Towards Highly Storage Efficiency of Optical Quantum Memory Based on Electromagnetically Induced Transparency Protocol

Towards Highly Storage Efficiency of Optical Quantum Memory Based on Electromagnetically Induced Transparency Protocol
Long-distance quantum communication based on quantum repeater protocol [mehr]

Probing dynamical properties of Fermi-Hubbard systems with a quantum gas microscope (Prof. Waseem Bakr)

Probing dynamical properties of Fermi-Hubbard systems with a quantum gas microscope
The normal state of high-temperature superconductors exhibits anomalous transport and spectral properties that are poorly understood. Cold atoms in optical lattices have been used to realize the celebrated Fermi-Hubbard model, widely believed to capture the essential physics of these materials. The recent development of fermionic quantum gas microscopes has enabled studying Hubbard systems with single-site resolution. Most studies have focused on probing equal-time spin and density correlations. [mehr]

Trapped ion optical clocks and tests of the equivalence principle (Dr. Ekkehard Peik)

Trapped ion optical clocks and tests of the equivalence principle
Optical clocks based on different atoms and ions with uncertainties in the low 10-18 range allow for frequency comparisons that can be used in tests of fundamental physics, like in quantitative tests of relativity and searches for violations of the equivalence principle. [mehr]

Laser-cooled molecules for quantum science and tests of fundamental physics (Prof. Michael Tarbutt)

Laser-cooled molecules for quantum science and tests of fundamental physics
Ultracold molecules can be used to test fundamental physics, simulate many-body quantum systems, process quantum information, and study ultracold chemistry. [mehr]

Probing our understanding of particle- and astrophysics with neutrons (Prof. Stephan Paul)

Probing our understanding of particle- and astrophysics with neutrons
Precision experiments probing the properties of neutrons and details of their decay can reveal important information for both particle and astrophysics. [mehr]

Passion extreme light (Prof. Gérard Mourou)

Passion extreme light
Extreme-light laser is a universal source providing a vast range of high energy radiations and particles along with the highest field, highest pressure, temperature and acceleration. It offers the possibility to shed light on some of the remaining unanswered questions in fundamental physics like the genesis of cosmic rays with energies in excess of 1020 eV or the loss of information in black-holes. [mehr]

Automatic Differentiation of Tensor Expressions

Automatic Differentiation of Tensor Expressions
Automatic differentiation is a powerful tool that allows to compute derivatives not only of mathematical expressions but also of functions that are given as a computer program. [mehr]

Double Feature: Towards attosecond and femtosecond spectroscopy at extreme limits (Dr. Hanieh Fattahi)

Towards attosecond and femtosecond spectroscopy at extreme limits
This talk is devoted to modern methods for attosecond and femtosecond laser spectroscopy, with the special focus on applications that require extreme spatial resolution. [mehr]

Double Feature: High Precision Direct Frequency Comb Spectroscopy in UV (M.Sc. Alexey Grinin)

High Precision Direct Frequency Comb Spectroscopy in UV
In the last two decades frequency combs became an essential tool for spectroscopyexperiments around the world, allowing for simple and convenient referencing of laserswith dierent wavelengths to each other and to radio frequency standards [1]. A numberof other interesting applications in applied spectroscopy, astronomy, quantum informationand other elds are being investigated [2, 3]. [mehr]

Exploring matter-wave emission phenomena in optical lattices (Prof. Dominik Schneble)

Exploring matter-wave emission phenomena in optical lattices
The quantitative understanding of spontaneous emission harks back to the early days of QED, when in 1930 Weisskopf and Wigner, using Dirac's radiation theory, calculated the transition rate of an excited atom undergoing radiative decay. Their model, which describes the emission of a photon through coherent coupling of the atom's transition dipole moment to the continuum of vacuum modes, reflects the view that spontaneous emission into free space, driven by vacuum fluctuations, is inherently irreversible. [mehr]

Learning and artificial intelligence in the quantum domain (Prof. Hans Briegel)

