Instant Genius - How to build a quantum computer

Episode Date: April 18, 2024

There is little doubt that the advent of the computer has had one of the most far-reaching impacts of any invention in the history of mankind. These days, it’s difficult for most of us to imagine life without them. But building ever faster processors is becoming something of a challenge. The solution to this could be quantum computers – machines so powerful they can tackle problems that would take even the biggest supercomputers we have today billions of years to solve. In this episode I speak to Prof Winfried Hensinger, director of the Sussex Centre for Quantum Technologies. We talk about his work on creating the world’s first large-scale quantum computer, how it works, and how quantum computers could help scientists do everything from breaking complex forms of encryption to creating innovative new medicines. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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alongside French acoustic specialist focal, combine handcrafted tradition with cutting-edge innovation and high-end materials, delivering digital precision with analog warmth, so you can experience exceptional sounds. at home. Music just as the artist intended. Visit name audio.com to learn more. Hello and welcome to Instant Genius, a bite-sized masterclass in podcast form. Each week you'll hear world-leading scientists and experts talking about the most fascinating

ideas in science and technology today. I'm Jason Goodyear, commissioning editor at BBC Science Focus. There's little doubt that the advent of the computer has had one of the most far-reaching impacts of any invention in the history of mankind. These days, it's difficult for most of us to imagine life without them. But building faster and faster processes is becoming a challenge. The solution to this could be quantum computers. Machines so powerful they can tackle problems that would take even the biggest supercomputers we have today billions of years to solve. In this episode, I speak to Professor Vinfried Hensinger, director of the Sussex Centre for Quantum Technologies. We talk about his work on creating the world's first

large-scale quantum computer, how it works, and how quantum. Quantum computers could help scientists do everything, from breaking complex forms of encryption to creating innovative new medicines. So first off, welcome to the show. Thanks very much for joining us. Could you introduce yourself and tell us a little bit about your background, please? My name is Winfred Hensinger. I'm a professor of quantum technologies at the University of Sussex.

I'm a director of the Sussex Center for Quantum Technologies. I'm also a deputy director of a new doctoral training center to teach doctoral students in quantum information science and quantum technologies. And finally, I'm also chief scientist and chairman of a company, Universal Quantum, that actually makes quantum computers. So, yeah, we'll get into that in a little minute. So today we're talking about quantum computing, fascinating subject. So first off, why do we want to make one?

You know, what are the advantages of a quantum computer, compared to a more traditional computer. So quantum computers have sometimes been referred to as a holy grail of science. And the reason for that why people are so fascinated by that is that quantum physics is really the underlying theory that explains everything in nature. Now, why is this important for a computer? There's a lot of problems in the world, for example, to create new pharmaceuticals,

which are really hard because of the very nature. of trying to simulate, for example, chemical reaction of how to create a new pharmaceutical. Real big problem is that conventional computers really quickly run out of speed when simulating such a complicated system. This is the reason why you have to go to the laboratory and do lots of experiments to make a new pharmaceutical, for example, make a new material. Now, quantum computers offer the opportunity to actually simulate the very dynamics, of the system itself. That means they can solve problems.

They can enable us to create new pharmaceuticals. But this is only one of many examples. So quantum computers are known to break encruptions. So in fact, any encryption. So if you put your credit card details on the internet, to buy something, quantum computer could break that. Quantum computers are also known to optimizations in a way that it's inconceivable to do in a conventional computer.

means you could optimize financial transactions. In fact, you'd nearly revolutionize a lot of the financial sector altogether. So quantum computers really will play a role in nearly any industry sector, whether it's making more fuel-efficient aircraft engines, without reducing drastically energy consumption, because you can make fertilizer more energy-efficient, whether it's just optimizing a delivery route for a truck, to make deliveries. So the applications are far and wide in nearly any field you can imagine.

