Wydział Fizyki UW > Badania > Seminaria i konwersatoria > Seminarium Optyczne

Seminarium Optyczne

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Zapraszamy na spotkanie o godzinie 11:50

Hilton B. de Aguiar (Laboratoire Kastler Brossel, Paris)

High-speed and ultrafast chemical sensing enabled by quantum-optical resources

The seminar will exceptionally take place at the Institute of Physics, Polish Academy of Sciences, Leonard Sosnowski Auditorium, al. Lotników 32/46, Warszawa

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Mateusz Winkowski (Faculty of Physics, University of Warsaw)

Optofluidic dye laser based on the hollow-core antiresonant fiber

"We present an alignment-free, optofluidic dye laser based on an anti-resonant hollow core fiber. Its compact all-fiber design enables direct integration of the optofluidic laser with standard fiber components. As a proof-of-concept we show a custom developed antiresonant fiber filled with Rhodamine 6G, serving as an organic activemedium. The laser exhibits tunable emission with a peak wavelength ranging from 569 to 595 nm (visibleyellow to orange), depending on dye concentrations. Developed optofluidic platform operates with microliter-scale dye volumes in a compact, sealed configuration and interfaces directly with standard fiber componentswith FC/PC connectors. The modular, all-fiber and mechanically robust architecture enables alignment-free,turnkey operation and straightforward integration with standard optical fiber components.Presented optofluidic fiber dye laser is a matching solution to existing and widely used fiber lasers based onrare-earth doped active fibers, since the existing fiber lasers offer wavelength emission only in a limited rangerelated to bandgap properties of existing rare earth elements, whereas organic dyes covers full visible spectrumwithout any gaps and offers wide wavelength tuning. Moreover, the proposed laser design advances greenphotonics by enabling the replacement of rare-earth elements with organic dyes as active medium."

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Sanjay Kapoor (IFD UW)

Electro-optic spectral manipulation: from ultrafast pulses to single photons emitted by a quantum dot

There is growing interest in interfacing diverse quantum systems into a hybrid quantum network. However, their implementation is bottlenecked by incompatible timescales and spectral bandwidths, necessitating coherent manipulation of bandwidth and central wavelengths. Spectral bandwidth manipulation and spectral tuning of heralded single photons from spontaneous parametric down-conversion have been demonstrated using electro-optic phase modulation (EOPM) and dispersive propagation [1]. In this talk, I will introduce a new analytical model that significantly improves the foundational performance of sinusoidal time lenses [2]. Additionally, I will discuss the spectral tuning of photons emitted by a solid-state single-photon source using electro-optic modulation [3].I will first introduce the foundational concept of spectral bandwidth manipulation and frequency conversion using the optical space-time analogy, showing how a time lens based on electro-optic phase modulation can perform the temporal equivalent of spatial focusing, thereby compressing or expanding the spectral bandwidth. I will present a new analytical tunable-aperture model that significantly reduces temporal aberrations in conventional sinusoidal time lenses [2]. Then I will demonstrate central-wavelength tuning of quantum light using serrodyne modulation (a sawtooth waveform) to precisely shift the frequency of single photons emitted by a quantum dot by up to ±5.25 GHz. We experimentally confirm that this electro-optic technique preserves the single-photon number purity and indistinguishability between subsequent emitted photons [3]. This work establishes EOPM as a versatile tool for quantum interface engineering, with the potential to scale through future integration onto integrated photonics platforms.[1] M. Karpiński et al., Adv. Quantum Technol. 4, 2000150 (2021).[2] S. Kapoor et al., APL Photonics 10, 096111 (2025).[3] S. Kapoor, A. Rodek et al., Nanophotonics 14, 1775–1782 (2025).

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Ulf Leonhardt (Weizmann Institute of Science & Technical University Vienna)

Geometry, light and a wee bit of magic

When light enters an optical material, the material acts as if it changes the geometry of space - distances get longer or shorter, depending on the refractive index. This is the basis of optical illusions, and also for many fascinating connections between optical media and the physics of space and time: general relativity. It gives a recipe for making things invisible in cloaking, but also for shedding light on the physics of black holes and perhaps for explaining the enigma of dark energy.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Mariusz Klimczak (Faculty of Physics, University of Warsaw)

