Seminarium Optyczne
2006/2007 | 2007/2008 | 2008/2009 | 2009/2010 | 2010/2011 | 2011/2012 | 2012/2013 | 2013/2014 | 2014/2015 | 2015/2016 | 2016/2017 | 2017/2018 | 2018/2019 | 2019/2020 | 2020/2021 | 2021/2022 | 2022/2023 | 2023/2024 | 2024/2025 | 2025/2026 | Seminarium na YouTube
2026-04-09 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15 
Piotr T. Grochowski (Palacký University, Olomouc, Czech Republic)Optimal control of mechanical systems in the quantum regime
Contrary to the qubit-based, discrete systems, continuous quantum platforms enable encoding increased complexity into fewer physical systems through large-scale non-Gaussian states. Motion, as an exemplary continuous degree of freedom, underpins numerous nonlinear phenomena—from Cooper pair dynamics and optical wave packets to the macroscopic levitated objects. Despite significant progress in harnessing mechanical nonlinearities and generating quantum non-Gaussian states in low-energy regimes, their full potential remains untapped. Achieving high-quality, high-energy, and spatially large quantum non-Gaussian states is essential for progress in quantum sensing, quantum simulations, and foundational tests of quantum mechanics.In the talk, I will present the following control tasks for various nonlinear mechanical systems, including trapped atoms, levitated particles, and clamped oscillators with spin-motion coupling.(i) Nonharmonic potential modulation: Optimal control of a particle in a nonharmonic potential enables the generation of non-Gaussian states and arbitrary unitaries within a chosen two-level subspace [1].(ii) Macroscopic quantum states of levitated particles: Rapid preparation of a particle’s center of mass in a macroscopic superposition is achieved by releasing it from a harmonic trap into a static double-well potential after ground-state cooling [2].(iii) Phase-insensitive displacement sensing: For randomized phase-space displacements, quantum optimal control identifies number-squeezed cat states as optimal for force sensitivity under lossy dynamics [3, 4].These approaches exploit either intrinsic nonharmonicity or coherent nonlinear coupling, providing a unified framework for motion control in continuous-variable quantum systems—from levitated nanoparticles to optical and microwave resonators—paving the way toward universal quantum control of mechanical degrees of freedom.[1] PTG, H. Pichler, C. A. Regal, O. Romero-Isart, Quantum control of continuous systems via nonharmonic potential modulation, Quantum 9, 1824 (2025)[2] M. Roda-Llordes, A. Riera-Campeny, D. Candoli, PTG, O. Romero-Isart, Macroscopic quantum superpositions via dynamics in a wide double-well potential, Phys. Rev. Lett. 132, 023601 (2024)[3] PTG, R. Filip, Optimal Phase-Insensitive Force Sensing with Non-Gaussian States, Phys. Rev. Lett. 135, 230802 (2025)[4] PTG, M. Fadel, R. Filip, Distributed Phase-Insensitive Displacement Sensing, arXiv: 2602.03727 (2026)
2026-03-26 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Marcin Gronowski (IFT UW)Electronic structure studies of ultracold polar molecules
Ultracold polar molecules are crucial components in a wide range of cross-disciplinary experiments, including controlled chemistry, quantum simulation, and precision measurements. Thus, the design and interpretation of such experiments require detailed knowledge of molecular properties. Many of these properties can be predicted using modern ab initio electronic structure methods, which I will demonstrate on a few examples. In the first part, I will discuss high-accuracy predictions for two diatomic molecules: NaLi in the a3Σ+ state [1] and LiCr in the a8Σ+ state [2]. In both cases, we employ a hierarchy of coupled-cluster wavefunctions and extended Gaussian basis sets. Additionally, we account for nonadiabatic, relativistic, and quantum electrodynamic (QED) effects. The resulting potentials enable reliable predictions of ultracold scattering properties in complex many-electron systems directly from first principles. In the second part, I address the properties of intermediate triatomic complexes formed during nonreactive collisions between an ultracold alkali-metal molecule and an alkali-metal atom. For the KRb (X1Σ+) + Rb(2S) system [3], we identify an energetically accessible conical intersection between the ground and first excited electronic states, accompanied by an enhancement of spin-rotation coupling. This interaction may be involved in the experimentally observed hyperfine-to-rotational energy transfer. In the NaLi(a3Σ+) + Na(2S) system [4, 5], nonadditive three-body interactions reshape the potential energy surface. The combined effects of electron spin-spin and spin-rotation interactions, together with potential anisotropy, alter the collision dynamics. Together, these results demonstrated the intrinsic complexity of ultracold atom-molecule collisions, which involve vibrational, rotational, and spin degrees of freedom. [1] Gronowski, M., Koza, A. M., and Tomza, M. (2020) Ab initio properties of the NaLi molecule in the a3Σ+ electronic state. Physical Review A, 102(2), 020801.