MPL Distinguished Lecturer Series

The 'Distinguished Lecturer Series' will follow a colloquium format for a broad audience and will be followed by a reception to provide an opportunity for meeting the speaker. 

Speakers - tenth round

November 2nd - 2017 - 3 pm
Watching and sensing single molecules by confining light to the atom scale

Prof. Jeremy Baumberg
University of Cambridge

Coupling between plasmonic metal nano-components generates strongly red-shifted resonances combined with intense local field amplification on the nanoscale. This allows directly seeing molecules as well as excitations in semiconductors. We have recently explored plasmonic coupling which can be tuned dynamically, through reliable bottom-up self-assembly using the nanoparticle-on-mirror geometry (NPoM) [1-5]. We recently demonstrated how individual molecules can be strongly coupled to these ultralow volume plasmonic cavities as well as how they act as optomechanical constructs with enormously enhanced coupling.

We also demonstrate the possibility to track few molecules using the extreme enhancements. We are able to watch individual electrons hopping onto and off molecules in the gap, and watch redox processes in real time. These have encouraging prospective applications in (bio)molecular sensing as well as fundamental science. The ability to track and watch molecules interact and react opens up the ability to study chemistry molecule-by-molecule and potentially to control single reaction pathways.

[1] Nature 491, 574 (2012); Revealing the quantum regime in tunnelling plasmonics,
[2] Nature Comm. 5, 4568 (2014); Threading plasmonic nanoparticle strings with light
[3] Nature Comm. 5, 3448 (2014); DNA origami based assembly of gold nanoparticle dimers for SERS detection
[4] Nature 535, 127 (2016); Single-molecule strong coupling at room temperature in plasmonic nanocavities
[5] Science 354, 726 (2016); Single-molecule optomechanics in picocavities

Time and Place: 15:00, Max Planck Institute for the Science of Light, Seminar Room A1.500, Staudtstr. 2, 91058 Erlangen

November 23th - 2017 - 3 pm
Parity Violation in Chiral Molecules: From Theory towards Spectroscopic Experiment and Evolution of Biomolecular Homochirality

Prof. Martin Quack
ETH Zurich

Symmetry and asymmetry are concepts, which are used in a wide range of contexts, from the  fundamental sciences, mathematics, physics, chemistry and biology to the arts, music and architecture [1]. We shall start with an introductory discussion of three fundamental questions on symmetry, relating physics to molecular quantum dynamics and stereochemistry.

(i) To what extent are the fundamental symmetries and conservation laws of physics and their violations reflected in molecular quantum dynamics and spectroscopy, in general?

(ii) How important is parity violation for the quantum dynamics and spectroscopy of chiral molecules, in particular? 

(iii) How important is parity violation for biomolecular homochirality, i.e. the quasi exclusive preference of L-amino acids and D-sugars in the biopolymers of life (proteins and DNA)?

The observation of biomolecular homochirality can be considered as a quasi-fossil of the evolution of life [1], the interpretation of which has been an open question for more than a century, with numerous related hypotheses, but no definitive answers. We shall briefly discuss the current status and the relation to the other two questions. 

The discovery of parity violation led to important developments of physics in the 20th century and is understood within the standard model of particle physics, SMPP. For molecular stereochemistry it leads to the surprising prediction of a small energy difference D of the ground state energies of the enantiomers of chiral molecules, corresponding to a small reaction enthalpy for the stereomutation between the R and S enantiomers [2].This reaction enthalpy would be exactly zero by symmetry with exact parity conservation. Theory predicts  D to be in the sub-femto eV range, typically, depending on the molecule (about D= 100 aeV for ClSSCl or CHFClBr, corresponding to  a reaction enthalpy of about 10 pJ/mol). We have outlined three decades ago, how this small energy difference D  might by measured by spectroscopic experiment [3], and recent progress indicates that experiment might be successful in the near future [4-7]. We shall discuss the current status of our experiments including alternatives pursued in other groups and the possible consequences for our understanding of molecular and biomolecular chirality. For background reading  see [1-7].

[1] M. Quack, J. Hacker (Eds.), Symmetrie und Asymmetrie in Wissenschaft und Kunst, Nova Acta Leopoldina NF Band 127, Nr. 412, Wissenschaftliche Verlagsgesellschaft, Stuttgart, 2016 (book, 275 pages with contributions in German and English)
M. Quack, Adv. Chem. Phys., 2014, 157, 249-290, Chapter 18.
[2] M. Quack, Fundamental Symmetries and Symmetry Violations from High Resolution Spectroscopy, in Handbook of High Resolution Spectroscopy, Vol. 1, Chapt. 18, pp. 659-722 (Eds.: M. Quack, F. Merkt), Wiley, Chichester, New York, 2011
[3] M. Quack,  Chem. Phys. Lett., 1986, 132, 147-153.
[4] P. Dietiker, E. Miloglyadov, M. Quack, A. Schneider, G. Seyfang,  J. Chem. Phys., 2015, 143, 244305, (and references cited therein).
[5] R.Prentner, M. Quack, J. Stohner, M. Willeke, J. Phys. Chem. A, 2015, 119, 12805-22.
[6] C. Fábri, Ľ. Horný, M. Quack, ChemPhysChem, 2015, 16, 3584–3589. S. Albert, I. Bolotova, Z. Chen, C. Fabri, M. Quack, G. Seyfang, D. Zindel, Phys. Chem. Chem. Phys. 2017, 19, 11738-11743.
[7] S. Albert, I. Bolotova, Z. Chen, C. Fábri, L. Horný, M. Quack, G. Seyfang, D. Zindel, Phys. Chem. Chem. Phys., 2016, 18, 21976-21993. A.Albert,F.Arn,I.Bolotova,Z.Chen, C.Fabri, G.Grassi, P.Lerch, M.Quack, G.Seyfang, A.Wokaun, D. Zindel, J.Phys.Chem. Lett. 2016, 7, 3847-3853  

Time and Place: 15:00, Max Planck Institute for the Science of Light, Seminar Room A1.500, Staudtstr. 2, 91058 Erlangen

December 7th - 2017 - 3 pm
Subcycle quantum physics

Prof. Rupert Huber
University of Regensburg

Latest progress in ultrafast optics has enabled scientists to accelerate electrons in solids directly by the carrier wave of light. A fascinating quantum world unfolds on the sub-optical-cycle scale, including Bloch oscillations, quasiparticle collisions, and high-harmonic generation. By combining this approach with ultramicroscopy we take the first femtosecond snapshot image of a molecular orbital and the first femtosecond single-molecule movie.

