:49:36,839 NARRATOR: In a radical theory-- known as the holographic universe-- 981 00:49:36,908 --> 00:49:40,776 space and time are created by entangled quantum particles 982 00:49:40,845 --> 00:49:44,880 on a sphere that's infinitely far away. 983 00:49:44,949 --> 00:49:47,616 What's happening in space 984 00:49:47,685 --> 00:49:50,987 in some sense all described 985 00:49:51,055 --> 00:49:54,290 in terms of a screen outside here. 986 00:49:54,359 --> 00:49:56,258 The ultimate description of reality 987 00:49:56,327 --> 00:49:58,427 resides on this screen. 988 00:49:58,496 --> 00:50:01,630 Think of it as kind of quantum bits living on that screen. 989 00:50:01,699 --> 00:50:04,700 And this, like a movie projector, 990 00:50:04,769 --> 00:50:08,437 creates a illusion of the three-dimensional reality 991 00:50:08,506 --> 00:50:10,806 that I'm now experiencing. 992 00:50:13,044 --> 00:50:16,379 NARRATOR: It may be impossible to intuitively understand 993 00:50:16,447 --> 00:50:19,515 this wild mathematical idea, 994 00:50:19,584 --> 00:50:21,150 but it suggests 995 00:50:21,219 --> 00:50:23,152 that entanglement could be 996 00:50:23,221 --> 00:50:28,591 what forms the true fabric of the universe. 997 00:50:28,659 --> 00:50:32,028 The most puzzling element of entanglement, 998 00:50:32,096 --> 00:50:36,365 that, you know, somehow two points in space can communicate, 999 00:50:36,434 --> 00:50:38,000 becomes less of a problem, 1000 00:50:38,069 --> 00:50:39,835 because space itself has disappeared. 1001 00:50:39,904 --> 00:50:43,539 In the end, we just have this quantum mechanical world. 1002 00:50:43,608 --> 00:50:46,275 There is no space anymore. 1003 00:50:46,344 --> 00:50:50,212 And so in some sense, the paradoxes of entanglement... 1004 00:50:50,281 --> 00:50:53,883 The EPR paradox disappears into thin air. 1005 00:50:53,951 --> 00:50:58,220 ♪ ♪ 1006 00:50:58,289 --> 00:51:01,057 CARROLL: Truly understanding quantum mechanics 1007 00:51:01,125 --> 00:51:03,192 will only happen when we put ourselves 1008 00:51:03,261 --> 00:51:04,727 on the entanglement side, 1009 00:51:04,796 --> 00:51:08,597 and we stop privileging the world that we see 1010 00:51:08,666 --> 00:51:10,266 and start thinking about the world 1011 00:51:10,334 --> 00:51:11,267 as it actually is. 1012 00:51:11,335 --> 00:51:14,070 ♪ ♪ 1013 00:51:14,138 --> 00:51:17,506 KAISER: Science has made enormous progress for centuries 1014 00:51:17,575 --> 00:51:21,043 by sort of breaking complicated systems down into parts. 1015 00:51:21,112 --> 00:51:23,212 When we come to a phenomenon like quantum entanglement, 1016 00:51:23,281 --> 00:51:24,680 that scheme breaks. 1017 00:51:26,150 --> 00:51:29,051 When it comes to the bedrock of quantum mechanics, 1018 00:51:29,120 --> 00:51:32,621 the whole is more than the sum of its parts. 1019 00:51:32,690 --> 00:51:34,657 ♪ ♪ 1020 00:51:34,725 --> 00:51:37,560 ZEILINGER: The basic motivation is 1021 00:51:37,628 --> 00:51:39,995 just to learn how nature works. 1022 00:51:40,064 --> 00:51:42,598 What's really going on? 1023 00:51:42,667 --> 00:51:44,033 Einstein said it very nicely. 1024 00:51:44,102 --> 00:51:46,402 He's not interested in this detailed question 1025 00:51:46,471 --> 00:51:47,670 or that detailed question. 1026 00:51:47,738 --> 00:51:50,306 He just wanted to know 1027 00:51:50,374 --> 00:51:55,077 what were God's thoughts when He created the world. 1028 00:51:55,146 --> 00:51:58,447 ♪ ♪ 1029 00:52:13,064 --> 00:52:16,065 To order this "NOVA" program on DVD, 1030 00:52:16,067 --> 00:52:20,536 visit ShopPBS or call 1-800-PLAY-PBS. 1031 00:52:20,538 --> 00:52:25,074 This program is also available on Amazon Prime Video. 1032 00:52:25,076 --> 00:52:28,144 ♪ ♪