Archiv Talks

IQOQI Seminar Room, 2nd Floor, Boltzmanngasse 3, 1090 Vienna

Albert Schließer, EPFL Lausanne

Strong optomechanical coupling in the quantum regime

Abstract:

We demonstrate strong optomechanical coupling between an optical and a mechanical mode of an optical microcavity, which is simultaneously cooled close to the quantum ground state. The employed silica toroidal microresonators exhibits a large optomechanical coupling and small dissipation; in a cryogenic environment this enables the exchange of energy between mechanical and optical degrees of freedom at a rate (>5 MHz) exceeding both the cavity decay rate as well as the thermal decoherence rate of the mechanical oscillator. This observation constitutes a first step towards optical control of quantum states of a mechanical oscillator.

IQOQI Seminar Room, 2nd Floor, Boltzmanngasse 3, 1090 Vienna

Paul Altin: Australian National University

Supernovae, entanglement and falling apples: experiments with Bose-Einstein condensates

Abstract:

In the last decade and a half, experiments with Bose-Einstein condensates by groups the world over have explored new regimes in condensed matter and atomic physics, tested foundations of quantum mechanics and promised applications from precision metrology to quantum computing. In this talk, I will present three experiments encompassing a variety of BEC physics. I will describe our progress towards squeezing-enhanced interferometry beyond the classical limit, and present results from a BEC gravimeter using large-momentum-transfer beamsplitting. I will also discuss our recent work on the 'bosenova' phenomenon: the collapse of Bose-Einstein condensates with attractive interactions.

IQOQI Seminar Room, 2nd Floor, Boltzmanngasse 3, 1090 Vienna

Sylvain Gigan, Institut Langevin, ESPCI ParisTech, France

Measuring the transmission matrix of a complex medium: from imaging to quantum information

Abstract:

Scattering of coherent light in heterogeneous biological media and tissues ,  leads to strong scattering and interferences phenomena which destroy both the spatial amplitude and phase information of any laser illumination. At the spatial level, it gives rise to the well-known "speckle" interference patterns. At the temporal (or spectral) level, a short pulse entering a scattering medium will be stretched due to the multiplicity of path lengths in the propagating medium. Consequently this greatly limits the imaging of an object through a scattering medium.

Multiple scattering is a highly complex but nonetheless deterministic process: it is therefore reversible, in the absence of absorption. Speckle can be coherently controlled. By « shaping » or « adapting » the incident wavefront, it is in principle possible to control the propagation and to overcome the scattering process.

Liquid crystal spatial light modulator (SLM) is a tool of choice to shape a laser beam over a very large number of modes, in order to match the high complexity of a multiple scattering medium. I will show how, using a SLM, one can measure the transmission matrix which links the input - output modes of the scattering medium. We present our original approach of solving the inverse problem for the reconstruction of an arbitrary image through the scattering media. I will detail our recent experiments with phase SLMs applied to, spatial - temporal focusing, imaging and phase conjugation through a thick opaque multiple scattering media. These experimental results confirm that phase-only SLMs are well suited to control laser light propagation in scattering media. Beyond imaging, this technique opens interesting perspectives for coherent control and even possibly quantum information.

IQOQI Seminar Room, 2nd Floor, Boltzmanngasse 3, 1090 Vienna

Lutz Waldecker: Max-Planck-Institut für Quantenoptik, Garching

Characterization of focussed harmonic radiation from solid density plasmas

Abstract:

Coherent harmonic radiation, emanating from the interaction of ultra-short, intense laserpulses with surfaces of solid density plasmas, holds promise for the generation of isolated attosecond pulses with intensities orders of magnitude higher than those produced in gaseous media. They pave the way towards future xuv-pump/xuv-probe type experiments whose time-resolution may deliver insight into fundamental dynamical processes of nature, not accesible with todays methods.

The next step towards the application in such experiments ist the complete temporal characterization of the attosecond pulses. This, however, requires full control over beam transport and focussing.

We present data, demonstrating the ability to directly image focussed XUVlight by means of the intensitiy distribution in the focal spot. Scintillationcrystals of thin (100μm) YAG:Ce serve as a medium to shift the wavelength into the visible range, thus allowing the direct observation with standard optics. Form and shape of the focus permits conclusions to be drawn about the process of generation of the harmonics and the possibility of single shot observation will be a usefull diagnostical tool in future experiments.

IQOQI Seminar Room, 2nd Floor, Boltzmanngasse 3, 1090 Vienna

Andrew Manning: Australian Centre for Quantum Atom Optics (ACQAO),Research School of Physics and Engineering, Australian National University, Canberra, ACT, Australia

Quantum Correlations as a Probe for Ultracold Atomic Systems

Abstract:

We have developed several techniques which have improved the measurement of quantum correlations in ultracold atoms. Using a pulsed source from a magnetic trap has increased data acquisition rates significantly compared to previous experiments, while using an optical dipole trap allows us to produce extremely cold thermal clouds with large correlation lengths. In particular, we are now able to obtain correlation function measurements with near-ideal bunching signals, which allows us to probe the quantum state of ultracold gases.

IQOQI Seminar Room, 2nd Floor, Boltzmanngasse 3, 1090 Vienna

Ulrich Schmid: Department for Microsystems Technology, Institute of Sensor and Actuator Systems, Vienna University of Technology

Title: "Robust Microsystems for Automotive and Airborne Applications"

Abstract: In my talk I will give an overview on current as well as completed R&D activities.

One topic will comprise the development and system integration of a novel type of hot film anemometer targeted for the detection of important injection parameters in Common Rail systems, such as injection begin/end and injected fuel quantity. The robust sensor element is completely integrated into an injection nozzle and based on LTCC (low temperature co-fired ceramics) and thin film technology, as the device needs to withstand hydraulic pressures up to 1350 bar. The sensor signals are evaluated in respect to standard measurement equipment and to hydraulic simulations performed on system level.

The LTCC technology is in addition of high interest for the realization of a compact radar module operated at 79 GHz for mid range (< ~80 m) surveillance purposes in automotive and for the detection of vortexes in airborne application scenarios, respectively. Besides the micro- and nanopatterning of the LTCC substrate enabling the local modification of dielectric properties results on the hardware realization and on the device performance of a high-temperature stable RF-MEMS switch are presented which withstands fabrication temperatures up to 450°C.

Furthermore, novel approaches for the fabrication of high temperature stable pressure sensors are discussed designed for temperatures up to 700°C in e.g. gas turbines and rocket engines. As substrate materials sapphire, a nickel-based superalloy or modified LTCC tapes are used. In this context, the high temperature stability of dielectric (i.e. sputter-deposited Al2O3) and metallic (i.e. Ti/Pt) thin films is investigated.

Finally, the actual activities in the field of resonant microstructures are addressed. Sputter deposited aluminium nitride (AlN) as piezoelectric thin film is used to excite micromachined test structures, such as cantilevers and two-sided clamped bridges, to study in depth the modal behaviour, especially when targeting an improved performance via a tailored patterning of the top electrode.

Inauguration lecture of the

"Erwin Schrödinger Distinguished Lecture Series"

by Sir Anthony J. Leggett (Nobel Prize in Physics 2003), University of Illinois at Urbana-Champaign (USA)

on "Schroedinger's Cat and her laboratory cousins". 

more...

Christian-Doppler-Hörsaal, Fakultät für Physik, Boltzmanngasse 5 / Strudlhofgasse 4, 3. Stock, 1090 Wien

Markus Aspelmeyer, Professor für Quantum Information on the Nanoscale

Title: "Quanten-Optomechanik: Was man von Sprungbrettern über Quantenphysik lernen kann"