Time and Place: 15:00, Max Planck Institute for the Science of Light, Seminar Room A1.500, Staudtstr. 2, 91058 Erlangen

December 14th - 2017 - 3 pm
Sensing and biosensing enabled by silicon photonics: opportunities and challenges

Prof. Roel Baets
Ghent University

In the past 10 years silicon photonics has matured to an industrially viable technology for high datarate transceivers for telecom and data center applications. In this presentation the question will be explored: what opportunities does the technology offer for sensing applications, in biosensing, in medical instruments? A variety of proof-of-concept examples will be discussed along with the associated scientific challenges.

Time and Place: 15:00, Max Planck Institute for the Science of Light, Seminar Room A1.500, Staudtstr. 2, 91058 Erlangen

December 21th - 2017 - 3 pm
Bose-Einstein Condensation of Light

Prof. Martin Weitz
University of Bonn

Bose-Einstein condensation has been observed in several physical systems, including cold atomic gases, exciton-polaritons, and magnons. Photons usually show no Bose-Einstein condensation, since for Planck’s blackbody radiation the particle number is not conserved and the photons at low temperatures vanish in the system walls. I here describe experiments with a dye-filled optical microresonator experimentally observing Bose-Einstein condensation of photons. Thermalization is achieved in a number conserving way by repeated absorption re-emission cycles on the dye molecules, and the cavity mirrors provide both an effective photon mass and a confining potential. More recently, we have investigated calorimetric properties of the trapped photon gas, and determined both the heat capacity and the entropy around the phase transition. In other work, we have realized lattice potentials for photons in the dye microcavity. Both tunneling between two microsites and effective photon interactions are observed. In my talk, I will begin with a general introduction and give an account of current work and future plans of the Bonn photon gas experiment.

Time and Place: 15:00, Max Planck Institute for the Science of Light, Seminar Room A1.500, Staudtstr. 2, 91058 Erlangen

Speakers - ninth round

April 20th - 2017 - 3 pm
Contactless photon-photon interactions

Prof. Charles Adams
University of Durham, UK

In 2007, it was written that 'no known or foreseen material has an optical nonlinearity strong enough to implement' a large single-photon phase shift [1], and also we started to study a new ‘material’ where photons couple to highly-excited Rydberg excitations that do exhibit strong interactions [2]. Ten years on, this new material based on ultra-cold Rydberg atoms has been used to demonstrate strong photon-photon interactions, large single-photon phase shifts, and single-photon transistors (see recent review [3]).

In this talk, I will review the physics of Rydberg quantum optics and discuss our most recent results including a ‘contactless' photon-photon interaction [4].

[1] J. L. O’Brien, Science 318, 1567 (2007).
[2] A. Mohapatra, T. R. Jackson and C. S. Adams, Phys. Rev. Lett. 98, 113003 (2007).
[3] O. Firstenberg, C. S. Adams, and S. Hofferberth, Nonlinear quantum optics mediated by Rydberg interactions, J. Phys. B 49, 152003 (2016).
[4] H. Busche et. al. Nature Phys. (to appear).

Time and Place: 15:00, Max Planck Institute for the Science of Light, Seminar Room A1.500, Staudtstr. 2, 91058 Erlangen

March 30th - 2017 - 3 pm
3D Printing of Complex Microoptics – Merging with Plasmonic Nanooptics

Prof. Harald Giessen
University of Stuttgart, Germany

Microoptics has a plethora of applications, ranging from miniature endoscopes in hospitals to beam shaping or imaging. 3D printing with a femtosecond laser and two-photon polymerization allows for manufacturing optical elements directly after their design with an optical CAD program on a computer, with a resolution better than 100 nm and a high accuracy and reproducibility.

The talk is showing first experimental results and discusses the different possibilities and perspectives. Triplett microscope objectives of only 100 µm diameter with excellent imaging properties, fitting into the inside of a syringe, are becoming available with this technology and can be useful for medical applications as well as for novel sensors or inspection methods.

Merging this technology with metasurfaces and plasmonics will be discussed.

[1] T. Gissibl et al., Optica 3, 448 (2016) .
[2] T. Gissibl et al., Nature Communications 7, 11763 (2016).
[3] T. Gissibl et al., Nature Photonics 10, 554 (2016).
[4] S. Thiele et al., Opt. Lett. 41, 3029 (2016). [5] M. Sartison et al., Scientific Reports 7, 39916 (2017).
[5] S. Thiele et al., Science Adv. 3 (2017).

Time and Place: 15:00, Max Planck Institute for the Science of Light, Seminar Room A1.500, Staudtstr. 2, 91058 Erlangen

March 16th - 2017 - 3 pm
Microresonator-Based Combs and Random Number Generators

Prof. Alex Gaeta
Columbia University, New York, USA

Time and Place: 15:00, Max Planck Institute for the Science of Light, Seminar Room A1.500, Staudtstr. 2, 91058 Erlangen

February 16th - 2017 - 3 pm
Polariton condensates: interactions and superfluidity

Prof. Benoit Deveaud
École Polytechnique Féderale de Lausanne, Switzerland

Polaritons are half-light half matter quasiparticles resulting from the strong coupling of photons confined in a microcavity with excitons confined in a quantum well. Polariton condensates may be created both spontaneously through a “standard” phase transition towards a Bose Einstein condensate, or be resonantly driven with a well-defined initial phase, speed and spatial distribution.

Thanks to the photonic component of polaritons, the properties of the quantum fluid may be accessed very directly, with in particular the possibility of detailed interferometric studies. This allows for example to probe the long-range coherence properties of a quantum fluid with unprecedented ease. This also allows testing superfluid properties with great precision in space and time.

I will describe the static and dynamics of superfluid flow in polariton condensates, obtained with a picosecond time resolution, in different configurations, with in particular their phase configuration. I will show in particular the dynamics of the creation of dark solitons and quantized vortex pairs.