Learning and artificial intelligence in the quantum domain
Quantum mechanics has changed the way we think about the scope and possibilities of information processing, and the foundations of computer science. [mehr]

Review procedures in Nature Photonics

Review procedures in Nature Photonics
Nature-branded journals (such as Nature, Nature Photonics, Nature Physics, etc.) are some of the most prestigious and important scientific publications in the world today. To maintain the quality and high impact factor of each journal, the editors rigorously select papers that provide conceptual or technological breakthrough according to stringent acceptance criteria and a unique reviewing process. [mehr]

Double Feature: Distillation of Single Photons based on Cavity QED (M.Sc. Severin Daiss)

Distillation of Single Photons based on Cavity QED
Custom-shaped single photons are an indispensable tool for many quantum communication applications. We distill them out of incoming optical pulses that are reflected from an atom-cavity system [1]. [mehr]

Double Feature: Geometry of variational manifolds and the Bose-Hubbard model (Dr. Lucas Hackl)

Geometry of variational manifolds and the Bose-Hubbard model
A key challenge in the theoretical study of quantum many body systems is to overcome the exponential growth of the Hilbert space with the system size. Many successful approaches are variational, i.e., they are based on choosing suitable families of states that capture key properties of the system. Prominent examples range from Gaussian states to matrix product states and tensor networks. [mehr]

From Precision Spectroscopy to Symmetry-Breaking Dynamics in Ion Coulomb Systems (PD Dr. Tanja Mehlstäubler)

From Precision Spectroscopy to Symmetry-Breaking Dynamics in Ion Coulomb Systems
Single trapped and laser-cooled ions in Paul traps allow for a high degree of control of atomic quantum systems. They are the basis for modern atomic clocks, quantum computers and quantum simulators. Our research aims to use ion Coulomb crystals, i.e. many-body systems with complex dynamics, for precision spectroscopy. This paves the way to novel optical frequency standards for applications such as relativistic geodesy and quantum simulators in which complex dynamics becomes accessible with atomic resolution. [mehr]

Table-top precision measurements to test fundamental physics: Measurements of the proton charge radius, the fine-structure constant and the electron electric dipole moment (Prof. Eric Hessels)

Table-top precision measurements to test fundamental physics: Measurements of the proton charge radius, the fine-structure constant and the electron electric dipole moment
Fundamental physics (including physics beyond the Standard Model) can be tested using table-top precision measurements. The talk will describe measurements of the size of the proton, the fine-structure constant and the electric dipole moment of the electron. Two recently completed measurements will be described. [mehr]

Non-perturbative Cavity QED (Prof. Peter Rabl)

Non-perturbative Cavity QED
In quantum optical systems the coupling between a single dipole and a single cavity mode is always much smaller than the absolute energy scales involved, which allows us to understand and model light-matter interactions in terms of well-defined atomic and photonic excitations. With recent advances in the field of circuit QED it is now possible to go beyond this well-established paradigm and enter a fully non-perturbative regime, where the coupling between a single artificial atom (e.g. a superconducting qubit) and a microwave photon exceeds the energy of the photon itself. Such conditions can be associated with an effective finestructure constant of order unity and in this talk I will give a brief introduction about the basics models and novel effects that govern the physics of light-matter interactions in this previously inaccessible regime. [mehr]

Optimized quantum photonics (Prof. Jelena Vuckovic)

Optimized quantum photonics
At the core of most quantum technologies, including quantum networks and quantum simulators, is the development of homogeneous, long lived qubits with excellent optical interfaces, and the development of high efficiency and robust optical interconnects for such qubits. To achieve this goal, we have been studying color centers in diamond (SiV, SnV) and silicon carbide (VSi in 4H SiC), in combination with novel fabrication techniques, and relying on the powerful and fast photonics inverse design approach that we have developed. [mehr]

SMT: Printing really small, really fast … … and what to do when you are at the end of your rope (Dr. Andreas Dorsel)

