15.01.2008 13:30	The motion of cold atoms interacting with an optical cavity field
Prof. Dan Stamper Kurn University of California, Berkeley
Abstract: In considering the fundamental quantum limits of measurement, one is led to consider the use of high finesse optical cavities to extract information efficiently regarding the properties of atomic ensembles trapped therein. Following a discussion of our developing understanding of the mechanical aspects of light-atom interactions inside such cavities, I will present results from recent work at Berkeley. Highlights of such work include the observation of optical cavity bistability at sub-unity average photon numbers, the quantification of quantum fluctuations of cavity light, and measurements of nm-scale collective atomic motion. Prof. Dan Stamper-Kurn
22.01.2008 13:30	Light-Atoms quantum interface
Prof. Eugene Polzik Niels Bohr Institute, Copenhagen
Abstract: Quantum states are vulnerable objects which cannot be copied or identified by measurements. In this respect one of the fundamental goals in quantum mechanics is to identify what is possible and what is impossible to do with an unknown quantum state. In particular, a faithful transfer of quantum states and encoded in them information between photons and atoms has been in the center of attention in recent years. An extremely fruitful approach to this light-atoms quantum interface involves spin polarized atomic ensembles, whose collective quantum states can efficiently interact with photonic states. Entanglement, quantum memory and quantum teleportation have been recently experimentally demonstrated using this approach. We will discuss these experiments and their importance for quantum information processing. Prof. Eugene Polzik
28.01.2008 13:30	Zitterbewegung and Ballistic Side Jump Motion in Semiconductor Structures Sonderseminar
Prof. Dr. John Schliemann Universität Regensburg
Abstract: Effects of spin-orbit coupling in semiconductors have attracted a very significant, partially also renewed, interest over the last years, mainly within the emerging field of spintronics. In this talk I will report on recent theoretical developments concerning zitterbewegung and side jump motion of electrons and holes in III-V semiconductor structures. In particular, the relativistic effect of electronic zitterbewegung has been a long-standing theoretical prediction which was not observed experimentally so far. I will outline the perspectives to detect such an effect in appropriate nanostructures. Prof. Dr. John Schliemann
29.01.2008 13:30	Cavity-free efficient coupling of photons and emitters
Prof. Vahid Sandoghdar Eidgenössische Technische Hochschule, Zürich
Abstract:   We examine the coherent interaction of strongly confined light with a single molecule at cryogenic temperatures [1, 2, 3] and show that a single molecule can leave a fingerprint larger than 10% on a laser beam. Furthermore, we discuss experiments and theoretical calculations for enhancing the coupling between a single molecule and light. We show how a single spherical gold nanoparticle can act as a nano-antenna to modify the excitation, radiation and dissipation processes of a single molecule by more than an order of magnitude [4] and provide guidelines for designing more complex antenna structures that result in even larger effects [5]. We also discuss an experiment which aims at the coupling of two independent Fourier-limited single photon sources [6]. [1] I. Gerhardt, G. Wrigge, P. Bushev, G. Zumofen, M. Agio, R. Pfab, V. Sandoghdar, Phys. Rev. Lett. 98, 033601 (2007). [2] I. Gerhardt, G. Wrigge, M. Agio, P. Bushev. G. Zumofen, V. Sandoghdar, Opt. Lett. 32, 1420 (2007). [3] G. Wrigge, I. Gerhardt, J. Hwang, G. Zumofen, V. Sandoghdar, Nature Phys., 4, 60 (2008). [4] S. Kühn, U. Hakanson, L. Rogobete, V. Sandoghdar, Phys. Rev. Lett. 97, 017402 (2006). [5] L. Rogobete, F. Kaminski, M. Agio, V. Sandoghdar, Opt. Lett. 32, 1623 (2007). [6] R. Lettow, V. Ahtee, R. Pfab, A. Renn, E. Ikonen, S. Götzinger, V. Sandoghdar Opt. Express 15, 15842 (2007). Prof. V. Sandoghdar
07.02.2008 13:30	Atoms in quantum optical potentials Sonderseminar
Prof. Helmut Ritsch Institute for Theoretical Physics, University of Innsbruck
Abstract: Light forces on atoms are strongly modified if the light fields are confined in high Q resonators. Here we consider the limiting case of ultracold atoms in an optical lattice, where the lattice fields are sustained by an optical resonator. This generates new types of collective and long range interactions, which can be controlled by changing cavity parameters. The atomic feedback on the cavity field allows for direct non destructive observation of the corresponding atomic lattice dynamics. The enhanced atom-light interaction directly allows to study and ultimately also modify the dynamics of quantum phase transitions. Resonant atom light interactions can be introduced via quasiparticles as excitons and polaritons in such cavity optical lattices generating further connections to solid state physics phenomena Prof. Helmut Ritsch
12.02.2008 13:30	Single molecule studies of electronic excitation energy transfer: From simple to conjugated polymers
Prof. Thomas Basche Johannes Gutenberg-Universität, Mainz
