June 26, 2022

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What does light teach us about space and time, as explained by the Nobel laureate who trapped it?

Segre Haroche, 77, says he felt the need to reconsider at the end of his career. He led a team of physicists in Paris who were able to measure light, literally, by confining it to a box, which earned him the Nobel Prize for Physics in 2012. La Sapienza chose it to keep Enrico Fermi Chair Lecture CourseEach year, it is entrusted to a distinguished international scholar who has made a significant contribution to specific areas of research. To tell the light, which positioned itself a little at the end of the story, it began anew, starting with Italy and Galileo, to reach quantum computers. at Lectures15 in total, from January 27 to May 12, also online on Zoom, showing everyone, not just students and colleagues, the research wonders that have led to the technological revolutions of recent decades.

He arrived in Rome a few months after the award of the Nobel Prize in Physics to Giorgio Baresi. What do you think?
“I was very happy. I think it is a good appreciation of what La Sapienza and Italy have given to science in general in the modern era. In my class there are great pictures of Amaldi, Fermi and even Galileo. But I think that countries like Italy and France do not invest enough in research and basic science and I’m sure That Giorgio Baresi highlighted it.”

Where does the science of light begin?
“When people began to ask profound questions about the nature of light, that was the period in which modern science was born. The seventeenth century was the century of Galileo and Newton. They led to the modern scientific method, observation, experiments, theory and predictions of new influences. It is the virtuous circle between experiment and theory. that have continued together ever since.In the 19th century, new questions led to the theory of relativity and quantum physics.Deep questions about light were the starting point for theories that revolutionized our lives, not only because they led to better understanding, but also because they led to tools New, new devices, like lasers, started my career when they were invented 60 years ago. Unusual technology.”

What does light and gravity represent for modern science?
“Light and gravity are the first things that a child notices, gravity is because things fall, and light is because it is thanks to it that we communicate with the world. And what is incredible is that we do not fully understand it yet, it is still there. the difference Between the deep levels of quantum physics and general relativity. Modern research is moving towards combining these two aspects.”

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What taught us the light in understanding the world?
“On a deep level, we have learned that space and time are mixed together, it is impossible to take into account the three dimensions of space separated by time, until we live in a four-dimensional space. When gravity is added to the problem, space becomes curved and light scattered along curved lines. But this was only understood since A century ago. And before that there were other questions. Light taught us that electricity and magnetism are closely related and that light is an electromagnetic wave. This led to their unification, 150 years ago, with Maxwell. Using light, once realizing that its speed was limited, it was possible to measure the size of the universe.”

What, in your opinion, are the great visions of the history of light science?
“I think one of the great ideas was that of Pierre de Fermat, a seventeenth century scientist, in the time of Descartes and Pascal. He said that light propagates on a line that takes the shortest time from one point to another, so it is in a straight line. But if it goes from air to water. , it bends because it “prefers” to go through air, where it is faster. It was a wonderful intuition: the assumption that light travels slower in water than in air. Another gentleman who had a wonderful intuition of course was Einstein who based the entire theory of relativity on the fact that The speed of light is the same for everyone. But to tell the truth, the intuition of relativity is derived from Galileo, who had it not for light but for the mechanics of bodies if you were on a ship (traveling at a constant speed soYou have no way of knowing if you’re moving, because experiences don’t tell you.”

Difficult and counterintuitive concepts, from relativity to quantum physics, how are they told to a non-specialist audience?
“You have to use metaphors and analogies with known phenomena that people might know. To understand relativity, you have to describe simple experiments, which give results that are counter-intuitive but you have to prove that they are true. For example, a so-called ‘twin paradox’, a twin who leaves and returns at a younger age. Who left it on Earth. In Einstein’s time it was hard to make him understand. Now we do experiments every day that prove it true. Atomic clocks of GPS systems around the Earth are going slower for this effect. And if this is not taken into account, GPS will not work ” .

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We come to the studies that earned her a Nobel Prize. Did you “touch” the light?
“The paradox of light is that when you see it, that light is dead because the photons are damaged when they receive the information, and it turns into a chemical reaction in your eyes. What we were able to do in Paris with my team is detect the light without destroying it, and measure the same photon over and over, and this might have Interesting applications of quantum information”.

There has been a lot of talk about applications on quantum supercomputers. Based on your research, do you see progress ten years after the Nobel Prize?
“The fact that a quantum system can be in several states at the same time, in a state of superposition, implies different realities, which leads us to the famous Schrödinger cat metaphor. What we have achieved in the laboratory are small copies of this system. If we could do that. To use this phenomenon on a large scale, we will be able to get calculations much faster than a normal computer, but the difficulties are many, one of them is decoherence, the fact that these quantum systems are very fragile and lose these properties very quickly.We have been working on this for ten years, And I’m not sure if we can build a quantum computer for practical use in the near future.

On the other hand, there are other systems such as quantum simulators, made up of a few dozen atoms or particles, which can be useful for example to obtain superconductivity at high temperatures, or to synthesize new molecules to produce new drugs. He used these counter-intuitive properties of cryptographic communications and quantum cryptography. You can also make systems sensitive to very small perturbations, or probes that can measure magnetic or gravitational fields with greater sensitivity. This is the New quantum technologyOur search was from the starting points.”

For what applications?
“If he had asked Einstein a hundred years ago about the applications of relativity, he wouldn’t have been able to predict GPS. Or lasers. The people who made the greatest discoveries weren’t very familiar with the applications, and they had never overstated the predictions…I think I will follow suit.”

However, quantum computers seem to be one step away. Isn’t that so?
“Maybe one day there will be one of these computers but it has to be kept protected in a chassis, and that’s only possible in some places in the world. It’s never going to be a laptop, but I might be wrong. It tells the story of an IBM CEO who argued over the course of forty year that there will be room for at most five computers around the world.”

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The Sapienza chair for which he will hold his lectures is named after Enrico Fermi. Scientific discoveries on light led to great technologies but also to the construction of weapons, the most powerful of them, such as the atomic weapon. Do you think humanity is more mature now than it was a few decades ago?
“I don’t think humanity is more mature. When you have power, it can be used to build weapons. Einstein was a pacifist, and yet he signed the letter to Roosevelt that started the Manhattan Project because it was important at the time that the allied forces were stronger than the Nazis. But Science is neither good nor bad, what you do with it is good or bad. For example, those who refuse to look for GMOs or mRna vaccines, because they are “not natural”, are wrong. You must gain knowledge and then decide how to use it. You can never Prevent humanity from feeling curious and knowledgeable Fermi, Curie, physicists of the last century were curious to understand nature and they did, they opened a kind of Pandora’s box What we said about weapons may also be true for the Industrial Revolution We’ve used oil and gas for more than a decade and now We are at risk from the climate and that is also the effect of science.”

Doesn’t seem optimistic
“I think we need to understand what the real progress is and we need to point the science in the direction of the problems we need to solve. And so we need more research and resources. We need to find an alternative to fossil fuels. I think we need nuclear power, because we won’t have enough.” From electricity to replace fuel cars with electric ones. The sun is not always there and the wind does not always blow. But to discuss all this, I note that it is not done on the basis of science but on the basis of ideologies. I am not optimistic because I see that many do not look at problems in a rational way, and the development of Fake news and conspiracy theories go in the opposite direction.”