you [Applause] yes and good evening ladies and gentlemen and even I saw some boys and girls so good evening to you too that's very good news as Martin said I've been given the honor to welcome all of you as deputy ambassador of the Netherlands embassy here in London and it's an honor I must also say that as a diplomat with a law degree I'm a little bit out of my comfort zone and intimidated by all of you around here and especially the two speakers I think but in preparation I visited the Science Museum this Sunday with my five-year-old daughter and we had a very good look at the mathematics exhibition which is very impressive for those of you who haven't seen it but I'm sure you all went so please consider me to be fully informed the Embassy is excited to work with with a partner which has over 200 years of experiencing in as it says here harnessing science for the maximum benefit of society that's its mission statement or part of it and I wanted to thank you for cooperating with us and especially you Martin for for doing this with us and this is as you said only the first in a series of lectures that we're hoping hope to run for this year and the close cooperation between us and this institute is a reflection we think of the very close relationship that we have between our two countries in general the UK and the Netherlands and science in particular as close nor see neighbours the UK and Netherlands have inspired each other for centuries in this domain as seafaring nations both of us sometimes at war sometimes the UK one and sometimes we did or actually a little bit more often than the other way around we both relied on telescopes for navigation of ships and hence we both excelled at studying the largest things so the galaxies telescopes as well as the smallest of things microscopes and as early as the 17th century my microscopy pioneers such as Robert Hooke and Antony van Leeuwenhoek shared their findings in academic publications and some of these works and exchange of ideas are actually exhibited outside and for those of you who haven't done so already I would recommend highly to see the beautiful things that are on exhibition here outside of us and one book is actually even the beginning of the topic that we are discussing I just learned the double-slit experiments and don't ask me what it was exactly but something with lights into tunnels yeah but it's certainly and that I would like to emphasize it's not only in the past that we had close cooperation these links and interactions carry on today between Dutch and British scientists and engineers they are plentiful and they're productive and we have no doubts that these this close cooperation will also continue in the future and we are still working both on the largest of things as well as on the smallest of things and just to give you an example joint work for example is going on on the design of the Square Kilometre Array telescope which is meant to study the very largest of things and on the very smallest of things the quantum realm enjoys the interest of both our scientific communities and I think we're going to learn more about that today these early scientists such as fan hook and Leeuwenhoek probably had no idea of the vast implications of their discovery but we have since learned that Science and Technology can of course transform society and I hope that our speakers might shine some light on this tonight I am looking forward to undoubtedly two very inspiring speakers professor Harvey Berman and professor Arthur Eckert but I leave it to you mr. ball to introduce them to the audience thank you again for coming tonight and I hope you will all have a wonderful evening thank you [Applause] thanks very much let's just see I've got the first of these ah I have there we go there's a quantum computer you until perhaps just a couple of years ago I used to consider it my duty as a science writer to titrate em for the hype around quantum computing by advising how limited they might be and saying you know you're not going to get your quantum laptop anytime soon and that remains true and of course it's still as I still have a duty to debunk the hype but I've been genuinely amazed how this field has progressed just very recently really just over the last two or three years and I I'm not alone in that in fact some people working in the field I'm quite sure have been taken by surprise at the pace of the change when IBM announced in 2016 for example that it had made this quantum computer with five quantum bits or qubits as they're called and that it was making this resource available as a cloud-based resource that anyone could register any of you could register and use it wasn't just a publicity stunt you can do real science on this device and in fact 60,000 people worldwide have registered to use what is today slightly sort of cumbersome lead called the IBM Q experience and hundreds of papers have been written on the basis of work done on this machine so it's a real resource for science I was lucky enough last September to get to go to the IBM labs in Zurich and this if I can get it to move on this is what I saw ah there we go yeah well this this actually is the interface this is you can just look this up online this is the interface for the IBM's to experience that you just sort of plan out your quantum circuit and use it but this is really what I wanted to show you if we're going to get there you wait until we have quantum technologies like this they're gonna go wrong in new ways but this is what I saw and this is one of these devices and it's you know it's this room filling device and I'm nervous use this now but it took me back to the days when computers used to look like this now I'm not quite old enough to remember that but I'm certainly old enough to remember mainframe computers that filled entire rooms and it made me think well if this is where we are now with quantum computing you know where are we going to be in 20 or 30 years now if you have any sense of the number of bits you know in the average laptop probably of the order of billions then five cubits might sound pretty pitiful but therein lies the power and the promise of quantum computing because by using bits that are governed by the laws of quantum mechanics rather than the classical rules that just allow every bit a binary one or a zero state this leads to a potential vast boost in computing power and speed and it also allows you to to do things that you simply can't do with classical computers in fact that promise more than the speed-up was what led richard fineman in 1982 to first suggest the idea of doing computing using quantum rules things of still moving on in a tremendous pace and in fact just last week we saw we heard the announcement of this next keep you in suspense which is produced by Google so it's not all IBM by any means and Google are in this game and this is their quantum chip which for some reason they've called Bristlecone and it has 72 qubits which is considerably more than the 50 or so that some researchers think is what was needed to reach a point slightly ominously called quantum supremacy when quantum computers become capable of things the classical ones can't do so it sounds as though the future is suddenly but of course it's never as simple as that for one thing there are big questions about how far you can continue to scale up these quantum computers and in particular how to handle the errors that inevitably arise when you're doing a computation because the fundamental laws of quantum mechanics prevent you from dealing with errors in the same way as we do for classical computers and it's one thing to create a prototype device like this but of course another thing to find a niche in such a well-developed industry as the classical computer business so what are the real prospects for quantum computers we have here tonight two speakers who are perfectly placed to give us some answers to that question when back in the 1990s quantum information technologies were still just a speculative idea in fact he just called it earlier on a family game in those days Arta Eckert was one of the key movers who drove the field forward and sustained the notion that it was really on to something and Artur is based at Oxford University where his invention of a form of quantum cryptography in 1991 triggered an explosion of efforts worldwide and he's contribute contributed to many important advances both in the foundations and in the experimental realizations of quantum communication and quantum computation I think it's fair to say I hope this isn't unfair that the Netherlands we don't always think of it as a vast hub of X or of activity in computer technology but it has become one of the most active countries in quantum information technologies and some of that is thanks to our second speaker Harry Berman Harry built the quantum computing group at the center for mathematics and informatics in Amsterdam the first in fact in the Netherlands to work on quantum information processing and his research focuses on quantum computing and algorithms and complexity theory and he's developed a kind of complex systems approach to thinking about quantum computing things like how to make the best of distributed quantum resources Harry has a background in computer science and he's looking at the vital question of how to give of algorithms that we desperately need to actually do anything with the resources that quantum computers are offering so I'm going to hand over to the the two of them who will speak for about thirty minutes and then we will open up the questions and I'm sure there will be plenty of questions to use so thank you very much then first of all please welcome after Eckert thank you for for this introduction i-i-i don't really feel like a prophet to be able to answer all your questions but i in preparation to effort for this particular talk i was thinking what and how i should present this subject because you know there's probably 125 ways to talk about quantum computing and then I concluded that perhaps the best approach would be to tell you where is the where this extra power for quantum computing is coming from and you know the that dead of course will take us to quantum physics and I will have to explain a little bit which part of quantum physics is responsible for this what we believe is an extra power in quantum computing I will have some equations for which I apologize but how do you know those of you who are familiar with probability and a complex number will probably find it quite easy those of you who are not well don't worry too much about it because you can just keep out those equations and and and hopefully you'll follow that the gist of the idea that there's something new there as field mention you know that about in the early 90s this field was a family business so Harry and I met in early 90s and it was one of those meetings where we were discussing the nature of randomness and somehow someone had idea that well maybe quantum has