Abstract: Electronic Excitation Energy Transfer plays a key role in various molecular assemblies. The functioning of natural light-harvesting complexes and light-emitting devices composed of conjugated polymers crucially depends on the efficiency of this process. As has been shown in recent years, single molecule spectroscopy allows new insights into the fundamentals of electronic excitation energy transfer in molecular aggregates. Important aspects relate to the transfer mechanism(s) and the proper treatment of static disorder typically encountered in a solid state environment. In order of increasing structural complexity we have studied simple molecular dimers and multichromophoric dendrimers and (conjugated) polymers [1,2]. It will be shown that the combination of frequency selective single molecule spectroscopy and confocal fluorescence microscopy at 1.4 K is a unique tool to study energy transfer processes in these systems. In particular, from the line widths of single molecule excitation spectra rate constants of energy transfer can be deduced directly. A detailed analysis shows that for several cases the mechanism of energy transfer cannot be described by the simple Förster model (dipole-dipole coupling). Furthermore, novel experiments will be presented which might allow for manipulate the excitation energy flow in molecular aggregates. [1] R. Metivier, F. Nolde, K. Müllen, Th. Basché, Phys. Rev. Lett. 98 (2007) 047802. [2] F. Feist, G. Tommaseo, Th. Basché, Phys. Rev. Lett. 98 (2007) 208301. Thomas Basché
15.02.2008 15:00	The 7th Framework Programme of the EU - Funding Overview and Experiences Sonderseminar B 0.22
Julia Epp und Verena Maier MPI für Quantenoptik		B 0.22
Abstract: Information event about funding opportunities in the 7th European Framework Programme plus reports of successful applicants on their experiences: Project MOLOC (Cooperation - STREP): Dr. Elva Torres Project SiMP (Ideas - ERC Starting Grant): Dr. Tobias Kippenberg Project QUOM (People - Marie Curie Intra-European Fellowship): Dr. Olivier Arcizet Project ELI-PP (Capacities - Combination of Collaborative Project and Coordination and Support Action): Dr. Stefan Karsch
19.02.2008 13:30	Hanbury Brown and Twiss and other atom atom correlations: advances in quantum atom optics
Prof. Alain Aspect Institut d'Optique, Palaiseau, France
Abstract:   Fifty years ago, two astronomers, R. Hanbury Brown and R. Q. Twiss, invented a new method to measure the angular diameter of stars in spite of the atmospheric fluctuations. Their proposal prompted a hot debate among physicists: how could two particles (photons), emitted independently (at opposite extremities of a star), behave in a correlated way when detected ? It was only after the development of R Glauber's full quantum analysis that the effect was understood as the result of a two particle quantum effect. From a modern perspective, it can be viewed as an early example of the amazing properties of pairs of entangled particles. The effect has now been observed with bosonic and fermionic atoms, stressing its fully quantum character. After putting them in a historical perspective, I will present our recent results and comment on their significance. I will also show how our single atom detection scheme has allowed us to demonstrate the creation of atom pairs by non linear mixing of matter waves. This result paves the way to experiments aiming at probing entanglement in atom pairs.
26.02.2008 13:30	Quantum source with pre-programmed number of photons and other experimental applications of entangled states
Prof. Aladar Czitrovszky Hungarian Academy of Sciences, Budapest
Abstract:   Non-classical states of light (e.g. entangled photons) can be used in a number quantum optical measurements in which special features characterising these states play substantial role. Experiments with entangled photon pairs correlated in all aspects (direction, energy, polarisation etc.) have opened a whole field of research. One of the most attractive applications of entangled state is the creation of a special photon source with pre-programmed number of photons having definite parameters. This source can be used in many optical measurements as a special light standard. Beside experimental realisation of such photon source we propose several other implementations of entangled photons for measurement of quantum efficiency of the detectors without optical standards, determination of single- and double-photon response, measurement of the refractive index, etc. Some of the proposed new techniques are utilized by THORN Co Ltd.
03.03.2008 13:30	Coherence and state control in self-assembled quantum dots system Sonderseminar B 2.46
Dr. José M. Villas-Bôas Walter-Schottky-Institut, TU München and Ohio University, Athens
Abstract: Semiconductor self-assembled quantum dots (QD), also known as artificial atom by their similarities, are nearly ideal systems in which to implement basic ideas of quantum system control and study the behavior under external probes and dephasing environments. In this talk I will give an overview of some of the works I developed as a post-doc at Ohio University and as a Humboldt fellow at WSI. I will initially review some basics concepts of optical quantum manipulation in this kind of QD, and follow with some of the relevant experimental advances used to address this task. The main part of the talk will center on the understanding of the coherent manipulation of excitonic and/or spin states in these artificial atoms and molecules and the various dephasing mechanisms present in these systems.