SMT: Printing really small, really fast … and what to do when you are at the end of your rope
This talk is intended to provide you with a solid notion of what can be achieved in nano-lithography today, what the present technical limitations are and what we consider at present fundamental boundaries of what may be possible in the future. Carl Zeiss SMT has been active in this field for more than 50 years and its history hence shows some of the technological milestones from the early beginnings of integrated circuits to present-day extreme integration allowing qualitatively new applications of micro- or rather nano-electronics. [mehr]

χ(2) Nanomaterials for Nonlinear Integrated Photonic Devices (Prof. Rachel Grange)

χ(2) Nanomaterials for Nonlinear Integrated Photonic Devices
Nonlinear optics is present in our daily life with many applications, e.g. light sources for microsurgery or green laser pointer. All of them use bulk materials such as glass fibres or crystals. Generating nonlinear effects from materials at the nanoscale can expand the applications to biology as imaging markers or sensors, and to optoelectronic integrated devices. However, nonlinear signals scale with the volume of a material. Therefore, finding nanostructured materials with high nonlinearities to avoid using high power and large interaction length is challenging. Here I will show several strategies to maximize nonlinear optical signals in nano-oxides with noncentrosymmetric crystalline structure and semiconductors. I will demonstrate how we enhance second-harmonic generation (SHG) by using the scattering properties of individual barium titanate (BaTiO3) nanoparticles1, and AlGaAs standing nanodisks2. Our results suggest that a strong increase of the SHG signal can be obtained without using plasmonics or hybrid nanostructures3 [mehr]

Quantum fluids of light in semiconductor lattices (Prof. Jacqueline Bloch)

Quantum fluids of light in semiconductor lattices
When confining photons in semiconductor lattices, it is possible to deeply modify their physical properties. Photons can behave as finite or even infinite mass particles, photons inherit topological properties and propagate along edge states without back scattering, photons can become superfluid and behave as interacting particles. These are just a few examples of properties that can be imprinted into fluids of light in semiconductor lattices. Such manipulation of light presents not only potential for applications in photonics, but is a great promise for fundamental studies. [mehr]

Connecting the Resource Theories of Purity and Coherence (Prof. Dagmar Bruss)

Connecting the Resource Theories of Purity and Coherence
The resource theory of quantum coherence studies the off-diagonal elements of a density matrix in a distinguished basis, whereas the resource theory of purity studies all deviations from the maximally mixed state. A direct connection between the two resource theories is established by identifying purity as the maximal coherence which is achievable by unitary operations. The states that saturate this maximum form a family of maximally coherent mixed states. Furthermore, purity bounds the maximal amount of entanglement and discord that can be generated by unitary operations, thus demonstrating that purity is the most elementary resource for quantum information processing. [mehr]

High Harmonic Generation Interferometry (Prof. Nirit Dudovich)

High Harmonic Generation Interferometry
Attosecond science is a young field of research that has rapidly evolved over the past decade. The progress in this field opened a door into a new area of research that allows one to observe multi-electron dynamics in in atoms, molecules and solids. One of the most exciting advances in atto-science is high harmonic generation (HHG) spectroscopy. It allows one to combine sub-Angstrom spatial with attosecond temporal resolution, holding the potential of resolving the structure of electronic wavefunctions as they evolve in time. [mehr]

Surface enhanced coherent Raman scattering (Prof. Eric Potma)

Surface enhanced coherent Raman scattering
Surface-enhanced Raman scattering (SERS) is a popular technique that makes it possible to boost the otherwise weak Raman effect to levels that allow single molecule detection. A coherent, nonlinear equivalent of single molecules SERS is highly attractive, because it would allow the use single vibrational quantum oscillators with a narrow line width for a host of interesting applications. The translation of SERS into the domain of coherent Raman spectroscopy (CRS) has, however, not been trivial. This presentation zooms into some of the recent accomplishments in this area, highlights single molecule CRS experiments and discusses the possibilities of performing single vibrational oscillator measurements without the use of nanoscale plasmonic antennae. [mehr]