[2] Finelli, S., Ciamei, A., Restivo, B., Schemmer, M., Cosco, A., Inguscio, M., Trenkwalder, A., Zaremba-Kopczyk, K., Gronowski, M., Tomza, M., and Zaccanti, M. (2024) Ultracold LiCr: A New Pathway to Quantum Gases of Paramagnetic Polar Molecules. PRX Quantum, 5, 020358.[3] Liu, Y.-X., Zhu, L., Luke, J., Babin, M. C., Gronowski, M., Ladjimi, H., Tomza, M., Bohn, J. L., Tscherbul, T. V., and Ni, K.-K. (2025) Hyperfine-to-rotational energy transfer in ultracold atom–molecule collisions of Rb and KRb. Nature Chemistry, 17, 688–694.[4] Park, J. J., Son, H., Lu, Y.-K., Karman, T., Gronowski, M., Tomza, M., Jamison, A. O., and Ketterle, W. (2023) Spectrum of Feshbach Resonances in NaLi+Na Collisions. Physical Review X, 13, 031018.[5] Karman, T., Gronowski, M., Tomza, M., Park, J. J., Son, H., Lu, Y.-K., Jamison, A. O., and Ketterle, W. (2023) Ab initio calculation of the spectrum of Feshbach resonances in NaLi+Na collisions. Physical Review A, 108, 023309.
2026-03-19 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Piotr Zdańkowski (Faculty of Mechatronics, Technical University of Warsaw)Computational Microscopy: New Approaches to Label-Free Quantitative Imaging
Traditional optical microscopy frequently struggles against the physical barriers of the Abbe diffraction limit and the inevitable trade-off between sample invasiveness and image contrast. To overcome these hurdles, the emerging field of computational microscopy merges innovative optical architectures with powerful numerical reconstruction algorithms. At the Quantitative Computational Imaging Lab (QCI Lab), we focus on developing stable, label-free imaging methods, primarily Quantitative Phase Imaging (QPI) and Fourier Ptychographic Microscopy (FPM). Our QPI systems are based on common-path interferometry, a robust approach that drastically reduces environmental phase noise by using amplitude and liquid-crystal polarization gratings as beam splitters. Unlike classic two-beam Mach-Zehnder setups, these naturally achromatic configurations allow both the reference and object beams to travel the same optical path. This unique architecture enables the use of low-coherence illumination, virtually eliminating parasitic speckle noise. I will showcase novel computational frameworks we have developed to maximize the potential of these optical setups. Furthermore, I will demonstrate how our polarization-guided holotomographic techniques enable precise, label-free biochemical differentiation of lipid droplets based purely on subtle differences in their refractive indices. Another method that we develop at QCI Lab is Fourier Ptychographic Microscopy (FPM). This computational technique synthesizes a high numerical aperture in the spatial frequency domain through sequential angle-varied LED illumination, effectively breaking the traditional compromise between a wide field of view and high spatial resolution. To make FPM more accessible and resistant to experimental errors, I will introduce our open-source "FPM app" for advanced phase and amplitude reconstruction. Alongside this software, I will highlight a robust, two-step automated hardware calibration method that precisely corrects LED translatory and rotational misalignments without the need for any specialized calibration targets. Lastly, we have recently built a novel FPM system based on micro LED array together with the new framework for the ptychographic reconstruction that fully models illuminating wave sphericity,
2026-03-12 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Piotr Fita (Faculty of Physics, University of Warsaw)Unconventional optical phenomena in upconverting nanoparticles
Upconverting nanoparticles (UCNPs) doped with lanthanide ions convert near-infrared radiation into visible emission through sequential absorption processes involving long-lived electronic states. While the basic mechanisms of upconversion have been extensively studied, recent experiments reveal that UCNPs can exhibit a number of less intuitive photophysical behaviors. In this seminar, I will discuss several examples of such phenomena. First, I will focus on the strong enhancement of upconverted emission under dual-wavelength near-infrared co-excitation, where simultaneous excitation of ground-state and excited-state transitions leads to emission intensities far exceeding those obtained under single-wavelength excitation. I will also briefly discuss collective emission phenomena, including upconversion superfluorescence, in which ensembles of emitters synchronize to produce intense, ultrafast bursts of radiation. These examples illustrate how the rich energy-level structure and long lifetimes of lanthanide ions give rise to unconventional optical dynamics, opening new directions for nanophotonics, sensing, and imaging technologies.
