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

Seminarium Optyczne

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Zapraszamy na spotkanie o godzinie 10:15

Adam Widomski (IFD UW)

Generation and detection of QKD symbols encoded in time and frequency

Today’s world is driven by huge amounts of critically important information, such as financial,industrial, medical, and military data. Secure exchange of the data is endangered by mathematicalprogress, increase in computational resources, and the developments in quantum computing.Quantum Key Distribution could provide a counter-method for all the mentioned threats as it isbased on fundamental laws of quantum physics instead of man-made algorithms. In thispresentation. I will discuss the progress towards experimental realization of a multidimensionalQKD protocol with time-frequency encoding. I will report on the generation and detection ofspectral and temporal symbols by means of fast electro-optic amplitude modulation combined withelectrical signal shaping and dispersive Fourier transformation. Influence of the RF bandwidth andtiming jitter on the dimensionality of the protocol will be described. Finally, I will discuss thepotential of our approach, possibilities of implementation within fiber optic network infrastructure,and opportunities for photonic integration.

Seminarium z użyciem połączenia internetowegohttps://zoom.us/j/97696726563(meeting ID: ID 97696726563, password: 314297)

Zapraszamy na spotkanie o godzinie 10:15

dr Radosław Łapkiewicz (IFD UW)

Breaking the diffraction limit by measuring photon correlations

Single fluorescent emitters in biological samples are probably the most common sources of quantumlight. Nevertheless, their quantum optical properties are rarely exploited. I will discuss how fluorescencemicroscopy can benefit from measurements of quantum correlations. Such measurements allowed countingemitters within a diffraction-limited spot [1] and enhancing the resolution of classical super-resolutionmethods further beyond the diffraction limit, as in the case of recently introduced Quantum Image ScanningMicroscopy (QISM) [2].We found that the classical analog of QISM relying on classical light correlations offers a higher SNR at shortmeasurement times and is less demanding experimentally. This method, termed Super-resolution opticalfluctuation image scanning microscopy (SOFISM) [3], exploits fluorescent emitter blinking as its imagecontrast. SOFISM offers a robust path to achieve high-resolution images with a slightly modified confocalmicroscope, using standard fluorescent labels and reasonable acquisition times.[1] Y. Israel, et al., Quantum correlation enhanced super-resolution localization microscopy enabled by a fibrebundle camera. Nat.Comm. 8, 14786 (2017).[2] R. Tenne, et al., Super-resolution enhancement by quantum image scanning microscopy, Nat. Phot., 13,116–122 (2019).[3] A. Sroda, et al., SOFISM: Super-resolution optical fluctuation image scanning microscopy, SOFISM:Super-resolution optical fluctuation image scanning microscopy, Optica 7, 1308-1316 (2020).

Seminarium z użyciem połączenia internetowegohttps://zoom.us/j/97696726563(meeting ID: ID 97696726563, password: 314297)

Zapraszamy na spotkanie o godzinie 10:15

prof. Jacek Waluk (ICHF PAN)

Single molecule spectroscopy and microscopy

Three complementary methods of investigating single molecules, based onfluorescence or Raman spectroscopy and scanning probe microscopy will be discussed and compared. Examples of applications of these techniques will include:(i) studies of mechanisms of intramolecular hydrogen transfer;(ii) environmental effects on photostability;(iii) demonstration of heterogeneity of the photophysical parameters of fluorophores embedded in polymer matrices.

Seminarium z użyciem połączenia internetowegohttps://zoom.us/j/97696726563(meeting ID: ID 97696726563, password: 314297)

Zapraszamy na spotkanie o godzinie 10:15

(IFD UW)

Today's seminar has been canceled

Zapraszamy na spotkanie o godzinie 10:15

prof. Roee Ozeri (Weizmann Institute of Science)

Quantum-Logic detection of atom-ion collisions

Ultracold atom-ion mixtures have recently emerged as a novel system in quantum physics research.I’ll describe experiments in which, by leveraging on the high fidelity quantum control of trappedions,we studied different elastic and inelastic processes in atom-ion collisions. The former resultsinnon-equilibrium energy distributions and the later includes the study of spin, charge andexcitation exchange. We furthermore developed a method to precisely control atom-ion collisionenergy by transporting a cloud atoms, trapped in an optical lattice, across a single trapped-ion.The exquisite quantum control of some trapped ions enables the investigation of the ionexternal and internal degrees of freedom following a collision. However, not all ions are amenableto high fidelity quantum control. In order to investigate the collision dynamics of such ions withneutral atoms, we have used a technique similar to quantum-logic spectroscopy. We used a highlycontrollablequantum logic ion to study the collision dynamics of an uncontrollable target ion withultracold atoms. This technique opens the possibility for the study of interactions between ultracoldatoms and practically all species of atoms and molecules.