04.03.2008 13:30	One-Electron Quantum Cyclotron: A New Value for the Electron Magnetic Moment and the Fine Structure Constant
Gerald Gabrielse Leverett Professor of Physics, Harvard
Abstract: Not since 1987 has the electron magnetic moment and the fine structure constant been measured more accurately. Now, a one-electron quantum cyclotron has made possible much more accurate measurements of both. The dimensionless electron magnetic moment (often called the electron g value) is measured 15 times more accurately than in a celebrated measurement that stood for 20 years. The fine structure constant is measured 20 times more accurately than in any independent measurement. A quantum non-demolition measurement reveals the quantum structure in the cyclotron motion of an electron suspended by itself for months at a time. Cavity-inhibited spontaneous emission and a one-particle self-excited oscillator (SEO) give the resolution needed to carry out quantum-jump spectroscopy of the lowest energy levels of the weakly-bound electron-apparatus system. The SEO is the classical measurement system for the quantum states of the electron cyclotron motion and spin. Gerald Gabrielse
06.03.2008 13:30	First Production of Antihydrogen Within the Fields of a Penning-Ioffe Trap Sonderseminar
Gerald Gabrielse Leverett Professor of Physics, Harvard ; Spokesperson for the ATRAP Collaboration, CERN
Abstract: Slow antihydrogen atoms are produced for the first time within a combined Penning-Ioffe trap. The well depth of a short-length nested Penning trap is slowly reduced to make the antiprotons and positrons stored within it to interact so as to form antihydrogen atoms within a small volume. Such antihydrogen production is compatible with a superimposed quadrupole Ioffe trap, intended to eventually trap extremely cold, ground-state antihydrogen atoms in low-field-seeking ground states. The number of detected antihydrogen atoms actually increases for a deep Ioffe trap, despite fears and predictions of inhibited production. This step brings closer the long-term goal of low-energy antihydrogen experiments -- to confine antihydrogen atoms so that relatively few atoms can be used efficiently enough to allow high precision laser spectroscopy, and thus much more stringent tests of CPT and Lorentz invariance with leptons and baryons. Gerald Gabrielse
20.03.2008 13:30	From photon bursts to quantum beats. Experiments in cavity QED
Prof. Luis Orozco University of Maryland
Abstract: The interaction of a Rb atom with the two orthogonal polarization modes of an optical cavity presents new possibilities for single atom detection and the evolution of quantum beats in the ground state. Experiments with moderate coupling between the atom and the modes show conditional dynamics visible through correlation function measurements. Work done in collaboration with Matthew Terraciano, David Norris, Rebecca Olson, Jietai Jing, Arturo Fernandez, and Eric Cahoon. Supported by NSF and NIST
02.04.2008 14:00	Locality and unitarity in the structure of quantum cellular automata
Prof. R.F. Werner
Abstract: A quantum cellular automaton is a discrete time quantum lattice system with strictly finite propagation speed. As in the classical case, the update of each cell depends on its neighbours, which means that each cell typically contributes information to several neighbours. Since copying information is forbidden in the quantum case, this implies constraints on the update rules, resulting in a non-trivial interplay between the requirements of unitarity and locality (finite propagation neighbourhood). Cellular automata avoiding the cloning problem can be easily be written down by specifying a local mechanism, like a gate array. We show that such a local mechanism exists for every quantum cellular automaton (in any dimension), provided we may use some additional local work space (local ancillas). When this is not allowed, we show that even in one lattice dimension not every automaton can be implemented. The problem is decided by determining all locally computable properties of cellular automata, which are summarized in a single rational number, the index of the autmaton. The index turns out to label the connected components of the group of cellular automata. Moreover, an automaton can be implemented locally without ancillas iff its index is trivial.
17.04.2008 13:30	Conditional dynamics of interacting quantum dots Donnerstag!
Prof. Dr. Atac Imamoglu Eidgenössische Technische Hochschule Zürich
Abstract:   Spins confined in semiconductor quantum dots (QD) offer new possibilities for realizing quantum optical systems with unique properties. Given their relatively long spin coherence times, it could be argued that QD spins can be used as solid-state qubits; from the perspective of spin-based solid-state quantum information processing, the demonstration of controlled interaction between two QDs is a key step. In this talk, I will describe the first experimental demonstration of optically gated interactions between two quantum dots, where the optical response of one quantum dot is conditioned on the quantum state of another dot. The underlying interaction mechanism is based on tunnel-mediated exchange-like-coupling and can be much larger than the dipole-dipole interaction that was previously proposed for the realization of conditional quantum dynamics. The results presented here constitute a major first step towards the realization of optically controlled spin-based two-qubit quantum gates that can be implemented in picosecond timescales that are unlikely to be matched by transport-based approaches. Prof. Dr. Atac Imamoglu
21.04.2008 13:30	Collective excitations in strongly correlated superfluids, Lorentz versus Galilei Sonderseminar in B 0.21
Sebastian Huber Theoretische Physik, ETH Zürich
29.04.2008 13:30	Spectroscopy of cold, gas-phase biomolecules
Prof. Dr. Thomas Rizzo Ecole Polytechnique Federale de Lausanne (EPFL)
Abstract.   The spectroscopic study of small, neutral biological molecules in supersonic free jets has provided a wealth of information on their energy landscapes and provides an important means to test the reliability of structure calculations. In such studies, the spectral simplification afforded by the cooling in a supersonic expansion is essential for being able to extract useful information. Many, if not most, biological molecules exist in the form of closed-shell molecular ions in solution, however, and one would like to have the same degree of spectral simplification for such species as for neutrals. Toward this end, we have constructed a tandem mass spectrometer with a linear 22-pole ion trap that can be cooled down to ~6K [1]. Ions produced by nanospray are mass-selected, injected into the trap and cooled through collisions with helium. We then irradiate the cold ions with different combinations of UV and IR laser pulses and measure spectra by detecting fragments that are produced after photon absorption as a function of the laser frequency. Our initial work focused on protonated aromatic amino acids, since these are the chromophores for the near UV absorption in peptides [1-3]. After a brief introduction using the results of these initial experiments to demonstrate the capabilities of our apparatus, this talk will focus on our most recent work on UV-IR double-resonance spectroscopy of small peptides [4] – in particular those that are thought to be helical in the gas phase [5]. We seek to establish infrared spectroscopic signatures of helix formation as well as test the limits of theory for predicting the conformations of peptides. Finally, after having characterized the spectra of such species, we demonstrate that we can induce isomerization between stable conformers of helical peptides via vibrational excitation. References [1] Boyarkin, O. V.; Mercier, S. R.; Kamariotis, A.; Rizzo, T. R. J. Am. Chem. Soc. 2006, 128, 2816. [2] Mercier, S. R.; Boyarkin, O. V.; Kamariotis, A.; Guglielmi, M.; Tavernelli, I.; Cascella, M.; Rothlisberger, U.; Rizzo, T. R. J. Am. Chem. Soc. 2006, 128, 16938-16943. [3] Stearns, J. A.; Mercier, S.; Seaiby, C.; Guidi, M.; Boyarkin, O. V.; Rizzo, T. R. J. Am. Chem. Soc. 2007, 129, 11814-11820. [4] Stearns, J. A.; Guidi, M.; Boyarkin, O. V.; Rizzo, T. R. J. Chem. Phys. 2007, 127, 154322. [5] Stearns, J. A.; Boyarkin, O. V.; Rizzo, T. R. J. Am. Chem. Soc. 2007, 129 (in press). Prof. Dr. Thomas Rizzo
05.05.2008 13:30	Multi-Wavelength Gravitational Wave Astronomy: A Dream will soon be reality! Montag!
