Serge Haroche explains why Einstein refused to accept the randomness with which the smallest particles of nature are governed
Albert Einstein was outraged.
It was December 1926 and physics or quantum mechanics was taking its first steps as the science that explains the world of the smallest particles, which is invisible to the eyes.
"Quantum mechanics is awesome," the German physicist wrote to his colleague Max Born. "But an inner voice tells me that, even so, it's not true."
He added: "The theory offers a lot but does not bring us closer to the Old Man's secret. In any case, I am convinced that he does not play dice"
The famous phrase - eternally quoted but not always understood in its right context - shows how even a brilliant scientific mind like Einstein's could not conceive that, At the scale of atoms and subatomic particles, the world was weird and unpredictable.
In 1935 the Austrian physicist Erwin Schrödinger explained one of those strange behaviors elaborating what is today the most famous metaphor of quantum physics: that of the cat in the box.
His mental experiment consists of enclosing a cat with a radioactive atom, which has a 50% chance of disintegrating and emitting a poison that will kill it. After a while, the cat is alive and dead at the same time, an unthinkable ambiguity in our daily life.
"The way nature behaves on this scale It looks strange because it is different from what we are used to in the macroscopic world that surrounds us"Says the French physicist Serge Haroche to BBC Mundo.
It is that, he continues, "quantum physics describes a microscopic world for which we do not have a direct intuition".
Haroche is clear: since he won 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 Prize Dialogue" organized in Santiago de Chile by the Nobel Foundation itself, talked about how the award changed his life, how it is to study the "cat" of Schrödinger in the laboratory and the importance of quantum physics even with the disapproval of Einstein.
What do you think of Einstein's famous phrase of what God does not play dice with the orniverse?
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, to 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 disgusted Einstein. And not just Einstein: Schrödinger was not comfortable with these aspects of quantum physics either.
But history has proven that, in this respect, God is effectively playing dice. So far, there is no single experiment that contradicts the fact that quantum physics includes randomness.
¿it's possible that the world on an atomic and subatomic scale random because not enough is known yet about him and what, sometime, science unveils a series of predictable rules like those of the world that we see in everyday life?
I think randomness is here to stay. In quantum physics there is no way you can predict with certainty what is going to happen. But that does not mean that we can not be sure of some things: we know that if we take certain measures, we will always obtain the same result. It also does not mean that you can not do very precise things. In fact, atomic clocks, which measure time with fantastic accuracy, operate according to the laws of quantum physics.
It is a theory that has registered the randomness and, at the same time, allows to take measures that are much more precise than those of classical physics. This is a paradox of quantum physics that makes it fascinating.
As a scientist, how does it make you feel this randomness?
Of course it feels weird, but I think it's because our intuition is linked to our evolution.
Our brains are the result of evolution for thousands of generations, in which we have been exposed to the macroscopic world. Then we have an intuition about what will happen if, for example, an object is falling and how to protect yourself from being hit in the head by it. This obeys the laws of classical physics.
Instead, we are not used 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 that we know work. This gives us another kind 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 other way around, it 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 fight.
Since it goes against intuition, How do you usually explain why you won the Nobel Prize in Physics in 2012?
(He laughs.) It is still difficult to explain. For the past 30 years, not only me but many physicists have been trying to learn to manipulate and measure isolated quantum systems, that is, 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 from it.
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 lasers that allow manipulating 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 for it. We are just two people who represent a large community of researchers from around the world who are doing this type of experiment.
For decades, scientists have known that isolated particles behave strangely, but they could not observe them in the laboratory. However, you managed to create an experiment that for the first time allowed to see the "cat" of Schrödinger decide if he was alive or dead. How was it possible?
A quantum system can exist in a superposition of states. In the metaphor of Schrödinger's cat, the superposition 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 classical realities.
Of course this does not work for systems like cats because it happens in very very short times. But we can observe this type of phenomena if we manipulate much smaller systems, which are not formed by "gazillion" atoms, but by just a few atoms or a few photons. Then you can prepare this type of superposition and study how the quantum characteristics of the superposition are lost as time passes. This is exactly what we did.
We managed to trap in a box a field formed by a few photons and prepare this field in a quantum superposition of two states, which we call using the metaphor of the living and dead state. Then, we studied how, after a short period, the system had to decide if it was alive or dead and not both at the same time.
This evolution from quantum to classical physics is called quantum decoherence. What it does is transform 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.
¿There is some practical application for this discovery?
Whether it is useful or not is still an open question. The field of quantum technology is expanding very fast nowadays. There are people trying to use or take advantage of quantum particles to do 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 it happened with other aspects of quantum physics that led to the development of lasers, GPS and computers that we use today, for example.
People like to call this "the second wave of the quantum revolution", but at the moment it is still very uncertain. Many of the things that we are thinking will happen, will not happen, but many others that we are not even imagining, will come true. This is what has always happened in the past. Scientists open new avenues and unexpected surprises are often presented.
Was the cquantum omputation a surprise for you?
When I started researching, I was just fascinated by the challenge of trying to manipulate a quantum system and find out how nature would behave. But back then, some people did not think we would be able to do it. Schrödinger himself said in the 1950s that we could never achieve this because it was necessary to manipulate isolated atoms for that, and he thought that it would always be in the domain 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 I was fascinated by the perspectives I opened to 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.
Then, in the 90s, 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 the experiments with a single atom were already too 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, which demonstrate the basic steps of a computer operation, but we still do not know how we could increase it to the size of a computer that does real tasks.
For me it is fascinating how in science the result is mostly unpredictable. The only sure 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, the tomographies or images by magnetic resonance (MRI), that allow to take images of inside of our body with a fantastic precision and that are used by doctors of all parts of the world, are an application of the magnetic nuclear resonance. Those who invented magnetic resonance in the 1940s were surprised when, 20 years later, it led to the creation of the MRI machine. Is that, for that, not only should you have magnetic resonance, 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 foreseen when the first experiments were made.
¿This is what this will be about the talk "The usefulness of useless knowledge" that will give in Chile?
What we call "useless" is the science that is driven by curiosity and the "useful" is the one that leads to an application and devices. What we say is that it is wrong to oppose this type of sciences: there is no way to have practical or "useful" applications if you do not do basic or "useless" science before. The science that moves only because of the need to increase knowledge is very important because it is at the base 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 can have societies that are 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 this is very important.
¿How did his life affect the win the Nobel prize?
It affected my life in many aspects, because I became someone who is wanted by the media and I receive many requests. They invite me to give talks and lectures, and I travel followed by the world. But I'm not complaining because I like to meet people, travel and give talks, especially to high school students, because I think it's very important.
In addition, I am formally withdrawn from the College of France, so I no longer have to teach weekly. If it was not for the Nobel, my life would be much calmer at this time, of course.
Thanks to the Nobel Prize, I was also able to maintain my laboratory at the Collège de France and my colleagues are working very hard to continue this type of research, and I try to be in touch with them and know what they are doing. I participate in the investigations through the writing of papers. I am very active, which certainly was made easier by the Nobel recognition.
¿Y how was that moment when he found out that he had won the Nobel?
It was the end of the morning in Paris and I was walking down the street, when I get a call and I see that the country code was from Sweden. Then I thought: "Either it's a bad joke or it's an important event". It was the second one.
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