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Seminarium Optyczne

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Zapraszamy na spotkanie o godzinie 10:15

prof. dr hab. Jakub Zakrzewski (Uniwersytet Jagielloński)

Cold atom inspired strongly interacting systems: Beyond ergodic paradigm, z użyciem połączenia internetowego https://zoom.us/j/97696726563?pwd=ajE2bmFXNUlWc1J3SVAyM3lvUWZ0Zz09 (meeting ID: 976 9672 6563, password: 314297)

Cold atom inspired strongly interacting systems: Beyond ergodic paradigm, with internet connection https://zoom.us/j/97696726563?pwd=ajE2bmFXNUlWc1J3SVAyM3lvUWZ0Zz09 (meeting ID: 976 9672 6563, password: 314297)

Closed interacting many-body systems were for some time believed to obey Eigenstate Thermalization Hypothesis. Many body localization (MBL) provides a robust counterexample.The recent puzzle of thermodynamic limit of MBL is illustrated with our recent results. We also show some other examples of nonergodic behavior, in particular Stark localization and its surprizing consequences as well as the nonergodic features in time dynamics of the boson Schwinger model.

Zapraszamy na spotkanie o godzinie 10:15

dr Benjamin Pasquiou (University of Amsterdam)

seminarium internetowe:A steady-state Bose-Einstein condensate as source for a cw atom laser https://zoom.us/j/97696726563?pwd=ajE2bmFXNUlWc1J3SVAyM3lvUWZ0Zz09 (meeting ID: 976 9672 6563, password: 314297)

A steady-state Bose-Einstein condensate as source for a cw atom laser, https://zoom.us/j/97696726563?pwd=ajE2bmFXNUlWc1J3SVAyM3lvUWZ0Zz09 (meeting ID: 976 9672 6563, password: 314297)

So far Bose-Einstein condensates (BEC) and atom lasers have only been demonstrated as the products of a time-sequential, pulsed cooling sequence. For applications such as next generation atomic clocks,superradiant lasers or atom interferometers for gravitational wave detection, a steady-state source of quantumdegenerate atoms offers great advantages.However, the goal of producing a steady-state BEC or steady-state atom laser has long been thwartedby the incompatibility of laser cooling with evaporative cooling.In this talk, I will describe how we produced a steady-state Bose-Einstein condensate, that is, a BECwhose atom losses are continuously compensated, so that the BEC shows no signs of ever decaying. I willdetail our scheme’s key ingredients. Initially a spatially distributed architecture cools atoms using first thebroad 30-MHz and then the narrow 7.4-kHz strontium transitions in two spatially separated regions [1]. Wethen optically guide, transport, and slow these atoms [2, 3] to a region with very little resonant laser coolinglight. Finally, we protect this region using a “transparency beam” that Stark shifts atoms’ energy levels out ofresonance from the narrow cooling transition [4]. A BEC is thus formed, whose 3-body losses arecontinuously compensated by the pumping of new atoms.This open-dissipative BEC made from a dilute gas echoes the realizations of condensation withmagnons, excitons-polaritons and photons. As such, the study of its intensity and phase fluctuations will be acritical characterization of this continuous source of quantum degenerate matter. Finally, this could pointtoward the long-coveted path for the production of a cw atom laser.[1] S. Bennetts et al., Phys. Rev. Lett. 119, 223202 (2017).[2] C.-C. Chen et al., Phys. Rev. Appl 12, 044014 (2019).[3] C.-C. Chen et al., Phys. Rev. A 100, 023401 (2019).[4] S. Stellmer et al., Phys. Rev. Lett. 110, 263003 (2013)..

Zapraszamy na spotkanie o godzinie 10:15

mgr Ludwig Kunz (IFD UW)

Classical Communication with displacement receivers via noisy quantum channels. Seminarium internetowe: https://zoom.us/j/97696726563?pwd=ajE2bmFXNUlWc1J3SVAyM3lvUWZ0Zz09 (meeting ID: 976 9672 6563, password: 314297