Seminarium z użyciem połączenia internetowegohttps://zoom.us/j/97696726563(meeting ID: ID 97696726563, password: 314297)

Zapraszamy na spotkanie o godzinie 10:15

Maciej Łebek (CFT PAN i IFT UW)

Many-body molecule formation at a domain wall in a one-dimensional strongly interacting ultracold Fermi gas

Zapraszamy na spotkanie o godzinie 10:00

dr Amanda Ross (CNRS and Université de Lyon, France)

Laser spectroscopy of MH molecules : a gentle approach to laboratory astrophysics

Spectroscopy – in whatever form – is still our only probe for distant objects where direct investigation is impossible.Molecular spectra have been identified in cool stellar objects (where cool implies temperatures around 3000 K). Sometransition metal monohydrides have been identified in sunspots and in the spectra of cool stars [1], FeH and CrH raisingspecial interest because they are good probes of magnetic field [2]. Laboratory spectra are required to supply reliableparameters for spectropolarimetric analysis of such remote objects, and this is the focus of my talk. One obvious hurdlearises from the equilibrium temperatures of 'cool' stellar objects, far higher than the range of temperatures typicallyaccessible in the laboratory, particularly when high spectral resolution is required. Another is the difficulty in modellingthe electronic structure of these species, characterised by non-zero spin and orbital angular momentum, and large spinorbitcouplings between them. The lowest-lying electronic states of NiH illustrate this very well [3-5]. Resolvedfluorescence probes multiple vibronic levels very efficiently in this context.We have also used cw laser excitation and Fourier-transform resolved fluorescence to study Zeeman patterns,working at magnetic fields typically 0.3-0.5 T provided by permanent magnets. Investigating the profiles of FeH linesobserved in sunspot spectra, recorded in Stokes V polarisation at the solar Telescope THEMIS in Tenerife[6], we findthat the field deduced from atomic lines (Ti,Fe) is around ~10 % higher than that found from FeHn suggesting thatmolecules form at higher altitudes in the solar atmosphere.References[1] L. Wallace, W. Livingston, P. Bernath, and R.S. Ram, N.S.O. Technical Report N° 1998-002, Available online :ftp://nsokp.nso.edu/pub/atlas/spot3alt (1998).[2] N. Afram, S.V. Berdyugina, D.M. Fluri, S.K. Solanki , and A. Lagg, Astron. & Astrophys. 482 (2), 387 (2008).[3] A.J. Ross, P. Crozet, C. Richard, H. Harker, S.H. Ashworth, and D.W. Tokaryk, Mol. Phys. 110 (17), 2019 (2012).[4] M. Abbasi, A. Shayesteh, P. Crozet, and A.J. Ross, J. Mol. Spectrosc. 349, 49 (2018).[5] I. Havalyova, I. Bozhinova, A.J. Ross, P. Crozet, and A.E. Pashov, Bilbao Poster P2-61 (2018). , 25th Int Conf. on High Res;Molecular Spectroscopy, Bilbao, poster P2, 61 (2018). Also, I. Havalyova, PhD thesis in progress, Univ. Sofia.[6] P. Crozet, G. Tourasse, A. Ross, F. Paletou, and A.L. Ariste, EAS Publications Series European Conference on LaboratoryAstrophysics 58, 63 (2013).

Seminarium użyciem połączenia internetowegohttps://zoom.us/j/97696726563(meeting ID: ID 97696726563, password: 314297)

Zapraszamy na spotkanie o godzinie 10:15

Jakub Ratajczak (Centrum Nowych Technologii UW)

The dark form of matter: on optical transmittance of ultra-diluted gas

This talk discusses a model of optical transmittance of ultra-diluted gas. The model considersindividual gas particles' non-locality, the quantum effect of wave function spreading derived fromsolving the Schrödinger equation for a free particle. I indicate some quantitative and qualitativeconsequences of this model. One of them is that measured transmittance depends on the detectorsize. Namely, for small detectors, such a gas's optical transmittance increases significantly, up to100%, compared to the classical predictions. I show the connection with classical models byderiving the Beer–Lambert law equation within its applicability range.The second part of the talk describes a conducted experiment that measures gas transmittance inparallel with a pair of detectors with different diameters ranging from 2 to 200 μm. We used aTunable Diode Laser Absorption Spectroscopy type system. The transmittance of ∼0.01 mbar watervapor on NIR absorption line 1.3686 μm was measured using the ~61.6 m long multi-pass cellplaced inside the ∼300 l vacuum chamber. I discuss results that are in agreement with the model.Dark and thin interstellar and intergalactic regions seem to be natural regions for such a gas. In thisregard, the talk concludes by indicating the possible related astrophysical phenomena, includingdark matter. I also show the impact on interpretations of quantum mechanics.