This work has been performed at EPFL by a dream team of Postdocs, PhD students and collaborators: H. Abbaspour, A. Adiyatullin, K. Lagoudakis, G. Nardin, T. Paraiso, G. Grosso, F. Manni, N. Takemura, Y Léger, S. Trebaol, M. Anderson, M. Portella Oberli, F. Morier-Genoud and the help of our theorists friends V, Savona, M. Wouters H. Flayac and T. Liew..

Time and Place: 15:00, Max Planck Institute for the Science of Light, Seminar Room A1.500, Staudtstr. 2, 91058 Erlangen

February 9th - 2017 - 3 pm
Trends and innovations in the digital energy world

Prof. Michael Weinhold
Chief Technology Officer, Siemens Energy Management Division, Siemens Erlangen

Die elektrische Energieversorgung wächst an Bedeutung ist aber gleichzeitig durch massiv stattfindende Veränderungen in Technologie und Marktordnung gekennzeichnet: Ohne elektrische Energie ist der Betrieb moderner Infrastrukturen wie Daten- und Kommunikationsnetze oder Industriebetriebe jeglicher Art nicht mehr möglich. Dies erfordert eine hochzuverlässige und kontinuierliche Stromversorgung.

Zudem ist die Nutzung elektrischer Energie ein wichtiger Hebel zur Steigerung von Energieeffizienz wie z. B. durch den Einsatz von elektrischen Wärmepumpen im Gebäudebereich.

Stromnetze gestatten eine sehr effiziente Integration von Erneuerbaren Energien wie Wind- und Photovoltaik-Kraftwerken auf allen Spannungsebenen. Durch den verlustarmen Transport von Energie über weiteste Entfernungen wird die elektrische Energie in die Lastzentren sowie von dort zu den Endanwendungen weitergeleitet. Hierbei wird das sichere Zusammenspiel von konventionellen und erneuerbaren Kraftwerken ermöglicht. Der Leistungselektronik kommt für den Transport und die Stabilisierung der Stromnetze eine immer größere Rolle zu. Beispiele dafür sind die Anbindung von Offshore-Windparks in der Nordsee an das Landesnetz sowie die im Bau befindliche Hochspannungsgleichstrom-Übertragung Ultranet. Vom Stromnetz aus gibt es zunehmend Übergänge in andere Infrastrukturen z. B. in den Wärmebereich, das Gasnetz oder die Mobilität.

Der Ausbau von Stromnetzen auf allen Spannungsebenen ist damit weltweit zu einem der wichtigsten Hebel zur Erlangung nachhaltiger Infrastrukturen geworden. Um die stark wachsende Komplexität zu beherrschen, müssen die Stromnetze allerdings weiter automatisiert und z. B. über Smart Meter digitalisiert werden. Die Digitalisierung startet schon mit der Netzplanung, wo ein "Digital Twin" des Systems entworfen und weiterentwickelt wird. Es setzt sich fort in dem Betrieb von Stromnetzen wo zunehmend Echtzeitmessdaten z. B. von PMUs (Phasor Measurement Units) und zukünftig vermutlich auch von Wind-, PV- und Speicherstromrichtern eingesetzt werden und reicht bis in den Betrieb von Marktplätzen und Kundenportalen. Ein exzellentes Beispiel ist der aktuell stattfindende Smart Meter Roll-out in Norwegen verbunden mit dem Aufbau einer Meter Data Management und Market Transaction Management Plattform.

Diese Entwicklung hin zu komplexeren Energiesystemen bedeutet, dass Innovationen im Stromsystem immer häufiger auch im Geschäftsmodell stattfinden. Das neue Energiesystem oder Energie 2.0 wird damit interdisziplinär. Ein hochspannendes Umfeld indem z. B. Ingenieure nicht nur mit Informatikern und Datenanalysten, sondern auch mit Sozialwissenschaftlern zusammenarbeiten. Und Energie 2.0 erfordert intelligente Stromnetze auf allen Spannungsebenen.

Time and Place: 15:00, Max Planck Institute for the Science of Light, Seminar Room A1.500, Staudtstr. 2, 91058 Erlangen

Speakers - eighth round

January 14th - 2016 - 4.30 pm
Laser spectroscopy applied to environmental and ecological research

Prof Sune Svanberg
Lund University, Sweden and South China Normal University, Guangzhou, China

Laser spectroscopy has been shown to be a valuable tool both in the detection and the therapy of human malignancies. The most important prognostic factor for cancer patients is early tumour discovery. If malignant tumours are detected during the non-invasive stage, most tumours show a high cure rate of more than 90 %. Even though there are many conventional diagnostic modalities, very early tumours may be difficult to discover. Laser-induced fluorescence (LIF) for tissue characterisation is a technique that can be used for monitoring the biomolecular changes in tissue under transformation from normal to dysplastic and cancer tissue before structural tissue changes are seen at a later stage. The technique is based on UV or near-UV illumination for fluorescence excitation. The fluorescence from endogenous chromophores in the tissue alone, or enhanced by exogenously administered tumour seeking substances can be utilised. The technique is non-invasive and gives the results in real-time. LIF can be applied for point monitoring or in an imaging mode for larger areas, such as the vocal cords or the portio of the cervical area.

Photodynamic therapy is a selctive treatment technique for human malignancies. To overcome the limited light penetration in superficial illumination interstitial delivery (IPDT) with the light transmitted to the tumour via optical fibres has been developed. Interactive feed-back dosimetry is of importance for optimising this modality and such a concept has been developed. The technique has special interest for tumours where there are no other options, such as for recurrent prostate cancer after ionising radiation. For correct dosimetry it is important to assess the optical properties of tissue; this can be done by time resolving propagation techniques.

Another technique which has been developed for medical application is based on gas in scattering media absorption spectroscopy (GASMAS). The technique is used to detect free gas (e.g., oxygen and water vapour) in hollow organs in the human body and has been applied to the detection of the human sinus cavities in the facial skeleton. The GASMAS technique might also be used for the surveillance of prematurely born infants. As the organs are not fully developed there is a risk of morbidities. In particular, the lung function is limited and the babies may develop respiratory distress syndrome resulting in decreased oxygen saturation affecting risk organs, such as the brain. GASMAS may also be developed for detection of other diseases, such as middle ear infection in small kids. A certain proportion of these infections are viral induced and in these cases no antibiotics should be prescribed. GASMAS has a potential to discriminate the origin of the disease and thus guide in the decision of appropriate therapy, trying to fight the global problem of antibiotic resistance. Many of these techniques can also be applied to study other organic materials, e.g., food.

