1 00:00:00,330 --> 00:00:04,830 Hello and welcome to this series on physics and philosophy from the University of Oxford. 2 00:00:06,160 --> 00:00:08,890 And bang! He disappeared. And a puff of smoke. 3 00:00:09,940 --> 00:00:16,270 The ability of genies to appear and disappear at will is a familiar idea in much of children's literature. 4 00:00:17,050 --> 00:00:22,510 The concept of teleportation has sparked our imagination and has often been explored in science fiction. 5 00:00:23,320 --> 00:00:28,780 But could we really transport ourselves instantaneously from one point in space to another? 6 00:00:30,010 --> 00:00:37,180 The possibility of teleportation is just one of the mind boggling phenomena that results from the theory of quantum mechanics. 7 00:00:38,070 --> 00:00:41,220 An exploration into the microscopic behaviour of the universe. 8 00:00:41,670 --> 00:00:46,230 Quantum theory has provided us with many surprising and unexpected results. 9 00:00:47,160 --> 00:00:50,880 How far into the realm of science fiction is modern science taking us? 10 00:00:51,840 --> 00:01:01,120 I am Ankita an urban. And I am speaking to Professor VLATKO Vedral, Professor of Quantum Information Science and Fellow at Wolfson College, Oxford. 11 00:01:02,520 --> 00:01:11,640 Professor Vedral has written a number of books on quantum theory, including the popular science book Decoding Reality, published in 2010. 12 00:01:12,690 --> 00:01:20,760 In this, he discusses the idea of the universe being made of quantum information and describes some of the surprising results. 13 00:01:20,850 --> 00:01:31,840 Quantum mechanics provides us with. These have consequences in fields such as quantum computing, quantum cryptography and perhaps even teleportation. 14 00:01:33,060 --> 00:01:38,130 This interview was recorded via Skype, so the sound quality is lower than previous podcasts. 15 00:01:39,680 --> 00:01:45,560 The advent of quantum mechanics in the 20th century marked a huge turning point and one in physics. 16 00:01:45,950 --> 00:01:49,130 What was it about this new theory that made it so revolutionary? 17 00:01:50,060 --> 00:02:00,260 I think the most revolutionary aspect probably was, first of all, to break away from causality of classical physics in classical physics, 18 00:02:01,190 --> 00:02:12,020 which is basically any physics before quantum physics and certainly includes Newtonian mechanics, but it also includes electromagnetic phenomena. 19 00:02:12,800 --> 00:02:19,490 Basically, anything at that time was causal in the sense that if you control your initial conditions, 20 00:02:19,490 --> 00:02:25,190 if you make your experiment and you make exactly the same preparation of your experiment, 21 00:02:25,250 --> 00:02:29,990 then you should always expect the same kind of outcome of your of your experiment. 22 00:02:30,710 --> 00:02:38,090 If you can control your system initially perfectly well, then you can say exactly deterministically what's going to happen in the future. 23 00:02:38,510 --> 00:02:44,030 And the first thing that quantum mechanics really violated is exactly this, that if you you know, 24 00:02:44,030 --> 00:02:48,739 if you control your experiment with hundred percent accuracy and efficiency, 25 00:02:48,740 --> 00:02:53,550 you still cannot predict what's going to happen in any individual experiment. 26 00:02:53,570 --> 00:03:00,790 And this was a big surprise. In fact, Einstein really disliked very strongly this feature of quantum mechanics. 27 00:03:00,830 --> 00:03:08,990 He kept saying, God doesn't play dice, and I can't believe that God would construct this kind of random universe in some sense. 28 00:03:09,560 --> 00:03:18,230 So this was a big really break away from classical physics. And the second thing, and interestingly enough, Einstein also complained about this a lot. 29 00:03:18,650 --> 00:03:25,100 He called this spooky action that the distance was nonlocality of quantum mechanics. 30 00:03:25,100 --> 00:03:29,270 The fact that it looks as though you can make a measurement on one part of 31 00:03:29,270 --> 00:03:33,950 the universe but affect something that's very far away from where you acted. 32 00:03:35,030 --> 00:03:39,089 And I think these two features are the key features of quantum mechanics. 