Common sense is useless in the world of the extremely tiny, where the rules of quantum mechanics apply. One of the most striking differences is that two particles such as two photons of light can be entangled in such a way that what happens to one determines what happens to the other, even if they are very far apart. This is what Einstein, a skeptic, called ghostly action at a distance. The 78-year-old physicist Anton Zeilinger, born in the Austrian town of Ried im Innkreis, has spent a quarter of a century proving that the most absurd predictions of quantum physics are correct. Just over a decade ago, his team managed to teleport a quantum state between two photons of entangled light. One photon was on La Palma and the other on Tenerife, both part of Spain’s Canary Islands. There were 89 miles (143 kilometers) between them.

Zeilinger, of the University of Vienna, won the 2022 Nobel Prize in Physics for teleporting information and pioneering exponentially faster and safer quantum computers. The Austrian physicist sat down for an interview over coffee on the terrace of a Valencian hotel overlooking the Mediterranean, during a break from his activity as a jury member of the Rey Jaime I Awards, which recognize achievements in research and entrepreneurship.

Request. You first heard about quantum entanglement at a conference in 1976. What do you think?

Answer. I did not understand what was happening. I just realized it must be interesting.

Q. How do you explain entanglement to people who have no experience in this field?

A. None are completely unprecedented. The entanglement of two particles is like having a pair of dice. The three is rolled on one die and the three on the other. If one die shows six, the other also shows six. And the same number always comes up on both dice.

Q. Einstein said that God does not play dice.

A. I believe God puts the numbers so that we believe He plays dice, but He doesn’t play dice. God says: now it’s three, now it’s two, now it’s six. And we believe that God plays dice.

Q. In your Nobel lecture, you said that not even God knows what information is in the particle.

A. Maybe he knows. Or maybe not. We can’t know.

Q. Do you use God as a metaphor or do you believe in God?

A. YES. Why not believe? The famous Isaac Newton has published books on many subjects, but he has written far more on religion than on physics. He was a religious person.

Q. Two entangled particles can be thought of as twin brothers who behave similarly at a distance because they share the same DNA, but that’s not how it works.

A. In entanglement, the two quantum brothers behave the same way, but without DNA.

Q. It’s more than counterintuitive. It’s crazy.

A. It’s crazy, yes.

Q. Einstein defined entanglement as a ghostly action at a distance. Does it look spooky to you?

A. Einstein used the German word geisterhaft, which means something like spiritual. It is a phantasmagorical phenomenon if one tries to explain it with the usual rules. But in quantum physics, you know how this works.

The Teide observatory in Tenerife, during Anton Zeilinger’s experiment in 2012.Austrian Academy of Sciences

Q. In your Nobel lecture, you projected a question onto the screen: Is the Moon there when no one is looking at it? What is your answer?

A. The important thing is that to demonstrate that the Moon exists, you have to look at it. If you don’t look at it, you can only use your own experience and logic to say there is. But, with quantum particles, you can’t tell the system is there if no one is looking. Einstein asked: Do you really believe that the moon is not there when nobody is looking at it? AND [Danish physicist Niels] Bohr replied: Can you prove otherwise? Can you prove that the moon is there when no one is looking? And no, you can’t.

Q. Niels Bohr said: It is a mistake to think that the task of physics is to find out what nature is like. Physics deals with what we can say about nature.

A. I would go one step further and say: what can be said about nature, in principle, also defines what can exist. So nothing can exist without the ability to say something about it.

Q. What is reality then?

A. In physics, we have always made great progress without answering the question of what it is. We just answer the question of what can be measured and how can we observe something. We can observe reality, we can make measurements, but I don’t think we can say anything about the essence of reality.

Q. You are a Christian?

A. Yes, I was raised Catholic, but my mom was Protestant, so I learned from both. Sometimes I went to Protestant church with my mother and sometimes to Catholic mass with my father. It was interesting.

Q. When you see this world of particles doing crazy things, how does that crazy fit with the idea of ​​an organized God?

A. The Jesuit theologian and philosopher Karl Rahner said: The Christian of the future will be a mystic or he will not exist at all. I agree. It cannot be said that God is organized or is like this or like this. God is not subject to our definitions.

Q. Perhaps God does not exist without the gaze of the observer.

A. It’s another kind of observation: it’s not with the eyes, it’s an observation with the soul.

Q. After your experiment in the Canary Islands, you said that information teleportation plays a vital role in the vision of a global quantum internet, providing secure communications without restrictions […] and an exponential increase in computational speed. When will we see these promises kept?

A. Good question. As for when we will have full quantum computing, we don’t know. In fact, today I would be more cautious with my statements, because the challenge is enormous. In small quantum computing systems there is a lot of work going on, but for large computers there is still a lot to do.

Q. Google is already making big announcements about upcoming quantum computers.

A. They have a quantum computer, but it’s small and can only be used for very specialized problems, not more general problems. To have a complete quantum computer, about 1,000 quantum bits are needed. And now we are talking about systems with 30 or 50 quantum bits.

Q. In a 2010 interview you predicted that in 15 or 20 years we would have an interesting quantum computer.

A. Yes, I would say the same today [laughs]. It is impossible to talk about 20 years from now.

Q. You also said, perhaps provocatively, that in the future we will have quantum computers on cell phones.

A. It will be in 50 or 100 years. I didn’t say it to provoke, but to challenge. When the first computers were built, they were huge and took up an entire room. And then no one thought that you could have it on a mobile phone.

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