Quantum Logic Spectroscopy with Trapped Ions (Prof. Dr. Dietrich Leibfried)

Quantum Logic Spectroscopy with Trapped Ions
Quantum logic spectroscopy uses the quantized motion of trapped charged particles as a means to indirectly control charged quantum systems and gain information on their properties. A highly controllable atomic "logic" ion indirectly helps to manipulate the system under study and to report information back to the experimenter. This allows for precise quantum control of charged systems that are hard or impossible to directly control with light fields, such as atomic ions without convenient laser cooling transitions, molecular ions or charged elementary particles such as the proton. This talk will introduce the basic ideas behind quantum logic spectroscopy and illustrate its power based on example experiments in the NIST Ion Storage Group. [mehr]

Synthesizing Light: New Tools, Wavelengths and Opportunities (Prof. Dr. Scott Diddams)

Synthesizing Light: New Tools, Wavelengths and Opportunities
Frequency synthesis is ubiquitous in all aspects of our modern technological society, with examples being found in wide ranging applications from computing, communications and navigation systems to sensors and scientific instrumentation. Historically, the generation and precise control of electromagnetic radiation has been confined to the radio frequency and microwave domains. How­ever, optical frequency combs, first introduced by Prof. T.W. Hänsch, dramatically expand the synthesis bandwidth to cover the entire terahertz and optical domains as well. [mehr]

Topology in finite‐temperature and non‐equilibrium systems (Prof. Michael Fleischhauer)

Topology in finite‐temperature and non‐equilibrium systems
Topological states of matter have fascinated physicists since a long time due to the exotic properties of elementary excitations and the topological protection of edge states and currents. The notion of topology is ususally associated with ground states of (many-body)-Hamiltonians. [mehr]

Cold and ultracold molecules for quantum information and particle physics (Prof. John Doyle)

Cold and ultracold molecules for quantum information and particle physics
Wide-ranging scientic applications have created growing interest in ultracold molecules. Heteronuclear bialkali molecules, assembled from ultracold atoms, enabled the study of long-range dipolar interactions and quantum-state-controlled chemistry, and recently have been brought to quantum degeneracy. Assembling such molecules one-byone in tweezers for quantum information applications is one exciting avenue of this work. [mehr]

Double Feature: One-dimensional superradiant photonic states for quantum information (Dr. Marti Perarnau)

One-dimensional superradiant photonic states for quantum information
Photonic states with large and fixed photon numbers, such as Fock states, are crucial in quantum technologies but remain an experimentally elusive resource. A potentially simple, deterministic and scalable way to generate these states consists of fully exciting N quantum emitters equally coupled to a common photonic reservoir, which leads to a collective decay known as Dicke superradiance. The emitted N-photon wavepacket turns out to be a highly entangled multimode state, which makes its characterisation challenging, and its potential for quantum information an open question. In this talk, after reviewing the basics of superradiance and 1d waveguide QED, I will show that Dicke superradiant states have a high quantum Fisher information (achieving Heisenberg scaling), implying they enable quantum-enhanced metrology. Then, I will discuss possible effective descriptions of such states, which would allow a clean understanding of their properties. [mehr]

Double Feature: Interacting polar molecules in a spin-decoupled magic trap (Frauke Seeßelberg)

Interacting polar molecules in a spin-decoupled magic trap
Interacting particles with long coherence times are a key ingredient for entanglement generation and quantum engineering. Ultracold polar molecules are promising candidates due to their strong and tunable dipolar interactions as well as their long single-particle lifetimes. They possess many internal degrees of freedom that can be utilized in quantum simulation. Particularly appealing are superpositions of rotational states because they readily give rise to strong, long-range dipolar interactions. In this talk I will introduce a novel trapping technique for rotating polar molecules, nuclear spin-decoupled magic trapping. With this technique we achieve very low single-particle dephasing rates for our fermionic NaK molecules. These allow us not only to obtain record rotational spin coherence times but also to directly observe dipolar interactions in the molecular gas. This paves the way for fascinating future experiments with ultracold polar molecules. [mehr]

