Anton Zeilinger: Quantum Information

Anton Zeilinger is an Austrian quantum physicist who received the Inaugural Isaac Newton Medal from the Institute of Physics in 2008 for “his pioneering conceptual and experimental contributions to the foundations of quantum physics, which became a cornerstone for the rapidly developing field of quantum information”. In 2022, he became a Nobel Prize Winner, jointly with Alain Aspect and John Clauser for their work involving experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science

He is a professor of physics at the University of Vienna and works at the Institute for Quantum Optics and Quantum Information IQOQI.

This conversation was made in March 2020, before the declaration of the pandemic, during the guest appearance of Professor Anton Zeilinger at the Faculty of Science and Mathematics in Sarajevo.

One of the metaphysical and philosophical implications of thinking about the phenomenon of quantum physics is that we begin to wonder if coincidence is really coincidence. Einstein did not want to accept it, but today we see this strange quantum world not as deterministic but as probabilistic. However – are probability and randomness just something that we cannot fathom yet, and that there is actually some order and determinism?

Zeilinger: When we talk about probability, it is a basic concept, which the scientific community accepts, and by it we mean that there is randomness in individual events and nothing can explain randomness. I find it to be one of the most interesting phenomena of science in general.

Is it that we still don’t understand something, we don’t have knowledge of some rule, something deeper, or is it really a coincidence?

Zeilinger: The old concept of randomness is that it is some information that is still unavailable to us, or at least we cannot imagine how this information exists. For individual quantum events, the idea that there is an explanation, that there is additional information that provides an explanation, is now at odds with observations.

This simply has to be followed by the question, what is your favorite interpretation of quantum mechanics? So – not which interpretation is correct, I wouldn’t even dare to ask, but which one do you like the most and is the most convincing in your opinion?

Zeilinger: The original Copenhagen interpretation is my favorite. A good interpretation implies the use of as few or no redundant assumptions as possible. For example, if you assume that there is a particle with its properties, without making any observations, that is an example of a redundant assumption.

I was taught that the phenomena of quantum mechanics are interpreted at the level of quantum particles. However, I keep coming across people and cases who try to explain some things from our macrocosm with quantum phenomena that they just heard about. Even worse, individuals borrow terms from such a beautiful field as quantum mechanics and turn them into mambo-jumbo, charlatanism. Let’s say, an example of this is quantum medicine. Or they try to interpret telepathy with the phenomenon of entangled particles. What is your reaction to this pseudoscience?

Zeilinger: Uh, it’s very bad that quantum physics is abused like that. The point is very simple – when you don’t know something, use quantum physics terms because others don’t understand quantum physics either. I want to say something important here, because I don’t often have the opportunity to talk about it with people: sometimes when I talk to people , I say that their image, their understanding of the basics of quantum theory is too simple, naive. People are often surprised at how strange quantum physics is – it’s stranger than anything you think, imagine, it’s stranger than telepathy. A colleague of mine used to say that if you say you understand quantum mechanics, it means you have rocks in your head.

Feynman said something like that… Do you have a special metaphor, a way of explaining how you would explain the EPR paradox (op. a. Einstein–Podolsky–Rosen paradox) and Bell’s theorem to laymen? Quantum entanglement is an interesting phenomenon that when one particle changes a property, another changes it too, no matter how far away it is – Einstein did not like this idea at all because it would mean that there is something faster than light in a vacuum, but it has been proven that this phenomenon there is a. In explaining this phenomenon, do you use something familiar to people, something picturesque, which would give those who are not from this field and are not physicists some picture of the phenomenon?

Zeilinger: You can try to explain quantum entanglement to people using the story of identical twins. They are related, true twins share the same set of genes, and “quantum entwined identical twins”, when you look at them, there is no difference that defines them. They can have opposite properties, or they can have the same, but as if they are bound by some quantum umbilical cord, “quantum” genes. They can have the same quantum properties, but in opposite directions. For example, you can have twins with the same hair color – both have blonde hair or both have black hair, but in the world of quantum entanglement there is nothing that determines why they are exactly blonde or black, it is completely random.

And the most interesting part of all – people, unfortunately, are often not interested in such phenomena or distort them, but they always ask “how will it benefit humanity”. There is always this human need to put knowledge from basic science into application and we can understand it.

Zeilinger: During my lectures, I did not get that impression – people were very interested in quantum mechanics and not necessarily in the benefits of it. However, the applications of quantum mechanics and the properties of particles are certainly interesting, such things could bring a revolution for humanity. Thus, one of the applications of the quantum phenomenon of superposition states would be quantum computers, and another would be quantum cryptography. How would quantum cryptography work? I could send you the information without anyone else being able to break into our communication channel and reveal the information, because a special decryption key is needed, which only we have. This is the future, and I am very optimistic about the future and the things it brings, regardless of the current situation, the emergence of a pandemic. I believe that the future of humanity is bright.