Seminarium Optyczne
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2025-12-18 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15 
Kazimierz Rzążewski (Center of Theoretical Physics, Polish Academy of Sciences)BEC 30 (100) years later
I will review most important experiments on Bose-Einstein condensate. Squeezed among them I will also include a few remarks about our own contributions.
2025-12-11 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Michał Suchorowski (Faculty of Physics, University of Warsaw)From Scale Invariance to Universal Droplets: A Framework for 2D Attractive Bose Gases
Ultracold two-dimensional (2D) Bose gases exhibit behaviour that differs markedly from their three-dimensional counterparts, making them a sensitive setting for studying symmetry and interaction effects. In the idealized Gross-Pitaevskii equation (GPE), scale invariance gives rise to unique phenomena such as Townes solitons, ‘strong’ self-similar collapse, and interaction-independent breathing-mode frequencies in tightly trapped systems. However, realistic bosonic systems exhibit a strong quantum anomaly, namely, a breaking of scale invariance and, in consequence, the formation of universal droplets. It remains unclear whether a simple, unified theoretical framework exists to analyse these phenomena. To address that, we introduce a density-dependent coupling into the GPE, which successfully describes this behaviour, while preserving a structure suitable for intuitive analytical and numerical exploration.In this talk, I will discuss the unique properties of ultracold low-dimensional Bose gases, with a focus on the 2D attractive Bose gas. I will show our limitations in the mathematical description of those systems and how we can overcome them with the recently introduced generalized GPE. The talk will address new experimental opportunities and theoretical challenges.
2025-12-04 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Alessio Ciamei (European Laboratory for Non-Linear Spectroscopy - LENS, Florence)Ultracold molecules beyond the bi-alkali paradigm: from quantum chemistry to new physics searches
Despite tremendous progress in direct laser cooling of molecules, the only strategy so far able to deliver molecular gases at high phase-space density relies on the assembly from pre-cooled atoms in a two-step process: atom pairs are first converted into weakly bound molecules across a Feshbach resonance and later transferred to the absolute molecular ground state via stimulated Raman adiabatic passage. However, this method has so far been experimentally demonstrated only for bi-alkali systems with singlet electronic ground states.In my talk, I will initially review our results, in collaboration with M. Tomza’s group (UWarsaw), on the association of alkali lithium and transition-metal chromium into polar paramagnetic molecules [1], and preliminary benchmarks of quantum chemistry methods on Cr-bearing diatomics. I will then focus on our recent joint proposal [2] for next-generation searches for new physics based on high-spin, Σ-state, polar molecules in the ultracold regime. I will explain how these can be realized by assembly of chromium and ytterbium atoms into YbCr and describe their favorable properties from the experimental point of view. [1] S. Finelli et al., PRX Quantum 5, 020358 (2024)[2] A. Ciamei et al., arXiv:2507.16760
Despite tremendous progress in direct laser cooling of molecules, the only strategy so far able to deliver molecular gases at high phase-space density relies on the assembly from pre-cooled atoms in a two-step process: atom pairs are first converted into weakly bound molecules across a Feshbach resonance and later transferred to the absolute molecular ground state via stimulated Raman adiabatic passage. However, this method has so far been experimentally demonstrated only for bi-alkali systems with singlet electronic ground states.In my talk, I will initially review our results, in collaboration with M. Tomza’s group (UWarsaw), on the association of alkali lithium and transition-metal chromium into polar paramagnetic molecules [1], and preliminary benchmarks of quantum chemistry methods on Cr-bearing diatomics. I will then focus on our recent joint proposal [2] for next-generation searches for new physics based on high-spin, Σ-state, polar molecules in the ultracold regime. I will explain how these can be realized by assembly of chromium and ytterbium atoms into YbCr and describe their favorable properties from the experimental point of view.[1] S. Finelli et al., PRX Quantum 5, 020358 (2024)[2] A. Ciamei et al., arXiv:2507.16760
2025-11-27 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Sebastian Blatt (planQC, Garching, Germany)Neutral-atom quantum computing in the Munich Quantum Valley
Analog quantum simulators based on ultracold atoms trapped in optical lattices can be used to study condensed matter systems with single-site resolution. The quest for more control over individual atoms in such systems has culminated in a new generation of experiments based on atom arrays assembled with optical tweezers. These atom arrays can be created rapidly in arbitrary two- and three-dimensional geometries, and atoms in these arrays can be entangled using long-range Rydberg interactions. Based on these developments, atom arrays have emerged as one of the most promising platforms to build digital quantum computers, because (1) atoms can realize qubits with many seconds of coherence time; (2) they have no manufacturing variations; and (3) it is easy to scale up to arrays with thousands of qubits. Here, I report on the digital quantum computer demonstrators developed in the academic projects within the Munich Quantum Valley and the commercial quantum computers developed at our spin-off, planqc.