Double Feature: The ATLAS laser: from Terrawatt to Petawatt and from MPQ to CALA (Prof. Stefan Karsch)

The ATLAS laser: from Terrawatt to Petawatt and from MPQ to CALA
Abstract will follow shortly... [mehr]
Schrödinger's famous cat Gedankenexperiment investigates how the laws of quantum mechanics extend into the macroscopic realm. An experimentally accessible model system in quantum optics is the superposition of two well-distinguishable coherent states - a so-called "cat state" - with a tunable degree of macroscopicity. Applying a high-finesse cavity we demonstrate a new method to create flying optical cat states. They are entangled to a single trapped atom, much like Schrödinger's original cat. I show control over various degrees of freedom of the cat states, which is a great asset for their potential application to continuous-variable quantum computing. [mehr]

Quantum optics using atomic arrays (Prof. Dr. Darrick Chang)

Ensembles of atoms or other quantum emitters are envisioned to be an important component of quantum applications, ranging from quantum memories for light to photon-photon gates to metrology. It has historically been an outstanding challenge to exactly solve for the quantum dynamics of an optical field as it propagates through and interacts with an ensemble. The standard axiomatic approach is to use the one-dimensional Maxwell-Bloch equations, which assume that excited atoms emit independently into unwanted directions. This ignores the wave interference of the emitted light, which depends on correlations between the atoms. [mehr]

Superfluidity and Bose-Einstein Condensation Coherence (Prof. Dr. Lev Pitaevskii)

In 1938 Petr Kapitza, investigating properties of the low temperature phase of liquid 4He, discovered that viscosity of the liquid is more than 104 times smaller, than that of all known liquids. Kapitza concluded, that the liquid is in a new state of matter, a “superfluid”, which to some extend analogous to superconductors. Landau (1941) explained the phenomenon and predicted several its unusual properties. It occurs, that in a superfluid in any point of space at finite temperatures simultaneously exists two flow with different velocities. One is “normal” and has finite viscosity and the second one is “superfluid”, which viscosity is exactly zero. This results in presence of two type of sound, which were discovered experimentally in 1946. [mehr]
Optical microscopy has been a fundamental tool to life science and materials science since its invention in the 17th century. [mehr]

Deciphering complex quantum systems (Prof. A. Buchleitner)

Not many ingredients are needed for a quantum system to turn complex, with the helium atom as the arguably most elementary example. [mehr]

Rotating molecules and fundamental constants (Prof. S. Schiller)

Molecules provide exciting opportunities for precision measurements - significantly extending those offered by atoms. [mehr]

Imaging in Biology and Biomedicine (Prof.Steven Chu)

In recent years, new imaging probes such as green fluorescent proteins, optical tweezers, single molecule FRET and super-resolution microscopy are having a profound impact on biological sciences. [mehr]

Precision spectroscopic measurements in H2, H2+, He2 and He2+(Prof. Merkt)

Few-electron molecules represent attractive systems for precision spectroscopy because their properties can be calculated with extraordinary accuracy by ab initio quantum-chemical methods. [mehr]

Combs and isotopic customization for trapped ion quantum computing (Prof. W. Campbell)

Since ions bind their valence electrons tightly, the light needed to work with them is often in the UV part of the spectrum, where laser light is difficult to produce and manage. [mehr]

Molecular spectroscopy with laser frequency combs (Dr. N. Picqué)

Almost twenty years ago, optical frequency combs – spectra made of millions of phase-coherent evenly spaced narrow laser lines – have revolutionized time and frequency measurements. [mehr]

How to count one photon and get a result of 1000 (Prof. A. Steinberg)

I will present our recent experimental work using electromagnetically induced transparency in laser-cooled atoms to measure the nonlinear phase shift created by a single post-selected photon, and its enhancement through "weak-value amplification." [mehr]

Correlations of a quantum system in real and momentum space (Prof. S. Jochim)