2026-03-05 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Tomasz Sowiński (Institute of Physics, Polish Academy of Sciences)Many-Body Correlations in Mesoscopic Multi-Component Fermionic Systems
One of the most remarkable manifestations of many-body physics is the collective emergence of quantum effects in the macroscopic world. The existence of phenomena such as superfluidity, superconductivity, giant magnetoresistance, or Bose–Einstein condensation relies directly on the macroscopic amplification of quantum properties, which are driven by mutual interactions and quantum statistics when the number of particles becomes sufficiently large. In order to better understand how this quantum collectivism emerges, it is worth considering strongly correlated quantum systems containing a small number of particles and searching for various precursors of macroscopic correlations. This approach has become particularly attractive in recent years due to the development of extremely precise experimental techniques that allow for the preparation and control of systems containing a small number of strongly interacting ultracold atoms. In my talk, I will first provide a brief review of recent progress in theoretical and experimental studies of mesoscopic ultracold systems, focusing primarily on two-component fermionic mixtures. In particular, I will explain how precursors of conventional Bardeen–Cooper–Schrieffer (BCS) and unconventional Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) pairing can be identified in mesoscopic systems. Next, I will present the first results for the simplest three-component fermionic mixtures, highlighting the existence of a surprising structural transition in the many-body ground state that has no counterpart in two-component systems.
2026-02-26 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Jacek Gębala (Faculty of Physics, University of Warsaw)Universality in Ionic Three-body Systems Near an Ion-atom Feshbach Resonance
We calculate bound and scattering properties of a system of two neutral atoms and an ion near an atom-ion Feshbach resonance. Our results indicate that long-range atom-ion interactions lead to significant deviations from universal behavior derived from contact or van der Waals potentials. We find that ionic systems display an overall suppression of inelastic transitions leading to recombination rates and lifetimes of Efimov state orders of magnitude smaller with respect to those for neutral atoms. We further characterize the dense spectra of triatomic molecular ions with extended lifetimes. Our results provide a deeper insight on the universality and structure of three-body ionic systems and establishing them as a promising platform for exploring novel few- and many-body phenomena with long-range interactions.
2026-01-22 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Kang-Da Wu (University of Science and Technology of China, Hefei)Nonlinear Non-Hermitian Physics in Dissipative Rydberg Gases：Liouville exceptional structure and stochastic resonance
This study explores the nonlinear non-Hermitian physics in dissipative Rydberg gases, focusing on Liouvillian exceptional structures and stochastic resonance for sensing applications. Using a thermal Rydberg vapor as a many-body open system, we experimentally demonstrate chiral switching between two collective steady states with distinct excitation and transmission properties. This dynamics is governed by a Liouvillian exceptional structure, where two exceptional lines merge at a higher-order exceptional point, underpinning both the bistability and the chirality of the state transfer under parameter modulation. Such a non-Hermitian perspective offers a paradigm for controlling many-body states via exceptional points. Furthermore, leveraging the strong nonlinearity and intrinsic noise in the Rydberg ensemble, we implement stochastic resonance to detect weak microwave fields. By harnessing noise, the sensor achieves a significant signal-to-noise ratio enhancement, surpassing heterodyne atomic detection sensitivity by 6.6 dB. These findings establish dissipative Rydberg gases as a versatile platform for investigating non-Hermitian physics and advancing noise-enhanced quantum sensing technologies.
2026-01-15 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Szymon Pustelny (Jagiellonian University)Non-Hermitian Dynamics and Exceptional-Point Sensing in a Hybrid Spin System
Incorporating non-Hermitian dynamics into quantum systems leads to a range of intriguing phenomena, including non-reciprocity, parity–time symmetry breaking, and the emergence of exceptional points, at which two or more eigenstates coalesce. These features can result in enhanced sensitivity to weak perturbations, offering a distinct approach to quantum sensing.During the talk, I will discuss the emergence of exceptional points in a hybrid system composed of two distinct gases—rubidium vapor and a noble gas—and demonstrate how this framework enhances sensitivity to magnetic fields. I will also show how such a system can be employed to search for non-magnetic interactions.
2026-01-08 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15
Krzysztof Jachymski (Faculty of Physics, University of Warsaw)Stone skipping with ions in degenerate quantum gases
The dynamics of a charged impurity immersed in a quantum medium can be quite complex due to the long-range nature of the interactions. The ion can excite the gas during its motion, changing momentum in a nonlinear way. I will describe the simplest theoretical approaches to this problem based on the transformation to the co-moving frame. Dressing the impurity with the host atoms can result in formation of a polaronic state characterized by effective mass, which may be detectable in state-of-the art experiments. I will also report on recent experimental efforts aiming to understand three-body recombination involving an ion, which is competing with many-body effects.
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.