Maybe one way to think of that is a quantum computer will really very much change the way we will work and live. So sort of in a simple terms, what's the computing power compared from a quantum computer to a traditional one? Quantum computers work extremely well for certain particular problems. So don't think of a quantum computer as the new computer you're going to buy and put on your desk in word processing or play computer games. He'll use a quantum computer for certain applications. Now in these applications, quantum computers are tremendously powerful. What means tremendously powerful? It means that a quantum computer can solve a problem where even the fastest supercomputer in the world may take billions of years to solve that problem. It's not a fast computer,

It is a computer that can solve a problem that would be entirely inconceivable to solve on even the fastest supercomputer that we have right now. So that's absolutely incredible. You mentioned earlier the idea of quantum physics underlying all things. So let's have a look at some of the ways that this applies to a quantum computer, like some of the underlying concepts. So a lot of people talk about quantum entanglement, and this is key, right? So what is that? Einstein referred to that as spooky. And there's a really good reason to.

It's one of the most strangest things you can possibly imagine. It means like two objects can be connected in a very spooky, magical way. It means that something you do with an object on your desk may impact instantaneously an object on the other end of the universe. And all of that with any information sent between the two objects. So they're strangely linked with each other, yet no information travels between them. And this property of entanglement has completely freaked out physicists. And there have been 50 years of experiments. Essentially, physicists try and to disprove that that could possibly be right,

because it's just so crazy, so mad, that we tried everything, somewhat trying to shout that that can't be right. But experiment after experiment after experiment, has shown that, yes, this works. And so then maybe around 10, 20 years ago, physicists asked themselves, can we tame this? Rather than just being essentially freaked out by that, can we actually use and tame this phenomena to make machines that can do something that no other machine could ever possibly do? So how does that apply then in the quantum computing situation?

So entanglement is used to actually do calculations inside a quantum computer. In fact, it's at the very core of what you use to achieve that. So let's start with a conventional computer because I want to talk a little bit about how a conventional computer actually does calculations. So conventional computer encodes what you type into your computer in bits. So what are bits, the string of zeros and ones and essentially any word you type into computer, essentially is a long string of zeros and ones. Now, in quantum computing, we also have bits, but they're not just bits, they're actually quantum bits.

And now here comes to strangeness. Now, quantum bit, rather than being zero or one, can be zero and one at the same time. It's one of these very strange things in quantum physics, and an object can be in two different places at the same time. You can be simultaneously sitting in the studio as you do and have breakfast at home. In quantum physics, that's an absolute possibility,

and very convenient indeed. Unfortunately, we can't make these superpositions yet with whole people, only with individual atoms. Otherwise, it would be very convenient, wouldn't it? So that's something called quantum superposition. That's right. And quantum superposition and quantum entangement actually intimately related in being used

to execute calculations inside a quantum computer. And I'm going to now explain and simplified terms how that actually comes about. So imagine let's start first with a classical computer. You have your processor and you input your data. Your data is a number of bits. Let's make this very simple. Let's imagine you have the world's most embarrassing memory stick. Like not a gigabyte, not a megabyte.

You're going to have two bits on your memory stick, right? So that's your memory in your computer. And now you want to do a calculation, what you've saved in that memory. You take that for the processor. And so these two bits go for the processor, and then out comes some kind of answer. Now, when you have a very fast computer,

all what happens, that that happens very fast. You put a number in the memory, you take it for the processor, get a result, and you put a next number. And so that goes very fast with gigahertz rate. Now, a quantum computer works entirely different. In a quantum computer, rather than having two bits, and for example, deciding I'm going to write 0-1 into my two bits.

