past events

Thursday 06. August 2015

IMPRS get-together

 

Organisation: Roland Lauter (FAU/ Institute for Theoretical Physics II)

Talk: Synchronization in the quantum regime

Speaker: Stefan Walter (Institute for Theoretical Physics II, FAU)

Place: MPL / Large seminar room (*435)

Abstract:

Synchronization is a universal phenomenon that is important both in fundamental studies and in technical applications. Here, we discuss the fate of synchronization in quantum systems. First, synchronization in the simplest quantum-mechanical scenario possible, i.e., a quantum-mechanical self-sustained Van der Pol oscillator coupled to an external harmonic drive, is investigated. Using the power spectrum we analyze synchronization in terms of frequency entrainment and frequency locking in close analogy to the classical case.

Next, synchronization of two dissipatively coupled quantum Van der Pol oscillators in the quantum regime is analyzed. In both cases, due to quantum noise strict frequency locking is absent and is replaced by a crossover from weak to strong frequency entrainment.
Moreover, a possible experimental realization of two coupled quantum Van der Pol oscillators in an optomechanical setting is described.

[1] S. Walter, A. Nunnenkamp, and C. Bruder, Ann. Phys. 527, 131 (2014)
[2] S. Walter, A. Nunnenkamp, and C. Bruder, Phys. Rev. Lett. 112, 094102 (2014)

Monday 06. July 2015

IMPRS get-together

 

Organisation: Eugene Kim (MPL/ Vollmer Lab)

Talk: Signal-reversing cavity-based Polarimetry: Ultrasensitive chiral sensing

Speaker: Dr. Peter Rakitzis (University of Crete)

Place: MPL / Large seminar room (*435)

Abstract:

Sensing chirality is of fundamental importance to many fields. The most widely used methods for optical chiral sensing are the traditional methods of circular dichroism and optical rotation. However, these chiral signals are typically very weak, and their measurement is limited by larger time-dependent backgrounds (such as spurious birefringence) and by imperfect and slow subtraction procedures. We discuss proposals [1] and demonstrations [2] of a pulsed-laser bowtie-cavity-ringdown polarimeter with counter-propagating beams, which solves these background problems: the chiral signals are enhanced by the number of cavity passes (typically >103); the effects of linear birefringence are suppressed by a large induced intracavity Faraday rotation; and rapid signal reversals are effected by reversing the Faraday rotation and subtracting signals from the counter-propagating beams. These advantages allow measurements of absolute chiral signals in environments where background subtractions are not feasible. Specifically, we measure optical rotation from of (+)-α-pinene and (-)-α-pinene in open air, as well as from chiral liquids in the evanescent wave produced by total internal reflection at a prism surface. Evanescent-wave optical rotations of various (+)-maltodextrin and (-)-fructose solutions confirm the Drude-Condon model for Maxwell’s equations in isotropic optically active media [2]. We discuss the limits of this polarimeter for chiral sensing in analytical chemistry, the possible extension to microresonators for chiral measurements of few or single molecules, and to the measurement of parity nonconserving optical rotation in atomic gases [1,3,4].

(1) L. Bougas, G. Katsoprinakis, W. von Klitzing, J. Sapirstein, T.P Rakitzis, “Cavity-enhanced parity non-conserving optical rotation in metastable Xe and Hg”, Phys. Rev. Lett. 108, 210801 (2012).

(2) D. Sofikitis, L. Bougas, A. Spiliotis, G. Katsoprinakis, B. Loppinet, T.P. Rakitzis, “Evanescent-wave and ambient chiral sensing by signal-reversing cavity-ringdown polarimetry” Nature 514, 76 (2014).

(3) G. Katsoprinakis, L. Bougas, T.P. Rakitzis, V. Dzuba, V.V. Flambaum, “Calculation of parity non-conserving optical rotation in iodine at 1315 nm” Phys. Rev. A 87, 040101(R) (2013).

