As a child, Sergio Boixo (León, 1973) devoured novels by Isaac Asimov, the writer who imagined how we would live in the future, without knowing that, years later, he would be dedicated to designing it himself. The director of quantum computing at Google has been working since 2013 on a challenge that could revolutionize the way we live: the creation of quantum computers with industrial uses in fields such as medicine, energy, or materials. A long scientific and technological career involving research centers and companies worldwide, where fundamental steps have already been taken, with this Spanish "brain" being one of the main architects.
One of the milestones in which Boixo played a leading role occurred in the US in 2019 when Google's quantum processor called Sycamore performed a calculation in 200 seconds that would have taken the world's fastest computer 10,000 years. "Quantum computing is about making possible problems that are practically impossible for traditional computers. Quantum computers are not faster, but they speak a different language and have different rules," explains this engineer accustomed to making the complex world of atomic and subatomic particles understandable, in which he moves like a fish in water.
"The first thing to understand about quantum computing is that it is based on quantum mechanics, which is modern chemistry and physics, that is, from the last 100 years. It is a very consolidated discipline, confirmed by thousands of experiments. Thanks to quantum mechanics, there was already a first quantum revolution that gave us the semiconductor chips that allow us to have conventional computers. And we have known for over 100 years that it is the language of nature, even though it has properties that seem a bit strange or counterintuitive to us," he reviews. "Almost 50 years ago, it was thought that if we wanted to be able to simulate nature, we would have to make a computer that spoke its language. And that's what we're doing. Making a quantum computer is about making a machine that operates according to the language of nature," Boixo summarizes.
As simple and as complex as that, because as he emphasizes, the whole world is at the beginning of quantum computing development: "It is a long-term race. We already have experimental quantum computers, with scientific but not industrial applications; there is still a significant gap to overcome," he acknowledges in the Google offices in Madrid's financial district, surrounded by skyscrapers. A quite different environment from his usual workplace in Los Angeles (USA), where he lives with his wife, also Spanish, and their three children. "Google's main headquarters in the US is in Mountain View (California), but I am in Los Angeles, in Venice Beach, so if we don't need to be looking at a screen, we often have meetings while walking on the beach."
One day a week, he travels to the company's headquarters in Santa Barbara, a couple of hours' drive from Los Angeles, as Google opened its main quantum center there in 2021: a campus with a data center, hardware research laboratories, and facilities for manufacturing quantum processor chips. "I go almost every week because part of my team is in Santa Barbara," he says.
What is a typical day in his life like? "I am an early riser, I get up at 6:30 a.m., and if I have to go to Santa Barbara, at 5:30. I usually go to the office every day, but Google allows two days of remote work. I start at 7:30. In the Venice Beach office, we all in quantum have lunch together because it gives us the opportunity to get to know people better on a personal level, but also to know their ideas and what they are working on."
He usually leaves the office at 5 p.m., spends time with his family, and then works a little more. "In the US, people work quite a bit, and the hours are sometimes challenging, so we try to travel a lot as a family, which is something we love and when we can spend more time together," says Boixo, who comes to Spain at least a couple of times a year. "My children spend almost the entire summer here, and we also come for Christmas," he says. "During the week, I play tennis, and I like to read and go birdwatching," he says when asked how he relaxes.
He has always enjoyed studying, as evidenced by his impressive academic resume - he holds degrees in Computer Engineering, Mathematics, and Philosophy. "It is true that I have always been very curious and eager to learn. I wanted to learn so many different things that I didn't know where to start," recalls Boixo, whose scientific vocation was encouraged by his grandfather, who was a veterinarian, and his grandmother, a chemistry teacher.
He began studying Computer Engineering at the Complutense University of Madrid, and in the second year, he combined this degree with Philosophy at the UNED. "Later, I worked for a few years as a computer consultant in Germany, at the European Central Bank and other places. After a few years, I saved some money and decided that what I really wanted to do was a Ph.D."
