1 00:00:00,000 --> 00:00:06,458 Could you tell me what is so fascinating about quantum mechanics? 2 00:00:08,125 --> 00:00:16,000 There are two aspects I find most fascinating about quantum mechanics. 3 00:00:16,208 --> 00:00:24,250 The first aspect is that... this is a difficult question actually, I have to think about it a little bit. 4 00:00:28,500 --> 00:00:42,000 What is so fascinating about quantum mechanics is that until now no one truly understands quantum mechanics, especially this interesting concept called quantum superposition. 5 00:00:42,625 --> 00:00:47,250 What quantum superposition leads to is this concept called quantum entanglement. 6 00:00:49,542 --> 00:00:55,250 Even though it has been over a hundred years since we have come up with quantum mechanics, we still don't understand why there is quantum entanglement. 7 00:00:55,833 --> 00:00:59,667 So the more you don't understand, the more interesting it becomes. 8 00:01:04,083 --> 00:01:08,250 And can you explain entanglement, what it is, what it means? 9 00:01:09,875 --> 00:01:12,208 The basic principles of quantum entanglement can be understood like this: 10 00:01:12,417 --> 00:01:18,500 Let's say we have two dice, like the ones we normally use for gambling. 11 00:01:20,875 --> 00:01:26,208 It doesn't matter how far apart the dice are, one could be in China and the other in the Netherlands. 12 00:01:27,000 --> 00:01:35,000 So if you roll your dice and then call to ask me, "Jian Wei, do you know what my dice says?" 13 00:01:35,208 --> 00:01:39,833 I just have to look at the dice in my hand and can tell you what your dice says. 14 00:01:40,417 --> 00:01:49,208 It's to say that no matter how great the distance between the dice is, according to Einstein there is some strange interaction between these two far away locations. 15 00:01:49,667 --> 00:01:54,708 When the result appears here, the far away dice has the same result. 16 00:01:55,958 --> 00:02:00,583 This is a typical result we get when we experiment with quantum entanglement. 17 00:02:05,000 --> 00:02:13,375 What I like about your work is that you somehow are able to put the theory into practice. 18 00:02:14,000 --> 00:02:16,000 Can you elaborate on that? 19 00:02:17,250 --> 00:02:23,833 There are two types of people study quantum mechanics. 20 00:02:24,708 --> 00:02:29,958 The first type goes, "This is what quantum entanglement is; we don't have to understand why it exists." 21 00:02:30,083 --> 00:02:36,208 They go straight onto testing physics phenomena within the physical system. 22 00:02:36,292 --> 00:02:39,833 And this has resulted in various useful applications such as 23 00:02:40,083 --> 00:02:47,833 semiconductor lasers, nuclear magnetic resonance, giant magnetoresistance, and even energy generation. 24 00:02:48,042 --> 00:03:00,000 Because these type experiments on condensed state and quantum phenomena but do not ask why entanglement exists, they have already greatly changed our lives. 25 00:03:00,100 --> 00:03:10,250 The other type, my and colleagues in the U.S. and Europe, including the Netherlands, also have had great results when last year 26 00:03:10,417 --> 00:03:15,083 we conducted experiments on the existence of quantum entanglement. 27 00:03:15,583 --> 00:03:28,000 During this process we gradually developed a technique to actively control one or more particles. 28 00:03:28,000 --> 00:03:32,000 Once you can actively control particles, a new field emerges 29 00:03:33,000 --> 00:03:35,500 called quantum information science. 30 00:03:35,833 --> 00:03:38,667 Quantum information science has some practical applications. 31 00:03:39,042 --> 00:03:43,000 The first is quantum communications. 32 00:03:43,208 --> 00:03:51,750 Quantum communication can theoretically provide us with an unfailingly safe communication method. 33 00:03:51,917 --> 00:03:57,583 This could transform cyber security 34 00:03:57,750 --> 00:04:06,458 This is very important to our daily lives and of our desires to keep our secrets secure. 35 00:04:07,000 --> 00:04:26,000 If I tangle up the tiny particles that make up the quantum world, they will gain a great computational ability that we can use for quantum computation. 36 00:04:26,417 --> 00:04:38,542 For example, if we combine all of the computational power on Earth we can perhaps count to 2^80 a year. 37 00:04:39,083 --> 00:04:53,750 But if we can harness only a hundred of those small, entangled particles, it may hold a counting power a million times more powerful than all of Earth's computational power combined. 38 00:04:54,000 --> 00:05:08,208 That's to say if there were a million Earths in this universe, all these Earths combined would have the same computational power as what we could achieve with 100 tiny particles. 39 00:05:08,333 --> 00:05:14,375 When you think about it this way, quantum communications can bring about a great advancement in computational power. 40 00:05:14,833 --> 00:05:21,417 The third aspect is that we can use quantum mechanics for getting close measurements, called quantum measurements. 41 00:05:21,625 --> 00:05:33,000 Quantum measurement could greatly advance GPS navigation and make it more precise. 42 00:05:33,208 --> 00:05:42,833 We could also use the same techniques to advance biomedical detection technology as well. 43 00:05:43,042 --> 00:05:55,417 Now you can see that this very fundamental, physics question can be used for many practical real life applications. 44 00:05:58,250 --> 00:06:10,667 When I visualise a quantum computer, what does it look like? 45 00:06:12,167 --> 00:06:16,042 People often ask me this question. 46 00:06:16,208 --> 00:06:26,333 If we try to picture a regular computing device, we would picture a everyday computer with computer chips, like a PC. 47 00:06:26,458 --> 00:06:38,000 However if we go back 200 years, people in China would have used an abacus made out of bamboo to do calculations. 