something to say about it and gradually talking about ideas that I you know I always thought it was just completely blue sky research I never ever thought at the time that it will ever be the case that someone from you know commercial world will or banking sector will come to me and and start talking about investing in this field but you know here we are today no one ever knows ok so before I tell you about quantum theory let me start with with probability now I have to just mastermind this classical technology first obviously just let's see how it goes here we are so and usually when I give when I when I give lectures in arts or to my students I usually like to start with giving them a little bit of a historical background and I honestly think if there's one person that is basically responsible in a way for mathematical tools that we use today in quantum physics is this guy's Girolamo Cardano is his name there's by the way very nice books written by Michael Brooks that appear recently about his life and so this person in in the you know in the sort of in the in the sixteenth century came up with mathematical foundation for two basic tools that we use in quantum physics first it is probability theory and if you think it was all done in France that's not quite true actually he was about 100 years earlier than Pascal another it just simply that he didn't publish it at that time so his work on probability was written down and was published a bit later and he was also the first person who spotted complex numbers so he he was in his work on I'm trying to sort of find a solution to cubic equations he noticed that there's this weird thing like the square root of minus 1 actually he was to be more precise was square root of minus 15 for some reason that that he was interested in and and he he thought well you know this is weird it's wacky and I you know it's not clear what to do it's probably completely useless and irrelevant and even you know in his book Aris manya he called those numbers you know strange and probably absolutely useless but but you can operate with them you know we just assume that you can take the square root of minus 1 is a symbol so you can be very instrumental and try to play with it so here we are we have two tools complex numbers which is basically like any numbers but every now and then you know the square root of -1 appears and we write it as I unless you're old-fashioned engineers then you write it as J and then the the probability is another is another thing and of course you know he's interesting probability was mostly because because of gambling and he was quite a gambling scholar and fascinating character by the way so but you know so let's let's start with probability so clearly most of you will have a feeling that there is a sort of as long as we can somehow control randomness or domesticated you know take advantage of it is a very useful tool and if you think that people have problems with understanding quantum physics I think people for a long period of time even today there's you know debate about the proper understanding of the the nature of randomness and the probability theory for a long time in fact mathematicians didn't even pay attention to probability because it was a little bit messy subject and it was not clearly defined and there were various possible interpretations and you can see here I pick up four people here that you know from Laplace this is you know it's a subjective thing then from neither says well maybe those objective things are related to frequencies and and definitely who may say well it's subjective and Karl Popper who may say well its objective so you know what exactly it is this probability thing how do you really assign a number that something will happen with such-and-such probability what is it so it was I will not go into details but but but will I just say is that at some point you know a Kolmogorov came in and in typical mathematical way you have all those physicists and philosophers discussing debating what it is and it says well I don't you know I'll define three properties three axioms and I call probability whatever satisfies those axioms of course it doesn't solve any philosophical and problems at all and physicists ill you know baffled you know but how do you make this number assignment but but Kolmogorov basically say well you know anything I can just make a mathematical structure that if you have a dice you can assign numbers so that you throw one two three and those numbers could be anything as long as they satisfy the three condition so the probability is a positive number for example if I toss a coin if it is a biased coin it could probability could be you know one three four heads and 2/3 2/3 four four four tails and so they add up to one and then there's this sort of the first two sort of axioms are kind of trivial but what is interesting is the third one which says that basically the probabilities of exclusive events adapt if something can happen in two mutually exclusive ways then we add the probabilities for the whole event we have the probabilities for as sort of you know for this happening one way and happening the other way so for example if I have say symmetric dice and I throw a dice and I ask you what is the probability of that event at a lower even number so the way you can calculate it is you say okay well even number that means throwing two four and six and probability for each probably would be one over six if it is symmetric dice so I add 1/6 plus 1/6 of 1 over six so that gives me three over six so that means half so this way we calculate probabilities for events that can happen in a mutually exclusive way now pay attention to this because this is actually the crucial point now I'm going to tell you something that that that really will almost introduced quantum physics right away to you so it seems you know this is this this additive 'ti axiom it's fine for a mathematician you know because you say well those are my rules of the game but the thing is Nature doesn't know about those axioms really so nobody told nature val kilmer grove axioms and the and there are phenomena in in in nature where the third axiom is obviously not satisfied we want to make the statistical predictions in some experiments and of course the double-slit the famous double slit experiment is one that we usually use to demonstrate this and we can then in this in this experiment you know our naive way of thinking our classical way of thinking would be to use probability in the way called makarov wanted to as to use it so we just look at for example a particle going from a source to some detector somewhere and you put this you know double slit thing just to force this particle to take one of the two mutually exclusive way so you can go from the source on the left to the detector on the right taking the upper slit or the lowest slit and you can assign probabilities to each event say P 1 and P 2 and the Kolmogorov axiom tells us that the probability that this particle will end up in this detector is P 1 plus P 2 because those are mutually exclusive events according to Kolmogorov and we just add probabilities well ok fair enough it is you go and set up this experiment and this is not what happens and it turns out that well I just mess up my slide a little bit nevermind so it turns out that that this is not the case it turns out that the probability theory as we know it's classical probability theory does not give you the right mathematical tools for making predictions in some experiments so so what do we do well you just think you know how to fix it and you know just a long history of how people discovered quantum physics but the way we understand it today it is like a different kind of probability theory so so we know how to fix it and the way we are going to fix it is to use complex numbers again back to Cardinal such we call them probability amplitudes and we make connections between those complex numbers with probabilities but saying that if you want to know the probability you have to take basically the square of strictly speaking the modulus square of square of the modulus of this of the complex number but but but when you want to calculate probability of mutually exclusive events you don't add probabilities you just add those complex numbers those probability amplitudes you add those two probability amplitudes and then you take mod squared of those and when you do this and it's a very simple algebra that you can do the calculations and you will see that indeed you have the kind of three terms you have P 1 and P 2 they appear there so this is like a classical part of the story and then you have a correction that comes from the fact that this physicists call it or everyone calls it the interference term so you can see that this interference term depends on on what you know the complex number can be always represented as a mod you lose and a phase factor and this those phases which I here called theta1 and theta2 you know this this this interference depends on the cause of the difference between those phases and you know even this equation is very puzzling because you know you may say well it depends on the difference how does the particle know the difference you know how does it know what is the phase on the other path so some people say well maybe actually those two events not mutually exclusive maybe this particle in some mysterious way it goes through the bus lists at the same time so somehow you know the particle reacts or acts as if it were sort of sniffing one path and the other path and sort of and the other thing that is very important for understanding quantum computation is that this term here this course can be either positive or negative you know the cause goes from minus 1 to 1 so you can then if you look at the black part p1 plus p2 so the interference term can either enhance the probability that this particle will go to this detector or can suppress it so if you have a positive interference that is when this term is positive then it is more likely that the particle will end up in this particular detector but if it is a negative then the chances are lower so now basically I can then tell you that quantum computing is like a huge multi particle quantum interference so you prepare input it's like you know setting up the initial condition and your quantum computer is a complex system but of course it goes through a number of different computational paths and it just can end up in different outputs and the art of quantum computing is really to design quantum interference in such a way that you enhance probabilities in the direction of correct answers to your computation so the chances that you get the right answer the output that is the answer to your problem is amplified by the interference term so this is exactly where the difference between classical and quantum computing comes from if you want to point it into one particular expression in physics that the quantum theory really differs