Quantum Computing with Andrea Morello

hi i'm here with andre morello who's a quantum computer good morning sorry professor andrei andrei it's okay from the university of new south wales uh quantum computing department uh well electrical engineering department really technically yes yes yes that's the department i'm on and we're creating you know the quantum engineering of the future so it's all blended together so for the benefit of my electrical engineering electronics engineering audience how would you explain quantum computing to electrical engineers all right so um electrical engineers will know that a classical computer that we use every day and that maybe some of your audience has helped developing the microelectronics engineers in particular are built with transistors and when they are used for logic they act essentially as switches that have two states you know a low voltage state and a high voltage state so that's your zeros and ones in digital logic and then you build a processor where you have you know a large interconnected array of nowadays billions of those transistors and those are the chips that you use today to do classical computations so information is encoded in the electrical state of a nanoscale transistor in silicon it's encoded in a in a binary mode zeros and ones corresponds to lower high voltages and then you do logic operations by having essentially the state of a transistor switching or not depending on the state of another transistor okay a quantum computer is something that retains the binary logic so it's still based upon zeros and ones but those zeros and ones are not the high or low voltage state of a transistor but they are one of the two quantum states of a suitable quantum mechanical object so the simplest example one can give is that of an electron that can jump between two atoms so in my particular research i work with dopant atoms in silicon again hopefully an electrical engineer will have done in their second year electronics some um you know introduction to what a semiconductor device is and how it works you take a crystal of silicon and introduce dopants which can be phosphorous or arsenic or i'm generally using phosphorus though aren't you i am but also antimony four other reasons that i can go into if you're curious but sure uh so they're n-type dopants okay um so normally that dopant will donate it's a donor it will donate an electron to the conduction band of of silicon and now imagine you set up your electronic device in such a way that you have two dopants close to each other and just one electron and you could say okay i'm going to encode a bit of information here i call a zero the electron on the left and the one the electron on the right okay it's a system that can have two options another possibility which is the one that i actually work on is to use the spin of the electron an electron not only as a charge but also as a spin the spin is the fundamental microscopic magnetic dipole of elementary particles like electrons protons and neutrons and so if i place this electron in a magnetic field the spin will have two basis quantum mechanical states pointing up or pointing down so i can call spin down the zero and spin up the one for example so i could make digital logic that way but an electron is not just like a transistor it is a genuine quantum object so again think of the two atoms and one electron shared between them that electron doesn't need to be choosing one atom or the other it can be in a quantum superposition of being on both which again when you say that way people go all crazy oh this counterintuitive will work quantum this is actually completely logical right if you have two identical atoms and one electron and the system is completely symmetric which atom will the electron choose it's going to choose either both both both the logical natural answer is that it spreads out across both right so i never let anyone get away with saying the quantum mechanics is counterintuitive you know it's actually completely logical you choose both when you have equal equal opportunities and equal choices so that means that you can make a quantum bit that is in the zero and one state at the same time yeah okay now this is that's entanglement no no that's superposition sorry superposition entanglement is the next step and that's where it gets really interesting again for the benefit of our electrical engineering friends um i quite often get the question from electrical engineer and say okay so you have this quantum bit that can be in an arbitrary superposition of being between zero and one isn't that the same as an analog circuit right so if i take an analog amplifier that can have a output voltage between 0 and 5 volts i can have any range of voltages between 0 and 5 volts so does that mean i've made a quantum computer no and to see why that is you need to take it to the next step which is the entanglement so the entanglement is a little bit more complicated but again it's you have to think of the the naturality of it okay so now let's say that um let me do the example what do you think is best the spin of the charge spin spin okay let's do this i'm more familiar with speed i think everyone else would be more familiar fantastic let's do spin which is my baby okay so now let's say you have two of these electrons close to each other right so they have a spin that you know in its simple state can be up or down but it can also be in a superposition okay let's say that this pin is pointing up right and really you can take the classical image that you've seen in all your little geography books when you were a kid of the magnetic field produced by the earth that makes these lines of magnetic field like these that come out of the north pole and wind around and get into the south pole okay so if you have a spin pointing up this way it makes a magnetic field that goes up and then winds back down on the side right what scale are we talking about there nanometers it's it's nanometers right well i mean the field spreads out to infinity but it becomes infinitely small as you go away so you know to have a significant effect you need to be nanometers close okay so i got a spin point in this way up and then i have another spin here right so this pin will be subjected to the magnetic field produced by the first pin so on the side the magnetic field is pointing down so this pin will prefer to point this way because that's the lower energy that's the lower energy state of the two magnetically coupled spin right so this is the preferred orientation for these two but what if i turn them this way then it's equally enjoyable as before right because this is now making a fear they're both happy so now what is the natural quantum state of these two spins that coupled through this magnetic interaction is it this one or is it that one they don't care they don't care they don't care they don't care it's both but things are now a little bit more cheeky because now if i ask you in that state where they are at the same time like this and like that which direction is this pin pointing it's going to be always opposite to the other one correct so if you know one you know the other yes hence why entanglement works yes is that correct yes it's correct but the point is this pin doesn't have a direction of its own anymore so if you ask me which way is this pin pointing the correct answer is nowhere nowhere nowhere and if you actually do the calculation it's really a simple calculation that i teach in third year to electrical engineers you can calculate very simply what is the expected value of the spin orientation and it's zero in every direction the spin has essentially evaporated so so the number pops out is zero for all directions for all their actions right right that's why you can't know uh that's why you have something that a classical system cannot reproduce got it right yes so if you now take two analog circuits and you couple them together you will always have some voltage you can measure at the output of that circuit whereas here you can't you can't right so once you get to entanglement that's where you really see the difference between classical you know continuous variables and quantum quantum systems now this quantum state here where they are in the up down and down up state at the same time constitutes a completely legitimate digital code for a quantum computer okay so in a quantum computer with two quantum bits i can encode four different combinations that are completely legitimate so i can have the down down the up up the combination of down up and up down where they are opposite to each other and then there's another one where they are parallel to each other but they point nowhere in the equatorial plane got it and that's the extra over yeah basic by like digital binary exactly so these entangled codes and now if you want to tell me which of the four combinations is that set of two quantum bits taking you need to give me the coefficient of each one of those four combinations so to completely describe those two quantum bits you need to give me four numbers right you need to give me the coefficient of the down down the up up the this one and this one and a number is a piece of information yes so you need four pieces of information two two questions if i had three you need eight if you have four you had 16. and so you see that the density of information contained in a set of n quantum bits is 2 to the power n to the power of n versus n in a classical computer exactly so this is why you only need say 300 odd bits or something as an exam 300 odd qubits we're talking about now this is a is a qubit one a qubit is one bit right is there other words other terms for like two bits and three um no but people use the word q-dit q-tip did for a d-dimensional system so you were asking me before you normally use phosphorus as the dopant where you call the information actually i also use antimony because antimony from an electrical point of view is equivalent to phosphorus it's on the same column of the periodic table right but the nuclear spin of antimony has a spin seven half which means it has eight possible orientation of the spin of the nucleus so that becomes an eight dimensional quantum system so you have eight possibilities instead of two so that's a q did with d equal eight dimensions is there any other advantage to that apart from information density um well for quantum computing you would i don't know if i if i can call it an advantage it's a difference one important aspect of quantum computing is how resilient they are to noise right right so quantum states are very fragile why they are yeah yeah so if you imagine having man let's say with an eight dimensional spin you it's the equivalent of having three cubits right because two to the three is eight so one atom of one nucleus of antimony is equivalent to three nuclei of phosphorus equivalent but is different because the way they will be subjected to noise will be different imagine you have magnetic field noise okay so there is a fluctuating magnetic field in the environment if you have three phosphorous atoms side by side the magnetic field might be slightly different on each one of them so you have noise which may be uncorrelated whereas in that single nucleus of antimony the noise is by definition correlated you know all the levels see because it's one atom they all see the same noise so this can be a bad things in certain encodings it can be a good thing in other encodings depending on how you run it so this is in the subtleties i probably don't want to go into but it's i wouldn't call it better or worse it's different okay but for this uh discussion we'll stick with the phosphorus let's stick with the qubits which is the simple thing okay right so can we think of a qubit as a storage register would that be an accurate is it a storage element it is with one cave yet that you cannot clone the information you cannot make a copy can't make a copy okay this is a fundamental theorem of quantum mechanics called the no cloning theorem you can transfer so for example i can encode a bit of quantum information on one phosphorous atom here and if i have another phosphorous atom next to it i can transfer the information from here to there but once i've done this this one is erased there is nothing left on this got it so it's