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Professor Ryszard Horodecki – from hand-built radio to quantum cryptography

Professor Ryszard Horodecki – from hand-built radio to quantum cryptography

Faculty of Mathematics, Physics and Informatics
Prof. Ryszard Horodecki

I’d like to ask you to share your memories of how your interest in physics began.

Those roots are, I think you could say, very complex. My fascination goes back to the end of the Second World War. As a young boy, my first contacts with physics were in a ‘landscape after battle’ in the Sopot forests


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I’d like to ask you to share your memories of how your interest in physics began.

Those roots are, I think you could say, very complex. My fascination goes back to the end of the Second World War. As a young boy, my first contacts with physics were in a ‘landscape after battle’ in the Sopot forests. A periscope taken from a tank demonstrated the laws of optics. Electronics was glaring out of the radios of German vehicles. These included NF2 lamps. My brother, who was seven years older than me, was building a radio. Some of the elements I brought to him with great pride. The radio was a five-lamp model and only one speaker lamp was bought in a shop. It picked up Radio Free Europe. That’s when my physics began. The lab was in the kitchen, that’s where the soldering iron was and where it smelt of flux – that was the beginnings of the physics experiments. We lived in very humble conditions. We had escaped from the eastern borderlands before the Red Army, first to the General Government and later to Sopot, so my parents couldn’t afford to send me far away to study physics. It didn’t exist in Gdańsk. I followed my brother’s footsteps to the Technical University of Gdańsk and the Department of Communications, later the Department of Electronics. It was purgatory for me until my maestro Professor Mościcki created a technical physics section. It was because of Professor Mościcki and my brother that I knew I would become a physicist. Gdańsk already had a Higher School of Pedagogy at the time, where my older brother worked. Once he suggested, “Listen, maybe you’d like to work in the countryside a bit, there’s a little village there, pretty quiet too”. So I chose that school and later the University was founded in 1970, where the first rector, Professor Sokołowski, played such an outstanding role.

At the time, owning a hand-built radio was dangerous.

There were unpredictable consequences at the time, even for the whole family. I admire the courage of my parents. They got it from the tough life in the borderlands, particularly during the occupation. You also have to remember the dangers in those early days. Once at a name-day party when trying to demonstrate an electric motor to my cousins, I clutched both brushes. By some miracle I escaped. Like all my peers I took shells apart and demonstrated rockets of my own construction in the garden.

To a great extent, my choice was dictated by the atmosphere at home. Mum, although a humanist by education, was fascinated by the great names of science – Fleming, Einstein and Pasteur. She read a lot on the subject. There were big biographies of them on the desk beside the classics. I could reach out for them. Father represented the exact sciences. It was him who presented me with Pelerman’s Physics Can Be Fun. All of this decided my interests. There was also the inner signals. I knew that I wanted to investigate the mysteries of nature and pry into its beauty in the hope that there might be some blank spots on its strange map. Much later, after the fall of the Iron Curtain, I had the good luck to be there at the beginning of the discipline, which still had no name and was arousing extraordinary interest, a process which is continuing. Although I’d never encouraged them into physics, my sons, as students, later went down the same route, so it turns out we can make a family team.

Can quantum physics, your specialisation, be applied to everyday life?

Our minds are not adapted to penetrating nature in its entirety, in its deepest resources. By sheer luck two men, Heisenberg and Schroedinger, discovered the quantum ‘Rosetta Stone’, analogous to the stone discovered in Rosetta by Napoleonic troops. This curious inscription ‘revealed itself’ in Hilbert’s abstract mathematical language of space. Our ‘classical’ mind even today is unable to interpret it. But what is important is that the quantum inscription is the instructions, a set of rules which define how we predict probability in the results of future lab measurements. So at the fundamental level Nature is indeterministic. This was the most radical divergence from the classical (deterministic) picture of the world in which the Newton-Einstein law allowed us to explicitly determine future events at any given time based on knowledge of past events. The world had become more uncertain than certain. On the other hand, the inscription predicts the existence of quantum correlations (entanglements) between distant particles, which, as John Bell has proved, cannot be explained by assuming that nature has all its properties before the measurement and that the process of measurement in one laboratory does not distort measurements in another, distant, laboratory. This fascinating phenomenon, quantum entanglement, has occupied our minds for many years. In 2009, we wrote a critical review for the prestigious American journal Reviews of Modern Physics called “Quantum Entanglement” – a handbook of sorts, which is used by the present generation of scientists all over the world who are occupied with quantum correlations (the article has been cited more than 1,500 times).