48 00:06:38,125 --> 00:06:50,542 If someone back then tried to imagine what a computer should look like, they would imagine something made out of wood, or bamboo, or perhaps marble. 49 00:06:50,875 --> 00:06:57,083 So I think that currently it is hard to imagine what a quantum computer would look like. 50 00:06:57,208 --> 00:07:03,625 I can tell you though, that I once had a dream about a quantum computer. 51 00:07:03,833 --> 00:07:21,500 That quantum computer was not like a typical computer, but was a pile of material that was neither solid nor liquid, and was constantly shifting and emitting a blue light. 52 00:07:22,125 --> 00:07:27,250 It is hard to imagine what an actual quantum computer from the future would look like. 53 00:07:27,542 --> 00:07:35,292 Currently many scientists around the world are taking different approaches to try constructing a quantum computer 54 00:07:35,583 --> 00:07:48,833 Some people are using photon, others are using atoms, and some are even using superconducting qubits. 55 00:07:49,417 --> 00:08:00,000 So in the future there might be many different types of quantum computers made out of different martials that can perform different functions. 56 00:08:00,208 --> 00:08:03,958 So it is very difficult to say what a quantum computer is going to look like. 57 00:08:05,292 --> 00:08:15,500 When I look at your work in quantum satellites, what big step is that? 58 00:08:16,250 --> 00:08:18,750 What happened last week, can you elaborate on that? 59 00:08:19,083 --> 00:08:29,083 We are ecstatic that we were able to successfully launch the first ever quantum science satellite. 60 00:08:29,333 --> 00:08:36,667 After the launch we went through several days of testing, and so far the satellite has been functioning stably. 61 00:08:36,792 --> 00:08:41,750 There were several reasons we wanted to launch this quantum science satellite. 62 00:08:42,292 --> 00:08:55,000 The first was that if we use fibre optics for quantum communication on the ground, because quantum signals cannot replicate it would be difficult for signals to get very far. 63 00:08:55,208 --> 00:09:07,917 One of our colleagues in Switzerland, Nicolas Gisin estimated that if we have a thousand kilometre of fibre optics 64 00:09:08,333 --> 00:09:17,542 and even if we use the very best technology available to make this quantum communications device 65 00:09:17,750 --> 00:09:22,417 we can only send a single byte(?) of information every 300 years . 66 00:09:22,958 --> 00:09:29,333 So this is not very useful for long distance quantum communication. 67 00:09:29,625 --> 00:09:46,792 But what is interesting is that if we have a quantum satellite which can send signals through the air, according to our theories and what we have tried to build, we can send several hundred kb(?) of information over a thousand kilometres, every second. 68 00:09:47,042 --> 00:09:54,292 This is enough to transmit important quantum information tasks securely. 69 00:09:54,583 --> 00:10:05,417 This also means after launching into the atmosphere, we are able to do experiments that were not to do on the ground. 70 00:10:05,625 --> 00:10:11,708 Also from a scientist’s perspective, this is an important contribution to fundamental research. 71 00:10:12,042 --> 00:10:24,917 Once we are able to send send quantum light particles through the atmosphere we have the ability to investigate whether quantum entanglement exists and 72 00:10:25,250 --> 00:10:35,083 what kind of changes will be happen to the quantum state under the influence of relativity and gravity. 73 00:10:35,208 --> 00:10:40,792 One likely possibility is that we will move towards testing quantum mechanics in space. 74 00:10:41,167 --> 00:10:49,000 And once we are in space, we we can conduct further investigations on quantum nonlocality on a larger scale. 75 00:10:49,417 --> 00:11:01,160 According an American colleague Tony Leggett, there is one last experiment in quantum physics nonlocality we have not yet performed 76 00:11:01,167 --> 00:11:20,375 To do the final test of quantum nonlocality, we have to observe quantum entanglement separated over a distance of 300 thousand km, when there will be only residual free will. 77 00:11:20,792 --> 00:11:27,292 So we will have the ability to conduct that final test of quantum nonlocality. 78 00:11:27,833 --> 00:11:42,208 Everyone really hopes that we can unify quantum and gravity theories into a theory of everything 79 00:11:42,458 --> 00:11:48,542 There are many models for this, but which one of these is compatible with the natural world? 80 00:11:48,875 --> 00:12:01,958 When we transport quantum photon hundreds of thousands of kilometres away, we can test many different quantum models. 81 00:12:02,292 --> 00:12:08,458 Let's see if we can shift the boundaries of physics exploration. 82 00:12:08,625 --> 00:12:17,000 It's mainly because of these two reasons: practical and fundamental research. 83 00:12:17,417 --> 00:12:23,250 The theory of everything; could you explain a little bit more what that is? 84 00:12:23,750 --> 00:12:30,083 Us physicists all have all have this ultimate dream. 85 00:12:29,000 --> 00:12:34,583 Currently we know of four fundaments forces of nature within the natural world. 86 00:12:35,042 --> 00:12:46,375 We have known of gravity the longest, and then we have electromagnetism, strong nuclear force, and weak nuclear force. 87 00:12:46,833 --> 00:12:57,917 We already have a standard model in which we have unified electromagnetism, strong nuclear force, and weak nuclear force. 88 00:12:58,292 --> 00:13:09,875 So what we dream of now, which Einstein had started to do, is to combine all four forces into one unified theory. 89 00:13:10,208 --> 00:13:17,375 But in this process of unifying has had many difficulties, and fitting gravity into this is a great challenge. 