non-volatile as long as you don't touch it yeah as long as you don't measure it yeah but you can't duplicate it you can't duplicate it right got it you can transfer it but you lose the original you got it you only ever have one copy excellent you can copy but you lose the original yeah so most people think okay a qubit is where we store the information that we're going to process in our quantum number but you also process is on the qubit yes uh the processing this is what we need to get into okay before we get into how the processing works the actual computation how does the quantum measurement works because you affect the state of it by measuring it is that correct so this is uh hopefully a nice example for our electrical engineering audience um so here is where we use actual transistors right for the measurement so the technology that i use um is based upon using the dopant atoms as the cubits the spin of the atom but the readout device is actually a essentially a modified mosfet right it's a small transistor that we fabricate in our clean room it's about 50 by 100 nanometers in size so it's it's small it's not even as small as the ones you have in the chip in your camera probably but you know that's what we can do now that transistor is designed in a way that we can make it very non-linear in its response so it's not it's not acting like a linear amplifier it's it's a switch that switches from the change in position of even a single electron in its vicinity this is actually not as hard as it sounds okay moving one electron in the vicinity of uh you know 50 nanometer size transistor actually has a significant effect on the bias point of that transistor it's it's equivalent to moving let me think it's equivalent to applying you know some about a millivolt on the transistor because you're looking at nanometer distances through it's just an electron charge but an electron charge at that distance has you know matters and then this whole system is cooled down to near absolute zero temperatures so it's you know the system is extremely sensitive and so this transition transistor can switch from off to on by simply displacing one electron in its vicinity right okay and then what we do is something that's called spin to charge conversion essentially we make the displacement of the electron dependent on the orientation of the spin so the idea is this and and that probably already answers the question that you may have had for later on which is why do you need to go to near absolute zero temperature and why do you need to do the things you do so if you came to my lab you will see some giant refrigerator that cools to 0.01 degrees above absolute zero and you will see a rack of electronics that is full of you know high frequency you know microwave generators and you know very sensitive amplifiers and super quiet voltage sources and one of the things i like the most when i explain it to the students is that you can look at this whole rack of instruments and refrigerators and everything is there in there is the result of ratios of constants of nature right it's the board magneton planck constant and boltzmann constant given those numbers you can this you can understand why you need that rack of instruments why you need that refrigerator right okay so the idea is this if you take the spin of an electron and you place it in a magnetic field of one tesla one tesla is a fairly strong magnetic field okay so it's um so the the earth magnetic field in sydney is about 60 micro tesla i think that's very something like so you put a one tesla magnetic field which we do either with a superconducting magnet or with we're using nowadays some small arrays of permanent magnets if you take a strong neodymium magnet it's actually 1.3 tesla so it's actually about right and so we make some little arrays and we bolt them to the to the coldest point in this refrigerator so an electron spin in a one tesla magnetic field has an energy difference between the spin down and the spin up state that is equivalent to 1.3 kelvin that is why you can't have anything above one point three kelvin because you will not see the difference now is this a fundamental will this always be a fundamental limitation of quantum computers or is there some do you guys have some grand vision to overcome this at like will room temperature um question is a little more subtle than this so okay uh maybe let me just finish explaining how i use the transistor and then i'll tell you how you can do some other things okay so you have this pin when it's down it's in the lowest energy state when it's up it's 1.3 kelvin above the lowest energy state in energy and in frequency units so now you divide the energy by the planck constant that corresponds to 28 gigahertz right so if you come to my lab you will see a 40 gigahertz microwave generator because that's what we need that's given by the planck constant so you have to excite it at the frequency at the frequency derived by the plane constant given the magnetic field how how tight does that have to be what tolerance on that very tight because these spins are extremely coherent meaning the resolution we have on what is the frequency at which they respond is about one kilohertz oh okay this is very very sharp and that's exactly what we want because the uncertainty on that frequency corresponds to an uncertainty on the quantum state as it evolves in time is like a clock right so you want to keep track of all the clocks you have in your system and if the clocks start to go slow or fast then you lost you lost the relation between the phase of the clocks right yeah so then we have this we have this pin that can be you know down or up if it's up it's 1.3 kelvin which is 120 micro volts for electrical engineers okay 120 micro volts above the lowest energy state and this electron is in the proximity of the transistor and when the electron is in the high energy state it has just enough energy to escape the atom and be sunk into the drain of the transistor oh i thought it got into the gate no no no it got into the drain the gate is isolated the gate is isolated so think of you know second-year electronics transistor you got a source and a drain you get a silicon oxide insulator and the gate is on the top the gate controls the potential but is electrically insulated and then in the body of the silicon you got the source and the drain this particular transistor is a little different it's called a single electron transistor it's got a little island of electrons between the source and the drain that's what makes it so non-linear but you know for the purpose of this discussion we can kind of forget about it just imagine the electron bound to the atom if it's in the high energy state can escape into the drain of the transistor and just fly away so now you have a positive charge in the vicinity of the transistor that positive charge will shift the bias point of the transistor and make it conduct and when it conducts we will give us about a nano amp of current that we can measure with a sensitivity we can measure nano amp we can measure it in real time so you can watch in real time with your eyes the quantum state of a single spin by watching a step in the in fact a blip in the current through a transistor so you can watch it on your screen as a digital waveform yes essentially it's just a blip on the oscilloscope that digitizes the output of our current amplifier fantastic so you can switch one nano amp of current essentially yeah which you can measure based on the spin spin yeah so that's just a single phosphorus that's a single phosphorus how does it but you talked about pairs yes so now let's say you have two of those phosphorus atoms side by side okay and they're close enough that they interact with each other they interact with this kind of interaction i gave you the example before of the magnetic field the magnetic dipole field but it's actually not how we do it we use what's called the exchange interaction which is what happens when the wave functions so the probability functions of the electrons actually overlap okay so they actually mingle with each other but then it works the same way you have the preferred state is the one where they are opposite so now you can do something where the resonance frequency of one electron depends on the state of the other right so if this one is pointing down this will have a certain frequency if this one is pointing up it will have another frequency so now i can do the following thing i can put this one in a superposition state which i do with a burst of microwaves at say 28 gigahertz and then i flip this one conditional for example on this being spin up okay so if i actually have flipped it all the way up i flip this and that will be the equivalent of a classical x sword gate so they flip if they started opposite yeah but what happens if this is a superposition of being up and not being up then this is a superposition of flipping and not flipping right so that naturally creates that entangled state where they are just existing in relation to each other so this is the quantum version of the classical xor gate that's called a control knot so it's a knot it's an inversion of the bit conditional on the state of the other so it's like feeding the one input back in as that no it's it's flipping one bit conditional on the state of the other but because the other can be made in a superposition then the flipping is also in a superposition of happening and not happening and that's how you create entanglement you would you would have inherent error in such a system wouldn't you how do you deal with yeah well so the error comes from a number of things yeah it comes from calibration of the classical control fields so to make let's say a perfect flipping of this bit quantum bit you need a burst of microwaves that needs to be exactly the right frequency at the right amplitude for the right duration and so just calibrating that is you know it's a task i wouldn't call it a challenge but it's a task and you will calibrate it to some precision which in our case we have demonstrated 99.94 precision in calibrating this case that's very good that's very good then you have errors that come from the free evolution so after you've done this operation which consists of applying some bursts of microwaves there will be some idle times during which these spins if they have been put in a superposition essentially precess like gyroscopes and when you continue to do the next operation the outcome of that operation will depend on where the spin is pointing in the equatorial plane so if for whatever reason there is something that has slowed down or accelerated this precession then the spin will be pointing in an incorrect direction in the equatorial plane and that counts as an error and so for that we do all sorts of research and development in materials for example we use not the silicon that's in your computer and mobile phone but we use a highly isotopically purified silicon so silicon in its normal form comes with three isotopes a silicon 28 which is the most abundant it's about 92 percent and it has zero nuclear spins so it's a completely non-magnetic atom then there is a 4.7 percent of silicon 29 which has an extra neutron in the nucleus and that neutron has a spin so it is slightly magnetic and that spin fluctuates in time so it creates a random magnetic field that randomizes the precession frequency of my qubit so it randomizes the speed of my clock in a sense why would you want to randomize this i don't want to oh i don't want to i want to avoid it right i want to avoid it and so i get from uh from colleagues in japan in fact um a special we call it an epi layer it's a micron thick extra layer of silicon grown on top of a silicone normal silicon wafer that has been grown using isotopically purified silicon 28 so there is almost no silicon 29 nuclear spin in the vicinity so that gets rid of the magnetic noise don't they use that for the kilogram the sphere the silicon sphere yeah exactly same stuff yeah oh okay yeah right how do they build that up that sphere up if you're saying it's coming in one micron layers oh that's not done that way so that's that's grown in a different way that's grown in big lumps lumps this big and then they chop it and then they kind of shave it off so in fact i have so most of the experiments