Thursday , July 29 2021

Serge Haroche: Einstein was wrong: "God is effectively throwing dice" in the quantum universe

Serge Haroche explains why Einstein refused to accept the randomness with which the smallest particles of nature are governed

Albert Einstein was indignant.

It was December 1926, and physics or quantum mechanics took their first steps as the science that explains the world of the smallest particles, invisible to the eye.

"Quantum mechanics is incredible," wrote the German physicist to his colleague Max Born. "But an inner voice tells me that, even then, it is not true."

He added, "The theory offers a lot, but it does not bring us closer to the old man's secret." In any case, I'm convinced he does not play dice"

The famous phrase – eternally quoted but not always understood in its correct context – shows how even a brilliant scientific mind like Einstein's could not conceive of this, On the scale of atoms and subatomic particles, the world was strange and unpredictable.

In 1935 the Austrian physicist Erwin Schrödinger explained one of these strange behaviors by elaborating what is now the most famous metaphor of quantum physics: that of the cat in the box.

His mental experience is to surround a cat with a radioactive atom, which has a 50% chance of disintegrating and emitting a poison that will kill him. After a while, the cat is alive and dead at the same time, an unimaginable ambiguity in our daily life.

Serge Haroche

Getty Images
Nobel Laureate Serge Haroche will give a lecture and will participate in several panels this Saturday in Santiago, Chile, as part of the conference "Nobel Prize Dialogue".

"The way nature behaves on this scale It seems strange because it is different from what we are accustomed to in the macroscopic world that surrounds us"Says French physicist Serge Haroche for BBC World.

That is, he continues, "quantum physics describes a microscopic world for which we have no direct intuition."

Haroche is clear: since winning the Nobel Prize in Physics in 2012, he travels the world trying to explain this counterintuitive reality.

The 74-year-old researcher, who This saturday participates of the conference "Nobel Laureate" organized in Santiago de Chile by the Nobel Foundation, talked about how the prize changed his life, how to study Schrödinger's "cat" in the laboratory and the importance of quantum physics, even with Einstein's disapproval.

What do you think of Einstein's famous quote from what God does not play dice with youdiverse?

Einstein did not speak of God in a religious sense, but for him God was a metaphor for nature. What he meant was that the laws of nature could not have an intrinsic randomness, which Born famously replied that who he was to say what God plays.

The phrase reflects the fact that the lack of determination of quantum physics was something that displeased Einstein. And not just Einstein: Schrödinger also did not feel comfortable with these aspects of quantum physics.

Dice on a violet background.

Getty Images
Einstein also wrote to Born: "You believe in God who plays dice and I believe in the law and the total order of a world that is objective."

But history has proven that, in this regard, God is actually throwing dice. So far, there is no single experiment that contradicts the fact that quantum physics includes randomness.

TheIt's possible that the world on atomic and subatomic scale because we do not know enough yet. about him what, someday, science reveals a series of foreseeable rules like the ones we see in everyday life?

I think randomness is here to stay. In quantum physics, there is no way to predict with certainty what will happen. But that does not mean that we can not be sure of certain things: we know that if we take certain measures, we will always get the same result. Nor does it mean that you can not do very precise things. In fact, atomic clocks, which measure time with fantastic precision, operate according to the laws of quantum physics.

It is a theory that has registered randomness and, at the same time, allows taking much more precise measures than those of classical physics. This is a paradox of quantum physics that makes it fascinating.

As a scientist, how does this make you feel this randomness?

Of course it sounds strange, but I think it's because our intuition is tied to our evolution.

Our brains are the result of evolution for thousands of generations, in which we have been exposed to the macroscopic world. So we have an intuition about what will happen if, for example, an object is falling and how to protect itself from being hit in the head by it. This obeys the laws of classical physics.

Instead, we are not accustomed to understanding what happens when an atom disintegrates, so we have to try to disconnect from our basic intuition and apply the equations of quantum physics we know as work. This gives us another type of intuition, a mathematical intuition, an intuition about what will happen if we do an experiment.

In fact, this is something that happens in science at all levels. As science progresses, it can cause events that are rare and that are opposed to popular wisdom. When Copernicus said that it was not the Sun that revolved around the Earth, but the opposite was a very difficult idea to accept on a general level and Galileo had a very bad experience trying to convince the Pope of it.

Fighting against false intuitions and false illusions is part of science, and in quantum physics the illusion of determinism is an important aspect of the struggle.

Since it goes against intuition, How do you usually explain why you won the Nobel Prize in Physics in 2012??

(He laughs) It's still hard to explain. In the last 30 years not only I but many physicists have been trying to learn how to manipulate and measure isolated quantum systems, ie how to work with them, how to put them into different types of quantum states, how to put them to interact and see what results this.

David Wineland and Serge Haroche

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David Wineland and Serge Haroche won the Nobel Prize in Physics in 2012 for developing innovative experimental methods for measuring and manipulating individual quantum systems.

These types of experiments that juggle isolated quantum systems have been possible thanks to the development of new technologies, such as lasers, in particular a type of high precision laser that allows the manipulation of atoms. This is where the Nobel Prize comes in: along with my friend (the American physicist) David Wineland, we won by representing two ways to achieve such manipulation.

Many other people could have won the Nobel Prize for it. We are just two people representing a large community of researchers from around the world who are conducting this type of experiment.

For decades, scientists know that isolated particles behave strangely, but they can not observe them in the laboratory.. However, you were able to create an experience that for the first time allowed you to see the "cat" of Schrödinger decide whether he was alive or dead. How was it possible?