Time and Place: 16:30-17:30, Günther-Scharowsky-Str. 1/Bldg. 24, Large seminar room (429/435)

January 14th - 2016 - 3 pm
Applications of Laser Spectroscopy to Meet Challenges in Medicine

Prof Katarina Svanberg
Lund University, Sweden and South China Normal University, Guangzhou, China

Laser spectroscopy has been shown to be a valuable tool both in the detection and the therapy of human malignancies. The most important prognostic factor for cancer patients is early tumour discovery. If malignant tumours are detected during the non-invasive stage, most tumours show a high cure rate of more than 90 %. Even though there are many conventional diagnostic modalities, very early tumours may be difficult to discover. Laser-induced fluorescence (LIF) for tissue characterisation is a technique that can be used for monitoring the biomolecular changes in tissue under transformation from normal to dysplastic and cancer tissue before structural tissue changes are seen at a later stage. The technique is based on UV or near-UV illumination for fluorescence excitation. The fluorescence from endogenous chromophores in the tissue alone, or enhanced by exogenously administered tumour seeking substances can be utilised. The technique is non-invasive and gives the results in real-time. LIF can be applied for point monitoring or in an imaging mode for larger areas, such as the vocal cords or the portio of the cervical area.

Photodynamic therapy is a selctive treatment technique for human malignancies. To overcome the limited light penetration in superficial illumination interstitial delivery (IPDT) with the light transmitted to the tumour via optical fibres has been developed. Interactive feed-back dosimetry is of importance for optimising this modality and such a concept has been developed. The technique has special interest for tumours where there are no other options, such as for recurrent prostate cancer after ionising radiation. For correct dosimetry it is important to assess the optical properties of tissue; this can be done by time resolving propagation techniques.

Another technique which has been developed for medical application is based on gas in scattering media absorption spectroscopy (GASMAS). The technique is used to detect free gas (e.g., oxygen and water vapour) in hollow organs in the human body and has been applied to the detection of the human sinus cavities in the facial skeleton. The GASMAS technique might also be used for the surveillance of prematurely born infants. As the organs are not fully developed there is a risk of morbidities. In particular, the lung function is limited and the babies may develop respiratory distress syndrome resulting in decreased oxygen saturation affecting risk organs, such as the brain. GASMAS may also be developed for detection of other diseases, such as middle ear infection in small kids. A certain proportion of these infections are viral induced and in these cases no antibiotics should be prescribed. GASMAS has a potential to discriminate the origin of the disease and thus guide in the decision of appropriate therapy, trying to fight the global problem of antibiotic resistance. Many of these techniques can also be applied to study other organic materials, e.g., food.

Time and Place: 15:00-16:00, Günther-Scharowsky-Str. 1/Bldg. 24, Large seminar room (429/435)

November 26th - 2015
Atom interferometers measuring the fine structure constant and probing the dark sector

Prof Holger Müller
University of California at Berkeley, USA

With new technologies, atom interferometers have become instruments for measurements accross physics at 10^-10 sensitivity [1]. For example, we are now close to reporting a new measurement of the fine structure constant alpha with an anticipated accuracy of 2.5x10^-10, allowing for ultra-precise tests of the standard model.
 
Chameleons are flexible models for dark energy. They become unmeasurably short-ranged in the presence of bulk matter but can now be probed in our cavity-based atom interferometer [2]. We rule out chameleons and a range of other dark energy candidates that would reproduce the observed cosmic acceleration [3]. With upgrades, we may sense any chameleons and a wide class of other exotic models for dark energy and dark matter, such as B-L bosons or f(R) gravity.
 
[1] Phys. Rev. Lett. 115, 083002 (2015),
[2] Phys. Rev. Lett. 114, 100405 (2015).
[3] Science 349, 849 (2015).

 

Time and Place: 15:00, Günther-Scharowsky-Str. 1/Bldg. 24, Large seminar room (429/435)

November 19th - 2015
Quantum optics and quantum information with trapped ions

Prof Ferdinand Schmidt-Kaler
University of Mainz, Germany

Abstract: The quantum states of ions are perfectly controlled, and may be used for fundamental research in quantum physics, as highlighted by the Nobel Prize given to Dave Wineland in 2012. In this talk, I will highlight the advantages of trapped ions for quantum information processing, taking advantage of modern trap technologies to pave a way for scalability. The laser-ion interactions allow for high fidelity quantum gate operations, while the application of well-suited trap control voltages realizes ion shuttles and reconfigurations of the ion quantum register. Alternatively, one may employ Rydberg excitations of trapped ions to allow for long-range interactions and quantum gate operation.

Time and Place: 15:00, Günther-Scharowsky-Str. 1/Bldg. 24, Large seminar room (429/435)

November 5th - 2015
Quantum simulations with atoms in nano-structures

Prof Ignacio Cirac
Max Planck Institute for Quantum Optics, Garching, Germany

Abstract: Many-body quantum systems are very hard to simulate with classical computers, as the running time increases exponentially with the size of the system. Quantum simulation offers a way to circumvent this problem. A quantum simulator is a system where interactions can be engineered, such that its dynamics correspond to the ones of the system one wants to emulate. Ultra-cold atoms in optical lattices can be used for that purpose; in particular, to simulate many-body problems that appear in strongly-correlated systems.

In this talk I will briefly review the field of quantum simulations and show how photonic crystal structures can be used to design subwavelength optical lattices in two dimensions for ultracold atoms, achieving a better peformance than current experimental set-ups. Furthermore, guided modes can be used for photon-induced large and strongly long-range interactions between trapped atoms, giving rise to quantum simulations which cannot be performed with other systems.

Time and Place: 15:00, Günther-Scharowsky-Str. 1/Bldg. 24, Large seminar room (429/435)

Speakers - seventh round

May 28th - 2015
Probing physics at TeV by measuring aeV

Prof Edward A. Hinds
Imperial College London, UK

Abstract: Cold atoms and molecules provide a sensitive way to search for new physics, e.g. variation of fundamental constants, dark energy, or new elementary particles. Laser cooling, already very successful in cooling atoms, can now be applied to molecules, bringing extraordinary new sensitivity to tests of fundamental physics. I will illustrate some of these ideas, with particular emphasis on the search for a permanent electric dipole moment of the electron, which now provides a strong constraint on possible super-symmetric theories of particle physics.