Prof. Dr. Karsten Danzmann Max-Planck-Institut für Gravitationsphysik, Hannover
Abstract: The first large laser interferometric gravitational wave observatories LIGO, VIRGO and GEO600 are sensitive to signals from solar mass systems in the frequency range from a few Hertz to a few kHz. They have just finished their first year-long science data taking run S5 and are currently analysing data and upgrading their sensitivity for the S6 run in 2009. The low-frequency range, occupied by signals from multi-million solar mass black holes, will be accessible with the space observatory LISA to be launched in 2018. Currently, the LISA precursor mission LISA Pathfinder is in the last stages of implementation with flight hardware being delivered and integrated for a launch in 2010.   Prof. Dr. Karsten Danzmann
13.05.2008 13:30	The Future of Photon Science at DESY
Prof. Dr. Edgar Weckert Deutsches Elektronen-Synchrotron, Hamburg
Abstract:   Researchers using Synchrotron radiation experience exciting times these days at DESY. During the year 2007 the VUV and soft X-ray free electron laser FLASH has been upgraded to its design electron energy of 1 GeV and produced first laser radiation at 6.5 nm wavelength in October 2007. Groundbreaking results have been obtained at FLASH during the last user run period e.g. in the field of nonlinear effects where it has been possible to generate Xe21+-ions with 93eV pho¬tons by focusing the FLASH beam into a Xe gas target. This is a so far theoretically as well as experimentally unexplored regime. Also for storage ring based sources large changes are taking place. Since July 2007 the construction work for the transformation of the 2304m circumference storage ring PETRA into a 6 GeV, 1 nmrad synchrotron radiation source (PETRA III) is ongoing. Meanwhile the almost 300m long experimental hall is nearly finished. More than 70% of the storage ring has already been refurbished. The installation into the new experimental hall is expected to start in April and after an extremely tight schedule the technical commissioning of the storage ring will start in October this year. The experiments to be built at PETRA III will mainly focus on high brilliance applications in the hard X-ray regime. DESY’s present work horse in terms of synchrotron radiation experiments, DORIS III, had a very successful user run during last year before this year’s extended shutdown due to the refurbishment of the DESY pre-accelerator chain. Experiments at DORIS III produced a number of exciting results mainly where high brilliance is not required or where a larger beam size is mandatory. Examples are element mapping by fluorescence analysis and in micro-tomography both of biological ‘samples’. The official kick off event for the European X-ray Free Electron Laser to be constructed in Hamburg has been celebrated summer last year. The first calls for tender have been published and signing of the convention by the participating countries is expected to take place soon. The talk will elaborate on the status of the various projects and discuss several scientific results achieved recently. Prof. Dr. Edgar Weckert
20.05.2008 13:30	Introduction of the ultrafast quantum optics group Double feature
Dr. Peter Hommelhoff Max-Planck-Institut für Quantenoptik, Garching
Abstract: On April 1 of this year a new Max Planck junior research group started at MPQ. Its tentative name is Ultrafast Quantum Optics group. We will give an overview of where we are heading and what future experiments will be based on. The idea is to investigate and make use of the high level of control of femtosecond laser emitted electrons from sharp metal tips. Dr. Peter Hommelhoff
20.05.2008 13:30	Simulating the quantum magnet Double feature
Dr. Tobias Schätz Max-Planck-Institut für Quantenoptik, Garching
Abstract. (1)  For experts in the field of quantum information/computation we describe the first demonstration of an analog quantum simulator based on trapped ions proposed in 2003[1]. (2)  For general recognition, we explain the complete mode of operation of a quantum simulator on the basis of a simple model case. We revile the difficulties in describing a quantum system classically for the case of a quantum magnet, where we introduce and explain the role of superposition states, entanglement and tunneling (quantum fluctuations) by means of our experimental data[2]. [1] D. Porras and J. I. Cirac Phys. Rev. Lett. 92, 207901 (2004) [2] A. Friedenauer, H. Schmitz, J. Glueckert, D. Porras and T. Schaetz. (arXiv:0802.4072v1) submitted (2008). Dr. Tobias Schätz
27.05.2008 13:30	Electron dynamics at surfaces
Prof. Dr. Pedro Echenique University of the Basque Country, San Sebastian, Spain
Abstract:  Due to progress in experimental techniques and development of refined theoretical tools the study of the electron dynamics in solids is feasible. Interaction between lattice, electron, and spin subsystems as well as interaction within each of these subsystems is crucial to understand the mechanism of single-particle excitation dynamics, i.e. the lifetime of excitations. The lifetime sets the duration of the excitation and in combination with the velocity determines the mean free path, a measure of the influence of the excitation. Interest on the study of particle dynamics is motivated by the important role that excited electrons and holes play in many processes, e.g. in energy, charge, and spin transport in bulk materials, at surfaces, across interfaces, and at nanosystems. In this presentation theoretical and experimental results on electron dynamics are discussed in terms of different decay mechanisms for bulk electronic states, surface and image states on metal surfaces. We will concentrate mainly in the electron-electron inelastic decay mechanism, and in electron transfer from single adatoms to surfaces. We will also show that, in contrast to earlier expectations, a low energy collective electronic excitation mode can be found on bare metal surfaces. This mode has an acoustic (linear) dispersion and it has been observed for the first time on Be(0001) but has a very general character and should be present on many metal surfaces.