90 00:13:17,500 --> 00:13:23,708 Scientists have developed many different theories about this, such as quantum gravity. 91 00:13:23,958 --> 00:13:30,333 Quantum gravity tries to combine the theories of relativity and gravity. 92 00:13:30,583 --> 00:13:41,708 If we can combine these theories, according to our current understanding we will have created a theory of everything, a theory that we can use to explain every natural phenomena. 93 00:13:42,042 --> 00:13:51,917 But there are many candidate theories, so which one is the one truly reflective of our natural world? 94 00:13:52,000 --> 00:14:06,792 You've got this theory of everything. The steps you have been taking in the past year, when you look at the theory of everything, how big of a step have you made? 95 00:14:07,208 --> 00:14:16,375 In order to do these kind of experiments the first important step is to move the laboratory to space. 96 00:14:22,000 --> 00:14:30,083 We have officially only started making satellites in 2007 and before that we have done related experiments on the ground for a while. 97 00:14:30,250 --> 00:14:33,417 The earliest we have done these kinds of experiments is in 2003. 98 00:14:33,625 --> 00:14:39,458 It is through many years of effort we could move our experiments to the atmosphere. 99 00:14:39,708 --> 00:14:44,625 On the way we have developed and refined techniques. 100 00:14:44,750 --> 00:14:52,292 The parameters of our satellite is based on the calculations done by an American colleague Paul Grant(?). 101 00:14:52,667 --> 00:15:03,667 With our techniques we can now make a highly precise telescope that can see a license plate on one of Jupiter's moons. 102 00:15:03,000 --> 00:15:11,208 This is because our spacial resolution is very high. 103 00:15:11,625 --> 00:15:19,292 We also have to be able to accurately detect of low-level light. 104 00:15:19,750 --> 00:15:24,667 Now lets say we are on the Moon, and you light a match to smoke a cigarette. 105 00:15:25,000 --> 00:15:31,375 When you strike the match you produce light, and we need to be able to perceive that light on Earth. 106 00:15:31,500 --> 00:15:36,542 When we have the refined technology to do so, if we are successful in our experiments this time 107 00:15:36,667 --> 00:15:51,042 we hope for our next step that we can work with China's lunar landing programme and experiment with distanced quantum entanglement of 300 thousand kilometres apart. 108 00:15:51,125 --> 00:15:56,125 Currently we have completed some experiments on the ground 109 00:15:56,458 --> 00:16:04,083 so if the upcoming tests are successful, we should be able to achieve hundreds of thousands of kilometres distanced quantum entanglement. 110 00:16:04,542 --> 00:16:18,417 After these tasks have been completed, I think we can then conduct the primary investigations into the accuracy of proposed quantum models I have mentioned earlier. 111 00:16:18,667 --> 00:16:23,667 So we have three steps, and this is just the first. 112 00:16:26,250 --> 00:16:32,375 When you say three steps, what are the three steps? 113 00:16:34,375 --> 00:16:46,875 The first step is hopefully to conduct important tests in the air, test if it feasible to do so. 114 00:16:47,167 --> 00:16:51,792 After testing, we will be able to realise new quantum ground 115 00:16:52,083 --> 00:16:56,667 that can be used for secure quantum communication. 116 00:16:56,833 --> 00:17:02,500 The second step is for a 1200 kilometre quantum entanglement distribution 117 00:17:02,958 --> 00:17:12,500 to discover if quantum engagement can still occur with a separation of thousands of kilometres. 118 00:17:12,667 --> 00:17:24,667 With the foundations from these two experiments, we can go on with the second step, which is to have a satellite between the Moon and Earth 119 00:17:25,250 --> 00:17:29,875 at the Lagrangian point, from where we will distribute two points of quantum entanglement. 120 00:17:30,208 --> 00:17:43,792 This way we achieve free willed quantum nonlocality from a great collective distance of 300 thousand kilometres. 121 00:17:43,917 --> 00:17:50,833 According to our colleague Tony Leggett, if after we conduct this experiment we will prove the nonlocality of quantum mechanics. 122 00:17:50,917 --> 00:17:57,250 The theory of quantum nonlocality will be confirmed and the debate will end. 123 00:17:57,417 --> 00:18:05,292 With these foundations we will then use the techniques we have developed to transmit light over a great distance 124 00:18:05,833 --> 00:18:11,042 to investigate quantum gravity models. 125 00:18:11,958 --> 00:18:14,458 These are the three steps 126 00:18:18,542 --> 00:18:23,917 Entanglement communication, how does that work, what do you mean by that? 127 00:18:25,083 --> 00:18:32,167 We have two kinds of experiments with quantum key distribution 128 00:18:33,125 --> 00:18:41,583 The first type is using a single photon, and not using quantum entanglement 129 00:18:41,000 --> 00:18:44,208 This occurs between a satellite and the ground. 130 00:18:44,333 --> 00:18:53,792 There will be a weak light source from the satellite which will shoot several hundred individual photons to the ground every second. 131 00:18:54,125 --> 00:18:58,667 On the ground there is a ordinary antenna that will receive the signal 132 00:18:58,958 --> 00:19:04,167 and can conduct classical communication with the satellite. 133 00:19:04,333 --> 00:19:10,250 After a couple exchanges we come up with a indecipherable key together. 134 00:19:10,708 --> 00:19:13,875 Here we have used two fundamental principles. 135 00:19:14,125 --> 00:19:17,958 The first is called quantum indivisibility. 136 00:19:18,125 --> 00:19:25,083 Let's say we are drinking a glass of water and I split the glass of water into two half glasses of water 137 00:19:25,458 --> 00:19:29,208 And we split the half glasses of water, which are now a quarter full. 138 00:19:29,667 --> 00:19:41,167 After slowly dividing we now have single water molecules 139 00:19:41,375 --> 00:19:45,583 but we can’t have half molecules or quarter molecules. 