Research Highlights
Generation of optical Schrödinger “cat” states in intense laser-matter interactions
In a theoretical and experimental study published in Nature Physics, an international team of researchers (from ICFO/ICREA-Spain, Technion-China, MBI-Germany, ELI-ALPS-Hungary, UoC and FORTH-Greece) led by Prof. Maciej Lewenstein (ICFO-Spain) and Dr. Paraskevas Tzallas (Research Director at FORTH and academic visitor of the Physics department of the UoC), demonstrates the generation of highly non-classical states of light in intense laser–atom interactions. The theory has been developed by J. Rivera-Dean (ICFO), M. F. Ciappina (Technion-China), E. Pisanty (MBI-Germany), P. Stammer (ICFO) and M. Lewenstein, and the experiment has been performed at FORTH-IESL by Th. Lamprou (PhD student in the Department of Physics of the University of Crete) and P. Tzallas, Researcher at IESL/FORTH and Academic Visitor at the Dept. of Physics of the Univ. of Crete. Over the past four decades, astounding advances have been made in the field of laser technologies and the understanding of light-matter interactions in the non-linear regime. Thanks to this, scientists have been able to carry out extremely complex experiments, using ultra-fast light-pulses in the visible and infrared range, to accomplish crucial milestones such as using a molecule’s own electrons to image its structure, to see how it rearranges and vibrates or breaks apart during a chemical reaction. The development of high-power lasers allowed scientists to study the physics of ultra-intense laser–matter interactions which, in its standard version, treats ultra-strong ultra-short driving laser pulses only from a classical point of view. The famous theory coined as the “simple man’s model” or the “three-step model” – which had its 25th anniversary in 2019 – dealt with the interaction of an electron with its parent nucleus sitting in a strong laser field environment, and elegantly described it according to classical and quantum processes. However, due to the fact that these laser pulses are highly coherent and contain huge numbers of photons, the description of the interaction in the strong field has so far been incomplete, because it treated the atomic system quantum mechanically, but the electromagnetic field classically.
In the recent study published in Nature Physics, the authors have demonstrated that intense laser–atom interactions can lead to the generation of highly non-classical states of light. Such results have been obtained by using the process of HHG in atoms, in which large numbers of photons, from an infrared driving-laser pulse, are up-converted into photons of higher frequencies in the extreme ultraviolet spectral range. The quantum electrodynamical theory, formulated in this study, predicts that if the initial state of the driving laser is coherent, it remains coherent, but shifted in amplitude after interactions with the atomic medium. The researchers accessed the full quantum state of this laser pulse experimentally using quantum state tomography. To achieve this, the coherent amplitude of the light first needs to be reduced in a coherent way to only a few photons, on average, and then all of the quantum properties of the state can be measured. Research Article: “Generation of optical Schrödinger “cat” states in intense laser-matter interactions” by M. Lewenstein, M. F. Ciappina, E. Pisanty, J. Rivera-Dean, P. Stammer, Th. Lamprou and P. Tzallas, Nature Physics (2021). |
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