33 00:03:39,090 --> 00:03:48,810 So the fundamental randomness and and the possibility of having correlations between events that are very far from from one another. 34 00:03:50,120 --> 00:03:53,840 So the results that it provides seem quite counterintuitive to me. 35 00:03:54,200 --> 00:04:02,000 So as you said, Einstein was a famous critic. Could you please tell us about a little bit about the EPR paradox that he postulated as a. 36 00:04:02,080 --> 00:04:03,470 Yes, as a criticism? 37 00:04:04,070 --> 00:04:12,920 Yes, I think that was that was really a revolutionary paper in many ways, and especially from our perspective now that we really understand that, 38 00:04:13,520 --> 00:04:17,870 that we can even base some of our technology on on these ideas, in fact. 39 00:04:17,870 --> 00:04:23,839 But but they. So EPR paper was really meant as a criticism of quantum mechanics. 40 00:04:23,840 --> 00:04:27,440 And it was in particular criticism of the uncertainty principle, 41 00:04:28,640 --> 00:04:33,770 which is also at the root of this randomness is very much linked to the randomness that I mentioned. 42 00:04:33,920 --> 00:04:41,390 Basically, Uncertainty Principle says that if we know one property of our system really well, like a position of an object, 43 00:04:41,870 --> 00:04:48,620 then we have really no information about another property like the momentum or velocity of of this object. 44 00:04:49,190 --> 00:04:54,200 And, and this is not so in, in stark contrast with Newtonian mechanics, with classical mechanics, 45 00:04:54,200 --> 00:04:59,359 where you can basically measure any property of any system with any accuracy. 46 00:04:59,360 --> 00:05:02,840 And this is independent of any of the measurements that you make. 47 00:05:02,930 --> 00:05:09,230 So you can certainly make the position and velocity measurement of a classical object to any desired accuracy. 48 00:05:09,590 --> 00:05:11,270 So I haven't had a problem with that. 49 00:05:11,270 --> 00:05:19,399 And his colleagues, Podolsky and Rosen, who wrote this paper together with him, and basically what they said is they said, 50 00:05:19,400 --> 00:05:30,050 imagine if we have these two quantum objects which are so highly entangled that their properties behave in perfect synchrony. 51 00:05:30,740 --> 00:05:37,520 So if I if I measure position of one of them, then I can immediately tell what the position of the other one is. 52 00:05:37,520 --> 00:05:44,540 And if I measure velocity of one of them, then I can immediately tell what the velocity of the other one is because they are perfectly correlated. 53 00:05:44,540 --> 00:05:49,189 They have all the properties perfectly correlated. And then Einstein said, Look, 54 00:05:49,190 --> 00:05:54,170 this can actually allow us to violate the uncertainty principle because I can measure a 55 00:05:54,650 --> 00:05:59,959 position on one of the particles and thereby learn about the other particle's position. 56 00:05:59,960 --> 00:06:04,670 And then I can measure momentum on the other particles, the speed on the other particle, if you like. 57 00:06:05,090 --> 00:06:11,240 And this should allow me to have the position and the momentum measured to any desired accuracy. 58 00:06:11,570 --> 00:06:15,110 And big seems to go beyond the uncertainty principle. 59 00:06:15,120 --> 00:06:24,229 So it's a little bit funny the argument because he was using one property of quantum mechanics to invalidate another property of quantum mechanics. 60 00:06:24,230 --> 00:06:32,540 So he was using entanglement, which we know is also a genuine quantum property to somehow go beyond beyond the uncertainty principle. 61 00:06:32,810 --> 00:06:38,900 And it was the revolutionary idea because somehow he really identified exactly what where the. 62 00:06:38,980 --> 00:06:49,510 About quantum mechanics. And it took at least another another 30 years before that was really formalised into into an inequality by John Bell. 63 00:06:50,080 --> 00:06:56,050 And you could even test to what degree quantum mechanics is with you know, you can quantify this weirdness. 64 00:06:56,890 --> 00:07:00,400 And in fact, now, like I said, we can even use it for technology. 65 00:07:00,400 --> 00:07:07,730 So it's advanced quite a bit from from that time. So could you please explain the idea of entanglement a bit more? 66 00:07:07,750 --> 00:07:12,370 You mentioned that if the particles are entangled, you can look at one and see what's happening with the other. 