140 00:19:46,000 --> 00:19:47,542 This is the same with light. 141 00:19:47,708 --> 00:19:55,750 If you take a 25 W light bulb and magnify it, you can see that the light is composed of individual particles. 142 00:19:55,875 --> 00:19:59,917 We call these particles photons, a single quantum. 143 00:20:00,042 --> 00:20:07,333 If someone tries to eavesdrop, he cannot divide the photon in half 144 00:20:07,500 --> 00:20:12,417 so either the eavesdropper steals away the photon or it will not be stolen and the photon reach the ground. 145 00:20:12,583 --> 00:20:17,917 The photons that reach the ground are the ones that were not stolen by the eavesdropper. 146 00:20:18,125 --> 00:20:24,250 Using this method you can say if you have been eavesdropped on, you won't receive a signal and you can give up on those signals. 147 00:20:24,500 --> 00:20:27,125 This is its first principle. 148 00:20:27,375 --> 00:20:34,167 The other principle is quantum superposition 149 00:20:34,667 --> 00:20:43,417 Quantum superposition guarantees the quantum no cloning theorem. 150 00:20:43,667 --> 00:20:53,208 When a photon is being transmitted, if you take a picture of it with a camera and you want to measure and make a copy of it 151 00:20:53,417 --> 00:21:02,500 this influences the photon’s state of being so that when you receive the signal on the ground you will know that the signal has been observed by someone else. 152 00:21:02,708 --> 00:21:04,750 You can then reject the signal 153 00:21:04,750 --> 00:21:06,333 Because quantums have two characteristics 154 00:21:06,458 --> 00:21:10,542 the first being indivisibility, which says it is individual and whole 155 00:21:10,750 --> 00:21:15,750 the second being that it cannot be copied 156 00:21:15,917 --> 00:21:19,375 we can guarantee the security of the quantum key. 157 00:21:21,667 --> 00:21:23,167 This is the first type of quantum key distribution, which has nothing to do with quantum entanglement. 158 00:21:23,458 --> 00:21:29,042 Once we can apply quantum entanglement to quantum key distribution 159 00:21:29,500 --> 00:21:35,333 we can have our satellite be our source of quantum entanglement during our experiments. 160 00:21:35,583 --> 00:21:43,583 It will produce several tens of millions of entangled photons every second and 161 00:21:43,958 --> 00:21:50,167 they will be distributed to two points on the surface of the earth that are approximately 1200 km apart. 162 00:21:50,667 --> 00:21:56,833 If you detect a photon on one point it is guaranteed we will detect an entangled photon on the other point. 163 00:21:57,042 --> 00:22:02,208 If you don't detect anything at that point than the other point will also come up empty. 164 00:22:02,417 --> 00:22:03,875 If there is one here, there is one there. 165 00:22:04,042 --> 00:22:08,083 This kind of situation is called a state of quantum entanglement. 166 00:22:08,208 --> 00:22:15,375 With this connection, you can achieve quantum key distribution. 167 00:22:15,542 --> 00:22:22,292 You can either use single photons or quantum entanglement to achieve quantum communication. 168 00:22:25,917 --> 00:22:36,125 Why is your team, your lab, so ahead of other labs in the world? 169 00:22:36,458 --> 00:22:39,750 I think this is because of three reasons. 170 00:22:40,292 --> 00:22:50,708 First of all I was lucky to be in Austria to join Zeilinger's team in 1996 when they were first starting out. 171 00:22:51,083 --> 00:23:00,625 I was a PhD student at the time, and was very lucky to be a part of the first wave of people working on quantum communications. 172 00:23:01,083 --> 00:23:14,625 By chance I was one of the founding members of the team that grappled with the first theories and techniques of quantum communications. 173 00:23:15,125 --> 00:23:23,042 Later in China, we started to work with quantum communications and we needed the latest technology to get a satellite launched. 174 00:23:23,042 --> 00:23:32,625 Our team is composed of those who have picked up the latest lab skills from all around the world 175 00:23:32,917 --> 00:23:43,625 For example, I myself was first in Austria then in Germany, so we have quantum storage technology and quantum entanglement control technology. 176 00:23:43,792 --> 00:23:51,375 We have students who went to Stanford and brought back the best single photon detection technique back to China. 177 00:23:51,583 --> 00:23:56,875 We also have students who went to Cambridge and brought back the best quantum light source techniques. 178 00:23:57,333 --> 00:24:06,125 At the same time I have colleagues who brought back from Canada and Japan the latest theories on quantum key distribution. 179 00:24:06,292 --> 00:24:15,875 Because we are a relatively large team whose skills complement each other, 180 00:24:16,042 --> 00:24:22,833 we are able to do things that my supervisor back in Austria, who had a smaller team, could not do. 181 00:24:23,042 --> 00:24:29,250 This an critical reason why we have come to the forefront of fundamental research in our field. 182 00:24:29,625 --> 00:24:34,583 The third aspect is our project is supported by the Chinese Academy of Sciences. 183 00:24:34,750 --> 00:24:42,833 If we, for example, need very precise adaptive optics 184 00:24:43,125 --> 00:24:48,125 China has already has been supporting this technology as well as space technology for several years. 185 00:24:48,250 --> 00:25:01,042 China had dozens of labs in Shanghai, Beijing, Chengdu, and others just in the field of quantum communications. 186 00:25:01,125 --> 00:25:11,708 They have joined our group and we now have a new and very complementary group with collective knowledge of many of the latest technologies. 