03.06.2008 13:30	Quantum information processing and quantum metrology with trapped ions
Dr. David J. Wineland National Institute of Standards and Technology Boulder, Colorado, USA
Abstract:   Over the last decade or so, there has been an explosion of activity in quantum information processing (QIP). Arguably, Shor’s algorithm for factoring large numbers stimulated much of the interest; however experimentally, this application remains a distant goal. Nearer-term possibilities include practical quantum communication and quantum simulation. In addition, we can begin to apply some simple QIP procedures to metrology; for example to improve detection sensitivity in interferometry and spectroscopy. These applications to metrology in the context of trapped ions will be discussed. * Supported by IARPA, ONR, and NIST Dr. David J. Wineland
10.06.2008 13:30	Single-photon bus between spin-wave quantum memories
Prof. Dr. Vladan Vuletic MIT-Harvard Center for Ultracold Atoms, Cambridge, USA
Abstract:   Atomic ensembles can store individual photons in the form of quantized collective spin excitations (magnons) that can be converted into single photons with high efficiency. Using the strong magnon-photon coupling, we demonstrate the on-demand generation of entanglement between two macroscopic ensembles. The entanglement is accomplished by partial transfer of a single magnon via an optical resonator that in the ideal case is only virtually populated. We also show that it is possible to announce the successful storage of an incoming photon, while its polarization state remains unmeasured and intact, such that the photon can be recreated at a later time with high fidelity.
17.06.2008 13:30	Learning about order from noise
Prof. Dr. Eugene Demler Harvard University Cambridge, USA
Abstract:   The probabilistic character of measurement processes is one of the most fascinating aspects of quantum mechanics. In many-body systems quantum noise can reveal the non-local correlations and multiparticle entanglement in the underlying states. In this talk I will review recent theoretical and experimental progress in applications of the quantum noise analysis to the study of many body states of ultracold atoms in optical lattices and fluctuating low dimensional condensates. Prof. Dr. Eugene Demler
18.06.2008 13:30	Microwave cavity optomechanics: Measuring and cooling the motion of nanomechanical oscillators with microwave "light" Sonderseminar
Prof. Dr. Konrad W. Lehnert JILA and University of Boulder, USA
Abstract: Cavity optomechanics has recently blossomed into a vibrant field of research. In cavity optomechanical systems, the intracavity light intensity is tightly coupled to the motion of a mechanical oscillator through the radiation pressure force. These systems hold the promise of observing manifestly quantum behavior in a tangible mechanical oscillator. In addition to detecting the motion of the oscillator with nearly quantum-limited sensitivity, light can be used to cool or to amplify that motion. In this talk, I will describe our implementation of a cavity cavity opto-mechanical system that uses microwave "light" instead of optical light. I'll show that the apparent disadvantage of using lower momentum microwave photons can be overcome by employing microfabricated, superconducting cavities integrated with nanomechanical oscillators. Because we operate these nano-electromechanical systems below 50 mK in a dilution refrigerator, less than 1000 thermal phonons occupy the mechanical oscillators, which have MHz resonance frequencies. With optomechanical forces it should be possible to remove most of these remaining phonons and cool the oscillator close to its ground state. In our recent measurements, we have achieved both optomechanical cooling and amplification of mechanical motion. Furthermore, we have demonstrated a displacement detector with sensitivity 18 times the standard quantum limit and we have created 1 aN/Hz1/2 force sensor.
23.06.2008 13:30	Exploring ultracold collisions with Feshbach dimmers Montag Sonderseminar
Dr. Francesca Ferlaino Universität Innsbruck
Abstract:   Ultracold 133Cs atoms are an excellent system to study few-body physics with bosons at large scattering lengths because of the unique scattering properties. A large variety of broad, narrow and overlapping Feshbach resonances have been found together with a variety of weakly bound Cs2 molecular states. We experimentally study three- and four-body physics by investigating ultracold (30-250 nK) atom-dimer and dimer-dimer collisions with Cs Feshbach molecules in various molecular states and Cs atoms in different hyperfine states. Resonant enhancement of the atom-dimer relaxation rate is observed in a system of three identical bosons and interpreted as being induced by a trimer state, possibly an Efimov state. A strong magnetic field dependence of the relaxation rate is also observed in a atom-dimer mixture made of non-identical bosons. Dimer-dimer inelastic collisions have been studied in a pure, trapped sample of Feshbach dimers in the quantum halo regime. We identify a pronounced loss minimum with varying scattering length along with a further suppression of loss with decreasing temperature. This observations provide insight into the physics of a few-body quantum system that consists of four identical bosons at large values of the two-body scattering length.