i've done are from material that doesn't come from that avogadro sphere but i actually have a little piece so you just take the chips off it and then okay but there's not a lot of it it's right it's a rare thing okay right so you need to use that otherwise your condom computer is just going to be a mess it's going to be much more noisy the point is you can tolerate some noise okay so this is probably the most important realization in the history of quantum information is that you have the ability to do quantum error correction okay so if you read the the papers on quantum computing in the early 1990s there were a lot of very eminent luminaries who were really kind of laughing at the idea of a quantum computer because they said oh come on this thing has no protection from noise and it doesn't latch okay it doesn't latch i i never met him in person but there is a really eminent scientist called ralph landauer he was working at ibm in the us and he's one of the fathers of you know both classical and quantum information science and there is this legend that he once called in his office a colleague who was working on quantum computing called him in his office and he slammed the door closed and he said you see this is why quantum computers will never work because they don't latch like a door does except he was wrong right it doesn't matter it doesn't matter it doesn't matter right because you can do quantum arrow correction you can actually correct some fraction of errors if it's below a certain threshold there are ways to encode quantum information where you use multiple qubits to encode one what's called a logical qubit and that gives you some tolerance to errors so when you ask how accurate is your qubit how protected from more noise is it i mean we're all working as hard as we can to reduce these errors as low as we can but we don't need to get to zero we have some slack some slack right this will lead into a question later hopefully i don't forget about why we're not near uh to decode in using quantum computers to decode cryptography so yeah hopefully we'll get on we won't sidetrack that now so does that error correction happen at the computational level or does it happen at the cubit hardware level uh both okay both so this is a very interesting question you asked there is so the arrow correction is built into the quantum hardware so the simplest quantum error correcting code you could make use is simply redundance so you could encode a zero into three qubits that are down down down and then one into three qubits that are up up up okay and then you say okay you're gonna look at these qubits and if there is up up down you'll say well there was probably an up up up and then this qubit flipped by mistake okay so that's a cr set that's like a built-in hardware error hardware quantum error correction through redundancy yes but of course the the clever listener will say but wait a minute you can't just measure the cubits because it will destroy the quantum information that's encoded in them so you need to be a little clever in the way you detect the errors so you don't actually measure the actual state of each of the spins but you do often something that's called a parity measurement so you can find out if you have an even or an odd number of qubits everyone's familiar with parity error correction yep same thing without actually destroying the quantum information that's on it and you do this repeatedly as you run your computation and this will generate a lot of data that then a classical computer somewhere up at room temperature will have to keep track of and manipulate and then understand in order to correct the errors so quantum error correction schemes involve both a quantum hardware encoding and a classical computing decoding and correction so in fact it's challenging both the quantum and the classical if you look at the computational requirements on a classical computer to keep track of the error correction necessary to run a quantum computer it's really really large so it's you know we need to you know we'll never we'll always need to be good friends with our classical computing uh colleagues because we need to do this all together that's probably a question for the end is quantum computers are not a replacement for classical computers they never will be is that a claim i believe so right okay okay so the cubers can store information we can store information in qubits we can store more information than what's in the universe potentially in a handful of huberts so how do we construct how do you physically construct the c naught gates what is the architecture what's the computing architecture how do you construct the computational aspect of it is it like a fpga matrix do you have like the individual quantum bits are storing the information then you have the computational fabric around it what is the so the architecture this is still essentially working progress right so i don't think there is a universal agreement on what is the way to do it but the most popular one involves a two-dimensional array of qubits some of which are essentially data qubits and some others are parity measurement qubits so you have to imagine this two-dimensional array where you have interspersed data qubits and measurement qubits and so you will do the operations by applying you know pulses of microwaves and um with certain timings and also by controlling which pairs of qubits interact with each other so this depending on the physical implementation you are using to encode the qubits will be done by for example controlling some voltages on some gates that you may have in an electronic circuit or it may be done by changing the flux through a little loop of superconducting material with two tunnel junctions that couples to superconducting qubits so you know depending on the details there will be different ways to turn the coupling on and off and then there will be ways to you know flip the spins from zero to one or to some superposition and then there will be measurements on the measurement qubits but broadly speaking you have to imagine some two-dimensional grid of qubits with data and measurement qubits interspersed where you can switch interactions and you can do operations and measurements in a clocked way okay in a clocked way do you mean that they're all parallel they're all clocked in parallel essentially this is one of the benefits of quantum computing obviously just to do processing in parallel i didn't expect there to be one best way to do the computation the architecture has probably still been so the physics of the quantum uh community and all that is pretty much fairly well understood now of course people are still working on sort of out of field options uh we have this topological qubits that have a built-in error correction they basically have well they're supposed to have they're expected to have some intrinsic resilience from noise which means you need to do less steps of error correction to keep the computation going one thing that's worth noting is that so depending on how you lay out the architecture and the operations you will have a different threshold for quantum arrow corrections so the most famous architecture is called the surface code which is the one i was telling about these two two-dimensional arrays of sort of interlaced measurement and data qubits it gives you a one percent about one percent tolerance on errors which is a lot right it's quite a comforting number but at one percent it means that you have you have essentially an infinite number of physical qubits encoding one error corrected logical qubit so you want to go below the threshold and the further below you go the less overhead you have to implement the quantum arrow correction so if you are a factor 10 below the threshold you will probably need hundreds of physical qubits to encode one error protected qubit but if you go a factor hundred or a thousand below the threshold then you only need a handful so you're more resource efficient so it's always a good idea to have as low errors as possible right so this is the second time we've covered this so i think we should probably ask now one of the there's probably what a handful of applications for quantum computers they because they're not a replacement for general purpose like a dozen there's a handful of applications we know of you know of yes and and i want to make this point really clear it's hard to imagine applications for something that doesn't exist yes right i remember years ago i was fortunate enough to meet um charlie towns who is the guy who got a nobel prize for inventing the laser he was in his 90s at the time he but still came to the conferences and one day i saw in there at the lunch buffet and i sat next to me oh yeah and you know very very nice guy very friendly old man and i asked him so when you you know invented the laser what did you imagine that it would be used you know to cut frozen chicken to read data from from a dvd and play a movie or to you know correct eyesight i said well of course not it was just a curiosity how could he right so i want to make this absolutely clear before we talk about applications yeah the main and also about um sort of short-term quantum computer prototype the main role of near-term quantum computers is to give us a playground to understand what to do with real quantum computers right right got it there is no quantum computer in the world right now that does a useful computation that a classical computer cannot do okay there has been a big result from google last year when they showed what they call quantum supremacy which means the execution of an algorithm that would be really intractable by even the most powerful classical supercomputer and that's a genuine result it's a real breakthrough but that calculation that was executed is not a useful calculation as such it was just to prove just to prove quantum supremacy exists but the important point and the google people are very explicit and honest about it is that having a machine like that in your hands is what you need for quantum software developers to learn what you can do with a quantum computer once you have one it's just really hard to write code for a computer that you don't have exactly so it's actually i find it i find it remarkable and almost a miracle of human intellect that we do have quantum algorithms that people have cooked up in their head without actually having a computer to run it on yeah yeah well that's a well there's a whole history of that in in in computing people writing simulating so can we quickly talk about because that brings up d-wave for example a lot of people say that's not really a quantum computer it's a quantum annealer but again for d-wave i will say in their defense a lot of quantum algorithms have been invented and developed just by the sheer existence of the d-wave machine now the results that those calculations yield are not results that you couldn't have achieved using a classical computer so not quantum supremacy but just by having the machine there a lot of clever people have had the opportunity to develop quantum algorithms that own a more powerful machine will then actually be useful okay so it's more of a development platform really than any producing any useful at this point it is yeah okay i mean they all are right yeah we don't really have a quantum computer that's doing useful work really no okay so we've got quantum quantum supremacy has been proven what about classical supremacy are there for want of a better term is that a term i don't know where there are things that can that can be done on classical computer that will never be able to be performed on a quantum computer uh well okay so first of all there are theorems that show that any classically computable function can be computed on a quantum computer it's just that you would you would never do it it's just it's like taking a boeing 747 to go and buy a loaf of bread at the shop up there you know you could but would you you know yeah um there's one really interesting thing that's happening um in the last couple of years they call it dequantizing quantum algorithms so this is so i'll get to that so there's some clever people who invent quantum algorithms that are at face value superior to the known classical algorithms that are known to exist and then the classical computer