187 00:25:11,917 --> 00:25:17,125 Also because the Chinese economy has been good the past few year 188 00:25:17,292 --> 00:25:23,708 we have been able to ask for a quite substantial amount of funding and thus advance quickly. 189 00:25:26,583 --> 00:25:27,667 So it's almost China's pride 190 00:25:27,875 --> 00:25:29,542 Yeah 191 00:25:29,875 --> 00:25:35,417 In what way? In what way is China proud of this project? 192 00:25:35,583 --> 00:25:45,542 In China we are trying to understand approach a satellite launch from a different angle. 193 00:25:45,958 --> 00:25:54,625 Before when we came to science, we've always been following and imitating 194 00:25:54,750 --> 00:25:58,208 but very rarely were in at the international forefront. 195 00:25:58,333 --> 00:26:08,042 Eventually we want China to be running with the rest, and perhaps in some areas lead the way. 196 00:26:08,208 --> 00:26:17,167 From a certain perspective, when it comes to quantum communication field our satellite has put us in the front of the international footrace. 197 00:26:17,292 --> 00:26:26,250 So when naming our satellite, after consulting with Chinese colleagues, we decided to name our Satellite Micius. 198 00:26:26,375 --> 00:26:34,833 Micius was an ancient Chinese philosopher, educator and scientist. 199 00:26:35,042 --> 00:26:44,833 According to literature he is the first in the world to suggest that light travels in a straight line. 200 00:26:45,000 --> 00:26:53,083 This was something that was not suggested in the West until much later. 201 00:26:53,292 --> 00:27:08,333 Micius when it came to the study of light, of particles, but others also thought of particle theory too later (Micius was the first to theorise of particles, but it was others after him that thought of particle theory???) 202 00:27:08,583 --> 00:27:16,000 By naming the satellite Micius, we wanted to explain that as long as we have the opportunity to challenge ourselves 203 00:27:16,125 --> 00:27:21,042 us Chinese people can make meaningful contributions to science. 204 00:27:21,167 --> 00:27:27,500 We also have another reason, which is that throughout this project we benefited from a flow of international collaboration. 205 00:27:27,583 --> 00:27:37,667 Therefore, after we finish our first round of scientific missions we are opening our project to scientists from all around the world. 206 00:27:37,792 --> 00:27:40,167 We welcome everyone to work with us. 207 00:27:40,333 --> 00:27:46,375 We are working toward international collaboration, firstly with Austria's scientific society 208 00:27:46,667 --> 00:27:54,667 to achieve quantum communication between the satellite and Beijing, and between the satellite and Vienna. 209 00:27:54,917 --> 00:28:01,333 From there we can achieve quantum communication between Vienna and Beijing 210 00:28:01,458 --> 00:28:07,708 We also currently have agreements for collaboration with our German and Italian colleagues. 211 00:28:07,875 --> 00:28:17,125 We want, with everybody’s help, work towards advancement in quantum communication science and quantum technology applications. 212 00:28:22,333 --> 00:28:34,042 When you look at your dream this was a big step you made by sending out the satellite. What are the steps, what are you striving? 213 00:28:34,292 --> 00:28:41,708 If this satellite is a success, we have two further steps to consider. 214 00:28:42,083 --> 00:28:50,667 This satellite does have the latest technology 215 00:28:50,792 --> 00:28:55,292 If you want to guarantee that the satellite is able to successfully complete its missions 216 00:28:55,458 --> 00:29:02,458 the quality and stability of its engineering is very important. 217 00:29:02,708 --> 00:29:05,417 Currently this satellite can only work at night 218 00:29:05,583 --> 00:29:11,875 because the photon signals are too weak compared to sunlight. 219 00:29:12,000 --> 00:29:20,292 The satellite is only functional at night when there is no sunlight and it is easier to do experiments. 220 00:29:20,417 --> 00:29:25,667 So the next step is to develop a technology that can make sure we can conduct experiments during daytime too. 221 00:29:25,833 --> 00:29:32,333 Then we can perform experiments both day and night. 222 00:29:32,583 --> 00:29:41,500 We need this ability in order to do the experiment I mentioned before with the distance of 300 thousand kilometres. 223 00:29:41,667 --> 00:29:56,500 Once we have the technology to do experiments throughout the day we want to use it for secure quantum communication 224 00:29:56,667 --> 00:30:05,625 and also link our experiments with the moon landing programme 225 00:30:05,750 --> 00:30:11,333 , towards big scale quantum nonlocality validation. 226 00:30:11,458 --> 00:30:18,250 China's moon project could you explain a little bit what this project is? So I can understand what it means? 227 00:30:18,333 --> 00:30:25,042 China's moon landing plan is also called the Chang'e moon landing plan 228 00:30:25,208 --> 00:30:27,833 and has already been going on for several years. 229 00:30:28,000 --> 00:30:33,792 The first Chang’e, I don't remember when it launched 230 00:30:33,958 --> 00:30:41,250 but currently they have a long term plan to send people on the moon in the near future. 231 00:30:41,375 --> 00:30:50,250 When it comes to China's space exploration there are some ambitious plans. 232 00:30:50,375 --> 00:30:56,625 When it comes to the details, because I am not directly involved 233 00:30:56,833 --> 00:31:00,375 I am not sure about the time scale. 234 00:31:00,583 --> 00:31:08,542 However they have started to seriously consider sending a satellite to the moon. 235 00:31:08,708 --> 00:31:17,125 We have some equipment on the moon that is working because of Chang'e. 236 00:31:17,333 --> 00:31:29,333 Chang'e is goddess from a famous Chinese fairy tale who drank an elixir of immortality 237 00:31:29,458 --> 00:31:37,458 and flew to the moon; this is why the programme is called Chang'e. 238 00:31:38,208 --> 00:31:42,625 Chang'e is the first Chinese satellite to orbit the earth. 