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

Seminarium Optyczne

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Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00

Prof. Nicolas Treps (Laboratoire Kastler Brossel - Sorbonne Université)

Optical Frequency Combs, from highly multimode entanglement to quantum information applications

Advanced quantum technologies require scalable and controllable quantum resources. Gaussian states of multimode light, such as squeezed states and cluster states, are scalable quantum systems, which can be generated on demand. We propose here to use the many frequency modes contained within femtosecond optical frequency combs as the carrier of such quantum states. We demonstrate how, without changing the photonics architecture, our source is able to generate many different cluster states, or allows to study fundamental quantities such as EPR steering.However, all these properties are based on Gaussian statistics, while non-Gaussian features are indispensable in many quantum protocols, especially to reach a quantum computational advantage. We demonstrate, using mode dependent photon subtraction, controllable non-Gaussian quantum networks and show theoretically and experimentally the prospective of this approach both for fundamental studies and quantum information applications.

Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00

dr Leon Karp z Albert-Ludwigs-Universität Freiburg (IFD UW)

Ion-atom interactions in optical dipole traps

Radiofrequency (RF) traps for atomic ions offer a unique level of control accompanied by e.g. long coherence times, excellent state preparation and readout efficiencies and record-worthy qubit gate fidelities. However, in some applications, most notably in investigations of ultracold ion-atom interactions, the presence of RF fields and the resulting driven motion has also been shown to be responsible for undesired or detrimental effects. In the case of ion-atom collisions, they manifest themselves as the so-called micromotion-induced heating [1]. The latter invokes restrictions with respect to the accessible collision energies which so far have been limited to the range of mK and above for the most available ion-atom combinations [2]. I will discuss an alternative experimental approach to studying ion-atom interactions aiming to combine several key features of ions, foremost their long-range Coulomb interaction, with the versatility of optical traps. This technique known as optical ion trapping allows for confining single ions or ion Coulomb crystals without RF fields [3] and offers comparatively long lifetimes on the order of seconds [4]. I will present our most recent results demonstrating sympathetic cooling of an ion immersed into an ensemble of ultracold atoms overlapped in a set of optical dipole traps [5], and discuss their potential applications in several fields ranging from quantum chemistry to novel quantum simulations. [1] M. Cetina, A.T. Grier, V. Vuletic, Phys. Rev. Lett. 109, 253201 (2012)[2] Härter, J.H. Denschlag, Contemp. Phys. 55(1), 33–45 (2014);M. Tomza, K. Jachymski, R. Gerritsma, A. Negretti, T. Calarco, Z. Idziaszek, P.S. Julienne, Rev. Mod. Phys. 91, 035001 (2019)[3] J. Schmidt, A. Lambrecht, P. Weckesser, M. Debatin, L. Karpa und T. Schaetz, Physical Review X 8, 021028 (2018)[4] A. Lambrecht, J. Schmidt, P. Weckesser, M. Debatin, L. Karpa and T. Schaetz, Nature Photonics 11, 704 (2017)[5] J. Schmidt, P. Weckesser, F. Thielemann, T. Schaetz, and L. Karpa, arXiv:1909.08352

Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00

mgr inż. Weronika Lamperska (Politechnika Wrocławska)

Original microtools for optical tweezers – from ideas to applications

Over the years, optical tweezers have been enriched with various features, such as fluorescence microscopy, Raman spectroscopy, cells sorting. However, most of them require specialized and expensive equipment. In contrast, I report on unique and relatively simple microtools manufactured with 3-dimensional two-photon laser lithography. I demonstrate different types of optically-trapped microtools, each designed for specific applications. I confront the ideas with experimental results and discuss the most successful projects.

Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00

dr hab. Jarosław Korbicz (Centrum Fizyki Teoretycznej PAN)

Decoherence, objectivity, and Spectrum Broadcast Structures

I will present refined forms of decoherence known as quantum Darwinismand, recently introduced, Spectrum Broadcast Structures. I will show theirlinks to one particular aspect of the quantum-to-classical transition,namely how come that the classical world is objective. I will also makean overview of both concrete model as well as general problems studied sofar, putting main emphasis on the Spectrum Broadcast Structures.

Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00

dr Philipp Haslinger (Politechnika Wiedeńska)

Probing the forces of gravity, blackbody radiation and dark energy with matter waves

Atom interferometry has proven within the last decades its surprising versatility to sense with high precision tiniest forces. In this talk I will give an overview of our recent work using an optical cavity enhanced atom interferometer to sense with gravitational strength for fifths forces1,2 and for an on the first-place counterintuitive inertial property of blackbody radiation3. Blackbody (thermal) radiation is emitted by objects at finite temperature with an outward energy-momentum flow, which exerts an outward radiation pressure. At room temperature e. g. a cesium atom scatters on average less than one of these blackbody radiation photons every 108 years. Thus, it is generally assumed that any scattering force exerted on atoms by such radiation is negligible. However, particles also interact coherently with the thermal electromagnetic field4 and this leads to a surprisingly strong force acting in the opposite direction of the radiation pressure3.If dark energy, which drives the accelerated expansion of the universe, consists of a light scalar field it might be detectable as a “fifth force” between normal-matter objects. In order to be consistent with cosmological observations and laboratory experiments, some leading theories use a screening mechanism to suppress this interaction. However, atom-interferometry presents a tool to reduce this screening5 on so-called chameleon models6. By sensing the gravitational acceleration of a 0.19 kg in vacuum source mass which is 10-8 times weaker than Earth´s gravity, we reach a natural bound for cosmological motivated scalar field theories and were able to place tight constraints1,2. [1] P. Hamilton, M. Jaffe, P. Haslinger, Q. Simmons, H. Müller, J. Khoury, Atom-interferometry constraints on dark energy, Science. 349 (2015) 849–851. doi:10.1126/science.aaa8883.[2] M. Jaffe, P. Haslinger, V. Xu, P. Hamilton, A. Upadhye, B. Elder, J. Khoury, H. Müller, Testing sub-gravitational forces on atoms from a miniature, in-vacuum source mass, Nat. Phys. 13 (2017) 938–942. doi:10.1038/nphys4189.[3] P. Haslinger, M. Jaffe, V. Xu, O. Schwartz, M. Sonnleitner, M. Ritsch-Marte, H. Ritsch, H. Müller, Attractive force on atoms due to blackbody radiation, Nat. Phys. 14 (2018) 257–260. doi:10.1038/s41567-017-0004-9.[4] M. Sonnleitner, M. Ritsch-Marte, H. Ritsch, Attractive Optical Forces from Blackbody Radiation, Phys. Rev. Lett. 111 (2013) 23601. doi:10.1103/PhysRevLett.111.023601.[5] C. Burrage, E.J. Copeland, E.A. Hinds, Probing dark energy with atom interferometry, J. Cosmol. Astropart. Phys. 2015 (2015) 042–042. doi:10.1088/1475-7516/2015/03/042.[6] B. Elder, J. Khoury, P. Haslinger, M. Jaffe, H. Müller, P. Hamilton, Chameleon dark energy and atom interferometry, Phys. Rev. D. 94 (2016) 44051. doi:10.1103/PhysRevD.94.044051.

Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00

Maciej Łebek (Centrum Fizyki Teoretycznej PAN)

Statistical properties of cold bosons in a ring trap

Experiments with the Bose-Einstein condensates performed in the recent years prove that it is now possible to measure equilibrium statistical quantities that were more challenging than the average number of atoms in the condensate. In particular, fluctuations of the condensate occupation have been observed for the first time [M.Kristensen, et al. PRL 122, 163601 (2019)]. In this context, we present broad theoretical analysis of statistical properties of cold Bose gas confined to a ring trap. In my talk I will discuss methods that we use to deal with interacting system and present results concerning fluctuations and several other macroscopic state functions calculated for interacting and ideal gas of bosons.

Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00

Dr Krzysztof Jachymski (Forschungszentrum Jülich, Niemcy)

Quantum simulation of extended polaron models using hybrid ion-atom platform

Hybrid quantum systems of ultracold trapped atoms and ions provide> exciting opportunities for quantum chemistry, few-body physics and> quantum simulation. In contrast to optical lattices, trapping atoms> within ion crystals allows to make use of the intrinsic phonon structure> of the medium. This allows for natural realization of analogues of solid> state systems with tuneable properties. Strong ion-atom interactions> naturally give rise to to atom-phonon coupling needed for polaron> physics to emerge. I will discuss the prospects for simulation of> different parameter regimes from weak to strong coupling polarons and> the possibility of tuning the range of the effective interactions in> order to realize exotic many-body states.

Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00

mgr Aleksandra Sierant (Instytut Fizyki UJ)

Tailored optical near field potentials for cold atoms

Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00

dr inż. Przemysław Głowacki (Wydział Fizyki Technicznej Politechniki Poznańskiej)

Laser spectroscopic characterization of the nuclear-clock isomer 229mTh

The thorium isotope 229 possesses a unique, low-energy nuclear isomeric state (denoted 229mTh) at8.28(17) eV [1]. This fact has stimulated the development of novel ideas in the borderland between atomicand nuclear physics. For example, the isomer could be used as an optical nuclear clock, using a -transitionas a reference - instead of a transition in the electron shell - which offers many advantages [2, 3]. Anotherapplications of this system can be: a sensitive probe of temporal variations of fundamental constants, a 3Dgravity sensor in relativistic geodesy, a sensor for detection of topological dark matter.Many experimental attempts to induce and detect an optical excitation of this isomer have failed. Thenuclear moments of the isomer 229mTh have been estimated from nuclear structure models. Apart from thespectroscopic determination of the nuclear spin and indirect measurements of the excitation energy [4, 5],no experimental data on the nuclear properties of the isomer have been available until recently. Using recoilions from the decay of 233U as a source of 229mTh, electrons emitted from the internal-conversion decay ofthe isomer in neutral thorium were detected [6], the half-life for this process was measured [7] and the mostprecise value of isomer energy 8.28(17) eV was determine [1].The availability of the isomer through recoil ions provides a way to measure the unknown nuclear propertiesof 229mTh via laser spectroscopy of electronic transitions. In this presentation we report the opticaldetection of ions in the 229mTh isomeric state and of the resolved hyperfine structure (HFS), which arisesfrom the interaction of the isomer nucleus with the valence electrons.This measurement yielded the first experimental determination of the nuclear moments and the meansquare charge radius of the isomer [8]. Our results constitute a key issue in the ongoing experimental searchfor the direct optical excitation of the nuclear transition, as well as the future nuclear clock operation.This work was supported by European Union’s Horizon 2020 Research and Innovation Programme underGrant Agreement number 664732 (nuClock), from DFG through CRC 1227 (DQ-mat, project B04) andTH956-3-2 and from the LMU Department of Medical Physics via the Maier-Leibnitz Laboratory.References[1] B. Seiferle, L. von der Wense, P. V. Bilous, I. Amersdorffer, Ch. Lemell, F. Libisch, S. Stellmer,T. Schumm, Ch. E. D¨ullmann, A. P´alffy, P. G. Thirolf, Nature, 2019, 573, pp 243-246[2] E. Peik, Chr. Tamm, Europhysics Letters, 2003, 61, pp 181-186.[3] E. Peik, M. Okhapkin, Comptes Rendus Physique 2015, 16(5), pp 516-523.[4] B. R Beck, J. A. Becker, P. Beiersdorfer, G.V. Brown, K. J. Moody, J. B. Wilhelmy, F. S. Porter,C. A. Kilbourne, R. L. Kelley, Physical Review Letters, 2007, 98, pp 142501-4.1

Zapraszamy do sali B2.38, ul. Pasteura 5 o godzinie 10:00

dr Denis S. Kharenko (Novosybirsk State University)

SRS-Driven Evolution of Dissipative Solitons in Fiber Lasers: from limitations to unique sources

It is a history about how the effort to build high power femtosecondfiber laser resulted in discovering in a new kind of solitons - Ramandissipative solitons. A brief review from eliminating the effect ofnonlinear polarization evolution overdriving in mode-locked fiber lasersto generation of femtosecond pulses near 1.3 micrometer in an external passivephosphosilicate-fiber cavity will be presented. Pulse coherence issues,different kind of pulse-mixing and prospects will also be addressed.

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