Time and Place: 15:00, Günther-Scharowsky-Str. 1/Bldg. 24, Large seminar room (429/435)

May 21st - 2015
Semiconductor devices for quantum technologies

Prof Jonathan Finley
Technische Universität München, Germany

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.
 
Time and Place:
Thursday, May 21 at 15:00
Large seminar room (building 24) 429/435

April 30th - 2015
Topological Phases of Sound and Light

Prof Florian Marquardt
FAU Erlangen, Germany

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).
 
Time and Place:
Thursday April 30 at 15:00
Large seminar room (429/435), building 24

Speakers - sixth round

January 22nd - 2015
From electric quantum walks to the quest for exactly two interacting quantum atoms

Prof Dieter Meschede
University of Bonn, Germany

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.

January 15th - 2015
Quantum Imaging and the Role of Information

Prof Anton Zeilinger
Institute for Quantum Optics and Quantum Information, Vienna

To be announced

November 20th - 2014
Quantum Optics with Cold Atoms

Prof Peter Zoller
Institute for Quantum Optics and Quantum Information, Innsbruck

To be announced

Speakers - fifth round

July 10th - 2014
Superfluid Fermi gases

Prof Christophe Salomon
Directeur de Recherche au CNRS, Paris, France

Superconductivity and superfluidity are spectacular macroscopic manifestations of genuine quantum collective effects with, today, vast domains of applications. In this family of quantum solids or fluids, ultracold gases and polaritons are the last born. Thanks to the great flexibility of laser cooling and trapping methods, ultracold gases offer to study these quantum correlated systems with a new twist. It is possible for instance to tune the strength and sign of the interaction between atoms. Optical lattices, realized by interfering laser beams, create periodic optical potentials that mimic the crystalline potential seen by electrons in solids. Controlled disorder can be introduced to study the localization of matter-waves predicted by P.W. Anderson more than 50 years ago. Dilute atomic gases can thus be considered as model systems to address some pending problem in Many-Body physics that occur in condensed matter systems, nuclear physics, and astrophysics. In this talk, we will discuss the seemingly simplest case of attractive spin 1/2 fermions with tunable interaction. We will show that the gas properties can continuously change from those of weakly interacting Cooper pairs described by Bardeen-Cooper-Schrieffer theory to those of strongly bound molecules undergoing Bose-Einstein condensation. A new imaging method enable us to probe with high precision the thermodynamics of locally homogeneous ultracold gases [1,2,3] and to perform stringent tests of recent many-body theories. The equation of state of fermions has been measured as a function of interaction strength and temperature. Despite orders of magnitude difference in density and temperature, our equation of state can be used to describe low density neutron matter such as the outer shell of neutron stars. We will finally describe our recent production with Lithium isotopes of a dilute mixture of a Bose superfluid with a Fermi superfluid [4], a long thought goal of helium 4 and helium 3 quantum liquids.

[1] S. Nascimbène, N. Navon, K. Jiang, F. Chevy, and C. Salomon, Nature 463, 1057 (2010)
[2] N. Navon, S. Nascimbène, F. Chevy, and C. Salomon, Science 328, 729 (2010)
[3] S. Nascimbène, N. Navon, S. Pilati, F. Chevy, S. Giorgini, A. Georges, and C. Salomon, Phys. Rev. Lett., 106, 215303 (2011)
[4] I. Ferrier-Barbut, M. Delehaye, S. Laurent, A. Grier, M. Pierce, B. Rem, F. Chevy, C. Salomon, ArXiv :1404.2548

May 8th - 2014
Quantum microwave photonics

Prof Andreas Wallraff
ETH Zurich, Switzerland

Using modern micro and nano-fabrication techniques combined with superconducting materials we realize quantum electronic circuits in which we create, store, and manipulate individual microwave photons. The strong interaction of photons with superconducting quantum two-level systems allows us to probe fundamental quantum effects of microwave radiation and also to develop components for applications in quantum technology. Previously we have realized on-demand single photon sources which we have characterized using correlation function measurements [1] and full quantum state tomography [2]. For this purpose we have developed efficient methods to separate the quantum signals of interest from the noise added by the linear amplifiers used for quadrature amplitude detection [3]. We now regularly employ superconducting parametric amplifiers [4] to perform nearly quantum limited detection of propagating electromagnetic fields. These enable us to probe the entanglement which we generate on demand between stationary qubits and microwave photons freely propagating down a transmission line [5]. Using two independent microwave single photon sources, we have recently performed Hong-Ou-Mandel experiments at microwave frequencies [6] and have probed the coherence of two-mode multi-photon states at the out-put of a beam-splitter. The non-local nature of such states may prove to be useful for distributing entanglement in future small-scale quantum networks.

[1] D. Bozyigit et al., Nat. Phys. 7, 154 (2011)
[2] C. Eichler et al., Phys. Rev. Lett. 106, 220503 (2011)
[3] C. Eichler et al., Phys. Rev. A 86, 032106 (2012)
[4] C. Eichler et al., Phys. Rev. Lett. 107, 113601 (2011)
[5] C. Eichler et al., Phys. Rev. Lett. 109, 240501 (2012)
[6] C. Lang et al., Nat. Phys. 9, 345ñ348 (2013) 

April 10th - 2014
The quantum way of doing computations

Prof Rainer Blatt
University of Innsbruck, Austria

Since the mid nineties of the 20th century it became apparent that one of the centuries' most important technological inventions, computers in general and many of their applications could possibly be further enormously enhanced by using operations based on quantum physics. This is timely since the classical roadmaps for the development of computational devices, commonly known as Moore's law, will cease to be applicable within the next decade due to the ever smaller sizes of the electronic components that soon will enter the quantum physics realm. Computations, whether they happen in our heads or with any computational device, always rely on real physical processes, which are data input, data representation in a memory, data manipulation using algorithms and finally, the data output. Building a quantum computer then requires the implementation of quantum bits (qubits) as storage sites for quantum information, quantum registers and quantum gates for data handling and processing and the development of quantum algorithms. In this talk, the basic functional principle of a quantum computer will be reviewed. It will be shown how strings of trapped ions can be used to build a quantum information processor and how basic computations can be performed using quantum techniques. In particular, the quantum way of doing computations will be illustrated by analog and digital quantum simulations and the basic scheme for quantum error correction will be introduced and discussed. Scaling-up the ion-trap quantum computer can be achieved with interfaces for ion-photon entanglement based on high-finesse optical cavities and cavity-QED protocols, which will be exemplified by recent experimental results.