To finish with, let us mention yet another peculiarity of quantum inscription, i.e. one that predicts the existence of quantum information, which, as opposed to classical information, cannot be copied. This time we know for sure that life is inextricably bound with the copying (auto-replication) of DNA but the quantum world forbids such things. So if the quantum inscription is true, and so far we have no reason not to believe this, the fundamental question arises as to how to reconcile this inconsistency. The outstanding Polish physicist Wojciech Żurek, who for decades has been working in Los Alamos, attacked this paradox with great success, although his results were not completely clear. Working as a team in Gdańsk on Żurek’s idea, we managed to formulate mathematically , to prove, that in the quantum world there exists a minute path, called decoherence, which disrupts quantum information and spreads it ‘classical skeleton’ out into the surroundings. This implies the existence of incredibly subtle paths towards the creation of life.

Centuries ago, there was no division into branches of science and only later came physics with Newton and Einstein, electricity and the atomic bomb. Then physics evolved into quantum physics, which only a few people in the world understand and yet, paradoxically, is this physics closest to the original source?

First came the physics of Aristotle. The breakthrough started with Copernicus and Galileo, the latter of whom conceived a mathematical project which Nature was supposed to follow. And he succeeded.  In the Torricelli vacuum the metal ball and the feather fall at the same rate. Later there was the physics coded in the equations of Newton and Einstein. But as I said, these were deterministic descriptions of nature. Probability, if it came into the description, only showed our ignorance. It was not ontological in character.

And all this ‘divine harmony’ fell apart with the phenomenon which our ancestors experienced when they were baking bread and assessed the temperature of the oven by the colour of its walls. This is to do with the phenomenon of the radiation of a perfectly black body. In order to describe it, Planck had to assume, against the rule of Leibnitz, that Nature does not leap and that energy is quantised.  And so the tip of the quantum world revealed itself to us. The notion of quantum, indeterminism and the Born formula appeared. One can only envy the Renaissance scientists whose pride was symbolised by Laplace's demon. 

Such people are hard to come by these days, as our knowledge of the reality of physics has shown the immense ground still to be covered and, what is more, we have trouble bringing together two theories - the quantum inscription and Einstein’s theory of gravity. So far, despite the  great efforts of many excellent scholars, there is still no way of connecting these two great theories.

At the same time, quantum inscription teaches us that new resources exist in nature, e.g. quantum correlations (entanglement). These allow us to carry out tasks such as the secure transference of information with the aid of quantum cryptographic key, in a way protected by nature itself. The principles of Heisenberg’s Uncertainty Theory defend cryptography. While we don’t understand the quantum world, we can happily use it to our advantage to control several processes, thanks to which we move forward.

Your fascination with science has come full circle. At first there was fascination with unexploded bombs which remained after the war and now you specialise in physics which lays mines and then blows up the foundations of the popularly known classical physics. 

No new theory should completely “blow up” a previous theory. This would defy the logic of the development of world description. Each consecutive description is more isomorphic (similar) to the laws of Nature i.e. it describes a larger class of physical phenomena than its predecessor. A great number of phenomena in quantum physics cannot be explained by classical physics and it is only in this sense that the new quantum physics “blows up” classical physics. It is worth noting that gravity has so far not been conquered by quantum mechanics. This is good and beautiful. Science is not ending and there are still many generations of work, fascinations and discoveries ahead of us.

Even your hobby is so contrary. You didn’t call your volume of poetry Cogito ergo sum but the other way round - Sum ergo cogito.

The Cartesian formula cogito ergo sum seemed rather contrary to me. First the gift of existence, and then thinking. I have lost consciousness, I am not thinking, but I exist. Well, man is to some extent integrum humanum, with a great number of potential space. I work as a physicist but at the same time I am enchanted by the magnificent world of art, masterpieces, the venerable pageant of the giants of poetry, starting from the Roman ones, through Shakespeare, Mickiewicz and Słowacki, to Herbert, Miłosz, Szymborska and Tranströmer, all this  casts a spell which one finds hard to resist. I was torn in this respect, how to make a leap from the world of Nature to the world of the spirit of poetry and humanism. In grammar school our Latin teacher gave us exercises in translating fragments of Roman poetry. Then I started as much as publishing my own poems, in Tygodnik Powszechny or Poezja, amongst others. At a critical moment I was lucky to have met Zbigniew Herbert. I went to his lectures at the University of Gdańsk in the mid-1970s and showed him some of my poems. He said that he even liked them but warned me that poetry would squeeze me dry. He advised me to keep on creating in the area that I was in. Thanks to Herbert I chose poetry as a hobby, an addition to life.

Interview:  Krzysztof Klinkosz
Photos: Piotr Pędziszewski

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