67 00:07:12,700 --> 00:07:14,590 How does that work? How can that happen? 68 00:07:15,340 --> 00:07:23,890 I don't think we really have an explanation for that because it's so non-local that we can't really tell a story in the usual spacetime way. 69 00:07:24,730 --> 00:07:29,049 So, you know, we can't just say we did something here and then something changed and so on. 70 00:07:29,050 --> 00:07:36,490 We are forced to speak in terms of in terms of measurement outcomes on on these separated systems. 71 00:07:37,120 --> 00:07:42,009 In a way, I think it's one way of understanding what this tells us about reality. 72 00:07:42,010 --> 00:07:49,060 And in in the physics jargon, we would say that that entanglement holds out the possibility of hidden variables. 73 00:07:49,600 --> 00:07:57,520 So basically, people like Einstein also, you know, people who like to speak to the kind of classical picture of the world they would like to 74 00:07:57,520 --> 00:08:04,780 say that any property of any physical system exists independently of our measurements. 75 00:08:04,990 --> 00:08:10,540 It's just that we need to make a measurement to find out for our sense of what this property really is. 76 00:08:11,320 --> 00:08:18,700 But quantum mechanics tells us something different. It tells us that the property itself is not determined before you make that measurement, 77 00:08:18,700 --> 00:08:22,030 and it's not really independent of of you making the measurement. 78 00:08:22,660 --> 00:08:29,200 So it's not like the particle already has a position and it has a certain velocity such that we don't know it. 79 00:08:30,040 --> 00:08:34,479 What quantum mechanics says is that even nature itself, you know, even God, if you like, 80 00:08:34,480 --> 00:08:39,219 that metaphorical language doesn't really know the position and the velocity of the particle. 81 00:08:39,220 --> 00:08:42,100 So it's completely non determined. 82 00:08:42,940 --> 00:08:52,210 And I think this is really this big break away from causality and it tells us that properties don't really exist independent of making measurements. 83 00:08:52,840 --> 00:08:58,149 And I think this was also the thing to Einstein, because we like to think of the world as an objective world, 84 00:08:58,150 --> 00:09:03,340 which exists independently of us and independently of what we decide to do with it. 85 00:09:04,240 --> 00:09:10,450 But but it seems that everything we do in quantum mechanics indicates other ways that that our engagement is crucial, 86 00:09:10,450 --> 00:09:12,670 and we cannot really do anything without it. 87 00:09:14,350 --> 00:09:22,600 And so what are the some of the applications of entanglement is, for example, superfast quantum computing is that possibility? 88 00:09:22,840 --> 00:09:26,409 I think that that's actually what's exciting about it. And again, 89 00:09:26,410 --> 00:09:31,120 that's I think that's what's really beautiful about physics that you have this really 90 00:09:31,120 --> 00:09:35,920 fundamental mystery and we are still arguing in the physics community how to, 91 00:09:36,100 --> 00:09:43,900 you know, how do we really understand entanglement? And there are all sorts of people offering all sorts of different interpretations and so on. 92 00:09:44,260 --> 00:09:51,909 But in spite of the fact that we haven't quite understood all the implications of that, we actually see how to use it technologically. 93 00:09:51,910 --> 00:09:59,230 And I think the two big applications or maybe three in fact, are one of them is certainly superfast computing. 94 00:09:59,860 --> 00:10:08,350 And I think what's interesting is not that we could just solve certain problems faster and more efficiently. 95 00:10:08,650 --> 00:10:15,280 I think what's interesting to physicists as well is that we can simulate other physical systems more effectively. 96 00:10:15,760 --> 00:10:22,570 So in physics, you know, we want to understand more and more complex, and that usually requires much more computational power. 97 00:10:23,470 --> 00:10:28,210 And in fact, if you really want to properly simulate even a small number of atoms, 98 00:10:28,510 --> 00:10:34,750 I think conventional computers are already lost because they require more memory and power than than is available. 