scientists dequantize it meaning they find the better classical algorithm and they often take inspiration from the quantum one so the ideas and the insights of the quantum software developers inspire classical software developers to come up with a new algorithm that runs on a classical computer that they probably otherwise would not have come up with and inspire them to think outside their box yeah so ah that's interesting okay so yeah i think you covered it there there is no such thing as classical supremacy whether you said quantum computer could in theory do anything a classical computer yeah but it would normally do it much slower so for example one thing to keep in mind is um clock speed okay that's something we haven't talked about you know any classical microchip runs that are giggers or two or three nowadays you buy them for a few dollars from the shop um quantum computers have a clock speed that depends on the physical details of the hardware that is being chosen but the clock speed rarely exceeds a few tens of megahertz okay okay so even the fastest ones yeah okay even the fastest ones fastest ones rarely go past some tens maybe 100 megahertz can you see the future where that scale is higher or are there sort of fundamental at the moment anyway you can't say in a hundred years we're not going to do it you can't say but at the moment there there aren't the thing is that if you try and go faster the errors goes up the others go up is the speed affected by is the computational clock speed affected by the you talked about the logical elements so you could have logical sorry a logical cube it could be made up of you know a hundred physical qubits does that affect the speed um well so the logical the way in which you build the logical qubit will eat up hardware resources but the clock speed is the clock speed of the of the of the basic elements to answer your question um in a sense if you think of a fundamental you know speed limit it it usually boils down to the actual energy difference of the logical quantum state of the qubits so pretty much most of the useful qubits that we know of with some exceptions but most of them work in the gigahertz range of precession frequency right and then when you think about how you operate them you want an interaction between them that is a small fraction of their energy difference otherwise there's no qubits anymore they become like a blob so if you run this thing as 10 gigahertz you want it to couple to the other system by a hundred megahertz maybe a gigahertz maximum and that is fundamentally the speed at which you do things okay so there appears yeah there are other systems like there are atomic clocks there are optical clocks they work at of course you know tens of terahertz but then making them interact with each other is not easy so yes yeah right it's but but you know this is part of the beauty of quantum technologies we have some you know leading platforms that are well developed they're having great results but we haven't you know we don't have the equivalent of the cmos transistor in quantum computing yet right there is still a lot of platforms each one with its pros and cons and is that kind of the aim that you want you want this element that you can because the way they produce cpus these days is they have these elements they can just drop them in and they just work yeah but then again i'll i'll respond to this by saying that this is the way it was until maybe 10 years ago now you're getting a lot more of those application specific hardware right so the classic cpu that she always use for everything is not really the way it's done anymore i mean it's still there but if you really want to push now you get the gpu for this you get some mathematical six everywhere they're very expensive but they can they're more energy efficient yeah faster they're they can do it so we're kind of going out into the specialization there as well and for quantum computing for all you know it might always stay that way there might be certain types of hardware that are most suited for certain kind of simulation for example the things that d-wave makes the quantum annealers um they might remain the preferred platform for certain like optimization problem that's what they naturally do whereas for some other kinds of calculations you just need a different system which might be built in a completely different hardware will there will quantum computers be like general purpose computers or will they be like application specific as you said are they hard to tell so um people like myself and many colleagues around the world work on what we call a universal digital quantum computer so we we our goal is to make the equivalent of your pc you know you just you can program it and it does well um this if it ever happens will be a very long term goal i think for the next couple of decades we will have asics right rusty sessions specifically so there's other teams they think oh no look a seekers where we're going to focus on the asic type stuff yeah right so so you've got to essentially program you've got to build that silly if it's out of silicon you have to build that silicon for that specific task to solve prime number crunching to solve uh some specific tasks you're doing you're modeling how molecules work and things like that put this way the reason i'm working on silicon is because it seems to me and to a lot of people the one of the most plausible platforms for universal quantum computers the ones that will get way down the track the ones that will be really general purpose and really have a broad deep impact if i wanted to make a medium-term application specific device i may or may not have chosen silica okay silicon has well okay silicon from a physics point of view has some interesting advantages such as the time it can hold the quantum information in it because of this purification is up here again how long are we talking about uh for the electron we're coming near one second for the nucleus we have shown 35 seconds a couple of years ago in my group hi i expected much longer okay so it's got to do the computation in that time on that data yeah yeah i mean we arrive okay so the electron runs at 100 nanoseconds a few hundred nanosecond clock and it's got a one second lifetime so yeah okay right so the nucleus runs a bit slower so you've got a program but with the information and then process that information within essentially yes you don't need to get to the end of the computation in one second oh i can't no because as you run it you can correct for little errors right so you've got this clock at let's say a micro let's say a mega's clock and so in a second you can do a thousand clock cycles and among those clock cycles there will be cycles that do error detection and correct so as long as you process it so yeah as long as you're doing it it just keeps your life okay so is it the accumulation of errors that would cause if you do nothing with it if you're programming in the information if you do nothing then you go one second but if you run the quantum error correction then it keeps it up it's like so why does it essentially why does the information in there essentially why does it dissipate um well so that it's actually not it's not exactly a dissipation it's it's looking for a better term yeah dissipation is the word you use when it's dissipated in energy loss energy loss okay and actually our qubits have excellent energy loss actually non-loss and non-loss okay right so the electron actually is about 5-10 seconds the nucleus is literally the age of the universe so the energy loss of the nucleus is unmeasurable if you ask me how much it is i don't know i never had the patience to measure it like you can but what it's called it is dephasing is like clock desynchronization okay so imagine these qubits as little clocks and the quantum information is kept in something that you may think resembles the the relation between clocks you know like when you go to those uh old they don't do it anymore you know those airports or those offices and the multinationals well yeah they have all the clocks with all the time in all their main offices around the world you know imagine those clocks don't all run at the same speed they're all drifting at some point you just don't know what time it is anywhere right and you can't correct it at some point you lose the ability to correct it yeah okay but if you correct and check often enough there are some theorems that show you that if you do it well enough and often enough and the and the this synchronization is slow enough you can actually keep track of it fascinating okay i assume that they stayed there for that's that's interesting they don't need to that's the beauty they don't need to this is for our engineer friends you know there is it it is a genuine engineering problem there are tolerances like in any engineering design the tolerance is not zero it's finite that's on regular silicon cpus as well but tolerance is there you know you get cosmic ray impacts you get other you get electron migration and you get all sorts of other issues involved okay and you design the whole both the hardware and the software that runs it in a way that is capable of detecting and correcting these problems now going back to silicon so i just wanted to conclude this thought silicon has some advantages from the point of view of you know basic research of someone like me who works in a university it does pose some challenges because you know silicon nanoelectronics is expensive it's complex but keep in mind that if you look at the the devices that i make or my students make more precise in the in the university labs they are essentially the artisan version of silicon mosfets with individual dopants next to it okay if you put that side by side to the chip that's in your camera over there i mean that ship is so much more sophisticated because it's been made in a billion dollar foundry that i don't have but exactly it's there and it doesn't need to be reinvented right right that technology exists so what we are looking for is my job is to do the basic science and a little bit of the basic engineering that will then allow me to translate this you know design these quantum design rules that i've developed in this work into manufacturing design rules that can be put into place using facilities that are not too dissimilar or you know in my dreams identical to the ones that are used to make the classification in practice though i don't think you'd reach that they would have to modify there will be some modifications there will be some special of course but the the the goal is to not have to completely you know retool an entire 10 billion dollar fund right so are there any other silicon like silicon on sapphire and other sort of exotic processes do you benefit from no so there is some success people have found especially the ones who have access to you know proper foundry with the silicone and insulator okay yeah fully depleted silicone and insulator finfets okay you know they're really tiny essentially silicone nanowires with the wrap around gates those have some very interesting properties that uh that can be useful for for quantum computing that can confine electrons very tightly in the corners of the gates okay because at the moment you what you've got to physically deposit the one phosphorous atom within the essentially within the transistor yeah yeah which in itself ion implantation is the standard method by which dopants are introduced in any in any chip what we and in particular i want to acknowledge my colleagues at the university of melbourne the other ones who do the ion implantation what they do is to um they have an iron implanter and they've integrated that with a atomic force microscope with a tiny little nanometer hole in the tip it's a very nice design so we make in sydney the the silicon device and we can put some alignment marks on it that can be seen and then the atomic force microscope is a super sharp tip that can actually see if you have an atomically flat image you can see the individual atoms but at the scale even just seeing nanometer you know you can hover it over the surface and you can see our alignment marks and where we put all the all the circuitry so you can they get an image of the of the circuit and then you can move it with nanometer