Dr. Stephan Dürr
Stephan Dürr
Group Leader
Phone: +49 89 3 29 05 - 291
Room: A 2.22
Prof. Dr. Thomas Udem
Thomas Udem
Phone: +49 89 3 29 05 - 282 // -257
Room: D 0.21 // D 0.39

next colloquium

  • The colloquium series will resume at the beginning of the next term in April/October.



Our series of Colloquium Talks takes place from October till January and from April till July, on Tuesdays, at 2:30 p.m..

Attention! Due to the recontstruction of the foyer at the MPQ talks will take place at the interims Lecuture Hall in Room B 0.32.

Scientific organization of the talks: Dr. Stephan Dürr and Dr. Thomas Udem

If you wish to view the live stream of the MPQ colloquium, please use the link to subscribe to the corresponding mailing list. Detailed instructions will be sent to all subscribers.


"Localization of ultra-cold bosons in a 3D laser speckle disordered potential."

"We have observed 3D localization of ultra-cold atoms of a Bose Einstein Condensate, suspended against gravity, and released in a 3D optical disordered potential with short correlation lengths in all directions. Fluorescence imaging of the expanding cloud yields density profiles composed of a steady localized part and a diffusive part. A phenomenological analysis of the data allows us to determine the localized fraction and the diffusion coefficients of the diffusing part. I will present and discuss these results, in the context of Anderson localization." [more]

"Spinning electrons with intense circularly polarized pulses to generate circular attosecond pulses - a new tool for electron control."

"The main goal of the new attosecond (asec=10**-18s) science is the visualization, control and manipulation of electrons on their natural time scale, the asec (152 asecs being the orbital period of the H atom). High order harmonic generation (HHG) in atoms and Molecular High Order Harmonic Generation (MHOHG) in molecules driven by intense ultrashort low frequency laser pulses are the current main source of asec pulses.The mechanism for generation of harmonics is based on the three-step model of tunnelling ionization, acceleration and collision-recollision of the ionized electron with parent or neighbour ions [1]. So far only linearly polarized isolated asec pulses have been generated for which the recollision model predicts maximum energies [2]. Current research on asec pulse generation is focused on the polarization state in MHOHG [3]. Modelling of laser-molecule interactions in the nonlinear nonperturbative regime requires extensive (expensive) numerical solutions of Time-Dependent Schroedinger Equations (TDSE) from which one can study recollision dynamics with ultrashort intense circularly polarized laser pulses in order to produce circular asec pulses. Semiclassical models of laser induced recollision allow for determining the effect of various laser parameters such as polarization, intensity and duration of circularly polarized asec pulses. Such pulses due to their large band width will allow for the creation of circular coherent electron wave packets (CEWP), ie, « spinning » electrons. Chemistry and biology have lived through 2 centuries of molecular « structure ». Asec pulses will finally allow scientists to study molecular « function » on the electron`s natural time scale, the asec?"[1] PB Corkum, Physics Today, March 2011,p.16[2] AD Bandrauk, S Chelkowski, Intnl Rev Atom Molec Phys, 2, 1-22 (2011).[3] AD Bandrauk, KJ Yuan, J Phys B, S 45, 074001 (2012) [more]

"Recent experiments with ions on microfabricated surface traps."

"In this talk I will report on recent progress made at NIST Boulder in the manipulation of ions using microfabricated surface traps. A first experiment performs a laser-less two qubit logic gate, taking advantage of the high magnetic field gradients that can be generated on ion chips. A second experiment, operated at cryogenic temperature, shows the exchange of a single quantum of vibration between two ions trapped 40 micrometers apart. Lastly, I will describe an experiment where the anomalous heating rate of a trapped ion is reduced by a factor of 100 after in-situ cleaning of the surface of the trap." [more]

"Fundamental physics with ultra-cold neutrons at the FRM-2."

"Ultra-cold neutrons (UCN) are a unique tool to measure fundamental properties of nature. Due to the neutron’s comparably simple composition, it is also a favored system to perform searches for a permanent electric dipole moment (EDM) of a fundamental system that violates time reversal symmetry. Such a phenomenon is required in most theories in particle physics to explain the excess of matter versus antimatter in the Universe, a problem which the standard model of particle physics fails to explain by eight orders of magnitude. The search for EDMs is already ongoing for many years in different systems and has already ruled out or restricted many theories and already probes energy scales beyond the LHC. In this talk I will give an overview of the research with such very slow neutrons and focus on a new flagship experiment that is currently being set up at the FRM-2 reactor in Garching to measure the neutron EDM with a sensitivity of 10-28 This corresponds to a larger than a factor 100 improvement, which requires next to the strongest possible source of UCN also an elaborate effort to control systematic effects in small magnetic and electric fields." [more]

"Ultrahigh plasma acceleration by lasers possibly for nuclear energy without dangerous radiation."

"Sauerbrey’s measurement [1] of ultrahigh acceleration of plasma blocks by 1020 cm/s2 with ps laser pulses at very high intensity – confirmed by Földes et al. [2] – are 10,000 times higher than any acceleration with ns laser pulses. At ns, thermal pressure with losses and delays dominates the interaction, while the ps case is dominated by the instantly acting nonlinear (ponderomotive) force. The ps acceleration of 1020 cm/s2 was theoretically and numerically predicted in 1978 [3] (see p. 179). The mechanism is different from acceleration of ion beams due to relativistic self-focusing which has to be avoided using very high contrast ratio laser pulses. Based on the measurements [1,2] the mechanism of the ps acceleration in contrast to that with ns pulses can now be understood as the non-thermal >99% efficient transfer of optical energy into macroscopic motion of the irradiated electron cloud in the space charge neutral plasma, where the inertia is determined by the cloud of the attracted ions. After this plasma block acceleration has been clarified by several further measurements [4], this can be applied to the picosecond irradiation of uncompressed solid DT fusion fuel by side-on igniton [5] of a fusion flame. Computations for igniting solid density hydrogen-boron(11) is only less than 10 times more difficult and may lead to fusion energy production with less radioactivity than from burning coal [6]." [1] Sauerbrey R. Physics of Plasmas 3: 4712 (1996)[2] Földes I B, Bakos J S, Gal, K. et al. Laser Physics 10: 264 (2000)[3] Hora H Physics of Laser Driven Plasmas. New York: John Wiley 1981[4] Hora H., Badziak J., Jie Zhang, K. Jungwirth, K. Rohlena et al. Physics of Plasmas 14: 072701 (2007)[5] Hora H, Miley G H, Flippo K, Lalousis P et al. Laser and Particle Beams 29, 353 (2011)[6] Hora H, Miley G H, He X. et al.2010 Energy and Environmental Science 3: 479 (2010)[7] Hora H, Miley, G H, Yang X., Lalousis P. Astrophysics and Space Science 336: 225 (2011) [more]

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