from probably by this extra interference term yeah so things are indeed a little bit different in quantum physics you can so now do we see this quantum interference yes we do the people you know use all kind of experiments and you know you can see you can do it with photons you can see this interference with neutrons with atoms with ions you just force them to take different paths and then you can see that somehow you know that this quantum interference works and you know you can you can just usually in quantum information science we we come up with a sort of generic diagram so we use instead of telling you how this interference works for neutrons how it works for photons and so on so forth we just usually go into simple units and we call them quantum bits or qubits and we simply I think I just can I go back yeah so yeah so we just use we want to go to the higher level of abstractions and and simply talk about quantum interference as a sequence of elementary operations performance um on some quantum system as a qubit and the typical sequences you can see on the on the top here there's the yellow boxes are numbers the Hadamard transform whatever that means and then in between there is this phase shift and it turns out you know that you you saw before that this quantum interference depends on the difference instead of a phase setting for those two complex numbers and it turns out that this phase setting or the difference can be generated with a number of interesting physical phenomena and the whole interference pattern and how the difference in probability so the difference whether this detector will click on some other detector will click is a very very sensitive to this phase difference which is a good thing and a bad thing it's a good thing because you can use it for very sensitive detector so even if you just forget about quantum computers for a moment you can use this kind of face setting depending on what is the physical mechanism detect and to dead to detect something about you know the physics that generates this this phase difference so it could be gravitational field it could be rotation it could be you know we can have a very precise atomic clocks based on this interference thing you know you name it so so there's the whole area of quantum metrology where you build very sensitive detector simply because you are able to pick up the tiny phase difference introduced by by a certain physical phenomenon and use quantum interference to detect it you can you can also use those quantum phenomena this this this sort of idea that maybe you know this in this quantum interference when the particle goes through from the source of the detector maybe it isn't maybe you know those two slits somehow are not mutually exclusive gateways to the detector maybe it is indeed the case that the particle somehow goes through both and technical word for this we may say that you know at this point a particle may be in a superposition of being at the first lid of the second slit and this notion of superposition allows us to construct quantum operations that do not have classical counterpart quantum logic gates that do not have classical counterparts so one for example would be the square root of note so think about it this way you know the the basic logical operations on a single date right so you can basically there are four of them you take your input and you don't do anything so that's identity so 0 goes to 0 1 goes to 1 or you can negate your input so 0 goes to 1 and 1 goes to 0 or you can have you know whatever comes in the output is always fixed at 0 or whatever you put at the input the output can be fixed at 1 so you have 4 single bit logic gates and you don't have more but then if I ask if I give you the following puzzle so can you can you think about the logic gate such that think about it as a black box so that when it acts on bit and and and you and you take another one and put them in a sequence so that to a sequence of two identical independent logic gates together generates the operation logical note then you think for a moment so I call this guy the square root of not so you think for a moment say well now neither of those four gates the dimension would do the job so you say well no it's not possible and it's a logician so where is absolutely impossible you don't have such a thing but in fact you do you know you can if you can use quantum phenomena the superposition you have an operation which takes whatever input you have put it in some kind of a superposition of 0 and 1 and also can bring this position superposition back so the first gate square would have not can prepare the superposition and the other one can close it in such a way that it just works all together as a square as a logical note so it's it's and also you know you can you can design more complex logic gate so another way of looking at quantum computing is is it's just sort of use those logic gates that are somehow different you know somehow they don't have classical counter but they can be implemented I will not go into details but but you know it's interesting at the very beginning of this field when the physicists started talking to computer scientists and even to logicians and you would ask you know someone here your colleague your addition so you know do you do you really do you believe that there is such a thing like the square root of note and you know they would be very uncomfortable because there's no mathematical proof of that right but then you have a physicist and here I'm just you this is an imaginary conversation between Alan Turing and like you know my supervisor David Deutsch who who was one of the pioneers of this field back in the you know in the 80s so he so David could you know I could easily imagine him giving this answer to Alan Turing you know you have to accept that there is a square root of not operation because we have a faithful representation of this operation in physics so you know we can I can really just you know design experiment where I have one box identical box the quantum bit comes in only two states zero or one and you know acting together those two gates it generates logic or not so so we somehow you know another way of looking at quantum computing is that we take all those impossible gates and we put them together into some kind of a circuit and we you know use those square root of nots square root of swabs and a few other gates to create in fact this huge quantum interference that I was telling you about and so yet another perhaps way of telling you about quantum computation so I keep on repeating myself but I just you know maybe if if you take home at least one point you know where is the difference between classical and quantum then I will be very happy so so let me just repeat it in similar in a slightly different way so if you think about classical deterministic computation you think about a machine that goes you know from one configuration from input and goes click click click through different configurations until it stops at the output and then we can think about slicing possibly not powerful computation which is based on which is randomized computation you know some algorithm updates on random resume quite powerful or use a Monte Carlo methods and all kinds of things so so this we allow this computer the classical probabilistic computer is allowed to make random steps and go take this computational path of this computational path but then you know in this game we use classical probability theory to understand this extra power of randomized computation so we add up probabilities right and then here comes a quantum computing which is a little bit like probabilistic accepted relies on those quantum phenomena of interference and the probabilities that count are computed in a in a very different way so so the good thing about this quantum interference this phase think that I was telling you about is that it's it's very sensitive in a way that tiny change in this phase shift will generate difference in probabilities which is basically good because we use it as a detectors is a very sensitive device but it's also a problem because when you start when you cannot design the system in such a way that it only interacts with what you want it to interact it interacts with everything else and the this phase jitters and and therefore the this is the phenomenon we call the coherence so if you cannot keep this face fixed this cost function that you saw before rapidly fluctuates between plus 1 and minus 1 basically it Everage –is to zero and then you have addition of probabilities so you recover the classical computation in this particular way so this is the process known as the coherence and this is a big thing so on one way we have powerful devices with it possible and again you know think about in big quantum interference that's what it is we give it computation meaning and they could be more powerful and and the question is now of course we have to address the question what does it mean to be more powerful well as it happens you know computer scientists had a way of classifying problems into classes take out complexity classes so so some of those problems are considered easy and some of them are difficult and basically the way you classify a problem is that you look you pick up here a problem then you pick up an algorithm so this problem and then you ask yourself how good is my algorithm so one way to test how good it is is you asked this algorithm the problem the same problem but you increase the size of the input so for example you have multiplication you multiply to one digit numbers and then to two digit numbers three digit numbers and then you plot the diagram and you see how the execution time or the number of operation grows as the function of the size of the input and if it grows like any polynomial function then you say well it's easy it's kind of a good algorithm handle it but it grows exponentially fast then it's not good you call it difficult and so there are some problems for which we have good efficient polynomial time algorithm and there programs where we don't know whether we have polynomial time algorithm out to find them and sometimes you know problems we simply don't know how we have exponential algorithm I call them code those problem is difficult we don't even know whether there is an easy out efficient algorithm for example factoring is a good example it's a reverse of operation to multiplication if I tell you what are the factors of 15 then you say well 3 times 5 3 is a prime number 5 is a prime number 3 times 5 is 15 now if I increase the size if I give you a huge number then then it will take you in exponentially you will have to spend more and more time to be able to answer this not only you any computer any device so defining the difficulty as a scaling property makes it device independent so it doesn't really know this you if you have a factoring is equally difficult for a super duper computer as it is for your calculator there is you know