precision to where you want the atom to go and this tip acts like a mask it's like a movable mask and it's got a nanometer hole drilled in it so you start spraying ions with the iron in planter and then there will be one that goes through the hole and when it goes through the hole then we at unsw make the on-chip ion detector which is again a modified version of a radiation detector which when a high-energy particle hits creates a thousand electron hole pairs they get accelerated and collected by a very sensitive electronic circuit that tells us boom one atom has gone in you blank the beam and you got one atom right there wow do you see again this is not it's a modification but it's not a major modification from the way in which normal chips are made is the university of new south wales doing any research on any other types of well can you go through the different types of you you're doing silicon you're doing phosphorus on silicon primarily yeah what are the other methods that other research teams around the world are doing in at unsw we have three ways to do it so i use iron implanted dopants there is my colleague michelle simmons who makes also dopants as qubits but she puts them on the chip by a scanning tunneling microscope method so this is a case where you take a atomically flat silicon surface in ultra high vacuum you deposit a layer of hydrogen and then with a scan internally microscope you remove the hydrogen where you eventually want the phosphorus to go then you introduce phosphine gas which is ph3 and by some miracle of surface chemistry the phosphorus sticks to the surface it just magically happens and the rest just vanishes yeah and so then you get phosphorus where you want it and that does not only the the the cubit but also the classical circuitry is all made by highly doped phosphorus and then you encapsulate with another layer of silicon interesting so that's another way to make dopant-based quantum bits with a different fabrication process which has a higher positional precision but it's very different from the way classical computers are made and then there's my colleague andrew zurak who makes uh really he doesn't use uh dopants as the qubits he uses electrons kept inside the nanoscale transistor so he makes quantum dots what they're called they're essentially the super shrunk version of a silicon transistor shrunk so much that he holds just one electron so what he does is arguably the most you know cmos similar semi cmos compatible device you can make it's really just a super small modified silicon array of transistors and all these three methods have their pros and cons and we're all making progress and and there's a lot of synergy between between what about non-silicon methods right so non-silicon methods um some of the two probably most developed and successful ones at this moment are superconducting circuits so that's what google does that's what ibm does and that's what a number of other also smaller groups and companies around the world do so here you have a a circuit that's made from a film of superconducting material and on this film you make essentially what is uh it's a quantized nonlinear oscillator so imagine you make an lc oscillator just an lc circuit right it will oscillate at a certain frequency so if you just take a capacitor or an inductor and you put it here in a breadboard it's a tank resonance it's a tank resonant circuit and at room temperature it will have you know billions of four microwave photons in it now imagine this circuit resonates at 10 gigahertz 10 gigahertz is the equivalent of half a kelvin in temperature okay right so if you now cool down this tank circuit to 20 millikelvin how many photons are in there zero a week essentially zero so it's an it's an electrical circuit it's an lc oscillator in its quantum mechanical ground state wow okay and then you can introduce one photon in there and it goes in its quantum mechanical excited state so that's your zero and the one the problem is you can't just make a simple lc oscillator because then uh all the energy levels are equispaced so so you don't have only two levels you have one two three four you can put as many photons as you want in there right up to room temperature round room temperature and they're all liquid space okay so you need something that is non-linear and this is done with a superconducting circuit trick it's called the josephson junction it is essentially a non-linear inductor got it that's what they use for the voltage standard the josephine junction that's right right that's right okay so you you use that principle and you laid out in a clever way and you get what is essentially a non-linear lc oscillator that has the too low state with a certain energy difference and the third state has a different energy gap so if you apply a microwave photon at this energy it doesn't then jump up the other level you know there's only and and then so again for our electrical engineering friends these are really just quantized electronic circuits basically and the way they talk to each other is by either direct capacitive coupling right so the capacitances are talking to each other in a in a coulomb way or sometimes they talk to each other by sharing the microarray photon across a resonator so you can make you know if you make a 10 gigahertz half wavelength resonator it will be about a centimeter long or something so now you can imagine putting two of these little lc oscillators non-linear lc oscillator at the opposite ends of this centimeter long resonator and these two guys can share a microwave photon which acts as the coupler for them that's interesting so you can entangle electronic circuits at you know centimeters centimeter distance via this microwave photon that is shared through the resonator oh are there practical applications for that well that's how the most developed quantum computers are built okay is that like d-wave how no how does the wave do it the wave does it in a different so this the example i gave you is what google and ibm and some others are using d-wave does something different the wave uses what's called a flux qubit so it's also a superconducting circuit but you have to imagine it's a loop it's a loop of superconductor physical wire a physical physical loop now in a superconductor you can have current that flows without dissipation yeah it just flows forever so now you can imagine you could encode a zero or a one in the current flowing clockwise and the current flowing counterclockwise you place some magnetic flux and in fact that flux is quantized it's called the flux quantum but so if you when if you put a josephson john in fact three josephson junctions across this loop you can make a qubit where the current is in a superposition of flowing clockwise and counterclockwise this is another one of the things i love to teach to the students you know you kind of take them by the hand and you try to tell them quantum isn't weird don't worry about something and then when you really like do it in a lecture style you come to this inevitable conclusion that there is a current which is a sizable current it's like microamps right a current that is in a superposition of flowing clockwise and counterclockwise which is not the same as saying there is zero current right it's a superposition of flowing one way and flowing the other way and how do they read those they read them by essentially making it switch to one side or the other right so they can tell whether their current flows clockwise or counterclockwise and so if you if you have a superposition it will project it into one way or the other it's the same with the spin if i prepare the spin in a superposition of up and down and i go and read it i will project it into either up or down so i will half of the time get the spin in the up state which escapes and half of the time the spin on the downstate it does not escape this is why and we probably have to get into this now is why quantum computers please correct me if i'm wrong i'm sure it will be that okay you've got you know you're processing all this information but quantum computers are really only useful if you get like a single output or a limited output is that correct yeah yes yes so that is probably the the simplest way to understand why is it so hard to make useful quantum algorithms right because so you have this this exponential density of information you can encode in the quantum computer but you can't get it out you can only get it out in a limited form yes so what you need to do is to design an algorithm that converges to a form of to a kind of information where the quantum bits are not in a superposition anymore but they are in a sort of equivalent classical state one easy example and i'm gonna do some shameful advertising here i have some youtube videos myself there's something called i'm saying they're very good yeah there's the quantum computing concept that i show a brief example of the quantum search algorithm yes yes so that works exactly like that so let's say you want to search for an item in an unsorted database unsorted is important oh so if it were sorted then of course you'll find it but if it's unsorted and the the reason this algorithm is intellectually important is because it's one of the very few where we know mathematically that there is a quantum advantage for example for the factoring algorithm the famous one you know cracked uh we'll talk about yeah we don't know of any way to find the prime factor of a large number in a polynomial time but there is no proof that this way does not exist exist whereas in the search through an unsorted database you can very simply prove there is no better option to scroll into the database okay so if you have an old-school telephone book and i give you the phone number of someone and you want to find who is the person who has that phone number you have no better way than just scrolling through the whole thing or you can randomly jump around or randomly jump around there's no advantage in doing that okay in a quantum computer you get there in the square root of the number of steps so if you have you know one million entries like the sydney telephone book a thousand efforts a thousand a thousand steps on average on average so the way it works is this you create a superposition of all the entries in the database and then at every step at every operation you you do an operation which i won't go into but that concentrates the probability amplitude on the item you're looking for right so at the beginning all the entries are equally probable yep and at every step the other ones shrink and the one you're looking for sizes pops up so after about a thousand steps on a million you know entries phone book you will have essentially all of the probability concentrated in the one item you're looking for and nearly zero everyone else so now you do a quantum measurement of your register and with very high probability you'll find boom it's in there does it ever reach 100 probability um in theory does it ever reach a hundred percent well i mean eventually if you run the classical algorithm it will right right so yeah right okay yes got it that's the answer to that all right so if you want yeah if you do a million steps then eventually you your your equivalent to the classical algorithm and also there so in the classical case the we say that the run time is n over two so on average you will scan a half a million numbers but you know if you're unlucky that the number you look for was the last one then you need to scroll all a million of them on average it's 10 over two on average is square root of n so the advantage in this particular case which is one of the cases that we know of one of the few we're going from half a million to a thousand so yeah what's that you know yeah so it's only square root you see so it's not the kind of thing that really changes the complexity class so it doesn't go from exponential to polynomial but it's one case where you know the if you actually look at how it works it's reasonably simple and you see really this probability shrinking everywhere and peaking there so it tells you you know also the typical question is but how do you read out the quantum register if it's got all these superpositions the point is a good working quantum algorithm will not have a superposition as an output it will have