(4) L. Bougas, G. Katsoprinakis, W. von Klitzing, T.P. Rakitzis, “Fundamentals of Cavity-Enhanced Polarimetry for Parity-Nonconserving Optical Rotation Measurements: Application to Xe, Hg and I”, Phys. Rev. A 89, 052127 (2014).

 

 

 

Tuesday 23. June 2015

IMPRS get-together

 

Organisation: Mykhaylo Filipenko (FAU/ ECAP)

Talk: DNA-Origami and self-assemble DNA-structures

Speaker: Kerstin Göpfrich (University of Cambridge)

Place: MPL / large seminar room (*435)

Abstract:

DNA origami and other self-assembled DNA nanostructures have been used to create man-made transmembrane channels in lipid bilayers. We present three novel designs with diameters ranging from 0.8 nm to 8 nm. We utilize DNA tiles and scaffold origami with different scaffold length to create pores of variable size and architectural complexity.We compare the single channel behaviour these pores and confirm the correspondence between engineered design and single-channel behaviour. While the obtained conductance of the smallest pore is the lowest, the value for the 2 nm pore agrees with literature. With the 6 nm pore exhibiting a conductance of 10 nS, our pores span two orders of magnitude in conductance, comparable to protein pores encompassing small ion channels as well as large porins. We thus demonstrate the creation of artificial DNA-based pores inspired by the rich structural and functional diversity of natural membrane components.

Monday 01. June 2015

IMPRS get-together

 

Organisation: Yazgan Tuna (MPL/ Sandoghdar Division)

Talk: Active Brownian motion and artificial microswimmers

Speaker: Giovannni Volpe (Soft-Matter Lab, Bilkent University, Turkey)

Place: MPL / Large seminar room (*435)

Abstract:

In recent years, active Brownian motion has attracted a lot of interest. Differently from simple Brownian motion, which is dominated by random fluctuations, active Brownian particles, e.g. bacteria, feature an interplay between random fluctuations and active swimming. Various experimental model systems have been proposed for its study, e.g. Janus particles in a water-hydrogen peroxide. In this seminar, I will first give an overview of active Brownian motion and discuss how it can be numerically modelled and simulated. Then, I will focus on a new species of artificial microswimmers that we have recently developed where the swimming behavior of the particles can be tuned by the intensity of illumination. I will show how this leads to the possibility of studying the behavior of active Brownian particles under new conditions, e.g. swimming behavior depending on the particle position, and in new environments, e.g. non-homogenous and porous media. I will also show how this may have applications for the study of the behavior of biological microswimmers such as bacteria.

Thursday 21. May 2015

MPL Distinguished Lecturer Series
Semiconductor devices for quantum technologies

 

Speaker:

Prof. Jonathan Finley (Technische Universität München)

Place:

MPL / large seminar room (*435)

Abstract:

The application of all-optical techniques to control and probe discrete quantum states in solids benefits from the possibility to apply well established methods from the quantum optics toolbox such as coherent control, optical pumping, resonant light scattering and dynamical decoupling. When combined with advanced semiconductor nanofabrication methods and the ability to electrically tune quantum systems, such electro-optical approaches open the way to interconnect quantum systems via photonic channels in highly integrated architectures.
In this talk, I will discuss several research themes pursued in my group in which individual, optically active quantum dots (QDs) are embedded within a tailored photonic environment and addressed via resonant and near resonant optical pulses. For example, we have applied ultrafast optical methods to probe coherent exciton and electron spin dynamics in individual electrically tunable dots over timescales ranging from a few picoseconds up to ~50μs, elucidating the processes responsible for spin decoherence. Typically, environmental coupling is detrimental to the exploration of such quantum phenomena. However, we show how controlled optically induced dissipation arising from exciton-LA phonon interactions can actually be exploited for high fidelity state preparation. Our focus will then move to nanostructures for integrated quantum photonics. We will discuss how slow light phenomena in GaAs photonic crystal waveguides can be used to efficiently direct single photons into propagating waveguide modes on a chip and illustrate how one can detect quantum light in-situ using integrated NbN superconducting single photon detectors. By temporally filtering the time-resolved luminescence signal stemming from individual resonantly excited dots, we demonstrate on-chip resonant fluorescence with a narrow linewidth <8μeV; key elements needed for the use of single photons to connect quantum systems in future quantum photonic circuits.