Speakers - fourth round

January 16th - 2014
Juggling with photons and raising Schrödinger cats of light in a cavity

Prof Serge Haroche
Collège de France, Paris, France

The founders of quantum theory assumed in "thought experiments" that they were manipulating isolated quantum systems obeying the counterintuitive laws which they had just discovered. Technological advances have recently turned these virtual experiments into real ones by making possible the actual control of isolated quantum particles. Many laboratories are realizing such experiments, in a research field at the frontier between physics and information science. Fundamentally, these studies explore the transition between the microscopic world ruled by quantum laws and our macroscopic environment which appears "classical". Practically, physicists hope that these experiments will result in new technologies exploiting the strange quantum logic to compute, communicate or measure physical quantities better than what was previously conceivable. In Paris, we perform such experiments by juggling with photons trapped between superconducting mirrors. We count these photons in a non-destructive way and we prepare states of the quantum field reminiscent of the famous cat which Schrödinger imagined to be suspended between life and death. I will give a simple description of these studies, compare them to similar ones performed on other systems and guess about possible applications.

December 12th - 2013
Spin Hall Effect for Electrons and Photons

Prof Henry van Driel
Department of Physics, University of Toronto, Canada

Hall effects have provided important insights into the electronic properties of solids since 1879. In the spin Hall effect, a pure electrical current produces a pure transverse spin current while the inverse spin Hall effect describes the converse situation. I describe the generation and detection of both these spin Hall effects in GaAs using coherence control optical techniques. An analogous spin Hall effect for light is also demonstrated wherein a linearly polarized light beam incident on, e.g., GaAs is split transversely into its spin, that is, right and left circularly polarized, components.  Both electron and photon spin Hall effects involve nanometer displacements of charges or photons but can nonetheless be resolved optically.

November 28th - 2013
From Extreme Nonlinear Optics to Ultrafast Atomic Physics

Prof Anne L'Huillier
Department of Physics, Lund University, Sweden

The interaction of atoms with intense laser radiation leads to the generation of high-order harmonics of the laser field. In the time domain, this corresponds to a train of pulses in the extreme ultraviolet range and with attosecond duration. This presentation will introduce the physics of high-order harmonnic generation and attosecond pulses and describe recent developments including multicolor schemes or noncollinear geometries. After the first decade where attosecond pulses were characterized, analyzed and used in –mostly– demonstration experiments, we begin to perform experiments where these pulses allow us to explore new physics. We will describe some of these applications, and in particular recent results concerning single and double photoionization dynamics.

October 31st - 2013
Quantum cascade lasers comb spectrometers

Prof Jérôme Faist
Quantum Optoelectronics Group, ETH Zurich, Switzerland

The quantum cascade laser has demonstrated operation over an extremely wide wavelength range extending from the mid-infrared at 2.9 μm to the Terahertz at 360 μm. One very important feature of this device is its ability to provide gain over a very broad wavelength range. Recently, we have shown that such broadband devices, when operated in continuous wave, emit as a coherent optical comb [1] in which the phase relation between the comb modes corresponds approximately to a FM modulated laser. These new comb lasers enables the fabrication of a dual comb spectrometer based on a quantum cascade laser that offers a broadband, all solid-state spectrometer with no moving parts and a ultrafast acquisition time.  We discuss also the extension of these ideas to the THz. 

[1] A. Hugi, G. Villares, S. Blaser, H. C. Liu and J. Faist, Nature 492 (7428), 229-233 (2012).

October 17th - 2013
Fiber-Laser Driven Accelerators and the path to Attosecond X-ray Lasers

Prof Robert L. Byer
Applied Physics, Stanford University, USA

The generation and control of light is critical for meeting important laser accelerator challenges of the 21st century. I review progress toward a laser-driven accelerator on-a-chip fabricated using modern lithographic tools.  The laser accelerator is ideal for driving a dielectric-undulator FEL for table top MHz repetition rate attosecond X-ray lasers.  Recent progress and issues that remain to be resolved are identified.

Speakers - third round

June 6th - 2013
Nanophotonics: gauge field for photons and control of heat

Prof Shanhui Fan
Stanford University, Ginzton Laboratory, Stanford, USA

Electromagnetic interaction, as one of the most fundamental
interactions of the universe, lies at the heart of much of modern
science and engineering. Novel mechanisms to control electromagnetic
interaction, as evidenced by the recent developments of a wide variety
of nanophotonic structures, therefore have broad implications for both
fundamental and applied research. In this talk, we present two separate
examples of some of our recent works in seeking to create novel
electromagnetic interactions, and to exploit these interactions for new
applications. We will show that one can achieve an effective gauge field
for photons, which leads to a rich set of new non-reciprocal physics
effects,  as well as a very promising avenue towards on-chip
non-magnetic linear optical isolator. We will also discuss some of our
recent works in using nanophotonic structures to control heat flow, in
both the near and the far fields.

May 23rd - 2013
Quantum optics with excitons in semiconductors

Prof Elisabeth Giacobino CNRS
École normale supérieure, Université Pierre et Marie Curie, Paris, France

In a semiconductor system, optical excitations can create excitons, which are bound electron-hole pairs. In semiconductor nanostructures the excitonic energy levels are quantized, leading to a strong size dependence of their optical properties and allowing engineering of classical and non-classical light generation. Two cases will be described, one involving quantum wells with 1D quantization, the other one involving quantum dots, with 3D quantization. When a quantum well is placed in a high finesse microcavity, the strong coupling regime between 2D excitons and light is reached, forming exciton-photon mixed quasi-particles called polaritons. Polaritons combine the coherent properties of photons with the highly interacting features of electronic states. These properties have allowed us to demonstrate nonlinear and quantum optical effects in the microcavity emission, as well as quantum fluid properties in the propagation of polaritons in the system. Quantum optical properties of quantum dots, or semiconductor nanocrystals, made of a few thousand atoms will also be described. Here, the strong confinement of electron-hole pairs leads to very interesting properties such as photon antibunching, opening the way to on-demand single photons sources at room temperature.