a measurable state a measurable state and that's what makes it hard to develop the quantum algorithms that that give you so even if we had a quantum computer tomorrow the algorithms would be severely lacking the there's a few like there's hundreds but oh yeah right there right there is a webpage that's kept up to date is the quantum algorithm zoo and there's uh there's some interesting ones like solving uh sparse systems of linear equations oh yes that's pretty broad okay and um one thing that's really interesting i'm just gonna tell you this because it fascinates me only recently discovered quantum finance quantum finance yes and so there's various ways in which you can do that so there are people who are looking into using quantum computers for optimization problems like portfolio optimization portfolio investment optimization basically you have this much money and you have some constraints on you know how many types of different stocks you want to buy these things become computationally very very hard very soon right and so there are suggestions that quantum computers might be able to run this kind of optimization problems in a in a in a more efficient way i wouldn't have thought that there'd be a place for quantum there no apparently there is okay and the thing that really blew my mind that only recently discovered is that um now i'm not a finance expert of course but apparently there is some model whose name i forgot some some economic economist who developed a mathematical model for how to um essentially model markets in the presence of arbitrage arbitrage is when you have for example exchange rate fluctuations so you know you buy tv in australia but if you went to buy it in new zealand you get some advantage because the fla you made money that way yeah and it turns out it's amazing if you look at the form of that equation it's like the schrodinger equation of quantum mechanics oh where the planck constant yeah is the degree of arbitrage oh no yeah it pops out it pops up so the quantum uncertainty we have in the scherniger equation in the economics model is the arbitrage is the uncertainty in the exchange rates mind-blowing right it's just it's just a mathematical coincidence there's nothing quantum about the finance but there's nothing quantum but it just so happens that the form of that equation has the same form as the basic equation that governs the time evolution of a quantum system so then if you want to model how will you know your investment in the presence of arbitrage across different markets evolving time you can just as well create a quantum system that is subjected to formally the same equation and watch it evolve interesting oh that is fascinating wow that's great let's talk about cryptography prime numbers because everyone freaks out oh quantum computers within five years we'll be you know okay yeah tell us why you're laughing at the right so thought of that with the present knowledge we have um the most let's say plausible architecture of a quantum computer that might be able to break and let's say rsa and coding would require about 200 million physical qubits because you need because you have and the error correct so that includes zero questions right 200 million physical cubes so you can't do it with just your 50 or 700 humans why is that because you're lacking the um you're lacking the ability to correct the errors so you could do it okay let me think uh so so we're talking hundreds of millions yeah of physical cures so you need a few thousand logical qubits so if you had a few thousand perfect qubits with zero errors you don't do it but you never will there will always be errors and so with some realistic know values for the errors we have for the ways we use to correct them you have to budget for a few hundred million physical qubits so that's a long way from where we are that is is there any shortcuts to that that you can foresee not that well well you see that's the thing about this field this is not like making a better washing machine or a better car right this is uncharted territory and so that the typical mistake that people have made in the past and i'm trying not to make it myself is to make prediction on the basis of what we know now yes okay i can tell you what i think based on what i know but tomorrow there could be someone that comes up with a better quantum error correction code with a better quantum algorithm and you just don't know this is uncharted territory okay so when you speak to you know people in you know in the banks the cto of a bank and you try and tell him you're all your eyes i say my come on it's 200 million cubits and i said no no you don't understand we cannot afford the risk that someone will do that in the do that in the next 10 years the other thing that again i only recently discovered cryptographic systems for especially for finance i mean for anything they have a very long time scale the time it takes to put a full cryptographic system in place is 20 years right it takes a long time so people really need to think 20 years ahead and so then if you ask me over a 20-year horizon can you see this happening well yeah okay two years probably not but i only say probably because for all you know tomorrow morning some you know research smarter guy with me will pop up with something and then and you know big financial institutions or governments or security agencies simply cannot afford to be left unprepared which is it brings one of the questions one of my audience had is where's the funding coming from i mean it's no secret i've been to your webpage the funding comes from who the nsa like various government agencies yes so my funding is from the australian research council i have funding from australian department of defense and i have funding from the us army research office and uh yeah so that covers it for now they're just hedging their bets yeah i mean the australian research council of course funds basic research so that's their job to do um the security agencies and the defense agencies are you know trying to stay ahead of the curve and but now there is private uh sector funding coming into place so we have at unsw a company that's called silicon quantum computing that is a partnership of unsw of telstra of the commonwealth bank okay of new southwest government and of uh commonwealth government right there's five partners and they are pushing the scanning tunneling microscope technology i was telling you about before right because they think that's the most bad reasons pick that one big one um there are other companies in sydney for example there is a startup founded by my good friend mike biersock and the company is called the queue control and it's essentially a quantum control software for the most part development companies so they get venture capital such a fully venture capital and uh there are various others you know medium to small size uh startups mostly in this in the topic of quantum algorithms quantum simulation quantum software quantum applications some also in quantum hardware there are some in europe um making prototypes silicon or superconducting qubits or ion traps some companies make specialized electronic uh circuits classical electronic circuits for controlling quantum uh quantum hardware so if you come to my lab now you will see the usual subspecs brands of your favorite top shelf you know microwave and digital electronics vendors and that's all very well but you can design and some of them are already doing it you can design dedicated you know fpgas digitizer microwave sources with super stable clocks all the things that you can kind of buy commercially but if you know what is the application you have in mind you can make like multi-channel boxes which are much more economical than just buy many you know arbitrary way from generation stacking them up in a room you know so these things are also happening it's an ecosystem that includes a lot of the classical control and electronics engineering at the moment um people don't need to be concerned that concerned about quantum computers breaking pride and moreover i would say the other side of the coin is that quantum technologies also give you the um opportunity to secure you're always going to get to the right and in many ways that is more advanced than the cracking side yes so you can already buy even in australia from quintessence labs a you know two boxes that plug on an optical fiber with which you can transmit quantum encoded data right right there's a couple of companies around the world and one of them is actually in australia these things already exist right so that's transmission of data that's not well encryption so because they're using entangled photons so they they encode it into entangled quantum states and then you transmit it and then you decode it also things like quantum random number generators which are very important for you know various cryptography and security aspects they they you know they exist and they are an improved technology over the classical ones because a lot of the existing encryption algorithms rely on a true random number generator so yeah yeah so you know i would like to remind people that you know quantum mechanics can be used for good or for evil you know like most things you know but the good is arguably more advanced and more developed than evil [Laughter] so you know it's okay so at the moment we're not that concerned but you you can't lower the girl you need to be prepared you can't ignore it so for example um some agency like the national institutes of standard and technology in the us they already a couple of years ago started this big initiative to make quantum safe encryption so they are they call for proposals and they are they are scanning various ideas for how to encrypt classical data in a different way that makes it protected from as far as we know now quantum attacks are they working towards an international standard for that like an ieee standard or something for probably yeah yeah so it's a pretty they cast the net pretty broad they called for proposals and i imagine that what they eventually want to get at is a standard that you know so quantum encryption is going to happen before quantum decryption well i would hope so decryption of existing yeah algorithms yeah right yeah i would think so okay so there you go we don't have to worry that stay alert that much participate in the in the development you know okay and this is the other thing i really want to say there is so much to do in this field like you know not only you don't have to worry but you have an opportunity to be engaged and to be involved there is a lot that we can do there is a lot that we can develop for the good and there is a lot of room and opportunities for engineers also classical engineers to get involved in this field so if you look at the biggest quantum computing initiatives in the world you know the ones of google and ibm and and intel and microsoft and also and also some of the small startups are in fact quite big when you go and look how many people they got on board there's a lot of you know just microwave engineers there's a lot of software developers there's a lot of people who have a classical engineering background and their role is indispensable excellent so you don't have to be a physics researcher you don't have to be a physics researcher but i think it will be good if in the very very very near future we train a new generation of quantum engineers that's actually the other one of my passions and goals in life yes i'm a researcher and i build quantum computing hardware but i'm also a teacher and so over the years at unsw with some colleagues have been developing some essentially quantum engineering courses that we are trying to kind of crystallize and formalize now it's within the within the the environment of electrical engineering i call it the the microelectronics and microwave engineering of the 21st century okay right so even now even if you don't care about building a quantum computer i would make the point that unless you abdicate your capacity to really be you know involved in the cutting edge of technology you need to have some understanding of how the quantum world works right the the transistor you have in your pocket is you know on the tens of nanometer scale you have no chance of understanding what's going on