239 00:31:42,750 --> 00:31:52,000 It later delivered equipment to the moon 240 00:31:52,417 --> 00:32:01,208 The next step is for China to perhaps send a satellite to the far side of the moon to bring back a sample to Earth. 241 00:32:01,333 --> 00:32:14,667 After this mission is complete I estimate that within 10, 15 years China could be able to send people to the moon. 242 00:32:17,000 --> 00:32:37,542 Looking at your work here in China is it how do the Chinese authorities look at your work? It is very important to be able to conquer space and time? 243 00:32:37,667 --> 00:32:41,000 I think there are many sides to this. 244 00:32:42,000 --> 00:32:45,542 I think everyone is very excited about this. 245 00:32:45,667 --> 00:32:55,374 Actually this quantum science satellite was launched in the twelfth...China has something called a 5-year plan. 246 00:32:55,375 --> 00:33:03,792 There is a first 5-year plan, a second... and now we are past the 12th and currently in the 13th 5-year plan 247 00:33:03,917 --> 00:33:08,417 The quantum science satellite is one of the several satellites that were a part of the 12th 5-year plan. 248 00:33:08,542 --> 00:33:17,167 Despite this being the first quantum science satellite, this is actually the Chinese Academy of Sciences' third science satellite. 249 00:33:17,292 --> 00:33:22,583 We previously had a dark matter detection satellite 250 00:33:22,708 --> 00:33:30,375 and another, the Shijian-10, to work with microgravity and the life sciences. 251 00:33:30,500 --> 00:33:33,292 The third is our quantum satellite. 252 00:33:34,000 --> 00:33:36,250 The reason why people were exited about our quantum satellite was because 253 00:33:36,417 --> 00:33:39,292 firstly, this satellite was the first of its kind. 254 00:33:39,417 --> 00:33:43,500 So despite it being the third, it was also the first. 255 00:33:43,583 --> 00:33:53,208 Besides that, this satellite incorporated techniques that we did not possess before. 256 00:33:53,333 --> 00:34:01,167 And because were not able to get what we needed from Europe or the US 257 00:34:01,292 --> 00:34:07,042 this satellite was manufactured with solely Chinese technology. 258 00:34:07,167 --> 00:34:16,042 With this in mind, we are very happy and satisfied with our technological progress. 259 00:34:16,167 --> 00:34:29,125 This satellite to our country is to certain degree a symbol 260 00:34:29,542 --> 00:34:41,125 that as time progresses, we are slowly able to do something meaningful. 261 00:34:41,208 --> 00:34:51,458 We are not only making purely technological progress but we are also contributing to fundamental research. 262 00:34:51,667 --> 00:34:59,250 We think that China should be able to contribute to global scientific advancement. 263 00:34:59,333 --> 00:35:05,875 However, we also often hear other sentiments. 264 00:35:05,958 --> 00:35:07,875 What are they? 265 00:35:08,083 --> 00:35:09,167 There are several different ones. 266 00:35:09,250 --> 00:35:16,667 The first is because quantum entanglement is a very difficult to understand concept. 267 00:35:16,750 --> 00:35:24,750 Before this kind of concept is universally accepted, those who are not familiar with quantum mechanics 268 00:35:24,875 --> 00:35:31,083 may have doubts or suspicions of whether quantum entanglement is real. 269 00:35:31,208 --> 00:35:39,000 However within the scientific community there is a general acceptance of quantum entanglement. 270 00:35:39,125 --> 00:35:44,500 We frequently hear criticisms online of quantum mechanics and the theory of relativity. 271 00:35:44,875 --> 00:35:49,500 However, I think with the advancement of science this kind of criticism should slowly dissipate. 272 00:35:49,583 --> 00:35:58,875 People also are anxious for our technology to become usable. 273 00:35:59,042 --> 00:36:01,708 Of course we think they should be of use. 274 00:36:01,833 --> 00:36:08,458 In the near future, we should be able to use quantum key distribution to secure quantum communication between Beijing and Vienna, for example. 275 00:36:09,000 --> 00:36:15,417 But when this would this technology be available to the public so everyone can benefit from this? 276 00:36:15,500 --> 00:36:21,750 I think we need to be patient and wait until we have refined the technology. 277 00:36:21,833 --> 00:36:29,333 Some people might think that after the satellite launch, we have solved all the problems. 278 00:36:29,458 --> 00:36:34,417 This is something that we often need to explain, that we need to wait, we need to have patience 279 00:36:34,542 --> 00:36:36,667 We have to wait for technology to improve. 280 00:36:38,458 --> 00:36:48,208 What kind of other applications can you imagine that are ahead for us with quantum mechanics and all the developments that are going on? 281 00:36:48,292 --> 00:37:02,000 The first thing, as I mentioned earlier, is to increase the security of our communication and our cyber security. 282 00:37:02,167 --> 00:37:08,333 The second is to use the developed technology to can see an image from very far away. 283 00:37:08,458 --> 00:37:22,750 We can use quantum imaging to from explore earth's resources (?). 284 00:37:23,125 --> 00:37:28,000 So far it seems these are the two main applications. 285 00:37:28,167 --> 00:37:31,500 In the a long term there are some interesting plans 286 00:37:31,667 --> 00:37:39,750 to use the quantum entanglement distribution in space and have two clocks on Earth synchronise. 287 00:37:41,500 --> 00:37:42,792 I'm talking about quantum clock synchronisation. 288 00:37:42,917 --> 00:37:45,625 We only have theorised about this. 289 00:37:45,750 --> 00:37:52,250 Mikhail Lukin from Harvard have recently published some interesting articles 290 00:37:52,375 --> 00:38:02,875 in which he proposes that we can use free space quantum engagement distribution to achieve two clock synchronisation on Earth. 