99 00:10:35,200 --> 00:10:39,909 But but if you go and use quantum systems to simulate other quantum systems, 100 00:10:39,910 --> 00:10:44,200 then of course that becomes much more efficient, in fact, exponentially more efficient. 101 00:10:44,200 --> 00:10:47,120 And I think I'm really excited by that prospect. 102 00:10:47,120 --> 00:10:54,980 So people use a handful of atoms now to simulate all sorts of transport properties in complex systems, even biological systems. 103 00:10:55,000 --> 00:11:00,340 Now we have we have an idea how to simulate complex biological systems with quantum computers. 104 00:11:00,340 --> 00:11:04,240 And I think I think there would be a big revolution actually in that direction. 105 00:11:04,690 --> 00:11:09,790 The third thing I wanted to mention is quantum cryptography, which which I think is really exciting. 106 00:11:09,790 --> 00:11:14,380 It's already out there in the market. I think you can buy quantum encryption if you really have enough. 107 00:11:14,750 --> 00:11:18,010 It's probably too expensive, but if you have enough money, you can buy it. 108 00:11:18,610 --> 00:11:25,690 And the idea is that if you really want something that's much more secure than anything classically available, 109 00:11:26,410 --> 00:11:31,540 then it seems that encoding information into quantum systems and manipulating it with quantum 110 00:11:31,540 --> 00:11:36,010 systems is actually gives you a higher degree of security than anything in classical physics. 111 00:11:36,160 --> 00:11:38,740 So if you want to send maybe a message that. 112 00:11:38,820 --> 00:11:47,459 Not too long, but you want to really guarantee that no one else can break this message between you and the receiver. 113 00:11:47,460 --> 00:11:50,820 Then you should really be using quantum mechanical systems for that. 114 00:11:51,300 --> 00:11:55,620 And it's again exactly a consequence of the indeterminacy. 115 00:11:55,620 --> 00:12:01,800 You know, the uncertainty principle basically protects you to some degree against any eavesdropping. 116 00:12:02,130 --> 00:12:06,900 And this is probably you know, this is the biggest breakthrough, I would say, in technology kind of thing. 117 00:12:07,980 --> 00:12:12,600 And what about the idea of teleportation? I know that's been linked to entanglement. 118 00:12:12,600 --> 00:12:16,140 Is that too much into science fiction or is that actually a possibility? 119 00:12:16,860 --> 00:12:20,280 I think, you know, it's been demonstrated on simple systems. 120 00:12:20,310 --> 00:12:26,760 It's a good question because the time when when this really becomes exciting is if we can teleport ourselves from A to B, 121 00:12:26,760 --> 00:12:31,079 you know, I travel a lot, for example, between Oxford and Singapore. 122 00:12:31,080 --> 00:12:39,360 And I think sometimes you really think, you know, wouldn't it be nice to just be teleported instantaneously, more or less at the speed of light, 123 00:12:39,360 --> 00:12:44,429 if you like, which is more or less instantaneous as far as we are concerned, between between Oxford and Singapore. 124 00:12:44,430 --> 00:12:52,230 But so far we've only been able to do this with very small objects, with particles of light, with photons, with a few atoms. 125 00:12:52,980 --> 00:12:59,580 But we haven't been able to go beyond that, and we certainly haven't been able to do it across large distances. 126 00:12:59,850 --> 00:13:06,650 You know, you can teleport an object from one side of your laboratory to another, which is maybe ten metres across. 127 00:13:07,170 --> 00:13:15,360 But what we'd really like to do is teleport things much further away and teleport a larger objects than just a few items. 128 00:13:15,360 --> 00:13:19,620 And I think this really is at the moment, I would say, you know, the right word. 129 00:13:19,620 --> 00:13:23,159 You know, it's still science fiction, although we see nothing wrong with it. 130 00:13:23,160 --> 00:13:27,810 So I think most of us are optimistic that one day this will be a real possibility. 131 00:13:27,870 --> 00:13:33,209 This might take a long time. That sounds very exciting, but thank you so much for your time. 132 00:13:33,210 --> 00:13:33,720 I know that you're.