Does the quantum theory bother you? Lieven Vandersypen at TEDxBreda

a really fun game to play with small children is hide-and-seek I just love it how our daughter hides her face and she thinks we can't see her or how my little cousin sees me step behind the curtain and then I see his face peek her antic curtain with his great tension on his face will I can't even be there for him it's not a lot clear that this is where I'll appear but over time children learn they learned that if I step behind the curtain I will not suddenly appear somewhere else they learned that I can't be in two places at once and in fact that I'll be behind the curtain whether or not they look they learn they look they learn the laws of physics but what they lose is imagination the thought that anything is possible as they grow older and get used to the world around us they quickly no longer can imagine anything else it may seem obvious that if I step behind the curtain that's where I'll be regardless of whether or not somebody looks but but really it's not quantum theory says it doesn't need to be that way content theory is the theory of small particles like atoms and electrons and it tells us that such small particles actually can exist in two places at once a so called superposition state so for instance when one single electron approaches a screen with two openings as it come closer comes closer we see that actually it can pass through both openings in the screen simultaneously bouncing or interfering with itself at the other end and when it then hits another screen behind the first what we find is that the location where these electrons hit the second screen shows a pattern an interference pattern which is mystic and only possible if every electron by itself really passed through both openings and it gets even better if we place a detector next to the openings to test to measure whether indeed electrons pass through both openings at the same time two things happen first the detector tells us that actually the electron passed just through one of the openings so you might say well okay so that's what we expected all along really there is nothing unusual but at the same time this characteristic interference pattern resulting from the simultaneous paths disappears so what this tells us is that the act of measuring not only changes what we know about the state of the electron and the path it took but it also changes the state itself well so when when I'm at a party and you know this cute girl comes up to me and she asks me what I do I begin to tell her about quantum superpositions electrons being in two places at once and so forth so so what do you think happens next well indeed she might say oh you must be very smart then she quickly walks away and and this actually does happen but on the other hand like my wife she may love it and start asking lots of questions what do you mean in two places at once I've I've never seen such a thing how can this be yeah and I don't understand and really what she means is I don't believe it I think and you might not believe me either and if you don't you're in good company Albert Einstein to his death rejected this notion of super positions he insisted that even if we don't know where an electron is that it's really just in one single place like you might expect and this was a hotly debated point throughout much of the 20th century between Einstein Bohr and others but by narrow experiments leave no doubt and we better accept like children they thought that alike was actually can be in multiple places at once so then how can we try to visualize do you imagine what this means this is this quantum world let's look at the screen of two people these are Fred and Kate and there are two dimensional people living in a two dimensional world the plane of the screen and imagine that whenever you're looking at Fred and Kate and you see them approach each other they bounce back what you learn over time is that people are solid objects and of course solid objects people cannot walk through each other so this begins to make a lot of sense but then suddenly did you see it suddenly Freddy Kate actually walked right through each other this is this is impossible if we thought this could never happen what what's what's going on and in fact if we zoom out now we see that the predicate living in the two-dimensional world were just shadows they were shadows of a three-dimensional Fred and Kate living in a three-dimensional world and in this three-dimensional world they can just simply walk besides each other so so there is nothing unusual really so similarly what the world that we see around us is such a shadow of a created reality a reality in which quantum superpositions are completely natural and there is nothing unusual about it this created a reality I embrace in my research I stopped philosophizing and wondering what it means superpositions and just go with it and and ask myself whether these superpositions electrons particles being in multiple places could be useful and scientists worldwide are actually developing what we call quantum technology a technology making use of these quantum effects it's about computers quantum computers faster than any computer we can imagine today about ways of communicating with each other that are just impossible today or invite sensors and imaging techniques with unprecedented accuracy and perhaps the most important applications we don't even know can't even imagine quite yet so let's look a bit more closely at the quantum computer a future computer that I've been working on for the last 15 years of my life like an ordinary computer it makes use of bits and we know that bits can be either 0 or 1 but in a corner computer a bit can be 0 and 1 simultaneously and again let's not ask what it means but if this is true and we compute on these bits then actually we can do two computations at the same time 2 for the price of one and with 2 bits it gets even better because 2 bits together can be 0 0 0 1 1 0 or 1 1 for combinations in the quantum world we can have these four values together and do 4 computations in parallel with 3 bits 3 contemplates we can do 8 parallel parallel computations with 4 bits 16 and so forth in fact by the time you have just 30 bits not very much you can do 1 billion computations at the same time just with just 40 bits it becomes 1 trillion so what we see is that for every bits that we add to our quantum computer the number of parallel computations doubles somehow there is an exponential computing power present in such a device and this exponential power we can use to solve problems that are simply impossible to solve on any conventional computer even a supercomputer for instance chemical reactions are extremely difficult actually impossible to simulate compute both accurately and efficiently on any existing computer but the quantum computer could simulate chemical reactions actually very easily and this can have far-reaching implications for instance for designing new medicine so what does a quantum computer look like different technologies are being considered my favorite one is based on a simple computer chip but then a chip the workings of which are entirely contem and in order to make it contem we need to cool it down to extremely low temperatures very close to absolute zero minus seven hundred minus 273 degrees Celsius and that temperature electrons can be in multiple places at once and we can manipulate a man and so forth the state of the art now is at this at a level of a handful of quantum bits and that's enough to test the predictions of quantum mechanics and test simple algorithms in fact for my PhD work I have used seven contemplates and manipulated them to show that the number fifteen can be pulled apart into three times five so that was the kind of my work it gathers a nice paper in nature at a time but the present challenge is to go from these toy experiments to a large-scale technology where thousands or millions of content bits are in in a very large quantum superposition doing this massive parallel computation and that's really quite a challenge not only because of the complexity involved of constructing this machine but also because the super positions are in fact extremely fragile and and easily lost but it's also a very exciting challenge one that I'm very excited about and with colleagues worldwide we're working very hard to make this happen so next time you play hide and seek with your daughter and she think you can be in two places at once well she's kind of right and if you can have the imagination of your children then entirely new worlds become possible like Columbus who thought that the earth might be a sphere and when I'd to test it to the beautiful world of quantum mechanics that is taking us from quantum surprises to quantum devices thank you

Channel: TEDx Talks

Views: 139,388

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Keywords: ted talks, ted talk, Quantum, ted, Theory, tedx talk, tedx, Nanoscience, Lieven, TED, Vandersypen, Breda, Belgium, Einstein, tedx talks, TEDx, ted x

Id: HfVi7iF9mjA

Length: 11min 1sec (661 seconds)

Published: Tue Nov 12 2013