2025-11-20 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Sid Wright (Fritz Haber Institute of the Max Planck Society, Berlin)Aluminum monofluoride: Three MOTs, and a molecule that bounces off surfaces
Aluminum monofluoride (AlF) is the first spin-singlet molecule to be laser-cooled and captured into a magneto-optical trap (MOT). Its electronic structure is distinct from other laser-cooled molecules, and results in several highly attractive properties: chemical and collisional stability; efficient gas-phase molecular production via a thermochemical reaction; simple optical cycling in any excited rotational level; and a narrow, spin-forbidden, vibrationally diagonal transition from the ground state.In this talk, I will present the latest results from the AlF group in Berlin, where we have now demonstrated a MOT for three different rotational levels of the electronic ground state. I will discuss the experimental challenges and improvements to be made, the prospect of trapping higher rotational levels, and some future plans. Recently, we discovered that AlF can survive collisions with (and therefore thermalise to) room temperature surfaces, despite it having a negligible equilibrium vapour pressure below about 500 K. I will present our first velocity- and angle-resolved measurements of single AlF-surface collision outcomes observed via laser-induced-fluorescence on a camera. We tentatively find that, as shown recently for atomic Yb and Fe, specific polymer-coated surfaces lead to very low sticking probability for AlF. This opens up prospects for cheap, compact and cryogen-free molecular sources for future experiments.
2025-11-06 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Roman Ciuryło (Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Toruń)Optical metrology of atomic and molecular systems
The energetic structure of atoms and molecules is determined by the interaction between their components and the surrounding space. Therefore atoms can be used to look for perturbation by dark matter fields. On the other hand, molecules are especially attractive to test quantum electrodynamics (QED) in systems more complex than a single atom and look for more exotic interactions like hadron-hadron fifth forces or short range non-Newtonian gravitation. It was demonstrated that even a single optical atomic clock can be sensitive to coupling with a possible dark matter field and the global network of such sensors was arranged. Doppler limited cavity-ring down spectra of D2 analysed with ab initio line shape profiles provided an accurate experimental test of QED calculations for this system. A proof-of-principle demonstration of use of photoassociation spectroscopy of weakly bound molecules was carried with ultracold Yb2 for determination of constraints on fifth forces or non-Newtonian interactions between atoms. Prospects for farther improvement of discussed techniques can be seen in a pure frequency dispersion spectroscopy, development of optical molecular clocks and use of ultracold systems involving Hg atoms. Moreover, new areas of investigations are opened by laser cooling of positronium.
2025-10-30 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Maciej Wojtkowski (International Center for Translational Eye Research - ICTER and Institute of Physical Chemistry, Polish Academy of Sciences)Spatio-temporal optical coherence tomography – new method for in vivo structural and functional imaging
Achieving in vivo optical microscopy with quality comparable to fixed samplescontinues to be challenging. We developed Spatio-Temporal Optical Coherence (STOC)Imaging, which dynamically randomizes the spatial phase relationships of the illuminatinglight to enhance image quality. When extended to three-dimensional imaging as Spatio-Temporal Optical Coherence Tomography (STOC-T), the method employs hundreds ofuncorrelated spectral interferograms to amplify ballistic photon signals while suppressingscattered photon contributions. STOC-T delivers rapid, high-contrast imaging and maintainshigh resolution at significant depths without the need for repeated measurements. In ocularimaging applications, STOC-T supports functional imaging methods such asOptoretinography (ORG), which measures photoreceptor responses to light stimuli. Weintroduced Flicker Optoretinography (f-ORG) for tracking rapid optical path-length changesunder photopic conditions, achieving reproducible sensitivity on the order of a singlenanometer in light-adapted eyes. This approach advances our understanding of retinalresponses and photopigment photo-activation processes.