The properties of a many body system are encoded in correlations between the particles. [mehr]
Colloquium on the Occasion of Prof. Dr. Karl-Ludwig Kompa's 80th Birthday! Following please find detailed information: [mehr]

Coupling spin and orbital dynamics with quantum light (Prof. D. Stamper-Kurn)

A trapped atomic gas within an optical resonator serves as both a mechanical oscillator and a spin oscillator, represented by the collective degrees of freedom of the gas. [mehr]

Label-free tissue classification by FTIR- and QCL-based IR-imaging (Prof. K. Gerwert)

Infrared imaging in combination with bioinformatics is an emerging tool for label-free, non-invasive annotation of tissue, cells, and body fluids. [mehr]

Connecting quantum systems through optimized photonics (Prof. J. Vuckovic)

Semiconductor quantum dot in cavity has been the workhorse of solid-state quantum optics, enabling many exciting demonstrations such as photon blockade, and some of the best quantum light sources and spin-photon interfaces. [mehr]

Ultrafast Transmission Electron Microscopy with High-coherence Electron Beams (Prof. C. Ropers)

Ultrafast Transmission Electron Microscopy (UTEM) is a powerful technique to study structural and electronic dynamics on the nanoscale. [mehr]

Atomic giants in a new light: Emerging photon interactions from highly excited Rydberg atoms (Prof. T. Pohl)

The combination of electromagnetically induced transparency (EIT) and strongly interacting Rydberg states in cold atomic gases has opened up new routes towards achieving few-photon optical nonlinearities. [mehr]

Quantum many-body dynamics under continuous observation (Prof. M. Ueda)

Quantum gas microscopy has revolutionalized our approach to quantum many-body systems where atoms trapped in an optical lattice can be observed in real time at the single-particle level. [mehr]

Experimental many-body physics using arrays of individual Rydberg atoms (Prof. A. Browaeys)

This talk will present our on-going effort to control the dipole-dipole interaction between cold Rydberg atoms in order to implement spin Hamiltonians that may be useful for quantum simulation of condensed matter problems. [mehr]

Prospects for a quantum electro-optic interface via micromechanical motion (Prof. C. Regal)

Superconducting qubits have become a powerful resource for the creation of arbitrary quantum states. [mehr]

Making quantum liquids from quantum gases (Prof. L. Tarruell)

Self-bound states appear in contexts as diverse as solitary waves in channels, optical solitons in non-linear media and liquid droplets. [mehr]

An overview of recent results for the non-equilibrium dynamics of isolated 1D models (Prof. P. Calabrese)

Since the early days of quantum mechanics, understanding how statistical ensembles arise from the unitary time evolution of an isolated quantum system has been a fascinating problem. [mehr]

Magnonic macroscopic quantum states and supercurrents (Prof. B. Hillebrands)

Finding new ways for fast and efficient processing and transfer of data is one the most challenging tasks nowadays. [mehr]
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Optically Trapping and Isolating Ions for Seconds (Prof. T. Schätz)

Isolating ions and atoms from the environment is essential for experiments, especially if we aim to study quantum effects. [mehr]

Convex Optimization Methods for Image-based 3D Reconstruction (Prof. D. Cremers)

The reconstruction of the 3D world from a moving camera is among the central challenges in computer vision. [mehr]

An Einsteinian Analogy Sheds Light on Light (Prof. D. Hofstadter)

Where does deep insight in physics come from? For those who view physics as a highly rational science grounded in strict mathematical deduction, it is tempting to think that great physics comes only from the purest and most precise of reasoning, following ironclad laws of thought that compel the clear mind completely rigidly. [mehr]

Status and prospects of fiber lasers and amplifiers (Prof. A. Tünnermann)

In the past years rare-earth-doped fiber lasers have emerged as an attractive and power scalable solid-state laser concept due to the outstanding thermo-optical properties of an actively doped fiber. [mehr]

Brillouin-based light storage in a photonic circuit (Dr. B. Stiller)

Brillouin scattering is a fundamental nonlinear opto-acoustic interaction present in optical fibres and other waveguides with important implications in fields ranging from modern telecommunication networks, signal processing and smart optical sensors. [mehr]

