Nobel Prize in Physics Serge Haroche on Quantum Computing: “There are still many difficulties to overcome” | science and technology

We can say that his motivation was to kill the father. Serge Haroche (Casablanca, 1944) was one of the winners of the 2012 Nobel Prize in Physics because he succeeded in trapping and manipulating individual particles while preserving their quantum nature. His feat was inconceivable. Erwin Schrödinger himself, one of the fathers of quantum physics, had declared nearly a century earlier that it was impossible to work on a single particle. Schrödinger’s solution was the principle of quantum superposition: since he could not isolate and observe a physical system like the electron, he assumed that it existed in all of its theoretically possible states. Thus, his famous cat was born: locked in a box, he was alive and dead until we could observe him. Then Haroche came along and changed Schrödinger’s “and” to an “or”.

From the first computer to the fiber optic connection, the great technological advances of our time have become reality thanks to quantum mechanics, and the latest prize from the Swedish Academy, awarded on October 6, has once again recognized a breakthrough in this domain. Three physicists have succeeded in controlling the communication between particles hundreds of kilometers apart. Until then, what was called quantum entanglement (communication between particles at a distance without any physical connection) was a mystery to science.

“The progress has been fantastic,” says Haroche, who recently visited Buenos Aires, invited by the Organization of Ibero-American States for the celebration of International Science Week. Retired from research, the French physicist and professor, former director of the physics department of the École Normale Supérieure in Paris and former director of the Collège de France was in the city with a very specific purpose: to defend research as an end in itself. in the face of the urgency of the market and the constant demand for results.

Question. Measuring individual quantum systems was a breakthrough, something unimaginable for the pioneers of quantum mechanics. What does this tell us?

Answer. It teaches us that the way we see science depends on the technology you have access to. The reason Schrödinger or Einstein said it was impossible to see was that they couldn’t design the technology we have now.

Q What doors have been opened by these investigations?

A. Our work on quantum technology was based on the idea that we could use quantum technology to accomplish tasks that are not possible according to classical physics. One example is atomic clocks, which are more accurate than those currently used on GPS systems. Another area is quantum communication using entanglement to share cryptographic keys that could not be spied on for secret communications. These fields are very active. And, of course, there’s the realm of quantum computing, which is the hardest to reach because there are a lot of challenges to overcome before it’s possible.

Q The Nobel Prize was awarded to recent developments in quantum communication. What do these achievements mean?

A. I am very happy because the investigators have been friends of mine for many years. The basic characteristics of entanglement have been explored for 40 years, trying to demonstrate what happens when photons stay connected by this intangible bond called entanglement even when they are miles away. At that time, there was no application for this experience. It took 20 years for experiments like ours to show that it is possible to manipulate isolated quantum systems. Now, quantum communication has become very fashionable and improved. Now people are going to believe it might be of some use.

Q You have very strong opinions about what we consider to be “useful” science.

A. I think it’s important to realize that things we think are done purely out of curiosity end up being useful in unexpected ways. Think of one of the big breakthroughs in this field: the laser. Its seminal idea was given by Einstein 40 years before the construction of the first one. And before the appearance of the first laser, no one believed that we would be able to connect the world using fiber optics, across the ocean with laser beams. Ten years after the invention of the first laser, we were able to communicate over thousands of kilometers using quantum repeaters. But the inventor of the laser had no idea that would happen. The laser is a result of basic science, something made possible by it and then applied to specific research later on.

Haroche, during the interview in a hotel in Buenos Aires.Silvina Frydlewsky (Silvina Frydlewsky)

Q We have heard of tremendous progress in the field of quantum computing over the past couple of years. What do you think of companies like Google or IBM who say we have achieved what they call quantum supremacy?

A. There are many difficulties to overcome. The first is quantum superposition, it’s very fragile. So far we have been able to control a few particles at a time and there are millions of particles that need to be controlled to achieve this. In my opinion, there is a lot of hype, a lot of overselling because of this competition between companies. The work they are doing is very interesting, but in the meantime there is a lot to do. This is very interesting research, but it should not be oversold. The history of science tells us that what happens in the development of new technologies and devices is often surprising and not what people were originally trying to achieve. The gap between fundamental science and application is often long and comes with many unexpected twists. We have to be careful.

Q Are companies not careful?

A. No, I do not think so. I have the impression that they are betting on being able to show a marketable product. I look at this not from the point of view of someone who needs to make a profit, I see it from a purely scientific point of view. We have to be careful because it can backfire; you can’t talk about something that will happen in two or three years, because these developments take much longer and a lot can happen along the way.

Q It’s not something we’ll be getting in our phones anytime soon…

A. No. But it also explains the great challenges that a quantum computer should be able to overcome. The phone you have in your hands right now is more powerful than the computers that monitored the first man to walk on the moon. The progress has been fantastic. The next step, bringing it to large numbers, is always much more difficult.

Haroche, after the interview.
Haroche, after the interview.Silvina Frydlewsky (Silvina Frydlewsky)

Q What has changed in the way of doing science in our century?

A. Scientists like Einstein or Schrödinger were supported, they had a good salary. It is true that research was less expensive at the time, but it has become more difficult, more expensive. And the competition between scientists has also increased; we now have tens of thousands of people vying for very limited funding. The whole system has become harder to work with. This is a problem: we need young people to invest their creativity in science, but the opportunities for them are very limited.

Q What is the role of politics in investigation?

A. Governments must understand that science is a long-term adventure. What is missing is a long-term commitment to science that should not depend on political changes. We tend to think this happens in countries with unstable political systems, but we see it elsewhere, like in the United States. Science was in terrible shape under the Trump administration, and that’s very worrying, because we need science to deal with the challenges we face today, like climate change. We need consistent policy to be strong for decades, and that cannot happen without political commitment.

Q Do you consider that science has lost its authority in today’s world?

A. Yes. Science is under threat. Scientists are challenging the truths that govern our times. But it’s a rational doubt, it’s a doubt based on challenging theory when it doesn’t explain a fact. This is why conspiracy theories are perverse: they rely on doubt based on the idea that you can challenge anything with opinions, and that opinions are as valid as theory.

Q Why is that?

A. I think the explanation must be given by anthropology or sociology, but an explanation may be that we are entering a dangerous phase of globalization, which has left people on the sidelines, feeling helpless and isolated from the developments promised to our world. So they started criticizing everything. Then you can create small communities, bubbles that share beliefs. Scientific tools are very difficult to integrate into this because science is universal, it is addressed to everyone because it is objective and rational.

Sherry J. Basler