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Aljaž Kavčič and doc. dr. Matjaž Humar from the Laboratory for biological and soft photonics, Department of Condensed Matter Physics, along with dr. Nerea Sebastian from the Department of Complex Matter at the “Jožef Stefan” Institute, in collaboration with colleagues from the “Max-Planck Institute for the Science of Light”, have published an article in Nature titled Tuneable entangled photon pair generation in a liquid crystal. In their work, they, for the first time, demonstrate the generation of entangled photons in liquid crystals and, with this, in any organic material. In addition to the fact that the efficiency of entangled photon generation in liquid crystals is comparable to the best existing sources, their main advantage lies in the tunability of the state of photon pairs. This tunability can be achieved by applying an electric field or by arranging the liquid crystal molecules into the appropriate configuration. The ability to tune the quantum state indicates significant practical potential for numerous quantum technologies. A summary of the research can also be viewed in a short video.

Iztok Urbančič and Boštjan Kokot (Laboratory of Biophysics, Condensed Matter Physics Department, F5) have, together with colleagues from the Institute for Applied Optics and Biophysics (Jena, Germany), published a paper titled Effects and avoidance of photoconversion-induced artefacts in confocal and STED microscopy in Nature Methods. Authors have shown that high laser powers in fluorescence microscopy should be used with care; besides the well-known photobleaching, the dye’s emission spectrum can shift towards lower wavelengths (“photoblueing”). The fluorescence signal is consequently detected in another spectral channel attributed to another dye, possibly leading to erroneous experimental conclusions. The characterization of this phenomenon was made possible by a unique combination of a STED microscope equipped with a spectral detector, implemented at JSI.

https://www.nature.com/articles/s41592-024-02297-4

Assist. Prof. Žiga Kos, PhD published a paper with colleques from Ulsan National Institute of Science and Technology titled Symmetrically pulsating bubbles swim in an anisotropic fluid by nematodynamics in Nature Communications. Swimming at low Reynolds numbers typically requires breaking of the time-reversal symmetry and centrosymmetry of the swimming strokes. The authors show that symmetrically pulsating bubbles can swim in anisotropic fluids, where the required symmetries are broken by the fluid’s internal structure, suggesting a new possible mechanism of micropropulsion.

Franci Bajd, PhD, Mikac Urška, PhD, Assist. Prof. Aleš Mohorič, PhD and Prof. Igor Serša, PhD from the Department of Solid State Physics F5 have published an article titled The Effect of Polymer–Solvent Interaction on the Swelling of Polymer Matrix Tablets: A Magnetic Resonance Microscopy Study Complemented by Bond Fluctuation Model Simulations in the journal Polymers.

Understanding the tablet hydration process is important for the development of drug delivery systems that exhibit high drug loading capacity and controlled release potential. In this study, MRI was used to experimentally analyze the water hydration process of xanthan-based tablets and to characterize their swelling process with erosion, swelling, and penetration fronts. These results are complemented by numerical simulations of the polymer-matrix hydration process by the Bond Fluctuation Model, in which the polymer tablet matrix is modeled as an assembly of interacting chains with embedded drug particles, while its hydration process is mediated by interaction with solvent particles.

Matija Koterle, Jure Pirman, Tadej Mežnaršič, Katja Gosar, Erik Zupanič and Peter Jeglič from the Department of Condensed Matter Physics F5 and colleagues form the Department of Theoretical Physics F1 and Faculty of Electrical Engineering have published a paper in EPJ Quantum Technology with the tittle Mbit/s-range alkali vapour spin noise quantum random number generators.

Spin noise based quantum random number generators first appeared in 2008 and have since then garnered little further interest, in part because their bit rate is limited by the transverse relaxation time which is typically in the kbit/s range for coated alkali vapour cells. In the paper the researchers present two advances to spin noise based quantum random number generators. The first is an improved bit generation protocol that allows generating bits at high rates with only a minor increase of serial correlations. The second is a significant reduction of the transverse relaxation time itself by removing the coating, increasing the vapour temperature, and introducing a magnetic-field gradient. In this way they managed to increase the bit generation rate to 1.04 Mbit/s. They analysed the quality of the generated random bits using entropy estimation and they discuss the extraction methods to obtain high-entropy bitstreams. We accurately predict the entropy output of the device backed with a stochastic model and numerical simulations.