Subcycle quantum physics (Prof. R. Huber)

Atomically strong light pulses in the terahertz window of the electromagnetic spectrum form a unique toolbox to trace and control electronic and ionic quantum motion faster than a cycle of light. [mehr]

Fundamental Physics with (weird) Magnetic Resonance (Prof. D. Budker)

I will discuss the ongoing experiments (CASPEr and GNOME) searching for ultralight galactic dark matter using magnetic-resonance techniques and a new approach to measuring parity violation in chiral molecular systems. [mehr]

Optical Atomic Clocks: From Laboratory Experiments to International Time Keeping (Dr. H. Margolis)

Optical atomic clocks based on laser-cooled atoms or single trapped ions have made rapid progress over the past few years, with the most advanced now having reached levels of stability and uncertainty that significantly surpass the performance of caesium primary frequency standards. [mehr]

Are we quantum computers, or merely clever robots? (Prof. M. Fisher)

Of course quantum information processing is not possible in the warm wet brain. There is, however, one \loophole" - oered by nuclear spins - that must be closed before acknowledging that we are merely clever robots. [mehr]
Generic, clean quantum many-body systems approach a thermal equilibrium after a long time evolution. In order to reach a global equilibrium, conserved quantities have to be transported across the whole system which is a rather slow process governed by diffusion. [mehr]

Quantum Measurements on Trapped Ions (Prof. J. Home)

Measurement as defined in quantum physics rarely corresponds to what is performed in the laboratory. [mehr]

Manipulating nuclei with laser light: the quest of Thorium-229 (Prof. T. Schumm)

The radio isotope Thorium-229 is expected to present a remarkably low-energy excited (isomer) state of the nucleus which is expected around 7.8(5) eV. [mehr]
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Quantum optics with trapped ions – from single ion heat engines to ions in vortex laser fields (Prof. F. Schmidt-Kaler)

Trapped single ions and ion crystal exhibit excellent control of the internal spin– and the external motional-degree of freedom. Multi-particle quantum entangled states are generated with high fidelity in view of a future quantum computer with trapped ions. [mehr]

The Alchemy of Vacuum - Hybridizing Light and Matter (Prof. T. Ebbesen)

Strong coupling of light and matter can give rise to a multitude of exciting physical effects through the formation of hybrid light-matter states. [mehr]

First principles modeling of Light-Matter interactions within QED-TDDFT: From Weak to Strong Coupling in QED-Chemistry and Materials (Prof. A. Rubio)

Computer simulations that predict the light-induced change in the physical and chemical properties of complex systems, molecules, nanostructures and solids usually ignore the quantum nature of light. [mehr]

Genome editing and the CRISPR/cas revolution (Prof. K. Förstemann)

I will present the origins of the prokaryotic (i.e. bacteria and archaea) CRISPR/cas systems, then describe how one particular variant (Streptococcus pyogenes cas9) has been adapted and optimized for use in eukaryotic cells. [mehr]

Potential Energy Surfaces and Berry Phases beyond the Born-Oppenheimer Approximation (Prof. E. Gross)

The starting point of essentially all modern electronic-structure techniques is the Born-Oppenheimer approximation. It not only makes calculations feasible, it also provides us with an intuitive picture of chemical reactions. [mehr]
Recent remarkable experimental progress in ‘circuit QED’ now allows realization of extremely strong dispersive coupling between superconducting qubits and microwave photons in resonators. [mehr]
Molecular systems that can be remotely controlled by light are gaining increasing importance in bio-sciences. High spatial and temporal precision is achievable with short laser pulses and in principle there are three approaches for light regulation. [mehr]
Controlling the interaction of light and matter is the basis for diverse applications ranging from light technology to quantum information processing. Nowadays, many of these applications are based on nanophotonic structures. [mehr]
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. [mehr]

Searching for dark fields with atom interferometry (Prof. P. Hamilton)