in there unless you understand some quantum and you know some people and some places may have a bit of a black boxing attitude it's like oh you know there's someone out there in silicon valley understands that stuff i just want to make an app to deliver pizzas you know and that's okay but i think it's a bit unambitious you know we can we can do better than that and australia has a strong presence and a strong background in the quantum technologies and i think we have a real opportunity to be a hub for quantum engineering which doesn't mean forgetting all we know about the classical electronics engineering it just means blending it and upgrading it to what are the nanoelectronics microwave engineering technologies that are coming up do you ever see a point where people will be doing quantum computing a straight quantum computing agree at university instead of classical will there be that much demand that oh you know there will be whole courses devoted just to quantum computing learning quantum computing yes i would call it quantum engineering quantum engineering so okay so there might be when does it become when does a stop be in engineering and becomes just general computing well so okay i'm speaking maybe from my you know background of electronics engineering i see mostly the hardware part of things and then we also teach of course a bit of software and some of the communication protocols in the you know computer science department they might think wow one day we will have a whole school of quantum software and in fact some places like uts here in sydney they have masters oh really okay so we are working more at the undergraduate level so at unsw we are developing essentially a quantum engineering offering that is at the undergraduate level okay so which is really quite unique elective course that they can take as part of their normal degree yeah okay that is that's already there now and then we are looking at in the near future really making it an actual stream an actual degree that you can right because a lot of engineers will find you know regular practical electronics design engineers won't believe it until they can buy the chip on digikey or somewhere you know they just won't believe it until they can physically that tv is called a quantum dot tv for a reason right oh true huh i just bought this tv two months ago it's a q-lead that q stands for quantum dots i mean it's not it's not science fiction it's on the wall but as we talked about before you can't at the moment you can't really see a practical way of doing it without going to the super low temperatures that's perfectly fine there's no issue with that on the topic before i forget um there's a very important document that was launched by csiro just maybe three weeks ago is the quantum technologies roadmap for australia they spent a significant amount of time and effort really mapping out what is the the prospect for quantum technologies industry in australia and they estimated uh four billion revenues and sixteen thousand jobs by twenty forty twenty next twenty twenty fourteen yeah and if you speak to the they had a webinar sort of launch of this quantum technologies roadmap and there were a number of people participating there including a venture capitalist and he as a you know an investor he thought that zone numbers were really really underestimated oh okay somebody wanted to know is there any way that you know people interested in this sort of stuff can experiment in their own labs is there any like or do you really need the you know the liquid helium and do you need the you know the 40 gig transmitters in there um okay so in the context of these quantum engineering courses that we teach at unsw we've actually developed labs for students okay yeah right so um some colleagues of mine have in fact built up this little lab that the students do where you can control and measure a single spin that that's all i'm talking about just you know not at room temperature oh okay there is a particular system is called the nitrogen vacancy center in diamond it's a color center in diamond it's one of those defects in the diamond crystal let's give it a bit of a color yes and it turns out this defect has a spin and this spin has an energy splitting that's created by the crystal field so you don't even need a magnetic field for it if you apply magnetic field you can shift it a bit but it has an intrinsic splitting of 2.7 gigahertz which is a nice number which is doable it's doable and then you say okay but at room temperature 2.7 gigahertz is much less than the thermal energy yes in fact it works nonetheless because diamond is a very stiff crystal which means that the thermal the frequency of the thermal vibrations of the diamond crystal is extremely high is like imagine a master spring model is like having very light masses because carbon is a light atom and very stiff springs whereas this spin has barely any interaction with that crystal lattice so the spin essentially doesn't know what the temperature is oh interesting spin i mean it will eventually like after a couple of milliseconds you will find out what the temperature is but you have a window of time where you can thermally insulate it and you can play with it and so um in fact my colleagues have published the paper where they describe how this little student's lab is built and you know it's it's it's it's actually on the public archive so if someone wanted to somebody wants to have a play with have a play you know there's i don't know how much you would call this probably a few thousand dollars you need some radio frequency sources you need some digitizers there's a few thousand dollar worth of stuff but it's not you don't need a refrigerator in your room you know exactly and especially if you are an electronics engineer you may have some of the instruments already in your in your lab you know in your exactly so okay no so it's not it's not out of this world it's not out of this world so people can have a little people can have a little place yeah the other thing people can do is to log on to the existing and openly accessible quantum computers that companies like ibm make available oh they do they do so there's something called the ibm quantum experience which is a five qubit superconducting processor that's in the cloud oh so you can go on that website make yourself an account and you can program that quantum computer it will give you back the results there's lots of people who use it for for teaching for example you know like you can get your students to log on to that you give them an assignment and they use that quantum ibm quantum experience for doing these things of course there you don't you know you interface with uh without it with your terminal it's not the same as making your own thing but it is it is a legitimate five qubit quantum computer that you can access remotely fantastic i've heard that there's um what languages are there i've heard about q hash and then there's quiz kit there's a couple of languages out there there's there's liquid that's the one for um simulations from microsoft there's a couple of them and how do they differ from regular procedural or object oriented uh they look a lot like assembler they're really low level they're reasonably low level languages right so you can just you know flip this quantum bit yeah read this one that kind of stuff yeah right there's even people there's colleagues of mine who i i don't know what stage it's at but some time ago they were telling them about they were developing some quantum games it's basically video games where the rules of the game are the quantum rules oh interesting okay at an abstract level i'm guessing kind of ah no there are no there's your rules yeah okay i i never had enough time to actually play with them right i wish i could yeah i wish i was a teenager and i had time to play with it exactly the responsibilities you know join the club all the things i would do if i had the time tell me about it give us your best and worst case predictions for say the next 20 years like like worst cases in oh no it all just peters out no there's nothing really practical it doesn't work and what's the uh you know i i know you said you don't like giving down please do you see i'm fundamental i'm an i'm a legitimate electrical engineer i've got a degree in electronics engineering and i teach you know electromagnetism in third year so you know i'm one of you okay but i'm also someone who has a genuine passion for the fundamental questions in science yep so for me you see quantum computing is a win-win bet i see two scenarios either it works like it actually works for are you talking practically for practical things so you can actually it works now yeah so either you can actually build a scalable quantum computer meaning you have figured out the fundamental logic gates you have an error budget that is under control you have protocols to detect and correct the errors that keep you below a correction threshold that the thing actually scales up right and you can manufacture it and your manufacturing tolerances are compatible with the arrows that you're able to tolerate for your quantum computer and you just make the thing and thing works and you can run algorithms on it that give you interesting and useful and beneficial results right that's scenario one great right yeah fantastic scenario two it doesn't it doesn't you can it doesn't because of some fundamental law of physics we haven't discovered yet got it so something you can't foresee it at the moment you can't see at the moment i can't rule it out that it may not be possible maybe there is some fundamental constant that limits the quantum information you can right encode there have been some you know people have been wondering in the sort of fundamental quantum science community you know the problem of how does the microscopic quantum world morph into the classical world we experience at the at the large scale right and some people think it's a known question it's just it's just a kind of you know stupid thing to even ask some people um come up with various theories or for what it could be and some people have even imagined that there might be some scale which could be a size scale it could be a mass scale or it could be an information density scale at which the for example the schrodinger equation as we know it which is a linear differential equation is no longer exact it gets some correction terms okay and those correction terms have a prefactor have a constant in front of it that if you're making you know a 10 cubit quantum computer is irrelevant if you're making a 10 000 cubic quantum computer starts to affect things ah interesting i'm not saying that this is what's going to happen right he could in theory but i i see two scenarios either we're done with physics i mean that's going to come back to haunt you that way either you know the physics we know is correct enough that we can use it to manufacture a quantum computer that works or it's not or it's not or it's not so for me both scenarios are fantastic i would take both i would take both is that um on dryer's cat is that like a schrodinger both scenarios are alive and dead at the same time yeah yeah okay you see my my wild dream is to you know have developed the technology to make you know quantum bits in silicon have it all under control have it you know have some deal with some foundry and we get it all manufactured with the latest equipment the fanciest technology and we make a 100 cubit circuit and you run it and it works you make a thousand cubit circuit and you run it and it works you make a ten thousand cubits scales scales and then eventually it just stops yeah that'd be disappointing that would be amazing that would be amazing they would be like directly watch in an in an engineered electronic device a new law of physics i knew how it could it could pop out and you learn electronics engineering listen to this my friends electronics engineering enabling the discovery of the new law of physics that's what i work for that's what i work for wow there's a nobel prize in that one yeah if i'm still alive to get it oh that is awesome thank you very much my pleasure thank you for your time and the very very clever questions it was a very pleasant conversation awesome thank you very much catch you next time you

