Seminarium Optyczne
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2019-03-28 (Czwartek)
Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00 
dr Mayukh Lahiri (Uniwersytet w Wiedniu)Path Identity and Its Application to Imaging and Quantum Information Science
2019-03-21 (Czwartek)
Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00
dr Florian Meinert (Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart)Rydberg atoms in ultracold gases - from electron to ion impurities
Rydberg atoms immersed in ultracold and degenerate atomic gases offer a rich experimental platform for studying giant impurities interacting with single, few, or many ground-state atoms from the host gas which reside within the Rydberg electron orbit. In this seminar, I will report on our endeavor to explore single Rydberg excitations with principal quantum number up to n=190 embedded in gases of different density regimes, ranging from comparatively dilute thermal ensembles to high-density Bose-Einstein condensates. More specifically, a Rydberg atom interacts with an ultracold atomic gas via electron-neutral and ion-neutral interaction. Typically, the electron-neutral interaction constitutes the far dominant scattering process and, in a low-density sample, leads to the formation of ultralong-range Rydberg molecules [1,2]. Differently, in the regime of a high-density Bose-Einstein condensate typically thousands of ground-state atoms collectively interact with the Rydberg impurity and the role of the Rydberg ionic core starts to play a role. By working with Rydberg electron orbits that by far exceed the size of the condensate, we suppress the typically dominant electron-neutral scattering and access the low-temperature ion-neutral interaction [3]. These results may open up ways to enter the quantum regime of ion-atom scattering for the exploration of charged quantum impurities and associated polaron physics. Finally, I will discuss recent results demonstrating Rydberg excitation blockade induced by a single low-energy ion, which we directly produce from the ultracold ensemble via a novel two-photon ionization scheme [4]. The observed blockade mechanism allows for tracing the ion’s trajectory in small applied electric fields, which when applied in dense ensembles may allow for studying ionic transport through quantum matter.Reference:[1] V. Bendkowsky, B. Butscher, J. Nipper, J. P. Shaffer, R. Löw, and T. Pfau, Nature 458, 1005 (2009).[2] K. S. Kleinbach, F. Meinert, F. Engel, W. J. Kwon, R. Löw, T. Pfau, and G. Raithel, Phys. Rev. Lett. 118, 223001 (2017). [3] K. S. Kleinbach, F. Engel, T. Dieterle, R. Löw, T. Pfau, and F. Meinert, Phys. Rev. Lett. 120, 193401 (2018). [4] F. Engel, T. Dieterle, T. Schmid, C. Tomschitz, C. Veit, N. Zuber, R. Löw, T. Pfau, and F. Meinert, Phys. Rev. Lett. 121, 193401 (2018).
2019-03-14 (Czwartek)
Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00
dr Monika Aidelsburger (Ludwig-Maximilians-University Munich)Synthetic gauge fields with ultracold atoms periodically in periodically-driven lattices
Synthetic gauge fields with ultracold atoms in periodically-driven lattices
Ultracold atoms in optical lattices are powerful experimental platforms to study a variety of phenomena ranging from condensed-matter to statistical physics. Recently, a promising new direction was opened by the successful realization of paradigmatic topological condensed matter models, in particular the Hofstadter and the Haldane model. I will introduce one of the most common experimental methods used to generate topological band structures in ultracold atoms, i.e., Floquet engineering, and report on recent results as well as challenges regarding its application to many-body systems. The basic idea of the method is to periodically modulate the system's parameters to emulate the properties of a non-trivial static system. Floquet engineering has further been proposed to engineer density-dependent gauge fields or even complete gauge theories, which require an interaction between matter and gauge fields. One example is the realization of $Z_2$ lattice gauge theories, which play an important role in condensed matter physics and quantum computation. Recently, we have implemented such a model with a two-component mixture of ultracold bosons in a double-well potential - the basic building block of $Z2_$ lattice gauge theories.
2019-03-07 (Czwartek)
Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00
mgr Monika Mycroft (IFT WF UW)Long-range distribution of multiphoton entanglement
We show that a long-distance quantum communication can be based on multiphoton bipartite entanglementand photon-number-resolved detection, the resources provided by the current quantumphotonictechnology. The protocol is robust to high transmission losses and o ers near-maximallyentangled states in realistic implementations. It can be realized in a delayed-choice scheme and itallows one to perform loophole-free Bell tests. The schema discussed can be employed as a sourceof entanglement for e.g. establishing an Earth-to-space quantum channel, quantum metrology andquantum key distribution.
2019-02-28 (Czwartek)
Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00
mgr Michał Nikołajczyk (IFD WF UW)Spectral characterization of single photons
I report on two-photon joint spectrum measurements with high resolution two-channel dispersive spectrometer. Theoretical limits of dispersive spectroscopy are studied in order to support the results. The results are used to characterize in-house build spontaneous parametric down-conversion source.
2019-02-21 (Czwartek)
Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00
dr Marcin Franczyk (Instytut Technologii Materiałów Elektronicznych)Active nanostructured core optical fibres
The nanostructurization opens new opportunities for development of active fibres for laser applications. This new technology allows to control precisely not only the refractive index distribution, but also the active dopants distribution or photosensitivity distribution in the fibre core. Recent developments of nanostructured core fibres made of ytterbium doped phosphate and silica glass will be introduced.
2019-01-17 (Czwartek)
Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00
dr Mateusz Borkowski (UMK Toruń)Optical Lattice Clocks with Weakly Bound Molecules
Weakly bound molecules promise unparalleled sensitivity to temporal variations of the proton-to-electron mass ratio [1] and in searches for new interactions beyond the Standard Model [2]. Both applications, however, rely on measurements of vibrational state positions of yet unrealized accuracy. To mitigate this, we propose to observe clock 1S0-3P0 transitions in weakly bound bosonic 174Yb2 molecules [3]. As in bosonic atomic clocks, a small transition dipole moment could be induced by means of a weak external magnetic field [4]. The positions of molecular clock lines can be determined to high accuracy: ground bound state positions have been measured with two-color photoassociation spectroscopy [5], while excited 1S0+3P0 0u- vibrational states can be predicted accurately using an interaction potential with ab initio long range parameters [6] and fitted to the recently measured 174Yb 1S0-3P0 scattering length [7]. The necessary ground state Yb2 molecules could be efficiently produced by STIRAP. Thanks to favorable Franck-Condon factors the magnetically induced molecular Rabi frequencies can be comparable to the atomic Rabi frequencies under same laser intensities and magnetic fields. Using new ab initio potentials [8] we evaluate the sensitivity of the excited clock states to changes in the proton-to-electron mass ratio and explore the prospects of using an ytterbium molecular clock for searches of temporal variation of this fundamental constant.
2019-01-10 (Czwartek)
Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00
dr inż. Karol Krzempek (Politechnika Wrocławska)Laser spectroscopy – modern approaches and concepts
2018-12-20 (Czwartek)
Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00
mgr Jan Szczepanek (IFD UW)Ultrafast all-normal-dispersion fiber lasers
We will present our recent results in developing environmentally stable all-fiber oscillators. Femtosecond pulse generation can be achieved for various dispersion maps of all-fiber laser cavity. We are focused on all-normal dispersion cavities working in dissipative soliton regime of ultra-short pulse generation. By using only Polarization Maintaining fibers and components we achieved environmentally stable laser cavities highly resistant to thermal and mechanical perturbations.
2018-12-13 (Czwartek)
Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00
dr inż. Sławomir Drobczyński (Politechnika Wrocławska)Optical tweezers. The Nobel Prize in Physics 2018
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