The quantum world had caught his interest a few years earlier. While studying Computer Science in the early 90s, the first works on quantum computing began to be published, which a professor passed on to him. "The original idea was from 1984, by Richard Feynman. I had a very theoretical inclination; I studied Theory of Computation and Complexity, which is the area that deals with the complexity of different problems, which can be solved in linear time and which in exponential time, or which problems we cannot solve."
Those complexity classes, he contextualizes, were established from Turing and subsequent developments: "What I found super interesting is when they started writing about how if we used a quantum computer, the complexity classes changed. I then decided to do a Ph.D. in quantum computing because it combined everything that vocally attracted me, which was to reach the fundamental questions of nature. From a fundamental point of view, it was already known that quantum computing would make possible problems that are practically impossible with classical computers."
Before embarking on that Ph.D., he completed a Mathematics degree at the UNED and a Master's in Theoretical Physics at the Universitat Autònoma de Barcelona. "And then I went to the US, with a scholarship from the La Caixa Foundation, to the University of New Mexico, in Albuquerque, which is not as well known but has a fairly pioneering group in quantum computing. In addition, in New Mexico, there is the Los Alamos National Laboratory, and I worked there in the summer and part-time."
He then did a postdoc at Caltech and Harvard, and after working as a research professor at the University of Southern California, in 2013 he joined Google's quantum laboratory, Google Quantum AI, founded and directed by the German computer scientist Hartmut Neven. "The group has been growing, and I am the longest-serving employee. I lead the computational science part, complexity theory, error correction...," he explains.
From this American technology company, Boixo fully entered the global race to develop a large-scale quantum computer. In practice, how will it differ from a conventional one? "The rules of classical mechanics trace back to Aristotelian logic, where you have predicates that are true or false. A switch - a bit - can be in zero or one, on or off. Or an abacus (an ancient calculating instrument) has beads that can be to the right or to the left. That's how classical computers work, with bits that can be zero or one, following rules similar to an abacus, but those bits move billions of times per second. They are like incredibly fast abacuses and do incredible things, like everything we are seeing with artificial intelligence."
But the language and rules of quantum mechanics are different from those of classical mechanics: "There is a very important property called superposition, and, although counterintuitive, it turns out that this is how nature works. For example, in quantum mechanics, an electron in an atom is both to the left and to the right. It is something that classically does not make sense, as the electron is either to the right or to the left, but not in both places at once. Well, in quantum mechanics, it is indeed in both places at once, it is in superposition," he explains.
Therefore, what they aim to build are computers that operate with superposition, and instead of having bits that are 0 or 1, they will have quantum bits or qubits, which can be both 0 and 1 at the same time: "That they function like Schrödinger's cat, which can be alive and dead at the same time. It is something that is hard for us to comprehend, but that is the language of nature."
Philosophy, he reflects, has directly helped him in quantum computing: "It gives you flexibility in understanding the world and helps you not to cling to preconceived ideas in science and other fields." And, "although quantum mechanics is over a century old, it still seems strange or contrary to our intuition about how the world works. It has properties that we do not see directly, relatively delicate experiments need to be done for them to emerge. But in philosophy, it is not so strange because the world does not have to behave in the way that seems intuitive to us." In the competition to develop a quantum computer, advances are being made year after year by different companies.
"We, from Google, have already achieved two milestones on our roadmap. In addition to the 2019 experiment to demonstrate that impossible problems become possible, last year we managed to create a quantum chip, Willow, which was the first experimental demonstration that error correction works." Error correction is a fundamental problem that they have to solve to achieve a large-scale quantum computer with industrial uses. An obstacle they have been trying to overcome for years: "Quantum computers are circuits that have logical gates, which are operations. Now, both us and other groups, can only execute a few thousand logical gates; we cannot create circuits with more gates because they fail. Each gate has a probability of error, so the more gates you have, the error probability increases too much and it will fail. The solution to this limitation we have is error correction, which will allow us to move from circuits with thousands of gates, which now allow us to make scientific discoveries, to industrial applications," he explains. The next milestone they want to achieve in this roadmap is what they call a logical qubit.