In a quantum computer, because a bit can be 0-1 at the same time, rather than essentially deciding on I'm going to write 0-1 in there and take it through the processor, I can actually write all possible numbers into these two bits. So rather than just putting in 0-1, I'm going to put simultaneously 0-0, 0-1, 1-0 and 1-1 in there. And then I process all of that simultaneously through the processor, making use of entanglement. Now, instead of, in a classical computer, I would have essentially done one calculation,

in a quantum computer I would have done four at the same time. It doesn't really sound that exciting yet, but take this for three bits. So in three bits, I can write one number in, but get nine different combinations and process them all at the same time. And it's two to the power of the number of bits. So imagine we have 100 bits,

100 quantum bits, he can write in there and simultaneously process. And what a quantum computer does, it is able to essentially compute all of these things simultaneously, and then the quantum algorithm, so the quantum software that is being used to essentially help us to provide such a result, that now makes use of all these calculations, brings them together and calculates one answer that is somewhat dependent on all these calculations. So that's absolutely mind-blowing. even more mind-blowing, you're working on building one. Yes, absolutely. So that's really,

it has always been my passion. So I started and got a long time ago, more than 20 years ago, I, as a PhD student, I was told by a theorist, by quite a famous theorist, he said to me that it's possible to have an atom move forward and backward simultaneously, or it should be possible. And I thought, okay, I'm going to try this, I want to see that. And so I did an experiment with atoms where we actually, for the first time in the world, managed to do exactly that. And that inspired me because the strangers of these quantum phenomena made me realize, wow, we need to tame this. We need to actually do something useful with that.

And so in probably 2001 or 2002, I decided I'm going to build a quantum computer. That was a time when nobody believed that would be possible. And people just rolled their eyes at me when I said, I'm going to build a quantum computer. But just as in high school or in pretty much most of my life, and people tell me you can't do something, I'm straight on that. And so I decided I'm going to actually build one. I don't care, but people say, this can be done and I will do it. And so I started figuring out what would be the best way to build such a machine,

and I traveled the world two and a half times around, and I visited a lot of laboratories trying to understand what kind of physical system would be most capable of actually realizing such a machine. And after a lot of conversations and a lot of analysis, I realized that individual charged atoms, call them ions, are really amazing system to do that. There are room temperature technologies, so you don't need to cool them to very low temperatures, and they're extremely resilient to other external factors that could destroy quantum effects. And so I decided then we're going to build a quantum computer.

And so if you're interested, I can tell you a long story. from the early years of when we said we're going to go there until what happened today. It's mind-boggling. It's really mind-boggling because the technology has now moved so much forward that now we can really say, it's just not, can we build a quantum computer, but when will we build a quantum computer? And we are now solidly on path to build a machine that can solve incredible problems. That's amazing. So you mentioned ions there. So your sort of idea is the ion trap. That's exactly right.

So how does that work? So an iron trap is essentially, originally it was a bunch of metal rods that they're used to hold to where we apply oscillating voltages. Now these oscillating voltages create electric fields. And these electric fields then exert a force onto a charged atom. And this force is being used to hold that iron still levitating. Now originally these iron traps were just made out of metal rods. And you can imagine building a quantum computer out of metal rods is probably not the easiest thing, especially if you want to scale this to millions of quantum bits.

So again, people told me with ions, you can't build a quantum computer. So I started developing the very first iron microchip. So rather than using metal rods, we developed a very first microchip that could be used to hold these ions. Instead of now having metal electrodes, we had tiny little structures, microscopic structures, where we could apply voltages to, that would allow us to hold ions. And the ions are now essentially levitating around a hair riff above the surface of a silicon microchip. So how do we make a cubit out of that? So the trap iron is essentially the cubit, and what actually holds the information is the spin state.

of the ion. What is a spin? A lot of people use that word, but doesn't really mean much. So the spin is essentially the atom as an electron that goes around the nucleus of the atom. And so the trajectory of this electron, you can think of that is the spin. And by putting in energy, for example, putting in either a laser beam or microwave radiation, you can change the state or the trajectory of that electron. And one trajectory would correspond to say the zero state, and another trajectory would correspond to the one state. Now, now we have a bit. One of the strange thing is that, again, this iron cannot just be in one trajectory or the other trajectory,

but it can be in both. And so now we can have this very strange to a position state. Flowing ad budget on metrics that look great, till the CFO sees them, that's bull's bend. And marketers are calling it out in Dashboard Confessions. I remember telling my boss It'll be good for the brand When leads were slow Yeah, it wasn't

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Visit focal powered by name.com for more information. So we're saying things are in multiple states all at once, but at some point we have to measure them. So what happens then? Essentially, when you measure the state of the iron, we say it collapses. into one or the other state. And so actually during the calculation, you never want to measure the state of the iron.

