# past events

## LANE 2014

8th International Conference on Photonic Technologies

**Conference Organisation:** Bayerisches Laserzentrum GmbH, Chair of Photonic Technologies FAU

**Call for papers:** until January 31, 2014

**Place:** Fürth, Germany

**More information and registration:** www.lane-conference.org

## IMPRS get-together

**Place:** MPL / Large seminar room (*435)

**Organisation:** Luo Qi (IOIP / Quantum Radiation)

**Talk: **Quantum Imaging with Undetected Photons**
**

**Speaker:** Dr. Radek Lapkiewicz (Institute for Quantum Optics and Quantum Information - Vienna; Research group: Zeilinger Group)

**Abstract: **

Indistinguishable quantum states interfere, but the mere possibility of obtaining information that could distinguish between overlapping states inhibits quantum interference. Quantum imaging can outperform classical imaging or even have entirely new features. We introduce and experimentally demonstrate a quantum imaging concept that relies on the indistinguishability of the possible sources of a photon that remains undetected. Our experiment uses pair creation in two separate down-conversion crystals. While the photons passing through the object are never detected, we obtain images exclusively with the sister photons that do not interact with the object. Therefore the object to be imaged can be either opaque or invisible to the detected photons. *
*

## MPL Distinguished Lecturer Series

From Ultracold Fermi Gases to Neutron Stars

### Speaker:

Prof. Christophe Salomon (Ecole Normale Supérieure, Paris, France)

### Place:

MPL / large seminar room (*435)

### Abstract:

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

## IMPRS get-together

**Place:** large seminar room / MPL

**Organisation:** Martin Finger (MPL / Russell Division)

**Talk: **Magnetic penetration depth of iron pnictide superconductors

**Speaker: **Dr. Clifford Hicks (Max-Planck Institute for the Chemical Physics of Solids / Research group: Physics of Quantum Materials)

**Abstract:**

The Meissner effect, expulsion of magnetic fields, is a key characteristic of the superconducting state. Magnetic fields applied to a superconductor penetrate only a small distance, typically around 100 nm, into the superconductor. This magnetic penetration depth is one of the more difficult quantities to measure in condensed matter physics. It is also an important measurement: variation of the penetration depth at low temperatures provides information on the superconducting order parameter, the collective quantum state that carriers enter when a material becomes superconducting. Knowing the order parameter is important in understanding why a material becomes superconducting. I will present penetration depth measurements on iron pnictide superconductors, a class of high temperature superconductors discovered in 2008.

## OPTICS BBQ

**Organisation:** hbar OMEGA OSA student chapter

**Place:** Barbecue area of the university's physics department (behind the tandem accelerator at Erwin Rommel Straße 1)

## IMPRS get-together

**Place:** large seminar room / MPL

**Organisation:** Daqing Wang (MPL / Sandoghdar Division)

**Talk: **Fundamentals and applications of Interferometric Scattering

**Speaker:** Prof. Leonardo Menezes (Universidade Federal de Pernambuco, Brazil)

**Abstract:**

In this talk, I'll present the principles of the interferometric scattering (iScat) technique, which allows performing microscopy and spectroscopy of various nanoscopic systems in the diffraction limited regime. Then I'll discuss applications of iScat in different situations: for detection of particles down to 5 nm, for studying single molecule absorption of light, for tracing the diffusion of a virus on a lipidic membrane and for 3D tracking of gold nanoparticles in a static electric potential.

## Distinguished Lecturer Series

Quantum Microwave Photonics

### Speaker:

Prof. Andreas Wallraff (ETH Zürich, Schweiz)

### Place:

MPL / large seminar room (*435)

### Abstract:

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)

## IMPRS get-together

**Place:** MPL (large seminar room)

**Organisation:** Eugene Kim (MPL / Vollmer Research Group)

**Talk: **Hybrid photonic-plasmonic whispering gallery mode sensors

**Speaker:** Dr. Matthew Foreman (Vollmer Research Group - Lab of Nanophotonics and Biosensing, MPL)

**Abstract:**

Optical resonator based biosensors are rapidly emerging as one of the most sensitive label free technologies, capable of fullling the requirements for next generation sensors. Whispering gallery mode (WGM) resonators, particularly, exhibit high sensitivity by virtue of their high quality (Q) resonances and large surface intensities. Commonly WGM biosensors utilize the reactive resonance shift produced by a protein or nanoparticle binding to the microcavity. This shift is proportional to the intensity jE(r0)j2 at the binding site r0 such that any mechanisms enhancing the local intensity while maintaining high Q factor can amplify the frequency shift. Exploiting plasmonic nanoantennae therefore represents a natural and powerful means by which to push the detection envelope beyond the current limits to the single molecule level. In this talk we discuss various theoretical aspects of WGM based sensors, including fundamental sensing principles, sensor optimisation and modelling of hybrid photonic-plasmonic WGM biosensors.

## IMPRS get-together

**Place:** lecture hall F (Staudtstraße 5, at the physics institute of the university of Erlangen)

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

**Talk: **Optomechanical Metamaterials: Dirac polaritons, Gauge fields, and Instabilities

**Speaker:** Vittorio Peano (FAU)

**Abstract:**

Freestanding photonic crystals can be used to trap both light and mechanical vibrations. These "optomechanical crystal" structures have already been experimentally demonstrated to yield strong coupling between a photon mode and a phonon mode, co-localized at a single defect site. Future devices may feature a regular superlattice of such defects, turning them into "optomechanical arrays". In this letter we predict that tailoring the optomechanical band structure of such arrays can be used to implement Dirac physics of photons and phonons, to create a photonic gauge field via mechanical vibrations, and to observe a novel optomechanical instability.

## Distinguished Lecturer Series

The Quantum Way of Doing Computations

### Speaker:

Prof. Rainer Blatt (Institute for Experimental Physics, University of Innsbruck and Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Innsbruck, Austria)

### Place:

MPL / large seminar room (*435)

### Abstract:

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.