"Last year we showed a prototype, but what we want to do around next year is a logical qubit that is not a prototype, but is the equivalent of a quantum transistor, and that already has the capacity to execute millions of gates. In other words, moving from thousands of gates to millions of gates. Once they have the logical qubit (capable of performing millions of operations), they will try to reach 100 logical qubits: "We are optimistic and think that in this decade we will achieve a quantum computer that will have some industrial applications, although we are not certain because it will have 100 logical qubits and not 1,000 and will be able to perform around millions of operations instead of billions of operations. And for the next decade, we will have a large-scale quantum computer free of errors that we know will have industrial applications," he anticipates. IBM, one of the companies competing with Google, recently announced that they aim to have a large-scale and fault-tolerant quantum computer by 2029. "For us, more than setting dates on a roadmap, the important thing is to make experimental demonstrations that show that quantum computing works, that it makes impossible problems possible, that error correction works. It already has applications in science and we are making scientific discoveries. But industrial applications have not yet arrived," explains this Google scientist. Where will they begin to be seen? "Quantum computers make classically impossible problems possible. Therefore, the first applications will be in all fields where you have to simulate natural processes in very detailed ways: chemistry, materials, drugs..."
Boixo gives a specific example they have studied: "To create fertilizers, which are crucial to feed 7 billion people, currently a chemical process of nitrogen fixation is used that consumes 2% of the world's energy because it is done at high temperature and high pressure. There are bacteria capable of fixing nitrogen, and when we have a quantum computer, we will be able to simulate this natural process. And if we can simulate and understand it, I believe we will be able to replicate it in the industry. Considering that 2% of the energy goes to this fertilizer creation process, perhaps we will save 1.5% of that energy in one fell swoop," he anticipates. He also believes that it could make nuclear fusion possible, which is a clean and inexhaustible energy source: "It is the energy that the sun uses but we are not able to reproduce it, although we have been trying for a long time. At Google, we have collaborated with an expert group in nuclear fusion from the Sandia National Labs company and we have seen that a specific part that cannot be simulated with traditional computers, we can simulate it with quantum computers."
We asked him to, as Asimov would have done, describe how he sees the world in 2050 if they manage to make these quantum computers a reality: "I hope we have clean energy and have solved the problem of nuclear fusion, that drug design has advanced a lot, and that we have much more efficient batteries. Now, to make a more efficient battery, if you have a million ideas on how to improve it, you have to manufacture a million different batteries. The idea of quantum computing is that, instead of doing something so costly, you do a million simulations to choose which one is more efficient. And I hope we have all this within less than 25 years," he points out. His cautious optimism is based on the advances they are achieving: "Things that were science fiction 10 years ago are already being done in the laboratory," assures this engineer, who considers that their competition is mainly with nature. "The more we are able to work collaboratively within Europe and the Western bloc in general, the sooner we can create this quantum computer. That's why we have so many collaborations with acad
emia, companies, and a lot of open-source software," he argues. For technological companies like Google, hiring talent from all countries is key: "Our team is very international because we have been fortunate to bring in very cutting-edge talent. In fact, one of the best things about this job is the group of people I am with and from whom I learn every day. It is a group that has to be very diverse because for us, it is important to hire the most qualified person for each position, the ideal candidate," he responds when asked about how the ban on foreign students in American universities that the Donald Trump government intends to implement could affect Google. Regarding the presence of women in the quantum world, he affirms that there are pioneers, such as Barbara Terhal, but the representation of women, in general, remains a minority. "In our group, we are fortunate to have outstanding female scientists, but we are not where we would like to be in that sense," he acknowledges. Boixo also tries to dedicate time to inspire children and young people. "When I can, I like to support science in all age groups. Last month, for example, I was at the University of León." His advice? "Do not limit yourself when you want to do something. And another important thing is to follow your vocation because if you want to stand out in something, you will have to work quite hard," he suggests.
From his point of view, opportunities in science and the technological world are becoming democratized: "We all have access to the internet, articles from all over the world are available from any computer, and artificial intelligence is a very powerful tool for learning. In fact, Google's motto is to make information accessible to everyone, anywhere, at any time, and this is something that is being fulfilled," he defends.