2025-10-23 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Jacek Szczepkowski (Institute of Physics, Polish Academy of Sciences)Electronic structure of diatomic molecules. New challenges
Ultracold molecules provide an ideal platform for exploring the fundamental aspects of quantum physics and chemistry. Diatomic molecules with permanent electric dipole moments have already been employed to achieve the first ultracold, controlled chemical reactions, perform precision measurements, and enable quantum simulations of many-body dynamics. Moreover, the prospects for their application in quantum computing have recently driven the development of single-molecule control using optical tweezers. The rapid progress in this field has motivated an increasing number of research groups worldwide to begin investigating polar molecules at ultralow temperatures. A detailed understanding of the molecular electronic structure is essential for the development of such experiments. This presentation will focus on the new challenges in the spectroscopic investigation of the electronic structure of selected diatomic molecules.
2025-10-16 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Joanna Olesiak-Bańska (Politechnika Wrocławska)Probing chiral one- and two-photon properties in noble metal nanoclusters
Noble metal nanoclusters (NCs) are ultra-small nanomaterials exhibiting optical properties intermediate to those of discrete molecules and bigger nanoparticles [1]. They possess exceptional linear and nonlinear optical characteristics, including tunable photoluminescence (UV-NIR), large Stokes shifts (>0.5 eV), high photostability, and significant two-photon absorption [2]. Importantly, many NCs display chirality, arising from chiral surface ligands, helical core motifs, or inherent kernel asymmetry [3]. These attributes make NCs excellent models for structure-property relationship studies and versatile tools in catalysis, bioimaging, and sensing.This work investigates the linear and nonlinear optical properties of NCs with diverse chirality origins. We synthesized and characterized NCs stabilized by: 1) chiral ligands within primary or secondary ligand shells (captopril, glutathione, arginin, single stranded DNA), and 2) achiral ligands where chirality was induced by the arrangement of staple motifs. To quantitatively assess chiral nonlinear optical properties, specifically two-photon circular dichroism (2PCD), we developed and employed two distinct methodologies: z-scan-based two-photon absorption measurements and fluorescence-detected two-photon excited luminescence measurements utilizing circularly polarized light [4, 5]. Our findings reveal that the 2PCD of these NCs is approximately 300 times stronger than their one-photon anisotropy factor. Furthermore, we successfully demonstrated the facile detection of both 2PCD and three-photon circular dichroism (3PCD) in chiral gold NCs [6]. This research provides critical insights into the interplay between chirality and nonlinear optical phenomena in NCs, opening new avenues for their application in advanced photonics and chiroptical technologies.References[1] I. Chakraborty et al., Chem. Rev. 2017, 117, 8208.[2] J. Olesiak-Banska et al., Chem. Soc. Rev. 2019, 48, 4087.[3] I. Dolamic, S. Knoppe, A. Dass et al. Nat. Commun. 2012, 3, 798.[4] J. Olesiak-Banska et al., RSC Adv., 2016, 6. 98748.[5] A. Pniakowska et al. Nanoscale 2023; 15, 8597-8602.[6] P. Obstarczyk et al. J. Am. Chem. Soc. 2024, 146, 51, 35011–35015.
2025-10-09 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Tomasz Karpiuk (Uniwersytet w Białymstoku)Three-dimensional Bose-Fermi droplets at nonzero temperatures
We numerically study the formation of self-bound quantum Bose-Fermi droplets at nonzero temperatures. We have previously shown that such droplets can exist at zero temperature. In this work the attractive atomic Bose-Fermi mixture is described in terms of quantum hydrodynamics, enriched by beyond mean-field corrections and thermal fluctuations, as well as by a simplified self-consistent Hartree-Fock model. Using the hydrodynamic description, we find low-temperature relatively long-lived droplets in a free space, provided that the attraction between bosons and fermions is strong enough. On the other hand, a simplified Hartree-Fock treatment supports the existence of Bose-Fermi droplets in equilibrium with the gas of thermal bosons and fermions, with the Bose-Einstein condensate itself being completely hidden inside a droplet. Both thermal and non-thermal droplets can be used to simulate astrophysical phenomena such as disruption of a white dwarf star by a black hole.