24.06.2008 13:30	Advanced Nonlinear Optics with Lithium Niobate Crystals
Prof. Dr. Karsten Buse Physikalisches Institut Universität Bonn
Abstract: Lithium niobate crystals are a wide-band-gap dielectric material with large second-order nonlinear-optical coefficients. The ability to structure lithium niobate on the micro- and nanometer scale has led to a boost of the interest in this material. The talk will review novel developments: Very-high-efficiency second-harmonic generation using quasi-phase matching in annealed crystals and in whispering-gallery-mode cavities, ultra-low-threshold optical parametrical oscillation, generation of terahertz waves, slowing down of light and enhanced nonlinearities in photonic crystal structures, sum-frequency mixing for making quantum detectors in the infrared, and soliton generation in photonic lattices became possible because of the remarkable properties of lithium niobate crystals.   Prof. Dr. Karsten Buse
26.06.2008 13:30	Quantum Imaging and Sensing beyond Rayleigh Resolution Sonderseminar Donnerstag!
Prof. Dr. Girish Agarwal Oklahoma State University Stillwater, Oklahoma, USA
Abstract:   One question of great importance in the field of imaging is the issue of the resolution which has been considered to be limited by the Rayleigh criterion. However recently one has developed several methods by which this limit can be overcome. Some of these newer possibilities include use of evanescent waves [plasmonics ] and the use of sources of light which produce entangled photon pairs. I would describe the progress made using entangled photon pairs. I would show how stimulated parametric processes along with spontaneous ones are especially useful in producing high visibility and large signals at high gains of the parametric process. I address both the questions of super resolution and super sensitivity. The entangled photon pairs have also very promising applications in the context of sensing with quantum light and in particular to light scattering. Prof. Dr. Girish Agarwal
01.07.2008 13:30	Open system (dis-)entanglement: What we do know, and what we would like to know
Prof. Dr. Andreas Buchleitner Physikalisches Institut, Albert-Ludwig Universität Freiburg
Abstract:   Quantum entanglement is considered as the precious "fuel" on which quantum computers will run. However, except for the very simplest case of the entanglement between two two-level systems, this fragile quantum feature is very hard to quantify already on the theoretical level, let alone to measure in the lab. In this lecture, I will recall the basic elements of entanglement theory, spell out the central obstacles for an efficient quantification, describe the dynamics of entanglement in noisy environments, and discuss strategies for its direct experimental measurement.
08.07.2008 13:30	Quantum information processing with individual neutral atoms in optical tweezers
Prof. Dr. Philippe Grangier Institut d’Optique Palaiseau, France
Abstract:   Individual neutral atoms are promising candidates to implement quantum bits, or qubits, which are the building bricks for quantum processors or computers. Such atoms can be stored in arrays of optical traps , generated using either interfering light beams (optical lattices), or strongly focused lasers (optical tweezers).   Here we will describe in detail how quantum information can be written and read out using an individual Rubidium atom trapped in a submicrometer tweezer. We will show that such a qubit can be coherently manipulated and transported over a few microns distance, simply by moving the tweezer [1]. We will also show how such trapped atoms can be used to generate indistinguishable single photons [2], and discuss perspectives for entangling atoms in two separate tweezers, using for instance transient excitation to Rydberg states.     [1] J. Beugnon et al, Nature Physics 3, 696 (2007)   [2] J. Beugnon et al, Nature 440, 779 - 782 (06 Apr 2006)
14.07.2008 11:00	Generation of Short Wavelength Radiation via Coherent Hyper Raman Superradiance Sonderseminar fällt aus
Prof. Dr. Marlan O. Scully Texas AM University and Princeton University
Abstract: We find that intense short pulses of XUV radiation can be produced by cooperative spontaneous emission from visible or IR laser pulses driving atoms or ions. The process depends on the generation and utilization of atomic coherence as is the case in lasing without inversion. However, the radiation process is not stimulated emission, but is rather cooperative spontaneous emission in the sense of Dicke. More precisely, the many atom mathematics of the problem is the same as that of coherent anti-Stokes Raman scattering. Prof. Dr. Marlan O. Scully
14.07.2008 15:00	Femtosecond Lasers: Tools for Attosecond Science Sonderseminar
Prof. Franz X. Kärtner Massachusetts Institute of Technology, Cambridge, USA
Abstract: Over the last decade, advances in femtosecond lasers have opened up the possibility to study physical processes, sample electronic signals and control optical and electronic systems on an attosecond time scale. Today, the field of attosecond science is mostly based on carrier-envelope phase controlled few-cycle lasers and we will review the progress we made towards such sources based on octave spanning Ti:sapphire lasers and optical parametric chiped pulse amplification. However, in parallel to these efforts on carrier-envelope phase controlled laser systems, there is increasing demand for low jitter optical and microwave signals and synchronization techniques that enable sampling of signals and long term stable synchronization of large scale facilities with femtosecond and in the future attosecond precision. The low noise properties of femtosecond lasers, to a large part also responsible for the high quality carrier-envelope phase stability achievable, enable the generation of low jitter optical pulse trains that can be used for precise microwave signal generation, high resolution and high speed sampling using photonic Analog-to-Digital Conversion as well as long term stable synchronization of large scale facilities such as x-ray free electron lasers. Advances made in these areas will be reviewed. Prof. Franz X. Kärtner