Mai 2nd - 2013
Atomic and Molecular Processes in Strong Fields at the LCLS X-ray Laser

Prof Philip Bucksbaum
Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, USA

The Stanford Linac Coherent Light Source (LCLS) at the SLAC National Accelerator Laboratory is the world’s first hard x-ray free electron laser. Atomic and molecular physics experiments at LCLS have concentrated on studies of fundamental processes of photoionization and subsequent relaxation. The signifi cant dynamical time scales involved are on the order of a few femtoseconds. Several strong-field and nonlinear effects have now been documented, and I will review the early results as well as the status of ongoing work.

April 18th - 2013
Rydberg blockade for manipulating atomic and photonic qubits

Prof Philippe Grangier
Institut d'Optique, Palaiseau, France

In this talk I will present recent experiments using Rydberg blockade as
a tool for either entangling atomic qubits [1, 2], or for creating  very
large optically  non-linear effects [3] that could  be applied to
process photonic qubits, or to prepare highly non-classical states [4].

[1] "Observation of collective excitation of two individual atoms in the
Rydberg blockade regime", A. Gaetan et al, Nature Physics 5, 115 (2009)

[2] "Entanglement of Two Individual Neutral Atoms Using Rydberg
Blockade", T. Wilk et al, Phys. Rev. Lett. 104, 010502 (2010)

[3] "Observation and Measurement of Interaction-Induced Dispersive
Optical Nonlinearities in an Ensemble of Cold Rydberg Atoms", V. Parigi
et al, Phys. Rev. Lett. 109, 233602 (2012)

[4] "Generating non-Gaussian states using collisions between Rydberg
polaritons", J. Stanojevic et al, Phys. Rev. A 86, 021403 (2012)

Speakers - second round

January 24th - 2013
Green Photonics – optical solutions for the future

Prof Andreas Tünnermann
Fraunhofer Institute for Applied Optics and Precision Engineering, Jena; Friedrich Schiller University, Jena

Humanity faces today multitude of challenges as energy consumption and climate change, healthcare in an ageing society, the knowledge society and public safety and security. The sustainable use of light “Green Photonics” can contribute to solve these pressing future issues.

Essential operation fields are

- alternative methods of energy conversion

- decreasing of energy consumption and efficient use of natural resources

- conservation of climate and environment

- food protection and health care

Green Photonics brings together the various application possibilities of light for protecting the environment and healthy living. These include optical and optoelectronic technologies which save energy, reduce emissions from greenhouse gases, avoid polluting the environment, or contribute to environmentally compatible and sustainable production. The use of resource and environmentally friendly, i.e. “green” optical technologies holds enormous economic potential, ranging from efficient lasers via optical metrology and sensor technology to power-saving lighting and effective CO2-neutral energy conversion.

A great amount of energy could be saved in the area of lighting. Today, around 20 percent of the total demand for electricity around the world is used for lighting purposes. Around 50 percent of this could be saved by using more efficient light sources, corresponding to the total electrical energy requirements of Western Europe and a CO2 equivalent of 600 million tons. In the field of resource-friendly power generation, photovoltaics and solar-thermal energy are increasing in importance. The aim here must be to continue increasing efficiency while simultaneously reducing costs with new concepts and alternative technologies. “Green Photonics” also play an important role in the development of sustainable and energy-efficient production processes, for example in laser welding or the manufacture of vehicle components in the automotive industry. In this regard, ultrashort-pulse fiber lasers which can be used highly efficiently in micro-material processing are particularly promising. The field of information and communication consumes two to three percent of world energy requirements today, and this power consumption is increasing by up to 20 percent a year in the light of rapidly rising data traffic. Here too, considerable energy savings could be achieved with improved optical networks. In climate research, optical sensors in satellite-aided earth observation systems help in detecting pollutants in the air or sea, early recognition of environmental disasters, and the development of countermeasures.

In this contribution, novel developments in the sustainable use of light are reviewed and perspectives of Green Photonics discussed.

December 20th - 2012
Attosecond Photonics: What we learn by transforming many photons into one

Paul Corkum
University of Ottawa

The extreme nonlinear optics that underlies attosecond science is very different from perturbative nonlinear optics.  Extreme nonlinear optics is understood through quantum trajectories of an ionizing electron wave packet.  A trajectory begins from a bound state and returns to the same state, following an excursion in the continuum. Quantum trajectories map onto an interferometer - an electron interferometer created by light.  A weak additional field can perturb these trajectories, manipulating the interferometer while simultaneously constructing a perturbative nonlinear optics on top of the extreme process.  Using interferometric concepts, I will show how we can measure the space-time properties of attosecond pulses, the space-time structure of electronic wave packets and follow chemical dynamics of small molecules.

December 6th - 2012
Coherent Back Scattering and Anderson Localization of Ultra Cold Atoms

Prof Alain Aspect
Institut d'Optique, Palaiseau France

We use ultra cold atoms in a disordered potential created with a laser speckle, to study Anderson Localization (AL) and Coherent Back Scattering (CBS). Localization has been observed in 1D and 3D, and 2D experiments are promising. Theory supports the conclusion that what we observe is AL, but a direct evidence of the role of coherence is desirable.  Recently, we have observed CBS, an indisputable coherent effect in quantum transport, related to the first order manifestation of localization (weak localization).

November 22nd - 2012
Controlling and Exploring Quantum Matter

Prof Immanuel Bloch
Max-Planck Institute of Quantum Optics, Munich

Over the past years, ultracold quantum gases in optical lattices have offered remarkable opportunities to investigate static and dynamic properties of strongly correlated bosonic or fermionic quantum many-body systems. In this talk, I will show how it has recently not only become possible to image such quantum gases with single atom sensitivity and single site resolution, but also how it is now possible to coherently control single atoms on individual lattice sites. I will demonstrate how 'Higgs' type excitations occur at 24 orders of magnitude lower energy scales than in high energy experiments and how they can detected in our experimental setting. Finally, I will present a new method to realize artificial gauge fields for ultracold atoms and show a novel method how to measure the Berry-Zak phase of topological band-structures using ultracold atoms.

