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Physics Nobel Prize winner Serge Haroche on quantum computing: ‘There are still many difficulties to overcome’

The French physicist defends research as an end in itself, and warns that the advances announced by private companies should be taken with a grain of salt

The French physicist Serge Haroche, during an interview in a hotel in Buenos Aires, on Friday, October 21.
The French physicist Serge Haroche, during an interview in a hotel in Buenos Aires, on Friday, October 21.Silvina Frydlewsky
José Pablo Criales

One may 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 managed to trap and manipulate individual particles while preserving their quantum nature. His achievement was inconceivable. Erwin Schrödinger himself, one of the fathers of quantum physics, had stated almost a century before that working on a single particle was impossible. Schrödinger’s solution was the principle of quantum superposition: as he could not isolate and observe a physical system like the electron, he would assume that it existed in all its theoretically possible states. Thus, his famous cat came into existence: locked in a box, it was alive and dead until it could be observed. Then, Haroche came along and changed Schrödinger’s “and” for an “or.”

From the first computer to the fiber optic connection, the great technological advances of our time have become a reality thanks to quantum mechanics, and the most recent prize from the Swedish Academy, awarded on October 6, once again rewarded an advance in this field. Three physicists managed to control the communication between particles that were hundreds of miles away. Until that moment, what was known as quantum entanglement (the communication between particles at a distance without any physical link) had been a mystery to science.

“The progress has been fantastic,” says Haroche, who visited Buenos Aires recently, invited by the Organization of Ibero-American States for the celebration of the International Week of Science. Retired from research, the French physicist and professor, former director of the physics department at the École Normale Supérieure in Paris and former director of the Collège de France was in the city for 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 that teach us?

Answer. It teaches us that the way we look at science depends on the technology that you have access to. The reason that Schrödinger or Einstein said that this was impossible to see was because they couldn’t conceive the technology we have available now.

Q. What doors were opened by those investigations?

A. Our work on quantum technology was based on the idea that we could use quantum technology to achieve tasks which are not possible according to classical physics. One example is atomic clocks, more precise than the ones currently used on GPS systems. Another field 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 field of the quantum computer, which is the hardest one to achieve because there’s a lot of challenges to meet before it can be possible.

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

A. I am very happy about that because the investigators have been friends of mine for many years. Basic features of entanglement have been explored for 40 years, trying to demonstrate what happens when photons remain connected by that immaterial link called entanglement even when they’re kilometers away. At that time there was no application for that experiment. It took 20 years until experiments like ours showed that it’s possible to manipulate isolated quantum systems. Now, quantum communication has become very fashionable and has been improved. Now people will believe that it could be useful for something.

Q. You have very strong views about what we consider “useful” science.

A. I think it’s important to realize that things that we think are done only for curiosity end being useful in unexpected ways. Think about one of the great breakthroughs of this area: the laser. Its seminal idea was given by Einstein 40 years before the first one was built. And before the first laser appeared nobody believed we would be able to connect the world using optical fiber, across the ocean with laser beams. Ten years after the first laser was invented we were able to communicate across thousands of kilometers using quantum repeaters. But the inventor of the laser had no idea this would happen. The laser is a result from basic science, something made possible by it and then applied on specific research later.

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

Q. We’ve been hearing about huge steps in the area of quantum computing in the last couple of years. What do you think about companies like Google or IBM that say that we’ve reached what they call quantum supremacy?

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

Q. Are companies not careful?

A. No. I don’t think so. I feel they’re betting on being able to show a marketable product. I’m looking at this not from the point of view of someone that needs to make a profit, I see it from a purely scientific perspective. We need to be cautious because it can backfire; you cannot talk about something that will happen in two or three years because these developments take much longer and many things can happen along the way.

Q. It’s not something we’ll have in our phones anytime soon…

A. No. But this also explains the big challenges a quantum computer should be able to beat. The phone you have in your hands right now is more powerful than the computers that were monitoring the first man walking on the Moon. The progress has been fantastic. The next step, taking it to big 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 science is done in our century?

A. Scientists like Einstein or Schrödinger were supported, they had a good salary. It is true that research cost less back then, but things have become more difficult, more costly. And the competition between scientists has also become stronger; now we have tens of thousands of people competing for very limited funding. The whole system has become more difficult to work in. It’s a problem: we need young people to invest their creativity into science, but opportunities for them are very limited.

Q. What is the role of politics on investigation?

A. Governments should understand that science is a long-term adventure. What is lacking is a long-term commitment to science that should not depend on political changes. We tend to think that this happens in countries with unstable political systems, but we are seeing it elsewhere, like the United States. Science was in a very bad shape during the Trump administration, and this is very worrying, because we need science to face the challenges we are facing today, like climate change. We need a constant policy to be strong for decades, and that can’t happen without a political commitment.

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

A. Yes. Science is threatened. Scientists question the truths that govern our time. But that is a rational doubt, it is doubt based on defying theory when it doesn’t explain a fact. That’s why conspiracy theories are perverse: they are doubt based on the idea that we can defy everything with opinions, and that opinions are as valid as theory.

Q. Why is that?

A. I think the explanation should be given by anthropology or sociology, but one explanation can be that we’re going into a dangerous phase of globalization, that has left people aside, feeling helpless and isolated from the developments promised to our world. So they started criticizing everything. Then you can make small communities, bubbles that share beliefs. Scientific tools are very difficult to include in this because science is universal, it’s for everyone because it’s objective and rational.

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