15.07.2008 13:30	Atomic Quantum Sensors on Ground and in Space
PD Dr. Ernst Maria Rasel Institut für Quantenoptik, Leibniz Universität Hannover
Abstract: Quantum matter gives unique insights into a broad range of phenomena in fundamental physics as well as it offers interesting prospects for novel quantum sensors. Reaching ever-new frontiers in low temperature physics and achieving full control of these elementary quantum systems were part of the central motivations for research on cooling and manipulation of atoms. The breaking of temperature records opened the way to many new scientific achievements, like atom interferometers and atomic clocks with highest accuracy, novel phase transitions or atom lasers. It is interesting to speculate if quantum degenerate gases will be of advantage for metrological applications. The perfect control of the external degrees of freedom is mandatory for a better control of systematic errors. Microgravity can extend the science of quantum gases towards inaccessible regimes of lowest temperatures below picokelvins, macroscopic dimensions, and unequalled durations of the unperturbed evolution of these distinguished quantum objects. These conditions set the stage for the study of the physics of ultra-dilute gases and giant matter-waves and the control of these macroscopic quantum objects and mixtures in an environment unbiased by gravity. In particular, microgravity is of high relevance for matter-wave as it permits the extension the unperturbed free fall of these test particles in a low-noise environment. This is a prerequisite for fundamental tests in the quantum domain such as the equivalence principle or the realisation of ideal reference systems. The QUANTUS team, formed by a consortium of the Leibniz University of Hanover, the University of Hamburg, Berlin, Ulm and ZARM as well as the Max-Planck Institute and ENS, realised a compact facility to study a Rubidium Bose-Einstein Condensate in the extended free fall at the drop tower in Bremen and during parabolic flights. The facility will permit to study the generation and outcoupling of BEC in microgravity, the study of decoherence and atom interferometry. The remote controlled and miniaturised facility, which produces Bose-Einstein condensates of Rubidium, is in operation since November 2007.   PD Dr. Ernst Maria Rasel
23.09.2008 13:30	Dynamics of coherent oscillations in nanostructures probed by ultrafast lasers Sonderseminar
Prof. Hans Schüssler Texas A&M University, College Station, USA
Abstract:  With a femtosecond pump-probe technique the electronic excitations, fast relaxation processes, optic and acoustic phonons in systems of different dimensionality, 3D(bulk material, thick films)-2d(thin films)-1D(nanowires)-0D(nanoparticles) were studied. In particular, the dynamics under action of ultrafast light and the processes related to electron-phonon coupling, carrier diffusion, softening of the lattice, strong inhomogeneity in the absorption region due to an induced gradient of electronic density excitations and the anharmonicity of the lattice oscillations at high excitation levels were investigated. Coherent acoustic oscillations in nanoparticles excited by femtosecond laser pulses provide information on their size and shape. By monitoring the relaxation of the non-oscillating component of the signal the characteristics of the thermalization of electronic and lattice subsystems and the electron-phonon coupling constant can be determined using a two-temperature model. The dephasing effect due to the size-distribution and modeling of the electronic and lattice contributions to the observed signal of coherent acoustic phonons are discussed Optical phonons in films and nanowires were studied at different excitation levels. The excitation of coherent optical phonons occurs via the displacive mechanism, when due to the electronic excitations with an ultrashort laser pulse the equilibrium positions of atoms in the lattice are abruptly displaced relative to their initial positions. Recent theoretical analysis revealed that the displacive mechanism in opaque materials and impulsive excitation in transparent materials can be considered as particular cases of stimulated Raman scattering. Laser-induced excitations modify the state of the lattice and interatomic potential, which is reflected in the changes of the optical phonon frequency. These changes at high excitation levels were also studied and modeled taking into account softening of the lattice, carrier diffusion, strong inhomogeneity in the absorption region due to an induced gradient of electronic density excitations and the anharmonicity of the lattice oscillations. Prof. Hans Schüssler
14.10.2008 13:30	Plasmons, phonons and light in ultra-long thin nanostructures
Prof. Dr. Philip Russel Max Planck Forschungsgruppe für Optik, Information und Photonik
Abstract:  Ultra-long silica-air nanostructures, both empty and selectively filled with metal or semiconductor, can be realized in photonic crystal fibre. The photonic and phononic characteristics of these structures will be discussed and their applications explored. Prof. Dr. Philip Russel
11.11.2008 13:30	Quantum-opto-mechanics: towards quantum entanglement of micromechanical resonators
Prof. Dr. Markus Aspelmeyer Institut für Quantenphysik und Quanteninformation, Universität Wien
Prof. Dr. Markus Aspelmeyer
14.11.2008 11:15	Deceleration of atoms and molecules using the Stark and Zeeman effect am Freitag um 11:15 Uhr!