November 8th - 2012
Plasmonics: From quantum effects to fano interference and light harvesting

Prof Peter Nordlander
Department of Physics, Rice University, Houston

The “plasmon hybridization” paradigm shows that the plasmon resonances in complex metallic nanostructures interact and hybridize in a manner analogous to how atomic orbitals interact and form collective states in molecules.[1] The insight gained from this concept provides an important conceptual foundation for the development of new plasmonic structures that can serve as substrates for surface enhanced spectroscopies, chemical and biomolecular sensing, and subwavelength passive and active optical devices.[2] The talk is comprised of general overview material interspersed with more specialized “hot topics” such as plasmonic radiative coherence and interference effects,[3] quantum plasmonics[4], quantum plexcitonics,[5] active plasmonic nanoantennas for enhanced light harvesting,[6] and plasmon induced chemical reactions.[7]

[1] E. Prodan et al., Science 302(2003)419

[2] N.J. Halas et al., Chem. Rev. 111(2011)3913

[3] B. Lukyanchuk et al., Nature Mat. 9(2010)707

[4] R. Esteban et al., Nat. Comm. 3(2012)825

[5] A. Manjavacas et al., Nano Lett. 11(2011)2318; ACS Nano 6(2012)1724

[6] M. W. Knight et al., Science 332(2011)702, Nano Lett. 12(2012)3808

[7] R. Huschka et al., J. Am. Chem. Soc. 133(2011)12247

October 18th - 2012
Femtosecond Optics: More Than Just Really Fast

Prof Erich Ippen
Massachusetts Institute of Technology, Cambridge

Advances in femtosecond lasers that are making it possible to generate pulses with durations on the order of one optical cycle are also providing the capabilities for better clocks, coherent broadband frequency combs, attosecond timing synchronization and precision sampling for improved analog-to digital signal conversion. By spatially separating and rapidly modulating many individual comb frequencies, truly arbitrary optical-frequency electric-field waveforms can be generated.  This talk will describe recent progress toward these goals based on Ti:sapphire and fiber laser technologies to cover the wavelength range of 500nm - 2µm.

October 11th - 2012
Dressing Molecules and Materials with the Vacuum Field

Prof Thomas Ebbesen
University of Strasbourg

Strong coupling of light and matter can give rise to a multitude of exciting physical
effects through the formation of hybrid states. Organic molecules have been increasingly used for the study of strong coupling since their large transition dipole moment permits the observation of vacuum Rabi splitting in the range of hundreds of meV at room temperature. Such large modifications in the energy levels have significant implications for molecular and material sciences as well as physics. After introducing the fundamentals of strong coupling, our recent research on this topic will be presented.

Speakers - first round

July 19th - 2012
Exploring new frontiers of quantum optical science

Prof Mikhail Lukin
Harvard University

We will discuss  recent developments  involving a new scientific interface between quantum optics, many body physics, nanoscience and quantum information science. Specific examples include the use of quantum optical techniques for manipulation of individual spins and photons using ultra-cold atoms and atom-like impurities in diamond as well as  control of light-matter interactions using sub-wavelength localization of optical fields. Novel applications of these techniques ranging from novel approaches to quantum computation at room temperature to strongly interacting photonic systems and nanoscale sensing will be discussed.

June 28th - 2012
Magneto-optics of quantum systems and nano-imaging

Prof Jörg Wrachtrup
Universität Stuttgart

Addressing magnetic degree of freedom in solids by light is a central challenge in data  storage, quantum information processing as well as metrology. Usually it is angular momentum conservation, i.e. parity, that governs interaction strength. Since solids – unlike atoms- in most cases are low symmetry system any kind of magnetism imprints low a fidelity signal on their optical response. There are notable exceptions to this rule, most importantly rare earth dopants or diamond defect centers. Here not only single spins can be read out but even quantum correlations, i.e. entanglement among spins and photons can be generated under ambient conditions. Details of the magneto optical behavior of those systems and highlight applications will be explained. For example high resolution imaging of magnetic noise fields is of use in material science and bioanalytics. Alternatively high angular momentum light beams generated for example in dedicated plasmonic structures may be used to significantly enhance the usually weak Faraday effect allowing for readout of weak magnetic moments.  The talk will describe the generation of those light fields and detection of the tiny Faraday effect caused by the magnetic field of a few nuclear spins.

May 31st - 2012
Classical radiation theory and Planck's constant

Prof Harry Paul
Humboldt-Universität zu Berlin

It is shown that Planck's constant that is well known to govern the microscopic world, follows already from classical physics, namely an entirely classical theoretical treatment of blackbody radiation. In fact, the existence of Planck's constant, as one of the universal physical constants, is a necessary consequence of the radiation law by Stefan and Boltzmann. Hence, even its quantitative value might be deduced from measuring the temperature dependence of the frequency-integrated radiation energy. In the second part of the talk, in a historical review, Boltzmann's proof of the Stefan-Boltzmann law and Wien's derivation of his distribution law (Verschiebungsgesetz) are described. Both derivations deserve to be remembered, be it only because of the ingenious gedanken experiments they are based on.

May 3rd - 2012
Controlling spontaneous emission with surface waves

Prof Jean-Jacques Greffet
Institut d‘Optique, Paris

Spontaneous emission can be dramatically modified by controlling the environment of the emitters. In this talk, we will deal with spontaneous emission of quantum dots embedded in a nanoantenna and with thermal radiation for the design of IR sources. In the first part of the talk, I will report the study of a patch nanoantenna. It consists of quantum dots deposited on a planar gold substrate and covered by a thin gold disk. Experimental results will be reported. It will be shown that the nanoantenna allows controlling the emission direction and the decay rate of a cluster of quantum dots. In the second part of the talk, I will discuss the possibility of taking advantage of recent advances in nanophotonics to design IR thermal sources. For fundamental reasons, spontaneous emission is rather inefficient in the IR so that incandescent sources are still used when cheap and compact IR sources are needed. Yet, these sources are quasi-isotropic, have a broad spectrum, cannot be modulated faster than a few tens of Hertz and are energetically inefficient. I will show that by taking advantage of recent advances in nanophotonics, it is possible to control the emission of IR radiation and design directional, quasimonochromatic sources. I will introduce new ideas that pave the way towards fast modulation of the emitted flux.