Seminarium z użyciem połączenia internetowegohttps://zoom.us/j/97696726563(meeting ID: ID 97696726563, password: 314297)

Zapraszamy na spotkanie o godzinie 10:15

Rosario González-Férez (z Instituto Carlos I de Física Teórica y Computacional and Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, Granada, Spain)

Polyatomic ultralong range Rydberg molecules

In cold and ultracold mixtures of atoms and molecules, Rydberg interactions with surrounding atoms or molecules may,under certain conditions, lead to the formation of special long-range Rydberg molecules [1,2,3]. These exotic moleculesprovide an excellent toolkit for manipulation and control of interatomic and atom-molecule interactions, withapplications in ultracold chemistry, quantum information processing and many-body quantum physics.In this talk, we will first discuss ultralong-range polyatomic Rydberg molecules formed when a heteronuclear diatomicmolecule is bound to a Rydberg atom [3,4]. The binding mechanism appears due to anisotropic scattering of theRydberg electron from the permanent electric dipole moment of the polar molecule. We propose an experimentallyrealizable scheme to produce these triatomic ultralong-range Rydberg molecules in ultracold KRb traps, which mightuse the excitation of potassium or rubidium [5]. By exploiting the Rydberg electron-molecule anisotropic dipoleinteraction, we induce a near resonant coupling of the non-zero quantum defect Rydberg levels with the KRb moleculein an excited rotational level. This coupling enhances the binding of the triatomic ultralong-range Rydberg moleculeand produces favorable Franck-Condon factors.Another type of ultralong-range Rydberg molecule is formed in collisions between polar molecules in cold andultracold settings [6]. The interaction of Λ-doublet nitric oxide (NO) with long-lived Rydberg NO molecules formsultralong-range Rydberg bimolecules with GHz energies and kilo-Debye permanent electric dipole moments. Thedescription includes both the anisotropic charge-molecular dipole interaction and the electron-NO scattering. Therotational constant for the Rydberg bimolecules is in the MHz range, allowing for microwave spectroscopy of rotationaltransitions in Rydberg bimolecules. The Rydberg molecules described here hold promise for studies of a special class oflong-range bimolecular interactions. [1] C. H. Greene, A. S. Dickinson, and H. R. Sadeghpour, Phys. Rev. Lett. 85, 2458 (2000).[2] S. T. Rittenhouse and H. R. Sadeghpour, Phys. Rev. Lett. 104, 243002 (2010).[3] V. Bendkowsky, B. Butscher, J. Nipper, J. P. Shaffer, R. Löw, and T. Pfau, Nature 458, 1005 (2009).[4] R. González-Férez, H. R. Sadeghpour, and P. Schmelcher, New J. Phys. 17, 013021 (2015).[5] R. González-Férez, S.T. Rittenhouse, P. Schmelcher and H.R. Sadeghpour, J. Phys. B 53, 074002 (2020).[6] R. González-Férez, J. Shertzer and H. R. Sadeghpour Phys. Rev. Lett. 126, 043401 (2021).

Zapraszamy na spotkanie o godzinie 10:15

Deeksha Kanti (Wydział Fizyki UW)

Laser-assister radiative recombination revisited

A comprehensive theoretical treatment of laser-assisted radiative recombination in the presence of alaser pulse or a pulse train is presented. Our formulation lacks in various unphysical effects likeoscillations and high-energy tails in the spectrum of emitted radiation. On contrary, it accounts for acontribution from the field-free process. As a result, the energy distribution of emitted radiationconsists of a point spectrum embedded in a continuum. We demonstrate that the features of thelatter are determined by the laser field. For instance, in the case of a train of pulses there appear thecomb structures in the radiation spectrum. We attribute them to constructive interference betweenprobability amplitudes of recombination assisted by each pulse from the train. Finally, we show thatthe vector potential describing the laser field is encoded in the spectrogram of emitted radiation.This suggests to use the spectrogram for a complete temporal reconstruction of the laser field,which is irrespective of whether it is an isolated pulse or a pulse train.

Seminarium z użyciem połączenia internetowegohttps://zoom.us/j/97696726563(meeting ID: ID 97696726563, password: 314297)

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