ansprechpartner

Dr. Stephan Dürr
Stephan Dürr
Gruppenleiter
Telefon: +49 89 3 29 05 - 291
Raum: A 2.22
Prof. Dr. Thomas Udem
Thomas Udem
Wissenschaftler
Telefon: +49 89 3 29 05 - 282 // -257
Raum: D 0.21 // D 0.39




kommende Kolloquien

Kolloquien

Kolloquien

Die Gastvorträge im Rahmen des MPQ-Kolloquiums finden von April bis Juli sowie von Oktober bis Januar jeweils dienstags um 14:30 Uhr statt.

Achtung! Ab Oktober 2017 finden die Vorträge, aufgrund der Bauarbeiten, vorübergehend im Interims-Hörsaal, Raum B 0.32 am Max-Planck-Instituts für Quantenoptik statt.

Ansprechpartner für die wissenschaftliche Organisation:

Dr. Stephan Dürr und Dr. Thomas Udem

Wenn Sie einen Vortrag im Livestream verfolgen möchten, ist es nötig, dass Sie sich in eine entsprechende Mailing Liste eintragen. Daraufhin erhalten Sie Instruktionen zum Empfang des Livestreams.

Monat:

“A toolbox for delocalization experiments with atoms, molecules and clusters of atoms and molecules.”

"Recent experiments in Vienna have shown that large covalently bound complexes, composed of several hundred atoms, can be delocalized over hundred times their own size and maintain quantum coherence over many milliseconds , even when heated to several hundred Kelvin. Two major motivations are driving this research: Nanoparticle interferometry turns out to be optimized for testing new measures of quantum macroscopicity. We will discuss the molecular beam methods and coherent manipulation schemes that are required to push the current state-of-the-art by the next orders of magnitude where new bounds will be set to non-standard quantum models at the quantum-classical interface. Molecular interferograms are quantum nanorulers either in position space or in the time-domain They have an intrinsic force sensitivity down to the Yoctonewton level and are therefore well-suited for novel measurements of magnetic, structural, electronic and optical properties of molecules, clusters and other nanoparticles with widely delocalized quantum states in controlled external fields."1. K. Hornberger et al., Rev. Mod. Phys. 84, 157 (2012).2. S. Nimmrichter et al., Phys. Rev. A 83, 043621 (2011).3. S. Gerlich et al., Nature Communs. 2, 263 (2011).4. T. Juffmann et al., Phys. Rev. Lett. 103, 263601 (2009).5. S. Gerlich et al. Angew. Chem. Int. Ed. 47, 6195 (2008).6. S. Gerlich et al., Nature Phys. 3, 711 (2007).7. L. Hackermüller, NATURE 427, 711-714 (2004). [mehr]

The shadow of a single atom

We have performed absorption imaging of a single atom for the first time [1]. A trapped Yb+ atomic ion scatters light out of an illumination beam tuned to atomic resonance at 369.5 nm. When the beam is reimaged onto a CCD camera, we observe an absorption image of 440 nm diameter and 5% contrast. The absorption contrast is investigated as a function of laser intensity and detuning, and closely conforms to the limits imposed by simple quantum theory and known properties of our imaging system. Defocused absorption images provide spatial interferograms of the scattered light, permitting accurate retrieval of the amplitude and phase of the scattered wave. We measure a phase shift of >1 radian in the scattered light as a function of laser detuning, which may be useful in quantum information protocols. The interferograms point to the possibility of observing the focusing of light by a single atom.[1] Streed et al., accepted to Nature Commun [mehr]

“Phase-resolved THz spectroscopy.”

"The generation of coherent THz pulses from femto-second sources has enormously progressed during the last 10 years. The band-width, intensities, as well as the efficiency has increased by using advanced semiconductor emitters and non-linear processes. In this way the spectral range up to 100 THz can be covered by quasi single cycle THz pulses. This frequency range – previously inaccessible for time-resolved spectroscopy - is an important part of the electro-magnetic spectrum due to a large number of fundamental resonances. Vibrational and rotational resonances of molecules are attractive for chemical sensing (chemical fingerprint analysis) and spectroscopic imaging. In solids, the resonance energies of phonons, plasmons and impurity transition are within the THz range. In particular also the transition energies of semiconductor nano structures occur in the THz band.Time-resolved THz spectroscopy allows phase-locked measurements – in particular phase-resolved detection. We take advantage of this fine capability to study the dynamics of semiconductor nanostructures. Phase-resolved THz spectroscopy allows unique measurements of stimulated emission form Quantum-Cascade Lasers. The knowledge of the phase of the THz response provides fascinating insights into the quantum mechanical processes. The study of highly excited nanostructures allows the prediction for coherent control schemes for optoelectronic devices. Together with novel resonator concepts we are able to show THz “switching” and strong coupling to quantized transitions." [mehr]

"Otto Stern: the nearly forgotten pioneer of atomic, molecular, and nuclear physics."

"Otto Stern is one of the great pioneers of modern atomic, molecular and nuclear physics. In 1943 he received the Nobel prize in physics for his development of the “Molecular Beam Method” and his “Measurement of the Magnetic Moment of the Proton”. The molecular beam method allowed physicists and chemists for the first time to perform experiments on single isolated atoms or molecules and determine inner properties of atoms and nuclei. For the exploration of the quantum world his invention has an importance similar to Gutenberg’s invention of single separated letters for printing of books. Stern was 81 times nominated for the Nobel prize in physics more than Planck, Einstein or any other of the great pioneers. Based on Sterns invention the Maser, the Atomic clock, the nuclear magnetic resonance etc. were developed. In 1933 Stern was forced to emigrate to the US since he was Jewish." [mehr]

"High repetition rate frequency combs: ultrafast optics starting with continuous-wave lasers."

"The introduction of mode-locked laser optical frequency combs during the last decade led to revolutionary progress in precision optical frequency synthesis and metrology. Such combs typically operate at repetition rates of hundreds of MHz. Combs at higher repetition rates are of interest for other applications, such as arbitrary waveform generation and radio-frequency signal processing, which do not require full stabilization of the offset frequency. In this talk I discuss two flavors of high repetition rate comb generation starting with a single continuous-wave laser. Continuous-wave lasers subject to strong periodic electro-optic modulation can be formed into optical frequency combs and compressed into trains of picosecond pulses at rates on the order of 10 GHz. Nonlinear optical propagation can extend comb bandwidths into the THz regime, allowing realization of pulse durations at the few hundred femtosecond level, and producing combs with extremely flat and smooth optical power spectra. We have exploited such combs for applications such as line-by-line optical pulse shaping, also known as optical arbitrary waveform generation, and programmable radio-frequency filtering. Generation of combs at much higher repetition rates can be achieved via nonlinear wave mixing in high quality factor (high Q) microresonators. Our group has investigated line-by-line pulse shaping of such combs generated in silicon nitride ring resonators. Our experiments reveal formation of two different types of combs which exhibit strikingly different time domain behaviors. One type can be compressed to nearly bandwidth-limited pulses, which indicates high coherence across the spectrum. A second type exhibits limited compressibility and degraded coherence. Accordingly, understanding and control of the coherence constitutes a topic of significant interest in the further development of microresonator comb generators." [mehr]

 
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