Classical Communication with displacement receivers via noisy quantum channels

For reliable optical communication state discrimination is a critical task. Quantum measurements can provide significant enhancement in information transfer compared to classical techniques and enable detection below the shot-noise limit. Noise in the communication channel or the measurement, however, limits the benefits of quantum-enhanced techniques. Whereas linear losses result in a simple rescaling of the complex field amplitude, the effects of phase diffusion are less trivial. Phase noise can arise as linear noise or nonlinear phase noise caused by nonlinear interactions. Already when communicating via a lossy Kerr medium nonlinear phase noise arises fundamentally and limits the information transfer.Here we consider a receiver based on a displacement operation followed by photon counting with finite photon number resolution. For binary alphabets of coherent states such a receiver provides a near optimal scaling of the error probability with the energy of the signal close to the Dolinar receiver, while having less stringent technical requirements. We analyze the performance of the displacement receiver compared to conventional measurements and present a novel strategy to mitigate the effects of phase noise, both linear and nonlinear.

Zapraszamy na spotkanie o godzinie 10:15

dr Sylvain Gigan (Sorbonne University, Paris, France)

seminarium internetowe: https://zoom.us/j/97696726563?pwd=ajE2bmFXNUlWc1J3SVAyM3lvUWZ0Zz09 (meeting ID: 976 9672 6563, password: 314297)

A sneak peek with light into opaque materials: how I learned to stop worrying and love randomness

Abstract:Complex heterogeneous materials, that scatter light in a highly complex way, presenta huge challenge for imaging (think of seeing inside or through milk or in biologicaltissues). Wavefront shaping has emerged as a powerful tool to focus and image atunprecedented depth, as I will illustrate through a few examples. We have recentlyshown that random light propagation in complex media can also be leveraged moredirectly for various tasks. I will illustrate this concept through various examples,ranging from brain imaging to optical computing (both classical and quantum).Instrukcja obsługi połączenia internetowego znajduje się na stronie:

Zapraszamy na spotkanie o godzinie 10:15

prof. Klaus Mølmer (University of Aarhus, Denmark)

Seminarium internetowe https://zoom.us/j/97696726563?pwd=ajE2bmFXNUlWc1J3SVAyM3lvUWZ0Zz09(meeting ID: 976 9672 6563, password: 314297)

Quantum physics with pulses of radiation

The ability to control quantum systems and prepare special superposition and entangled states of light and matter is pursued with many experimental platforms and forms the basis of strategies for quantum computing, communication and metrology. Such, task oriented research may confront us with “blind spots” in our knowledge, i.e., entire research questions that are not treated by our text book formalism, or are dealt with in manners that are not consistent and accurate. In this talk, I shall discuss one such case: the interaction of a quantum system with a single incident pulse of radiation. While crucial for multiple effects in quantum optics and for the entire concept of flying and stationary qubits, quantum optics textbooks do not provide a formal description of this foundational and elementary interaction process. I shall present a new (and simple) theoretical formalism that, indeed, accounts for the interaction of travelling pulses of quantized radiation with a local quantum system such as a qubit, a spin or a non-linear resonator. We discuss applications of our theory to quantum pulses of optical, microwave and acoustic excitations and we show examples of relevance to recent experiments.

Zapraszamy na spotkanie o godzinie 10:00

prof. Tilman Pfau (Universität Stuttgart, Germany)