a constant factor that you know that is the the clock speed but you know is exponential in both cases so there's also a class you know problems called NP which is which are problems which are difficult but once you have the solution you can add easy check in polynomial time and that the solution is correct not all the problems have this property factoring has right so if you if if you may work very hard to find the two prime factors but once you have them you can at least verify very quickly that you have the right answer so so this is the way computer scientists classify the problem and when I say then the quantum computers are more powerful what I really mean is that quantum computers change those complexity classes so for example factoring is easy for quantum computers because we have a polynomial time algorithm so those problems and you see what is important that you understand is not the technology per said that makes this possible it's it's not because we have a you know better technology that we can do technology can make only can change the rescale it by by by a constant factor so it's not going to change exponential into polynomial behavior by if you multiply by a constant factor so so the reason the only way to make difficult problem easy to find efficient algorithm creativity and find a way of doing it but but but you know the reason we can do it with quantum computers in some cases and we don't find a way to do it with classical computers is that quantum computers have a different set of instructions the larger set of instructions a quantum computer because of this sort of interference can accept instructions such as and now take a superposition of 15 and 42 for example you know so this this instruction makes sense to a quantum computer so having this extra set of instructions we can construct new algorithm any classical counterpart and this is actually the power of quantum computation it comes from the fact that now we are able to domesticate this interference by by you know dividing it into those quantum logic gates as simple steps and each step is inherently quantum doesn't have classical counterpart so so then we have to still use our way you know creativity to find good algorithmically how it works you know one can of course you know speculate about many things like impact of for example of quantum computing on mathematics so here is one hypothetical scenario so imagine the imagine that you have a mathematical problem a proposition that you want to prove and you want to know whether this is true or not and you know that basically you can do it if you analyze you know a number certain number of cases but at the same time you know there's no computer in the known universe classical computer that can do it because those number of cases is huge so it's equal to the number of atoms in the in the whole universe but you know the quantum machine can do it for you so it can you can in principle you know you can design it a proof that would just take a quantum machine and will just allow you to go into those super positions and it we can easily create a number of super positions equal to the number of atoms in the universe or those those are relatively easy things to do with quantum bits and and then through this huge quantum interference that we cannot really terminate at any point we have to just wait for this to come back to the sort of output and the quantum computer you know goes for a while and says well the answer is yes this proposition is true now here we have a very interesting situation because we have a man in you know we have a kind of mathematical proof but there's no method there's no physical record of this proof usually when a mathematician comes to you and says prove it to me that means you know he or she will expect you to go to whiteboards or write something on a piece of paper and says okay we start with the axioms and then we have this and we have this and we have this you're agreeing yes I agree and here is the answer you know QED I it so there's then a bunch of mathematicians can go and look into this and say well yeah maybe there's an error oh yeah I can correct it so but but this physical proof is an essential part at least in traditional mathematics right so you expect this kind of things but here we cannot produce a physical proof we have a physical process so are you prepared to put your trust into physical process rather than inspect the physical record to be able to believe that this proposition is true or not it's an interesting you know to talk to ask mathematicians and they kind of divide you know they say well I would never accept this kind of things you know it's just you know it doesn't worry if you cannot just write it on a piece of paper or if it is not something that you can in principle produce a physical record then how can I accept this as a valid proof because at this point in order to accept this mathematical truth you have to somehow put your believe in quantum theory because you know I explained to you how it works I tell you about quantum physics and then you know this black box input comes in goes the output is yes so it's actually interesting until today mathematicians are very much divided whether this is a valid mathematical proof or not but you know it's quantum computer relief at least may actually come to this point mathematics will have to debate at the moment I gave you a hypothetical scenario but it can happen for real now then we come to the questions about can we can we then the apart from demonstrating simple quantum interference can we scale up and build quantum computers the answer is basically yes there's no reason there's no law that tells us that it's not possible so therefore it has to be possible how exactly they will look like it's still not clear there are many possible quantum technologies on the agenda from trap ions to as you know superconducting circuits and all kinds of things are being considered at the moment so it's very difficult to say which particular technology will be the winner and you know you may you may as well say you know that if quantum computing is so cool and so good and you can see some advantage in quantum computing maybe nature where you figure this out you know maybe there are interesting quantum phenomena based on quantum interference in nature which gives you some kind of evolutionary advantage well maybe it's worth instead of building computers maybe you could just look for quantum computer somewhere in nature well we don't have many examples of that but there is at least one so there's one example where we have a case of the energy transferring purple bacteria so there are bacteria that live in this at a very dark environment at the bottom of the lakes there are not so many photons getting there so therefore those bacterias have to be very very efficient in grabbing a photon and transferring energy from the photon to the chemical reaction center in this bacteria and and in this process of the energy transfer from light harvesting antennae to this chemical reaction center we now have evidence that the quantum interference is used to boost to sort of channel the energy in the right direction to amplify the probability that will happen a very simple example not really quantum computing but nonetheless a coherent quantum phenomenon discovered whether we can discover now difficult to say so now the the last part maybe I should just mention something about problems with building quantum computers I told you about the coherence again mathematically speaking this interference term is it's something that you are happy about because you know this gives you advantage but also it's very very fragile any sort of uncontrolled interaction with the environment this cost factor goes up and down from minus one to one goes to zero you lose quantum effects so you're back into classical computing can we really control it to the point where we can scale up because you know this is the coherence actually becomes more and more conspicuous if you have more and more subsystems it just that's that's why we live in a classical world to some extent you know we are sort of complex entities and this interference is washed out pretty much now but but we discovered actually pretty early that you can not only work against the coherence by designing experiments where you nicely isolate you system you can never really perfectly isolate so there's a problem so if but but you know they're better ways and and we sort of we can use quantum error Corrections to equivalent of quantum error correction all kind of techniques to stabilize computation and we also have an interesting result which says you know up to a point it will be difficult to scale up but once you reach a certain level of complexity it's called a threshold theorem then it will be easy so to scale up you have to build your units with sufficient precision to be able to get into this you know magic number I wish it were 42 but it's not this somewhere somewhere around it you know depends on really on on the technology use and sound so forth so how should you understand probably the best analogy I could think about is about comes from architecture right so try think trying to think about building an art right it's it's not if you look at the history of architecture and how people got there it was it was not trivial you know if you look at the Greek beautiful temples as beautiful as they are they they're not very sophisticated they the Greeks couldn't covered a huge area simply because they didn't know how to build arches madam's the only Etruscans came up with this idea and you know so you have you put your brakes or stones and and you know you can see it's not easy right because at some point you know probably all those bricks will fall down you have to put this sort of a key stone at the top and then it will become stable out of the sudden and then you can construct and build up in once you have arch you can start building domes and but but to get there to this point where you have the stability requires lots of effort where probably you know the whole things will collapse many times so think about this threshold theorem in quantum computing the same way we kind of you know trying to build the arch and so we are at the level of you know basic blocks so we most in the labs we can do all those kind of things to be stable fault with building those basic blocks we try to make those quantum logic gates as good as possible as precise as possible because it's like having high quality bricks for building your arch you know slightly maybe slanted and adjusted to what you want to achieve and we are getting to the situations where we want to close this arch and have something a sort of fault tolerant stable unit where quantum error correction is designed in such a clever way that even though you there's some overhead there's some a little bit more computation but it corrects itself in some nice way and then you know it's still way to go you