Prof. Dr. Fréderic Merkt Laboratorium für Physikalische Chemie, Eidgenössische Technische Hochschule, Zürich
Abstract:   New experimental results on the manipulation of the translational motion of atoms and molecules in the gas phase using inhomogeneous electric and magnetic fields will be presented. In the experiments, cold atoms or molecules moving at high speed in the laboratory reference frame in supersonic beams are slowed down to low velocity, mirrored and loaded in electrostatic or magnetic traps. Two methods developed in Zurich in the past years will be described in detail with the example of atomic hydrogen: In the first, the atoms are excited to Rydberg Stark states with a large dipole moment, decelerated by time-dependent inhomogeneous electric fields and loaded in electrostatic traps. In the second, the ground state atoms are decelerated in a multistage Zeeman decelerator consisting of an array of solenoids though which high currents are switched on an off rapidly and loaded in a magnetic trap. The motivations for these experiments and future plans will also be presented. Prof. Dr. Fréderic Merkt
18.11.2008 13:30	Factorization of numbers, Schrödinger cats and the Riemann hypothesis
Prof. Dr. Wolfgang Schleich Institut für Quantenphysik, Universität Ulm
Abstract:   In this talk we connect the three different topics of factorization of numbers, Schrödinger cats and the Riemann hypothesis. The bridge between these areas is the concept of a Gauss sum. Gauss sums manifest themselves in various phenomena such as the Talbot effect, wave packet dynamics or quantum carpets. Moreover, Gauss sums can be used to efficiently factor numbers. In the meantime 7 experiments have used such an approach. They rely on NMR techniques, the physics of cold atoms and femtosecond pulses. At the moment the largest number that was factored using a Gauss sum algorithm is a 17 digit number. The talk summarizes these activities. Moreover, we propose an elementary quantum system which provides us with the Riemann Zeta function. We show that its zeroes are a consequence of the interference of two quantum systems with opposite phases. However, the preparation of such a superposition state (Schrödinger cat) is impossible unless one takes advantage of entangled quantum systems. In this sense analytic continuation familiar from complex analysis finds entanglement as its analogue in quantum mechanics. Prof. Dr. Wolfgang Schleich
20.11.2008 13:30	Coherent x-ray physics in attosecond and towards deptosecond am Donnerstag!
Prof. Dr. Toshiki Tajima Department für Physik, Ludwig Maximilians Universität München
Prof. Dr. Toshiki Tajima
25.11.2008 13:30	Quantum Diamonds
Prof. Dr. Jörg Wrachtrup Physikalisches Institut, Universität Stuttgart
Abstract: Controlling quantum degrees of freedom in solids is an outstanding challenge in physics. Owing to strong interaction with the solid environment usually dephasing in fast and hence control is imperfect. Spins have turned out to be ideal candidates for solid state quantum systems, especially when incorporated into an otherwise spin free lattice made up from carbon like e.g. in diamond. Diamond has outstanding material properties, including ultrahardness and higher thermal conductivity than any other solid material. In addition, diamond has recently become much more attractive for solid-state electronics, with the development of techniques to grow high-purity, single-crystal synthetic diamonds and insert suitable impurities into them (doping). Pure diamond is an electrical insulator, but doped with boron, it can become a semiconductor with outstanding properties. It could be used for detecting ultraviolet light, ultraviolet light-emitting diodes and optics, and high-power microwave electronics. But the application that has many researchers excited is quantum spintronics, which could lead to a practical quantum computer, ultra¬secure communication and has the potential for revolutionizing imaging schemes. This is based on the fact that spins in diamond are exceptionally well shielded from their environment, allowing e.g. multipartite entangled states to be observed over ms in a room temperature solid [1]. The very same fact renders electron spins in diamond to be exceptionally high resolution magnetic field sensors [2]. The talk will highlight recent achievements in solid-state quantum physics with diamond, which may also have important spin off to other areas like e.g. biophysics. [1] P. Neumann et al. “Multipartite entanglement among single spins in diamond” Science 320 (2008) 1326 [2] G. Balasubramanian “Nanoscale imaging magnetometry with diamond spins under ambient conditions” Nature 455 (2008) 648   Prof. Dr. Jörg Wrachtrup
02.12.2008 13:30	Strong correlations in ultracold quantum gases
Prof. Dr. Klaus Sengstock Institut für Laserphysik, Universität Hamburg
Prof. Dr. Klaus Sengstock
09.12.2008 13:30	LEDs for general lightning
Dr. Klaus Streubel Osram Opto-Semiconductors, Regensburg
16.12.2008 13:30	High-precision spectroscopy of cold trapped HD+: towards metrology of particle masses
Prof. Dr. Stephan Schiller Institut für Experimentalphysik, Heinrich-Heine-Universität Düsseldorf
Abstract.   Molecular hydrogen ions (H_2^+, HD^+, ...) are the simplest molecules, and their simplicity makes them interesting systems for fundamental physics studies and for methodological investigations in the novel field of cold molecules. The energies of molecular hydrogen ions, in particular the rotational and vibrational energies (in atomic units) are functions of the particle masses (electron, proton, deuteron), the Coulomb interaction, and to a lesser extent the magnetic properties of these particles. Significant theoretical advances now permit to calculate these energies ab-initio with an inacccuracy below 1 part in 10^9. This includes important contributions from relativistic and QED corrections. The dependence of transition energies on the electron-to-proton mass ratio makes these molecules also candidates for a laboratory search for a possible time-dependence of this fundamental constant. In this talk I will describe the status of the Düsseldorf experiment on precision laser spectroscopy of sympathetically cooled HD+, including the most recent developments towards enhanced precision. Prof. Dr. Stephan Schiller

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