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JU physicist to conduct a pioneering experiment in Australia

JU physicist to conduct a pioneering experiment in Australia

Prof. Krzysztof Sacha from the Faculty of Physics, Astronomy and Applied Computer Science of the Jagiellonian University will carry out a pioneering experiment featuring the realisation of time crystals functioning on the basis of his own original method.



Time crystals are a scientific concept according to which atoms or ions regularly undergo temporal self-organisation, that is perform a periodic motion. Prof. Krzysztof Sacha worked out a “ping pong” method which leads to the formation of such crystals.

Spatial crystals have been known for a long time and are a phenomenon both encountered in everyday life and used for complex applications, such as conductors and isolators. In contrast, time crystals are a relatively novel scientific concept and, until recently, were considered impossible to exist. It took some time to determine the conditions under which temporal self-organisation of a system of many bodies can be observed.

Prof. Krzysztof Sacha has discovered the possibility of movement re-organisation leading to the emergence of a new type of periodic movement in a system powered by an external force.

‘I imagined a system that is very simple in physical terms. Let me use a ping-pong bat analogy. We can bounce the ball up and down on the bat keeping it in motion. A properly chosen motion of the ball and bat will occur periodically in an intermittent manner. Now, going back to science, let’s replace the ball with a cloud of ultracold atoms and a bat with an atomic mirror’, says Prof. Sacha, adding that such a mirror is a beam of electromagnetic wave which has a form of a sheet that reflects atoms. If the atoms weakly interact with one another, a very specific state emerges, known by quantum physicists as “Schrödinger’s cat”, which is dead and alive at the same time.

‘Any disturbance of this system, such as observation or measurement leads to the self-reorganisation of movement in the entire system. A new crystalline structure emerges in time”, says Prof. Sacha.

The paper on this subject was published by Prof. Sacha in 2015. One year later American researchers managed to create time crystals, albeit using a different method.

Now, the time for a Polish-designed experiment has come. Prof. Sacha will carry it out as part of the research team of Prof. Peter Hannaford from the Swinburne University of Technology in Melbourne. The three-year research project is funded by the Australian Research Committee. The Australian group specialises in atomic mirrors, whereas the team from the JU Faculty of Physics, Astronomy and Applied Computer Science has calculated the parameters necessary to realise time crystals.

‘Together, we would like to show that solid-state physics can be observed in time. This is a brand new field of science. The system created by American researchers does not allow to test different properties of solid state physics in time. In our system with atoms reflected by the mirror, we can obtain very interesting effects known from the physics of spatial crystals. I hope that we are laying foundations for future applications’, says Prof. Sacha.

The JU researcher considers this new field of research very promising, stressing that the US Advanced Research Projects Agency (DARPA) has invited tenders for studies into time crystals. He also adds that more and more research teams are becoming interested in this topic, from both theoretical and experimental point of view and competition stimulates research efforts.

The world’s first conference devoted to time crystals will be held in Kraków in September 2019. Organised by Prof. Krzysztof Sacha and Dr Arkadiusz Kosior, it will feature some of the world’s most eminent quantum physicists. The speakers will include two Nobel laureates: Wolfgang Ketterle and Frank Wilczek, the scientist of Polish descent who came up with the idea of time crystals.

Professor Krzysztof Sacha works at the JU Faculty of Physics, Astronomy and Applied Computer Science, where he obtained a PhD in Physical Sciences in 1998. In the same year, he received the START scholarship from the Foundation for Polish Science. Having won prestigious scholarships from the Alexander von Humboldt Foundation and the Fulbright programme, he gained valuable research experience at the University of Marburg and in Los Alamos. Besides time crystals, Prof. Sacha’s research interests focus on the broadly understood physics of ultracold atomic gases. He also used to study quantum chaos and strong-field ionisation. In 2014 Prof. Sacha suggested the existence of the so-called discrete time crystals and is among the leading pioneers of research in this field.

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