know so it's so we are somewhere in them to the left I would say to at the arch level we're still far away for building beautiful buildings like hi yourself here whatever you see there and so you know that's basically a kind of story that I wanted to tell you sigh if there's one take-home message it's all about quantum interference quantum interference quantum interference quantum interference you know it's it's about what is it what quantum theory today is just like a different probability theory it's just we calculate probabilities in a different way because we discover that somehow nature doesn't know about classical probability theory it it's it's successful it's useful but it's there are phenomena in nature basically the classical probability especially this additive 'ti axiom this one doesn't work so we have to go one level down complex numbers probability amplitudes calculate probabilities but then we also over time learn how to take advantage of the whole thing and discovering this new quantum phenomenon was fantastic because then we can enhance probabilities in quantum computing build computational machines which sort of deliver but you know the same term this quantum interference term that that gives you this power is also a source of problems the coherence and then I try to tell you how to handle the coherence so let me end up with this puzzle but probably most of you probably know about it it's supposed to illustrate the main point that you know what sometimes when you discover something you are you taking to account something that that that allows you to solve if you discover a little bit of new physics or you understand a little bit more about physics it allows you to solve problems that you cannot solve in otherwise so so so I'll give you the answer to this but I like this puzzle you should give it to my students sometimes at interviews to see who is more who would be a good experimental physicist who would be good at theoretical physicists so so if you don't know this puzzle and and you if you have a problem to solve it before I tell you the solution that means you have probably logicians a mathematician but if you see the solution right away most likely you're an engineer so so the puzzle girl like there's this guy here and you know and there are two rooms one on the right one on the left in in the room on the Ryder sort of three electric switches initially all in position of and they connected with wires it's one-to-one correspondence to light bulbs which are in the room on the left you don't know what is this one-to-one correspondence and the rule is that you are allowed to go to each room only once once you leave the room you cannot go back to the same room and your task is to figure out what is this one-to-one correspondence so is it possible well if you a mathematically minded person you say well no and the reason for that is I can prove it to you because if you go to the first room and only make sense to go to the to the room on the right first with the switches and then you put one switch in position on and you go to the other room you see the one light belt it's on but there's ambiguity about the other to that off right oh if you go to the room on the right and put two switches in position on then the two light bulbs will be on and there's ambiguity about this one-to-one correspondence when those two are concerned so you can or you can come up even with more sophisticated Eric you man you can say well I can prove to you it's not possible but then if you're an engineer you say well it's easy all you do is of course go to the room on the right with the switches are put once we should say the first one in position on go to the second switch put it in position on say for ten minutes switch it off go quickly to the to the other room one light ballast on one is still warm right and the other one is result so so you see that you know what happened here is that if you have a very abstract model of computation if you think about it in mathematical way abstraction is a very powerful tool but sometimes it's just too narrow it doesn't give you the whole richness of things you can do so when the physicists that have entered the game and started looking at computation in physical terms especially they look into quantum physics so discovering this quantum phenomena is like discovering this heat dissipation in this case you know say oh yeah you know I have quantum interference it's a physical person maybe I can use it so therefore you know you discover out of the sudden that there are problems that you cannot solve if you are confined to the abstract classical model of computation but if you think about it as a physical process and you include physical phenomena involved then you can you can do it thank you very much [Applause] thank you very much out sir I'm going to crack straight on so that we might just have time for a question or two at the end but we'll see how we go can we ever build quantum cathedrals hurry oh yes hello let's get some water so that was nice artery actually this light thing nowadays doesn't work anymore because we have LED lights and they don't get one okay so it's a really great honor to be here at this historical place and I wanted to tell you about the quantum computers that are coming and the quantum revolution that is upon us and in doing so let's start with a little thought experiment actually you may close your eyes if you're tired or if you had enough and so imagine that you are in a in the distant future and you just bought your very first quantum computer online you're eagerly waiting and a few days a few weeks later a big black box arrives at your doorstep it says quantum computer so everything is good and then doubt said in because actually maybe this was an impulsive buy and actually he it wasn't that cheap and of course the very first thing that comes to your mind is what on earth am I going to do with this machine and so you quickly start googling and you find the Wikipedia pages and as it turns out it's programming a quantum computer is actually not at all that easy and it's actually completely different than programming a normal computer and actually maybe even more important finding problems that you can run on that machine are also hard to find it's a formidable task and actually buying a corner computer online is not at all that strange it is still in the future but small quantum computer says Arthur also explained with ten to twenty cubits already exists and slightly larger ones of 50 to 100 cubits are coming very soon or perhaps already there big big industry is investing into into building them and indeed with with somewhere between 50 and 100 cubits although it sounds like not too much these machines are potentially cable capable of performing computations that cannot be performed by even the biggest supercomputers that we have nowadays but before I venture on I have to say a little bit also about quantum physics and Arthur already said a lot and I will repeat a lot I hope that's okay for those who are not on the same page yet it's not about quantum touch that's something completely different also quantum healing is not what I'm gonna talk about and it's also another an all James Bond movie no it's none of that it's about this theory that they've was developed in the last century and you see here an illustrious company of people with famous names as Einstein and Lorenz Heisenberg Pauli Schrodinger and they were all debating and exploring quantum mechanics quantum physics and quantum physics was actually very counterintuitive Niels Bohr said if quantum physics hasn't profoundly shocked you you haven't understood it yet Albert Einstein said God does not play dice and richard fineman someone who is also very much into quantum computing as we will see later on said I think I can safely say that nobody understands quantum physics so it's kind of a controversial topic at least then and I think it's good to explore quantum physics by three principles and these three principles I can explain a lot of how quantum computers work and in in in a way Arthur also touched upon these these principles at least certainly the the first two so let's dive in the first one is the principle of superposition that says that an object can be in different states at the same time so for example a photon can be at multiple places at the same time and there's this famous thought experiment of Schrodinger where he took his cat while he didn't actually do it it's a thought experiment but he put the cat in the box and in the same box he put a vial with poison and some radioactive material and if this material decays it breaks the vial and the poison comes out and the cat is dead but when you close the box in you don't look inside quantum mechanics says that the cat is in a superposition of both being alive and dead at the same time and this superposition has been experimentally verified over and over with small systems such as photons and nowadays larger systems can be put into super positions like molecules and the idea of quantum computers is that we can even put larger objects like computers in superposition of course there's many jokes about this cat and at some point this cat really had enough was really angry he's alive and thirsting for revenge okay so let's do a little experiment that demonstrates the superposition Arthur had it's on its slide as well so imagine you have a source that can shoot photons and here I have a photon gun that shoots these photons at a semi permeable mirror called a beam splitter so the light can go through this mirror or it can be reflected and when you do so when you shoot this photon then quantum physics says that the photon goes into a superposition of going through the mirror and being reflected at the same time and so this photon actually sits in a superposition on this both positions very much like the cat you see in in the right right hand corner that's both dead and alive at the same time and now we have two detectors placed on either side of this little semi permeable mirror and these detectors can detect whether a photon is present or not and when we continue it turns out that in this case detector zero found the photon and now quantum mechanics quantum physics says that this superposition state has collapsed by looking at the system the system has changed and now it is become a definite state the zero and the cat is alive but we could have done this experiment again and again we get the superposition and now when we look we find that detector one clicks and this is like the cat is dead and when you do this over and over you find that 50% of the time detector zero clicks in about 50% of the time detector one clicks and actually this is a way of generating random numbers there's a little box that you can buy actually have it in my bag and I'll show maybe I can find it in here that you can you can hook up to your computer and it generates random numbers in precisely this this way see if I can