A quantum system can exist in a superposition of states. In Schrödinger's cat metaphor, overlap would be a situation in which the cat could be alive and dead at the same time. So to speak, he would be "suspended" between these two classic realities.

Of course this does not work for systems like cats because this happens in very short times. But we can observe this kind of phenomena if we manipulate much smaller systems, which are not formed by "gazillion" atoms, but only by some atoms or some photons. Then you can prepare this kind of superposition and study how the quantum characteristics of the superposition are lost over time. That's exactly what we did.

Illustration of cat Schrödinger

Scientific Photo Library
Haroche's projected experience with lasers allowed him to see Schrödinger's "cat" and decide whether he was alive or dead for the first time in history.

We were able to trap in a box a field formed by some photons and prepare this field in a quantum superposition of two states, which we call using the metaphor of the living and dead state. So we studied how, after a short period, the system had to decide whether it was alive or dead and not both at the same time.

This evolution from quantum physics to the classical one is called quantum decoherence. What she does is to turn the letter "y" into the word "o", so the cat is no longer alive and dead, but alive or dead. The study of decoherence was, then, one of the most important points of our investigation.

TheIs there any practical application for this discovery??

Whether it is useful or not is still an open question. The field of quantum technology is expanding very rapidly today. There are people trying to use or take advantage of quantum particles to perform useful tasks in communications, computing, and measurements. There are advances in many directions, but it is difficult to know which of these advances will lead to widely used inventions, as happened with other aspects of quantum physics that led to the development of lasers, GPS and computers we use today, for example.

People like to call it "the second wave of the quantum revolution," but at the moment it is still very uncertain. Many of the things we are thinking will happen will not happen, but many others that we do not even imagine will come true. This is what has always happened in the past. Scientists open new avenues and unexpected surprises are often presented.

Schrodinger dictating a class around 1950.

SSPL / Getty
Schrödinger believed that science would never be able to manipulate isolated atoms and that therefore quantum physics would not be studied in the laboratory.

It was cquantum omputation a surprise for you?

When I started researching, I was fascinated by the challenge of trying to manipulate a quantum system and discover how nature would behave. But back then, some people did not think we would be able to do that. Schrödinger himself said in the 1950s that we could never achieve this because it was necessary to manipulate isolated atoms for this, and he thought it would always be in the realm of imaginary experiments and not in the laboratory.

But Schrödinger died in 1961 and, in the 1960s and 1970s, the laser was developed. At that time I was a young researcher and was fascinated by the perspectives I opened for the laser. And I realized that it would indeed be possible to manipulate isolated atoms. But I had no idea that I could derive a quantum computer.

So in the 1990s, some people began to speculate that the quantum computer could be the result of this type of research. At that time I was skeptical because I realized that experiments with a single atom were already very difficult and to operate a quantum computer, you would have to manipulate millions of atoms at the same time.

This is still a challenge today, 20 or 30 years later. We are playing with small systems that demonstrate the basic steps of a computer operation, but we still do not know how we can increase it to the size of a computer that performs actual tasks.

For me, it is fascinating how in science the result is unpredictable. The only certain thing is that you will never have an application and technology if you do not have basic science before if you do not understand the phenomenon. What will happen next we do not know and there are many examples of this in modern science.

For example, CT scans or magnetic resonance imaging (MRI), which allow images to be taken from within our body with fantastic accuracy and used by doctors from all over the world, are an application of nuclear magnetic resonance. Those who invented magnetic resonance imaging in the 1940s were surprised when, 20 years later, they led to the creation of the MRI machine. For this, not only must you have magnetic resonance imaging, but also high magnetic fields, which were not possible at that time, and you should have computers, which did not exist.

All this is the result of a combination of basic science developed by different scientists in different areas and that crystallized in this machine in a way that could not be predicted when the first experiments were done.

TheThis is what this is going to be about O speaks "The usefulness of useless knowledge" that will give in Chile?

What we call "useless" is science that is driven by curiosity and "useful" is the one that leads to an application and devices. What we are saying is that it is wrong to oppose this kind of science: there is no way to have practical or "useful" applications if you do not do basic or "useless" science before. Science that moves only because of the need to increase knowledge is very important because it is at the basis of civilization.

Nowadays many people are talking about "alternative facts" and "post truth", and these are things that science opposes. The values ​​of science are the values ​​of truth, and if you teach them through education, you may have societies less likely to follow people who simply lie all the time.

Basic science may seem useless, but it creates an atmosphere where the values ​​of truth survive and that is very important.

TheHow your life affected to win the Nobel Prize?

It has affected my life in many ways because I have become someone who is sought after by the media and receives many requests. They invite me for lectures and lectures, and I travel the world followed. But I'm not complaining because I like meeting people, traveling and lecturing, especially for high school students, because I think it's very important.

Moreover, I am formally withdrawn from the College of France, so I do not need to teach on a weekly basis. If it were not for the Nobel, my life would be much calmer now, of course.

Thanks to the Nobel Prize, I have also been able to keep my laboratory at the Collège de France and my colleagues are working hard to continue this type of research, and I try to get in touch with them and know what they are doing. I participate in the investigations by writing documents. I am very active, which was certainly facilitated by the recognition of the Nobel.

TheY how was that moment when he discovered that he had won the Nobel?

It was the end of the morning in Paris and I was walking on the street when I got a call and I saw that the country code was from Sweden. So I thought, "Either it's a bad joke or it's an important event." It was the second.

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