You exactly the opposite. You don't look at it. You don't touch it. You just undertake all these calculations. And right at the end of the calculations, you read out the state. But the state, at the end of this calculation, now depends on all these interactions

and all the calculations and all the entanglement gates we have executed in the calculation. And so what we read out at the end is the answer to your problem. So if you ask like, hey, I want to understand of how can we make this molecule, making use of less energy, which might be an important thing when you make fertilizer, then the output of that calculation would tell us exactly that. So what's the current state of your project now then? So again, when I started, this was all a research group and it was trying crazy ideas.

And in 2017, together with Google, with Rican, Zigen, Aho's University, we published the world's first blueprint of how we go about building a practical quantum computer that can solve really important problems. And after we published this blueprint, we set out actually built the machine. And in particular, some of the features that we proposed in this blueprint, One of the things which he really need to sort out and settle when you want to build a quantum computer, you need to be able to do quantum computing with a lot of cubits. What is a lot?

It's a million, many, many millions of cubits. So it will always be impossible to fit all these cubits on a single chip. So you have to come up with some kind of modular solution to allow you to then scale your quantum computer to arbitrary computational power, meaning to arbitrary number of quantum bits. And so laboratories around the world developed an approach. This approach made use of optical fibers that would connect one quantum computing chip to another quantum computing chip.

Now, after 15 or 20 years of development, the world record set at 180 connections between chips per second and error rate of 6%. And that's just simply not good enough. So in 2017, we proposed an entirely alternative idea, we said, is it possible to connect these microchips using electric field links? In 2017, this was an idea and there's a lot of ideas out there. So you really have to demonstrate and show that this actually could work. So just last year, we were successful in demonstrating

this idea. And instead of having a connection rate of 180 links per second, we managed to make a connection rate of 2,400, so much, much faster. But instead of having a 6% error, we had seven orders of magnitude, a small error. So we managed to connect these quantum computing microchips with tremendous precision. Such good position that this technology is already suitable now to actually build a large-scale quantum computer. And now this is exactly what we do. So the research group here at Sussex still works and doing the underlying signs to invent new paradigms to really make it easier to build a quantum computer. But hand in hand works the company that is a spin-out from this university research,

and there we're completing now the really heavy-lifting engineering, and we've built real-world quantum computers now in the company that can tackle really interesting problems. And for that purpose, we managed to recruit some of the very best engineers from around the world. you know, this is not just a bunch of physicists having smart ideas. When you come into my lab at the University of Sussex, I mean, it looks a bit like a sci-fi film. So you have all these machines, all these hums. It blows your mind, blows my mind every day. I go on the lab.

But physicists don't really do good engineering. So physicists kind of do a little small, proof of principle machines, but there's cables everywhere, and if you press the wrong button, you want to get out of the room really quickly. You know, like this is all a bit more science. I don't know whether you like Rick and Morty, but there's certainly some tricks. and what we see in Rick and Modi. What we do in the company is to precision engineer these microchips, to really engineer big machines that have the capability to solve these really important

problems. And so this is a most exciting time now when we go about and actually take the technology and the ideas we develop and actually make real world machines. And that's happening right now. So can you put a timescale on when we'll have one of these? So quantum computers a little bit like classical computers and I always like to use a really nice example

and actually let me ask you a question. Do you know, when was there the first important application for a classical computer? A, the Lovelace movie, I would guess. Which year? Just approximately? It's the 19th century. So the first computer, the first impactful calculation of a computer

actually happened in Second World War and that was breaking the German Enigma Code. So that's the kind of first impactful calculation of a computer. There's a very big machine. You must go and have a look at these first machines. It's real amazing. So that happened in 1945. When I grew up in the 70s and 80s,