find it well it's a long story maybe I find a cat in here well maybe it demonstrated after that after the talk any help so when you when you plug it it's sort of a nice needle the box when you connect it to your computer you'll get an interface like this and you can then run it and you get a bunch of random numbers that that come out of here and by the way these random numbers you cannot get from your normal computer from a normal computer you always get to the random numbers but this way you get truly random numbers out of a quantum-mechanical box out of qubits so that shows item number one you can have super position of an object in different states and when you look at it this collapses you get one out of these super positions and you see it and this state has been destroyed now moving on to interference which are they also set interference it's all about that so let's see how this goes so here we have again our experiment that we just examined and a skeptic person might say well actually the superposition that's all nice but that's of call of course not happening because this mirror here it already determines whether the photon goes through or it's reflected right there's no superposition it might as well just all happen right at this mirror now let's go to a slightly more complicated set up called the Mach Zehnder interferometer and also Arthur had this on these slides and I think this I learned the first time of mark Zander interferometers from from your paper archer from the from the 90s so you reason classically let's say and we say that these beam splitters are 50/50 beam splitters right so the photon does it go in a superposition but it really goes through with 50 probability 1/2 or it reflects with probability 1/2 let's let's say it works like that so let's reason let's say the photon takes the upper tract and on either sides here we have bill mirrors right they really reflect always so photon gets reflected and now it's here and now what do you think that happens well now we have the same situation as we had in the first experiment right we have the photon here that is entering this semi permeable mirror and so what happens if you reason classically is that again these two detectives on either side at the end have to click 50 percent of the time this is as you expect but now if you really do the experiment it's not at all what happens because you do it and it turns out that detector zero always clicks you never see the Tector one clicking so it must be the case that these mirrors really behave differently and indeed quantum physics tells you you get the superposition and now at this point in time interference happens and you can mathematically make this precise in such a way that you will only see the photon that goes to detector zero and never you see detector one clicking so that gives me item two interference of an object in superposition and then the third one is even more mysterious it's called entanglement of two systems and they can get correlated in a certain interesting way and here I have again my two my two photon pesto's my guns and I have a box here the black box that is slightly more complicated so I've made it black so you cannot see what happens inside but it's really very much like you've seen before and let's see what happens so when I shoot my two photons into this little box they come out and now I straited this with this line in between them and they are entangled and it means the following if I let them shine onto these these beam splitters again they go into superposition as quantum mechanics says and again one of the two detectives goes off but as you can see detector one clicked on one side but detector one also clicked on the other side and when you do this again do it quickly again we get the superposition but now both zero detectors clicked and when you do this very often you will find that left and right always the same detector will click as if they are somehow linked together even if they are very far apart these two photons are entangled as we say and they behave in a cooperative manner in a very nice way and we can make use of that as we will see later on so have these two these three principles superposition and then they collapse if you measure it if you look at it we have interference of the superposition and we have entanglement and before I go on I have to say something about my favorite subject computer science I'm a computer scientist and computer science actually was also developed around the same time that quantum mechanics was developed in 1936 and here are the three heroes of computer science Alan Turing Alonzo Church and Amy post and I guess Alan Turing is your hero that's also my hero but it's certainly your hero who is probably the most famous of the three and it also is his name that is attached to a mathematical model of what a computer is we call it a Turing machine and it's a mathematical way of reasoning about computation and what you can and also what you cannot do with a computer and Alan Turing not only developed this notion of a computer Turing machine but he also showed in that same paper and from 1936 that there are certain problems that cannot be solved on a computer actually the problem that he showed that cannot be solved it's the following it's called the stop problem and this is something you encounter probably quite often depending on which operating system you use you're running some problem on your computer and suddenly this thing pops up that says please wait now wouldn't it be wonderful if you had a little window in the right-hand corner of your computer that said after seven minutes and 20 seconds this thing will end and give you an answer or maybe it says it will never answer and it will never stop and you know that you can safely terminate this calculation well such a thing cannot be programmed and it was Alan Turing who showed that it cannot be done but actually we're not interested that much in things that can or cannot be done we're interested in things that can be done quickly and for example a problem that can be solved quickly is the problem of finding the shortest route the shortest path from City a to city B for example from Amsterdam to London and and it was Ezio Dijkstra was a Dutch guy who in 59 at the Center for mathematics and computer science where I work developed an algorithm an efficient and fast algorithm for solving this task of finding the shortest way this is importance the shortest way from one point on a map to another point and we actually use this algorithm quite often these days because if you have a GPS in your car then you often then exactly what the GPS does is it tells you the shortest path from where you are now to where you want to go and by the way this s code I extend so that nicely connects the two now won the Turing award which is the highest award that you can get in computer science it's the Nobel Prize for computer science and he's the only Dutchman who who did that and also interesting enough he was working on this algorithm when there were no computers yet so I found a nice quote that said I became a programming of the mathematical Center that was how the Center for mathematics and computer science was called then in March of 1952 and they didn't have computers yet he says they were trying to build them so he was working on this question what can you do with computers before these computers were actually there and people were still trying to to make them actually it turns out that there's also many problems for which we don't know whether a fast saloon exists and actually find this kind of intriguing if you don't ask the shortest way from Amsterdam to London but you slightly modify the problem and you ask for the longest way seems similar thing then actually we have no clue on how to do this efficiently and of course I mean it's not that it's not a trick thing where you go from A to B and then from B to a and A to B right because then you can make it very long so the task is that you can only visit each city once and then finding the longest way from some point A to point B we only have exponentially slow computations now what does this mean exponentially slow I think it's best illustrated by the chess board where you put on the first tile one grain of rice and then on the next tile you double the rice that you have so on the second tile you get two grains of rice and then on the third tile you double again so you get four grains of rice eight and so on each time doubling and you can see that here you already have quite a nice little pile but when you go all the way to the to the last tile to the 64th tile you have 92 billion ton of rice which is an astronomic almost astronomic amount and it becomes truly astronomic if you put six chess boards next to each other and you would continue doubling then on the on tile number 300 you have 2 to the 300 rice grains which is more than the number of atoms that you have and then you have in the universe so this works really very fast and by the way you might wonder about this longest path problem as it turns out we don't know whether fast or quick solution exists and actually this is one of the biggest unresolved problems in mathematics and computer science it is one of the seven Millennium prize problems that is put forward by the Clay Institute and it's also called the P versus NP problem and I would love to tell you more about it but I don't have time for that let's go on let's now talk about what quantum computers are and they really merge these two great revolutions namely that of quantum physics and that of computer science and it could have actually been done already in the 30s but it wasn't it took much more time it was in the 80s when Richard Fineman and David Deutsch put these two things together and made the rigorous what a quantum computer is and it's explained probably most easily in the following way a classical computer has a basic building block a bit which is a 0 or a 1 you can view this as this detector which has clicked 0 or 1 and a quantum computer has a quantum bit which is a superposition of 0 and 1 and it is like before this this this photon which is here in superposition is measured by this detector in this case it's in the superposition of 0 and 1 and that's what you can use in a quantum computer you can use it as follows because you realize that if you have one qubit it can be in a superposition of two things when you have two qubits it can be in a superposition of four states and when you have three qubits and now you already guessed it you can have a superposition of eight states and you see here this nice exponential explosion happening in front of you five cubits 32 States 6 and when you have three hundred qubits it can be in a superposition of this astronomic amount of two to the three hundred states and now I ask you to make a little leap of faith with me and now I'm going to show to you why programming this quantum computer that you bought online is really difficult