Nonlinear Optical Response of MOVPE-Grown van der Waals Boron Nitride Layers

Nonlinear optical response in layered boron nitride (BN) is strongly governed by polytypism and vertical heterostructure design. In this seminar, I will discuss two manifestations of this effect in MOVPE-grown van der Waals BN layers. First, I will show how the spectral profile of second harmonic generation (SHG) in hybrid hBN/rBN stacks can be reshaped through the interplay of stacking-dependent optical interference and the dispersive second-order nonlinear susceptibility of rhombohedral BN, leading in particular to ultraviolet-enhanced SHG in selected heterostructure geometries. Second, I will turn to defect-related ultraviolet luminescence and demonstrate how nonlinear up-conversion enables excitation of the C300 emission band under sub-bandgap visible pumping. A comparison between centrosymmetric hBN and non-centrosymmetric rBN shows that while two-photon absorption dominates in hBN, SHG provides an additional and more efficient excitation pathway in rBN, extending access to UV defect luminescence toward longer wavelengths. Together, these results identify polytypism as a practical handle on ultraviolet nonlinear optics in epitaxial BN.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Maciej Gałka (Heidelberg University)

Seminarium jest odwołane

The seminar is cancelled

"Realizing integer and fractional quantum Hall states with a few rapidly rotating fermions" The fractional quantum Hall effect hosts strongly correlated, topological states with exotic properties such as fractional charge and anyonic statistics. Realizing these states in scalable engineered systems holds great potential for deepening our understanding of their microscopic origins, yet it remains a challenge. We realize a minimal instance of such physics by engineering the two-particle Laughlin wavefunction using rapidly rotating, interacting fermions in an optical tweezer. With single-atom, spin-resolved imaging, we directly probe its key signatures, including vortex structure and suppressed interactions. Extending this platform, we also realize a few-body integer quantum Hall state and observe its characteristic uniform density. These results open a path toward assembling larger quantum Hall states atom by atom.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Birgit Stiller (Leibniz University Hannover and Max Planck Institute for the Science of Light)

Quantum and classical light-sound interactions for photonic neuromorphic computing and quantum signal processing

Photonics has the potential to advance modern quantum technologies and high-speed applications such as communications and the processing of large amounts of data. However, to replace or improve the well-established systems with photonic solutions, there is still a way to go. A new promising approach to manipulate light all-optically is to use the link of optical waves with acoustic vibrations. Our research experimentally investigates how traveling sound waves can be used to process states of light in the classical and quantum regime. Via the nonlinear effect of stimulated Brillouin scattering (SBS), acoustic waves can be created all-optically by counter-propagating optical signals. With help of acoustic waves, we implement several building blocks for photonic machine learning, such as an optoacoustic recurrent operator, optical memory and a photonic activation function for all-optical neural networks. We experimentally demonstrate a temporary storage for light information and show how to extend the performance in terms of bandwidth and storage time. SBS is also a versatile tool for processing polarization states and orbital angular momentum (OAM), where we demonstrate a non-reciprocal device for OAM modes, a vortex laser and frequency conversion of OAM information. In order to enter the regime of quantum signal processing, cooling of traveling acoustic phonons is an essential precondition and we show experimental results of optomechanical cooling by 220K starting from room temperature. As a milestone towards quantum interactions of photons and traveling phonons, we present the first experimental realization of cavity-free strong coupling between groups of photons and phonons in a continuous optoacoustic system. This work can path the way to optical-fiber-based and chip-integrated quantum optoacoustic control for application to photon-phonon entanglement and quantum memory.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

João Pedro Mendonça (Centre for Quantum Optical Technologies, University of Warsaw)

Quantum Magnetism Meets Cavity QED

Interacting spin-boson models provide the foundational framework for exploring strong light-matter interactions across various platforms, such as atoms in optical cavities, superconducting circuits, and trapped ions. In the strongly interacting scenario, where both spin-spin and spin-boson correlations become critical to the underlying physics, standard mean-field treatments fundamentally fail. To tackle this problem, we develop a theoretical framework that goes beyond mean-field limits to accurately capture the closed-system dynamics. Applying this framework we uncover new phenomena, such as an intermediated coexisting phase where strong spin-spin and spin-photon correlations enhance the superradiant response. In the open-system scenario, we apply a distinct but related approach, which is particularly aligned with realistic setups like Rydberg atoms in optical cavities, in the fast-cavity limit, where the far-detuned cavity acts as a mediator of spin interactions. Finally, the effective spin Hamiltonians that arise from virtual photon exchange in this regime are shown to lead to highly efficient spin squeezing generation.

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)

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.

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