Does Google’s ‘mindboggling’ new chip bring quantum computers any closer?
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For a long time, they felt like the stuff of science fiction. Computers so fast and so powerful, they could give us new drugs in record time, allow MRI scans to be read in atom-level detail, and zip through calculations that would take today's most powerful machines longer than the age of the universe.

My favorite quantum application is teleportation of information from one location to another without physically transmitting the information. Sounds like sci-fi, but it is possible. Despite breakthroughs along the way, quantum computers we can actually use have always seemed to be just out of reach.

But recently, the drive for quantum has ramped up.

Countries are pouring tens of billions of dollars into research and development. Superpowers are already engaged in a kind of quantum's arms race. President Joe Biden has imposed export bans on quantum technology to China. And on Monday, Google made an announcement that felt significant.

Shares of Google jumping today after announcing that quantum computing breakthrough, saying that its new chip, Willow, can perform a milestone computing task in just five minutes and would have taken a classical supercomputer longer than the history of the universe to do. So today, what exactly are quantum computers? And are they any closer to fulfilling their promise? I'm The Guardian's science editor, Ian Sample, and this is Science Weekly.

I grew up in primary school. I decided that I wanted to study physics because I realized I wanted to be a science officer on the Enterprise and in Star Trek. So that was my first motivation to really get into science, work on teleportation. It's really now possible to work on these mind-boggling machines that are really part of sci-fi. Winfried Hensinger didn't make it onto the Starship Enterprise, but he did grow up to be a professor of quantum technologies at the University of Sussex.

Quantum computing is a notoriously difficult subject to understand, so I asked him to start by telling me about normal computers. How do they work? So normal computers process information, as you know, whether it's a Word document that you edit or a calculation you carry out. And essentially, conventional computers process data as bits, zeros and ones.

And so what your processor then does, it carries out a set of logical procedures. These are there to execute the calculation you want your computer to do, to solve a particular calculation using the information encoded as the string of zeros and ones, or we call them bits. Okay, so normal computers, classical computers operate with bits and they're either on or off.

But quantum computers harness this weird property that emerges at the scale of atoms, where things are neither sort of one thing nor the other. So, I mean, in the most basic terms, tell me about this aspect of quantum physics and how it's applied to computers. So quantum physics makes rather strange and weird predictions, predictions that really spooked quantum physicists for all the ages.

In quantum physics, we've discovered that an object can be at two different places at the same time. So that means really you can sit right now in the studio having a conversation with me and in principle, you could also be at home having breakfast. So that is a possibility in quantum physics that objects are two different places at the same time. And we refer to that as a superposition.

And you can't really see this in the bigger world with people, but you can actually observe these phenomena with smaller objects, with atoms.

And so what quantum computing does, it actually makes use of these very strange phenomena and creates bits. And now we call them quantum bits. And we call them quantum bits because now the bits aren't either on or off, aren't either zero or one, but it can now also be zero and one at the same time. And so we now bring this quantum effect together.

into building a machine that making use of these quantum effects could process information incredibly fast. So you've talked about superposition, but there's this other very strange phenomenon with quantum physics called entanglement. What's that and how does that come into play?

Entanglement is extremely strange and it's so strange that actually Einstein referred to it as spooky. Entanglement is a correlation. So that means something you do right now where you're based will have an immediate effect on an object that might be far distant, might be in America, might be the other end of the universe.

And this very strange correlation is measurable over and over again. It's very strange because information actually doesn't travel between these two connected objects. Yet on the other hand, something you do here may have an impact somewhere completely elsewhere. And physicists over many years investigated this and over and over verified that in the experiments, exactly what entanglement would predict became true.

And now then, after all this time of intense study and really trying to get ahead around these very strange phenomena, they realized they can make use of entanglement to build machines that could be fast in carrying out computations, or in fact, much broader, we often call this the general field of quantum technologies, and maybe the most impactful application is quantum computing. ♪

So instead of bits, quantum computers have these qubits and they can be in multiple states at once through this superposition effect you've been describing. They can also be entangled with each other. So tell me how this makes computers better or could make computers better. I mean, what can qubits do that normal digital bits can't? Okay.

Okay, so it may be helpful to give you an example of a memory stick. Imagine you have a really, really terrible memory stick, the cheapest memory stick you've ever gotten. The memory stick that only holds two bits, right? So if you then choose what you're going to write into your two bits on your memory stick, it could be, for example, 0, 1, and then the memory stick is full. Now, that is a classical memory stick with classical bits. Now, imagine you would have a quantum memory stick with quantum bits.

So rather than just being able to write 01, now your memory is full, you could now go ahead and actually write 00, 01, 10, and 11, all in these two bits. Because remember, quantum bits can be both 0 and 1 at the same time. So you can essentially encode all these different numbers simultaneously.

into these bits. If you have two quantum bits, you can encode four numbers. That doesn't sound very impressive, but if you now take this a little bit larger, so for example, three quantum bits, I can encode two to the power of three different combinations. And so very quickly you can encode an incredible amount of information into these bits.

And where then quantum computing comes in, a quantum algorithm is written in such a way that now all this information is processed via the quantum processor simultaneously.

And so rather than in the case of a classical computer, do one calculation, then the second calculation, the third calculation. Now this quantum processor now does all these calculations simultaneously. And so you can see now how a quantum processor can in principle be so extremely fast because now you make use of this idea of superposition in order to execute calculations in an entirely different way than a classical processor would do.