and different and it's fundamentally different because of the following so imagine that you have these three hundred qubits in your machine and you can run this massive parallel computation of two to the three hundred computations in parallel and that's the leap I'm asking you to take with me then you then use your reach right you can do this massive amount of computation and in an instant but the problem is how are you going to get the answer out if you're going to measure it as we've seen you destroy there's now a superposition and poof all this magic disappears and you see one computation it's not very good so what you have to do and Arthur said it you have to write a quantum program that uses interference to interfere positively the answer of your of the computations that you want to see and to interfere negatively the computations that you don't want to see I always say it's almost like having noise cancelling headphones where the noise coming from outside is canceled with anti noise in such a way that you can hear the noise music on your phones and I have another bad message for you this interference doesn't always work I mean there are problems and I will tell you of a few very soon for which we know it works but there are also many problems for which this whole quantum computation doesn't work so if you read somewhere in the newspaper and it says with the quantum computer you can exponentially speed-up any computation well that's false that's not true it only works for certain very specific specific problems and we are figuring out for which one it helps and for which ones it doesn't help and we have learned a few tricks but we need to learn a lot more so quantum computing and quantum program is really like composing I think like a composer who makes nice music he may have this sounds wave interfere in such a way that they interfere and create beautiful beautiful patterns music and a quantum programmer uses these qubits and makes them interfere in such a way that I do useful computations for you so making music composing and programming a quantum computer is is almost a similar thing so what can you do with it so one one thing that came on very early and actually actually bad news that you can do this is you can break a lot of cryptography online so for example when you buy this quantum computer at Amazon you get this now lock in your in your browser right it says that you have a secure connection with this with a server well it's not secure anymore when you have a quantum computer and this was demonstrated by Peter shor if you have a quantum computer you can break a lot of cryptography now you shouldn't panic right away because luckily there's also quantum cryptography which was developed by Bennett bazaar and Arthur Eckert sitting over there that shows that the same quantum mechanical effects can be used to actually give you back again some safe communication so that's good another thing that you can do is you can make communication more efficient so using this entanglement which I talked about and also qubit communication you can make something that we like to call quantum Internet and this internet you can use to do certain computations and distributed computations more efficiently and also an other application of quantum computers is that of simulating nature itself right nature itself is quantum mechanical and when you have these molecules they actually have a quantum mechanical description and when you try to compute how they move around and how do how they behave and you put it in your normal computer that actually you get an error because this thing is too large to put in your machine but when you have a quantum computer you can actually calculate how these molecules behave and so simulating quantum chemistry perhaps making new material designs perhaps new medicines this could all be something that could be helped with the quantum computer and of course there's lots and lots more that we have no idea what it is I think it's like being in the 50s when Etica Dijkstra was developing his shortest path algorithm it was also a famous quote of the the boss of IBM TJ Watson and he said I don't see a world market for more than five computers he had no idea what to do with it and now if I asked you how the computers we have at home you probably don't even know how many you have because they sit everywhere and so computers are everywhere and we are at the same point in time I think with quantum computers we're starting to build them we have some idea of what we can do with it but it's really still open and up in the air what will happen there's a lot of progress in in in actually building these qubits and here you see a few examples arthur also showed some of the paradigms that we have and i think it's interesting to look at this one where google announced 50 cubits last year i don't think i ever saw them but now a week ago they announced already 72 cubits and so the number of qubits seemed to be growing exponentially and also actually a lot of money is being poured into that so the focus is a lot on the hardware whereas i think it should be equally on the software they should also we should also be thinking about what to do with this quantum computer once it's there and i think it's time to put more effort now into this quantum software and actually the problems were facing are also also very formidable figuring out nice algorithms and nice applications is not at all easy and so in in light of this a few years ago i launched the research center which i called cue soft it was a cooperation between center for mathematics and the two universities in amsterdam and also luckily last year we got a reasonable grant from the government from the dutch government to explore this quantum software further here you see a nice scheme of the things we do a really bored us on physics you see that on the top computer science and mathematics and the things we're trying to explore here are what can you do with small quantum systems like the ones that become available now also what can you do with the larger quantum systems you should is this team over here then this cryptography angle how can you make the world a safe place again even if we have a quantum computer that's another theme and this purely quantum information science is the fundamental part of quantum computing and this needs to be nourished nourished as well as well so a few of the immediate challenges that I see is this question of what are we going to do with our 10 to 50 cubits and what are we going to do with the 50 to 100 cubits that are becoming available very soon and indeed in between 50 and 100 lies this point where we might be able to do computations that you cannot do on a classical computer it's very interesting also I think it's interesting to make small quantum networks where you can test this quantum crypto and you can do this efficient communication and you can test this entanglement over long distances and another thing is in Arthur it sort of touches also on what you said how can I verify that my quantum computer actually gave the right answer right for up to 50 cubits I can still calculate on my normal computer I need a supercomputer but ok I can compute still what what it did but when it is having more than 50 cubits a 100 I cannot verify anymore what this computer did and so I need some techniques to do that and luckily we have some ideas on doing that really but it really requires a lot of thought on how to do that then in the near future when we have more than a hundred qubits these qubits are really in stable Arthur also touched on that there's errors that pop up when you have them and the nice thing is that when you have a lot of noisy qubits not too noisy it has to meet this threshold but if we have enough of them then we can use them together to build one stable qubit so when you have more noisy qubits not too noisy you can actually use them to build very stable qubits which we call logical qubits and this is something that we can do when we have more than one hundred qubits and then things go on because then we can do this quantum distributed computing we can perhaps use it with learning theory you might have heard of learning theory we can do that perhaps in a quantum way quantum optimization we can optimize certain functions more efficiently using a quantum computer of course finding new quantum algorithms is something that needs to be done and Billy it's very interesting and this quantum theorem provers I think it also touches on the thing that Arthur said you can perhaps do mathematics in a completely new way and you can solve perhaps problems that we cannot solve nowadays with pen and paper or computers finishing up the social impact is something I think we should all be discussing security etc are consequences of quantum computers and not only quantum computers but computers as well may approach human reasoning abilities and we have to think about how to deal with that and I think we need a public debate it's not something that scientists on their own can do we will see loss of jobs for example self-driving cars are becoming a reality and that means that a lot of professions that that are in taking place in cars cannot be cannot be performed by humans anymore it will be computerized we also have to think about privacy versus safety this is also a debate that goes on and I think we we really need to think twice before we say safety goes before privacy and also it will be a debate about ease vs. ethics I mean we all know the book in 1984 Big Brother but and we were horrified by it but now we everyone is using Facebook as if it is nothing and Facebook is actually much worse than Big Brother ok so summing up I think designing quantum software is exciting it merges two great revolutions namely that of quantum and of computer science and there are really endless possibilities I already alluded to the famous quote of the boss by IBM in the 60s we are really at the same in time where we have a vast landscape of possibilities in front of us that's really exciting it's also urgent because medium size quantum computers will soon be there and with these quantum computers we can address urgent societal needs like perhaps drug design energy security and all kinds of other things I think we also now add a unique position in time where we can focus on this quantum software here in Europe and we can fuel a new quantum software industry here in Europe and in the Netherlands as well because these quantum computers are there and we are the leaders at the moment thinking about these problems so with a new paradigm comes with a new revolution also comes a manifesto so we wrote quantum software manifesto which if you agree with me that it's important to focus on quantum software you can sign for endorse and this was written together with people from academia and people from industry also big industry now starts to become interested and supports these kind of actions thank you very much [Applause]