Seminarium internetowe

Quantum Droplets and Supersolidity in a Dipolar Quantum Gas

Seminarium z użyciem łącza internetowego:
https://zoom.us/j/97696726563?pwd=ajE2bmFXNUlWc1J3SVAyM3lvUWZ0Zz09 (meeting ID: 976 9672 6563, password: 314297)Abstract:Dipolar interactions are fundamentally different from the usual van der Waals forces in real gases. Besides the anisotropy the dipolar interaction is nonlocal and as such allows for self organized structure formation. In 2005 the first dipolar effects in a quantum gas were observed in an ultracold Chromium gas. By the use of a Feshbach resonance a purely dipolar quantum gas was observed three years after [1]. Recently it became possible to study degenerate gases of lanthanide atoms among which one finds the most magnetic atoms. Similar to the Rosensweig instability in classical magnetic ferrofluids self-organized structure formation was expected. In our experiments with quantum gases of Dysprosium atoms we could observe the formation of a droplet crystal [2]. In contrast to theoretical mean field based predictions the super-fluid droplets did not collapse. We find that this unexpected stability is due to beyond meanfield quantum corrections of the Lee-Huang-Yang type [3,4]. We observe and study self-bound droplets [5] which can interfere with each other. We also observe self-organized stripes in a confined geometry [6] and collective scissors mode oscillations of dipolar droplets [7]. Very recently in the striped phase also phase coherence was observed in Dysprosium and Erbium experiments, which is evidence for a supersolid state of matter [8]. This transition to a supersolid is a beautiful example for the appearance of a Goldstone mode even in a finite system, which we have observed recently [9]. Also a Higgs mode was predicted [10] and observed in our lab recently.References[1] T. Lahaye, et al., Rep. Prog. Phys. 72, 126401 (2009)[2] H. Kadau, et al., Nature 530, 194 (2016)[3] T.D. Lee, K. Huang, and C. N. Yang, Phys. Rev. 106, 1135 (1957), D.S. Petrov, Phys. Rev. Lett. 115, 155302 (2015).[4] I. Ferrier-Barbut, et al., Phys. Rev. Lett. 116, 215301 (2016)[5] M. Schmitt, et al., Nature 539, 259 (2016)[6] M. Wenzel, et al., Phys. Rev. A 96 053630 (2017)[7] I. Ferrier-Barbut, et al., Phys. Rev. Lett. 120, 160402 (2018)[8] F. Böttcher, et al. Phys. Rev. X. 9, 011051 (2019), see also L. Tanzi, et al. Phys. Rev. Lett. 122, 130405 (2019), L. Chomaz et al., Phys. Rev. X 9, 021012 (2019)[9] M. Guo, et al. Nature (2019) https://doi.org/10.1038/s41586-019-1569-5[10] J. Hertkorn et al., Phys. Rev. Lett. 123, 193002 (2019)

Seminarium with internet connection:
https://zoom.us/j/97696726563?pwd=ajE2bmFXNUlWc1J3SVAyM3lvUWZ0Zz09 (meeting ID: 976 9672 6563, password: 314297)Abstract:Dipolar interactions are fundamentally different from the usual van der Waals forces in real gases. Besides the anisotropy the dipolar interaction is nonlocal and as such allows for self organized structure formation. In 2005 the first dipolar effects in a quantum gas were observed in an ultracold Chromium gas. By the use of a Feshbach resonance a purely dipolar quantum gas was observed three years after [1]. Recently it became possible to study degenerate gases of lanthanide atoms among which one finds the most magnetic atoms. Similar to the Rosensweig instability in classical magnetic ferrofluids self-organized structure formation was expected. In our experiments with quantum gases of Dysprosium atoms we could observe the formation of a droplet crystal [2]. In contrast to theoretical mean field based predictions the super-fluid droplets did not collapse. We find that this unexpected stability is due to beyond meanfield quantum corrections of the Lee-Huang-Yang type [3,4]. We observe and study self-bound droplets [5] which can interfere with each other. We also observe self-organized stripes in a confined geometry [6] and collective scissors mode oscillations of dipolar droplets [7]. Very recently in the striped phase also phase coherence was observed in Dysprosium and Erbium experiments, which is evidence for a supersolid state of matter [8]. This transition to a supersolid is a beautiful example for the appearance of a Goldstone mode even in a finite system, which we have observed recently [9]. Also a Higgs mode was predicted [10] and observed in our lab recently.References[1] T. Lahaye, et al., Rep. Prog. Phys. 72, 126401 (2009)[2] H. Kadau, et al., Nature 530, 194 (2016)[3] T.D. Lee, K. Huang, and C. N. Yang, Phys. Rev. 106, 1135 (1957), D.S. Petrov, Phys. Rev. Lett. 115, 155302 (2015).[4] I. Ferrier-Barbut, et al., Phys. Rev. Lett. 116, 215301 (2016)[5] M. Schmitt, et al., Nature 539, 259 (2016)[6] M. Wenzel, et al., Phys. Rev. A 96 053630 (2017)[7] I. Ferrier-Barbut, et al., Phys. Rev. Lett. 120, 160402 (2018)[8] F. Böttcher, et al. Phys. Rev. X. 9, 011051 (2019), see also L. Tanzi, et al. Phys. Rev. Lett. 122, 130405 (2019), L. Chomaz et al., Phys. Rev. X 9, 021012 (2019)[9] M. Guo, et al. Nature (2019) https://doi.org/10.1038/s41586-019-1569-5[10] J. Hertkorn et al., Phys. Rev. Lett. 123, 193002 (2019)

Zapraszamy na spotkanie o godzinie 10:15

Seminarium odwołane

The seminar is canceled

Seminarium zostało odwołane

The seminar is canceled.