I actually learned typewriting on a mechanical typewriter. So even then computers weren't really very common here. It's a C-64 and some of these really basic machines that happen at some stage, but computers weren't common at top. So you can see that from 1945, when a whole World War, this was decided with a computer. To the 70s, it took a long time to develop classical computers up to the point where we are today, where you probably wear a computer around your arm with some kind of computer

watch. You have your iPhone or Android phone or whatever not. You use a computer. You go on a train station. You buy tickets with computers. So this is a very gradual process. And think of quantum computers a bit like that as well. So it's not going to be like this.

It's not going to eat at one day when we all have a quantum computer. But there's already quantum computer. is out there right now, here in my lab, at the University of Sussex. So if you ever like to come, you can actually play with a quantum computer here. It's a very small machine, and it can't really do many useful things.

It can demonstrate the technology, but it can't really do useful things. And so right now, we kind of in the stage of quantum computers where we build first prototypes. And so the first practical application for a quantum computer might be around five years or on the corner. So we definitely get there, we verified that the tech works,

We show in like that we can run small circuits with qubits. We verified that the theory is correct. But now we need to do the heavy lifting engineering to scale this up from a handful of qubits to large numbers. And this is kind of where we are right now. So this is where, in fact, the company Universal Quantum is really making use of the technology innovations to actually bring this to a larger scale. So that's kind of where we are right now. And so I would say five to 10 years until,

maybe the first high-impactful application for quantum computers. But then after another year and after two years, you're going to have another application and another application. And so essentially, this is kind of a slow process, just like with conventional computers, where you're going to gradually see quantum computers having an impact on more and more industry sectors. So you kind of mentioned there.

As a final question, if anyone is listening and they're interested in learning more about your projects, do you have a website or something that you can point them to? where they can get more information. Absolutely. So one of the things, and I really want to tell you that because it's super exciting.

So here at the University of Sussex, we actually have done something that no university in the world has ever done before. We've created a new degree where you can study physics with quantum technologies. We can study quantum technologies, but not just study it. You can actually become part of one of our research groups

from day one of your degree. So rather than just sitting, in an lecture theater and studying math and whatever, all the basics that you need in order to excel later on in research and development, here at University of Sussex, you can actually come and participate in the research while you study. And so you can find out about this degree at the University of Sussex. There's, if you Google in Sussex Center for Quantum Technologies, you'll get the center and there, there's lots of web pages telling you about the research. You can learn really about how we build a quantum computer.

You can learn about the different research groups we have here. But if you want to make that next step and actually say, I want to actually build a quantum computer myself, let's just do this. I'm not going to let anybody tell me I can't do something. I can't change the world. Then actually do exactly that, change the world. Come here and help us build technology that can really revolutionize nearly any industry sector. And now is the time.

If you're a high school student right now and you hate math, that's absolutely fine, but you need to study for the math in order to do some really cool stuff, in order to do physics and can really change the world. If you're a little bit bored with the physics because it's a little bit boring, because the problems seem to be all a little bit boring, remember that physics is what actually enables us to do teleportation, to do entanglement, to do all the really cool things. Thank you for listening to this episode.

of Instant Genius, brought to you from the team behind BBC Science Focus. That was Professor Vinfried Hensinger, director of the Sussex Centre for Quantum Technologies. If you liked what you just heard, please consider subscribing to Instant Genius on your preferred podcast platform. The current issue of BBC Science Focus magazine is out now. Pick up a copy wherever you buy your favourite magazines, or download a copy on your app store of choice. You can also find us online at sciencefocus.com. by Name, Audio and Focal. The texture and emotional depth of music

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