Thursday 30. April 2015

MPL Distinguished Lecturer Series
Topological Phases of Sound and Light

 

Speaker:

Prof. Florian Marquardt (Professor of Theoretical Physics, Institute for Theoretical Physics II, University of Erlangen-Nuremberg)

Place:

MPL / large seminar room (*435)

Abstract:

Optomechanical systems, coupling light to nanomechanical motion, are now being investigated for many possible applications like sensitive measurements, quantum state manipulation, and quantum communication, as well as fundamental tests of quantum mechanics. These systems have now reached the stage where one can envisage making them into larger-scale arrays, coupling many vibrational and optical modes. In this talk I will first give a brief introduction to optomechanics. I will then recount our theoretical ideas on how to produce synthetic magnetic fields for photons via the optomechanical interaction.

Finally, I will describe our proposal for achieving topologically protected transport of sound waves, which is an outstanding challenge in any solid-state platform.

References:

* "Topological Phases of Sound and Light”, Vittorio Peano, Christian Brendel, Michael Schmidt, and Florian Marquardt, arXiv:1409.5375 (2014)

* "Optomechanical creation of magnetic fields for photons on a lattice”, M. Schmidt, S. Keßler, V. Peano, O. Painter, F. Marquardt arXiv:1502.07646 (2015)

Wednesday 29. April 2015

IMPRS get-together

 

Organisation: Ankan Bag (MPL / Leuchs Division)

Talk: Super-resolution microscopy

Speaker: Dr. Jonas Ries (European Molecular Biology Laboratory, Heidelberg)

Place: MPL / Large seminar room (*435)

Monday 13. April 2015

IMPRS get-together

 

Organisation: Ramin Beravat (MPL / Russell Division)

Talk: Fibre-optical black holes

Speaker: Maxime Jacquet (School of Physics and Astronomy, North Haugh, St Andrews, Scotland)

Place: MPL / Large seminar room (*435)

Topic:

One of the most fascinating aspects of laser physics and light interaction with materials is the ability to reproduce the features of completely different (and sometimes more complicated) systems. With this idea in mind, I will be studying the realization of an optical analogue to a Black Hole in the laboratory. 
More precisely, the leading idea of my project is to look for an electric radiation: the so named Unruh-Hawking radiation. This is, in terms of general relativity, the blackbody spectrum of the black hole. Its essential ingredients are a quantum field (electromagnetic field) and an event horizon associated with a curved space-time. As the radiation will probably never be observed directly from a gravitational black hole (due to its low temperature of about 1nK for a solar-mass black hole), the creation of an optical analogue to this phenomenon is a legitimate idea.

Thursday 29. January 2015

IMPRS get-together

 

Organisation: Georg Epple (MPL / Russell Division)

Talk: Coherent control of strongly interacting Rydberg gases in thermal vapor cells

Speaker: Dr. Harald Kübler (University of Stuttgart)

Place: MPL / Large seminar room (*435)

Thursday 22. January 2015

MPL Distinguished Lecturer Series
From electric quantum walks to the quest for exactly two interacting quantum atoms

 

Speaker:

Prof. Dieter Meschede (Universität Bonn)

Place:

MPL / large seminar room (*435)

Abstract:

Neutral atoms walking in a deep optical lattice (discrete quantum walks) are exploring a very large Hilbert space with spatial quantum coherence now preserved over 50 quantum sites and more in our laboratory. This situation allows to conquer new territory: With electric quantum walks momentum-space phenomena such as Bloch oscillations or Anderson like localization are realized in a single experiment, and a step towards quantitatively testing the “quantumness” at ever more macroscopic levels can be taken. Controlled interaction of exactly two atoms in such situations remains a daunting but highly attractive experimental challenge. We are zeroing in.