291 00:38:02,917 --> 00:38:09,750 Everyone knows that this clock synchronisation would be very useful when it comes to GPS navigation. 292 00:38:09,875 --> 00:38:16,917 So aside from communication there will be also real life uses in imaging and time synchronisation. 293 00:38:18,708 --> 00:38:22,292 Hopefully an answer to the theory of everything. 294 00:38:22,500 --> 00:38:31,208 Yes but it's a long-term project that will probably take another twenty years 295 00:38:31,625 --> 00:38:32,792 Maybe you can say that in Chinese? 296 00:38:32,917 --> 00:38:40,083 That is of course our most ambitious thought. 297 00:38:40,208 --> 00:38:49,500 If us Chinese scientists are able to investigate and contribute to the theory of everything 298 00:38:49,667 --> 00:38:53,208 it would something to be proud of. 299 00:38:53,333 --> 00:38:58,000 This would, according to our colleague Tony Leggett, 300 00:38:58,083 --> 00:39:02,333 take 30 years, or perhaps 100 years. 301 00:39:02,458 --> 00:39:09,958 However we are more inclined to believe that it won't take that long, it wont take a 100 years. 302 00:39:10,083 --> 00:39:18,625 I very much believe that within my lifetime I will we able to witness the ultimate proof of the theory of quantum nonlocality; 303 00:39:18,833 --> 00:39:27,000 perhaps in 15 years or perhaps in 20, but at least much shorter than 100 hundreds. 304 00:39:27,125 --> 00:39:31,458 It's magic right? There’s something magical about it 305 00:39:31,583 --> 00:39:44,250 And when you look at your personal dream, how do you envision the dreams you still have? 306 00:39:44,792 --> 00:39:52,208 My dream is not the about the application of quantum technologies. 307 00:39:52,375 --> 00:40:12,750 My dream is to do fundamental research and to work on and contribute to the theory of everything. 308 00:40:12,875 --> 00:40:22,083 A great wish of mine is to discover through experimentation with quantum entanglement 309 00:40:22,208 --> 00:40:23,583 why quantum entanglement exists. 310 00:40:24,042 --> 00:40:28,042 When I was learning about quantum physics 311 00:40:28,125 --> 00:40:29,625 at first i had some difficulties(?) 312 00:40:29,750 --> 00:40:34,875 Afterwards I learned about Einstein’s' work on quantum entanglement 313 00:40:35,000 --> 00:40:42,125 deep in my heart, even though there is innumerable proof that Einstein's thoughts were wrong and even though 314 00:40:42,208 --> 00:40:49,500 experiments with quantum mechanics again and again disprove Einstein’s theory on the principle of locality, 315 00:40:49,583 --> 00:40:56,000 deep in my heart I want to do experiments that could perhaps go on to prove that on a higher level 316 00:40:56,208 --> 00:41:04,333 we come back to a variation of Einstein's principle of locality theory. 317 00:41:04,958 --> 00:41:10,708 So in my heart I am still a believer in the principle of locality and I hope to do something in this field. 318 00:41:10,750 --> 00:41:14,833 Yet I don’t know if I can do discover something new within my lifetime. 319 00:41:14,917 --> 00:41:20,917 Those are my wishes; I think that us scientists spend so much money 320 00:41:21,000 --> 00:41:27,542 in hopes that the technologies we make are of some use and so we push it towards to it being used. 321 00:41:27,667 --> 00:41:33,542 I hope that these technologies can be put to good use in the future 322 00:41:33,667 --> 00:41:44,125 like in secure communication, or in imaging, or in clock synchronisation. 323 00:41:44,208 --> 00:41:49,083 Then, to the general public their investment in scientists 324 00:41:49,375 --> 00:41:55,333 is not in vain and they will give us even more money to let us spend on fundamental research. 325 00:42:02,292 --> 00:42:10,333 You were talking about quantum entanglement. I know I asked you before, but could you explain again what is quantum entanglement? 326 00:42:10,458 --> 00:42:21,708 Quantum entanglement is actually is an embodiment of the theory of quantum superposition multi-particle system. 327 00:42:22,333 --> 00:42:24,417 What does that mean? 328 00:42:24,500 --> 00:42:30,875 I'll give an example: to simplify this lets assume there are only two states. 329 00:42:31,042 --> 00:42:35,375 There is something we call spin, and it can be in a state of either up or down 330 00:42:35,458 --> 00:42:42,917 If we have two particles, according to quantum mechanics, a particles in superposition has a spin 331 00:42:43,083 --> 00:42:45,667 state of either up or down. 332 00:42:45,750 --> 00:42:47,583 This can occur simultaneously. 333 00:42:47,958 --> 00:42:52,125 So if there are two particles, it will exists in a strange state of being. 334 00:42:52,417 --> 00:42:59,458 Mathematically speaking, I will say it will be spin up up plus spin down down. 335 00:42:59,792 --> 00:43:07,333 So if there are two particles, one in Shanghai and the other in the Netherlands, 336 00:43:07,625 --> 00:43:12,042 and at this moment if we measure the particles, we discover that 337 00:43:12,292 --> 00:43:21,583 if you find that one particle has a upward spin, then the other particle will also have an upward spin. 339 00:43:21,833 --> 00:43:28,458 If you find that one particle has a downward spin, then the other particle will also have a downward spin. 340 00:43:28,792 --> 00:43:33,042 It seems that everyone thinks this is strange, but you can repeat this experiment many times 341 00:43:33,208 --> 00:43:35,917 and you can send many pairs of entangled particles to different places 342 00:43:36,250 --> 00:43:39,125 but every time the result, if the particles are in an entangled state, 343 00:43:39,292 --> 00:43:43,250 will be that either both particles have an upward spin, or both have a downward spin. 344 00:43:43,458 --> 00:43:52,042 Einstein called this strange phenomenon "spooky action at a distance." 