I love the fact that it's NOT sponsored by Squarespace; or @t; or Audible; or World of Tanks, etc.

Who needs a long introduction by a government clerk?

boringing

Quantum bits or 'qubits' can exist in a superposition state of both zero and one simultaneously. This means that a set of two qubits can be in a superposition of four states, which therefore require four numbers to uniquely identify the state. So the amount of information stored in N qubits is two to the power of N E R D S

i am going to use the n word N E R D S

7:01 why are those women cleaning the device?

It seems like the Royal i cannot untangle its own audio problems.

When parallel lines meet by small disturbance they create warp drive.

Babble, babble, random statement, basically. This untangled nothing for me, best of luck to the other viewers.

10:30 are you kidding me? Practically all computer scientists should know the Netherlands have spawned some of the greatest IT and software engineering innovators of all times! The Netherlands is also the 4th largest IT service exporter in the world – try adjusting that for population 🙂 Philip Ball maybe more informed about the physics, not computer technology.

A computer that can and will do whatever the hell it wants. There is your killer AI right there.

Until 1:08:58 zzzzzzzzzzzzzzzzz… and then FINALLY it gets a little bit exciting ._.

Very interesting. Intuitive analytics are in existence. If you do not understand this try surfing the web and wonder why the information that you were seeking suddenly popped up.

Having watched a significant portion of this video and skimmed the rest; I do not recommend it. It's mostly rambling.

It’s very interesting the way they keep trying to compare the old fashioned classical computers with the new quantum computers, there is a very big difference you didn’t actually need those computers to run the software you could do it all with pencil and paper if you wanted to, be very slow but can be done,but the problem with quantum computers is they don’t know how to program them even if they could afford a pencil and paper

Just because it won't be in your phone in the future unless huge changes happen. The P vs NP problems a Quantum computer could solve would itself propel us even farther into the future.

I have had arguments with people that Quantum Computing will only ever give you a range of probabilities, and never a definitive yes or no answer.

Quantum Computing is a probable mathematical system and nothing more. You will only get a list of things, and never a single answer. Mathematics is the basis of Quantum science.

The Angle particle: when mater and antimatter coexist.

Discovering QC Algorithm = processing formulae in a coherent "phys-chem" pulse-duration => degree of proof of conception in QM-Time Principle Actuality.., of Quantum Fields Modulation Mechanism of probabilities in potential possibilities Time Duration Timing in Eternity-now Superspin Superposition-point…-> Quantum Operator Interference. (It's leaky)

I've always wondered, how is a half-silvered mirror not a frequency-dependent diffraction grating/filter?

No difference in QM-Time Principle In-form-ation terms.., only linear and transverse frequency modulation, axially-tangentially e-Pi-i -> alignment/coherence.

Branes and Brains are the leaky devices of Universal Quantum Operator Computational Existence. Such is life.

Well composed lectures..

Do yourself a favor and find fineman's lecture on quantum mechanics. This lecture is convoluted.

Any explanation of Quantum theory or quantum computing has to be crystal clear, extremely well prepared, scripted, improved, tried, improved again, then delivered by someone whose language is equally clear. Unless these qualities are present, you might as well not bother because all you sew is confusion, misunderstanding and frustration. Quantum functions are so far apart from conventional logic and knowledge that in order to engage a lay audience the people who present the information must be far, far more able than those presenting conventional science. You need someone with the clarity of, say, Dawkins or, say, Alice Roberts, but with high level quantum expertise. I have yet to see a single video in which the communicator is anywhere near clear enough on this subject. That suggests that they themselves are struggling as to their own understanding.