So it sounds as if you're saying there is a sort of a benefit to be had in terms of the sheer density of information, because you can get more information into sort of quantum bits than you can into classical digital bits. But also that there could be a speed advantage because you can do processing of those bits simultaneously in parallel. But am I missing something? Is there more to it than that?

I think you've gotten it exactly right. In particular, the execution of calculations in parallel is what really gives rise to the amazing power of a quantum computer. I should be very clear, my explanation is rather simplified. And the way how quantum algorithms operate is a little bit more complicated, but the working principle you've expressed exactly correctly.

Give me a sense of how transformational you think quantum computers will be if we can get them right. I mean, what kinds of fields will they be particularly important for? And is it the case that quantum computers can, in principle, do things that classical computers, even super powerful classical computers, just cannot do because they operate differently?

So think of quantum computers not as a very fast computer, but think of a quantum computer as a machine that solves certain problems in an entirely different way than a conventional computer can ever do. What that means in practice is that for certain problems, a quantum computer can find a solution where even the fastest supercomputer in the world

would take essentially billions of years to solve that problem. So if you create new pharmaceuticals, you have to really understand the chemical reactions. You have to understand what the ingredients exactly do. And that's actually a really, really hard problem. And it typically takes over 10 years and in excess of 10 billion pounds to just develop one new pharmaceutical.

A quantum computer may be able to significantly speed up the development of pharmaceuticals. So instead of 10 years, it may only take three years and it may substantially massively reduce the cost. Quantum computers can make new materials, maybe very powerful, strong materials. They may also help us to make more fuel efficient aircraft engines.

Or they may simply help a distribution company to find the best route, the fastest route to visit a lot of different places. We call that the traveling salesman problem. So quantum computers will really affect most industry sectors in a rather profound way.

clearly then this huge potential, really broad potential. But talk me through some of the challenges of taking what at the moment feels like quite a theoretical idea and making it a practical sort of reality. Why

Why don't we have quantum computers already? When we started talking about quantum computing, I said a rather provocative statement. I said, in this quantum superposition, and in principle, you could be right now sitting in a studio and you could be sitting at home, right? Why don't we see

these very strange quantum phenomena in our day-to-day life. Why don't we see people or objects with two different places at the same time? The reason why we don't is because the environment, so the air molecules that surround you, even the light that is in your room actually destroys the quantum effects that could emerge and actually render our world exactly the way you're being used to this world.

Now, in order to make quantum superposition a reality, what we need to do is we need to prepare very intricate experiments where we cut off all the influences of the environment, of air molecules, anything that may interact with that system we want to realize quantum phenomena with. And we have to extremely isolate that system.

So to answer your question concisely, it is the difficulty of...

isolating and realizing these quantum phenomena in a highly controlled way that stops us from just very easily build a quantum computer using the tools that we have around us. We really have to go out of our way to isolate the quantum system and even then to correct for the errors that occur as we prepare atoms or other systems in these very strange quantum superpositions.

Winfred, on Monday, it seemed like there was a step forward in quantum computing. Google revealed what their PR at least calls a mind-boggling quantum chip. They named it Willow. What can this chip do that was so impressive?

So in quantum computing, one of the biggest challenges is actually to maintain these very strange quantum phenomena. But that is fundamentally not perfectly possible. In general, there will always be errors. There will always be small impact of the environment on these quantum systems.

So what Google has achieved with its new Willow chip is to demonstrate that it is possible to correct these errors in quantum computing successfully by means of adding extra qubits and making use of these extra qubits to learn about the errors that occur inside the quantum computer and then furthermore to reduce and to mitigate these errors altogether.

The more qubits you add, the smaller is the resultant error. Now, this has been a theory that has been known for quite some time. And this theory is very important because it kind of provides proof that indeed it is possible to build a quantum computer. It sounds like this willow chip from Google is...

Really a sort of proof of principle then that it's not in itself going to have practical applications. It won't really be used for anything in particular, but it's demonstrating that these more powerful computers are practical and feasible. That's exactly right. So there is not a single practical application the Willow chip can do. We should be very clear that none of the quantum computers that are available worldwide right now have much potential to do anything useful.

But these results are really, really important because they show us investment, time, money, and the people who are now working on this technology, that goes in the right direction because we really see these distinct success events where you can really see, wow, this was not just...

some crazy theorists who came up with this theory, but we have now an experiment which has proven that the theory is correct. And so that sends us on an incredibly exciting journey. There is now this global race to build quantum computers, to build very useful quantum computers. What is the next milestone we should all be looking out for? What is the next step where people like yourself are going to get

and think, okay, we're really getting somewhere now. In my opinion, the next step has to be to demonstrate that the technology can really successfully operate at a million qubit scale. And this is something where here in the UK, we made a

immense breakthroughs. And this is where everybody can play their part, whether it's an electronics company that can help us develop the electronics for quantum computing, a vacuum company that is able to work on vacuum systems, or high school students that now take a job choice

and say, hey, I want to really develop this amazing technology and get into physics, engineering, informatics in order to help us build such machines. Winfried, thanks so much for coming on. Thank you. Thanks again to Professor Winfried Hensinger. You can find more reporting on quantum computing at theguardian.com. This episode was produced by Joshin Chana and Madeleine Finlay. The sound design was by Tony Orachukwu and the executive producer was Ellie Burey.

We'll be back on Tuesday. See you then. This is The Guardian.

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