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

(IFD UW)

Seminarium odwołane

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

prof. dr hab. Przemyslaw Wachulak (WAT)

Laser-plasma source for spectroscopic experiments in the soft X-ray (SXR) range: NEXAFS/EXAFS spectroscopy and SXR coherence tomography

Short wavelength radiation with a wavelength of 10nm to 120nm is called Extreme ultraviolet (EUV) radiation. Radiation with an even shorter wavelength, i.e. 0.1-10nm, is called soft X-ray (SXR). EUV and SXR radiation is very strongly absorbed in matter in the surface, in a layer of about 100-500 nm thick, which allows the to study the properties of these materials using the near edge X-ray absorption fine structure, e.g. for determining chemical composition by NEXAFS spectroscopy [1-4] or atomic structure using EXAFS [5]. In addition due to possible large spectral bandwidth and small coherence length, it allows to record the interference between the beams reflected from the planar discontinuities of index of refraction in the soft X-ray range from nanometer periodic structures and record it as a modifies reflection spectrum. From that spectrum the depth profile of nanometer planar structures can be reconstructed in a spectral-domain optical coherence tomography scheme to study such multilayer structures with nanometer axial resolution and in a noninvasive way [6]. These properties of EUV and SXR radiation will be discussed during the presentation and supported by experiments, performed using compact laser-plasma source, illustrating the issues presented. The research was based on a compact, laser-plasma EUV and SXR radiation source with a double stream gas puff target, developed at the Military University of Technology. This source has been used in recent years for the research work of the Laser-Matter Interaction Team at the Institute of Optoelectronics, Military University of Technology, Poland. 1. “Compact system for near edge X-ray fine structure (NEXAFS) spectroscopy using a laser-plasma light source”, P. Wachulak, M. Duda, A. Bartnik, A. Sarzyński, Ł. Węgrzyński, M Nowak, A. Jancarek, H. Fiedorowicz, Optics Express 26, 7, 8260-8274 (2018), DOI: 10.1364/OE.26.008260 “Single-Shot near Edge X-ray Fine Structure (NEXAFS) Spectroscopy Using a Laboratory Laser-Plasma Light Source”, P. Wachulak, M. Duda, T. Fok, A. Bartnik, Z. Wang, Q. Huang, A. Sarzyński, A. Jancarek, and H. Fiedorowicz, Materials 11, 8, 1303 (2018), doi: 10.3390/ma11081303 “2-D elemental mapping of an EUV-irradiated PET with a compact NEXAFS spectromicroscopy”, P. Wachulak, M. Duda, A. Bartnik, A. Sarzyński, Ł. Węgrzyński, H. Fiedorowicz, Spectrochimica Acta Part B: Atomic Spectroscopy 145, 107-114 (2018), https://doi.org/10.1016/j.sab.2018.04.014 „NEXAFS at nitrogen K-edge and titanium L-edge using a laser-plasma soft x-ray source based on a double-stream gas puff target”, P. Wachulak, M. Duda, A. Bartnik, Ł. Węgrzyński, T. Fok, H. Fiedorowicz, APL Photonics 4, 030807 (2019); https://doi.org/10.1063/1.5085810 “EXAFS of titanium LIII edge using a compact laboratory system based on a laser-plasma soft X-ray source”, P. Wachulak, T. Fok, A. Bartnik, K. A. Janulewicz, H. Fiedorowicz, Applied Physics B 126, 11 (2020), https://doi.org/10.1007/s00340-019-7365-y “Optical coherence tomography (OCT) with 2 nm axial resolution using a compact laser plasma soft X-ray source”, P. Wachulak, A. Bartnik, H. Fiedorowicz, Scientific Reports 8, 8494 (2018), DOI:10.1038/s41598-018-26909-0, https://rdcu.be/QZQP

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

dr hab. prof. UMK Piotr Żuchowski (UMK Toruń)

Cold collisions - shape and Feshbach resonances

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