Channel: EEVdiscover

Views: 222,383

Keywords: Andrea Morello, quantum computing, quantum computers, quantum computers explained, cubit, electron spin, magnetic field, unsw, unsw research, andrea morello quantum computing, professor andrea morello, electrical engineering, electronics engineering, research, d-wave, university of new south wales, quantum computer, unsw sydney, quantum physics

Id: jDW9bWSepB0

Length: 105min 18sec (6318 seconds)

Published: Sun Jun 21 2020

Reddit Comments

[u/oncemoreforthe]

I"m so glad Prof Morello took TWO HOURS of his time to explain this. Also disappointed the interviewer was so rudely talking over him and charging ahead trying to say the answer first. Shhh. Let the genius talk please.

[u/theykilledken]

I'm an interpreter and I'm stuck with a lot of free time on my hands due to lockdown, so I'd like to translate this into my native tongue and do a voiceover. I want to be cool about copyright and ask permission. Any ideas on how do I best aproach this? What would be a good way to contact the creator of this content?

[u/gfrebello]

I don't understand the part in which he says "the information contained in a set of n qbits is 2ⁿ versus n in a classical computer" (the explanation starts at around 11:30). In a classical computer, the combination of 2 bits also generate 2² =4 possible states: 00, 01, 10, 11. What is the difference?

[u/bodhbh_dearg]

That’s a really good watch

[u/damned_subtle_barbs]

Dat sofa...