345 00:43:52,292 --> 00:43:59,000 This is what we mean when we talk about quantum entanglement. 346 00:44:01,500 --> 00:44:21,917 And when you look around now, can you see quantum mechanics working, are there machines, are there topics that somehow prove quantum mechanics? 347 00:44:22,250 --> 00:44:29,583 Up until now we have proven quantum mechanics is correct through many experiments. 348 00:44:29,750 --> 00:44:37,458 We have concrete examples like superconducting phenomena, nuclear energy, 349 00:44:37,667 --> 00:44:47,583 nuclear magnetic resonance, giant magnetoresistance and other 350 00:44:47,667 --> 00:44:53,458 and other examples from various scientific fields that prove quantum mechanics works very well. 351 00:44:53,583 --> 00:44:55,042 That it is correct. 352 00:44:55,167 --> 00:44:58,542 When it comes to detailed experiments into quantum mechanics 353 00:44:58,667 --> 00:45:03,125 ,what we call fundamental research into quantum mechanics, 354 00:45:03,250 --> 00:45:08,833 we often use quantum entanglement as an example. 355 00:45:09,042 --> 00:45:18,125 After quantum Schrödinger and Einstein proposed entanglement in 1935, 356 00:45:18,417 --> 00:45:24,833 people started doing experiments with it in the 70’s 357 00:45:25,000 --> 00:45:34,583 The earliest experiments were conducted by Clauser and his colleagues at the University of California, Berkeley. 358 00:45:35,000 --> 00:45:38,208 Later it was France's Alain Aspect 359 00:45:38,375 --> 00:45:40,917 who also did experiments in this field. 360 00:45:41,000 --> 00:45:44,292 Successively they proved the existence of quantum entanglement. 361 00:45:44,500 --> 00:45:48,667 But some people say there are gaps within these experiments. 362 00:45:48,958 --> 00:45:52,583 What I want to prove is "spooky action at a distance" 363 00:45:53,000 --> 00:46:01,458 because then you guarantee that during the experiments the condition of locality is met. 364 00:46:01,542 --> 00:46:12,917 The locality loophole was shut down in the 90's Weihs'(?) team in Innsbruck. 365 00:46:13,208 --> 00:46:17,583 Everyone then suggested the the detection loophole. 366 00:46:17,917 --> 00:46:25,000 Well, last year the detection loophole was closed by Dutch scientists 367 00:46:25,333 --> 00:46:28,000 who also simultaneously closed the locality loophole. 368 00:46:28,167 --> 00:46:38,083 Thus we are left with the final loophole, the freedom of choice loophole which is also called the collapse locality loophole. 369 00:46:38,375 --> 00:46:45,250 We hope to close this loophole within the next 10, 20 years. 370 00:46:45,500 --> 00:46:50,708 All the experiments until now already proved quantum mechanics works 371 00:46:50,917 --> 00:46:56,500 but quantum mechanics at long distance, and this final loophole, can they also be solved? 372 00:46:56,708 --> 00:46:58,292 Well we don't know that now. 373 00:46:58,417 --> 00:47:00,000 In the future there are two possibilities 374 00:47:00,167 --> 00:47:04,333 I think it is a great possibility is that we we go on prove quantum mechanics is correct 375 00:47:04,625 --> 00:47:06,250 and we close all the loopholes. 376 00:47:06,458 --> 00:47:12,167 But there is also a small possibility that we discover a new field of physics. 377 00:47:12,458 --> 00:47:16,125 Then it will get very exciting for us. 378 00:47:20,000 --> 00:47:21,375 Both can be exciting. 379 00:47:21,000 --> 00:47:22,500 Right 380 00:47:24,000 --> 00:47:28,250 What kind of other theories that can be found when you fantasize about that? 381 00:47:28,708 --> 00:47:34,833 I think throughout this process, when we are talking about the validation of quantum mechanics nonlocality 382 00:47:35,417 --> 00:47:42,000 it is still very fundamental, still the foundations of of quantum mechanics. 383 00:47:42,333 --> 00:47:45,667 The next step would be what I mentioned before: 384 00:47:45,833 --> 00:47:50,750 we can test quantum gravity models. 385 00:47:50,917 --> 00:47:55,917 This would be what we would do after we finish our second mission. 386 00:47:56,083 --> 00:48:03,542 Afterwards, theoretical physicists are very smart 387 00:48:03,792 --> 00:48:06,125 and they will propose all sorts of models. 388 00:48:06,292 --> 00:48:09,250 But each model the propose will be consistent with the natural world 389 00:48:09,458 --> 00:48:11,167 and while some scientists will say that's good enough 390 00:48:11,542 --> 00:48:13,792 this is when we need to do experiments. 391 00:48:14,000 --> 00:48:20,083 We wish that when we finish proving quantum mechanics nonlocality 392 00:48:20,292 --> 00:48:29,208 we will come back and to experimental research work in quantum gravity related theories and models. 393 00:48:29,375 --> 00:48:36,375 And quantum gravity, could you explain that? What is quantum gravity? 394 00:48:37,625 --> 00:48:42,417 I am not really qualified to discuss quantum gravity because this theory 395 00:48:43,250 --> 00:48:48,708 is something (theoretical physicists like) Hawking and other scientists have suggested. 396 00:48:48,875 --> 00:48:54,625 To an experimental physicists like me I just know that that they took quantum theory 397 00:48:54,875 --> 00:49:00,625 and gravity theory and combined them. 398 00:49:00,875 --> 00:49:04,583 After they were combined they proposed several further theories 399 00:49:04,875 --> 00:49:09,500 but which of them is the one congruent with our natural universe? 400 00:49:09,833 --> 00:49:11,583 This needs to be proved with experiments. 401 00:49:11,708 --> 00:49:17,083 When we do the experiments do the predictions from the theories align with our experimental results? 402 00:49:17,208 --> 00:49:24,208 The ones that match up are the ones that are more likely to approximate natural law. 403 00:49:24,625 --> 00:49:34,917 Because I am not an expert in quantum gravity, I can't elaborate on or criticise the models 404 00:49:37,917 --> 00:49:40,750 Thank you