One of the great mysteries of modern physics is the identity of nearly 95% of our Universe, which has been labelled as dark matter and dark energy. The high precision of atom interferometry gives a new way to explore this mystery. [mehr]
I plan to start this presentation with an overview of our work over the past decade on the efficient coupling of light and single quantum emitters, leading to the single-photon communication of two individual molecules at long distances [1]. [mehr]
Trapped atomic ions are a well-advanced physical system for quantum information science (QIS). QIS is meant to encompass the quest for a specialized, or even universal processor for quantum information, the investigation of fundamental questions of quantum physics, as well as applications of techniques emanating from these investigations to other fields, for example, precision spectroscopy and sensing. [mehr]
The field of thermodynamics is one of the crown jewels of classical physics. However, only comparatively recently, due to the advent of experiments in cold atomic systems with long coherence times, has our detailed understanding of its connection to quantum statistical mechanics seen remarkable progress. [mehr]
Ultracold quantum gases are usually well isolated from the environment. This allows for the study of ground state properties and unitary dynamics of many-body quantum systems under almost ideal conditions. [mehr]
The controlof polaritons are at the heart of nano-photonics and opto-electronics. Two-dimensional materials have emerged as a toolbox for in-situ control of awide range of polaritons: plasmons, excitons and phonons. [mehr]
Bose-Einstein condensation has been observed with cold atomic gases, quasiparticles in solid state systems as polaritons, and more recently with photons in a dye-filled optical microcavity. [mehr]
On September 14, 2015 the two LIGO gravitational wave detectors in Hanford, Washington and Livingston, Louisiana registered a coincident signal conforming to the gravitational waveform expected from the merger of two massive, compact objects. [mehr]
The precision of any measurement is limited by quantum mechanics. Yet, in practice, hardly any measurement reaches its quantum limits. This is because dephasing typically influences measurement device, rendering their sensitivity below its physical limits. [mehr]
The propagation of light in inhomogeneous media, and in particular in biological tissues, results in wavefront distortions and scattering which impose major limitations in many applications, from microscopy to nanosurgery. [mehr]
Magnetization manipulation is an indispensable tool for both basic and applied research. I will discuss some of the knobs to tune dynamics at ultrafast time scales. [mehr]
One aspect of metrology, the science of measurement, is the exploration of the ultimate precision limit. It is known for quite some time that the new possibilities in quantum mechanics allow the surpassing of the ultimate classical precision limit given by counting statistics. [mehr]
Future quantum networks will allow the secure distribution of encryption keys over extended distances, blind quantum computing, and networked quantum computers and atomic clocks. [mehr]
The beauty of topological materials is that their electronic properties can be essentially described by integer topological invariants associated with their band structures.  [mehr]
Synthetic ladders realized with one-dimensional alkaline-earth(-like) fermionic gases and subject to a gauge field represent a promising environment for the investigation of quantum Hall physics with ultracold atoms. [mehr]
The design of fundamental optical components such as lenses, gratings, and holograms has remained essentially unchanged for at least fifty years, relying on textbook refractive and diffractive optics. [mehr]
Device-independent quantum information processing represents a new framework for quantum information applications in which devices are just seen as quantum black boxes processing classical information. [mehr]

Entanglement of Complex Quantum Systems (Prof. N. Schuch)

Complex quantum systems exhibit a variety of unconventional phenomena, such as protected quantized edge currents or excitations with non-trivial statistics.  [mehr]
Attosecond pulses are generated by electrons that are extracted from a quantum system by an intense light pulse and travel through the continuum. [mehr]

Microscopy 2.0 (Prof. S. Chu)

There has been an explosion of new imaging technologies in biology that include photo-activation localization microscopy (PALM), stochastic optical reconstruction microscopy (STORM), and stimulated emission depletion (STED), structured illumination, and adaptive optics are revolutionizing optical microscopy. [mehr]
I will present recent work realizing topological phases of photons. [mehr]
Ultrafast time-resolved spectroscopy, and in particular its extension to multidimensional techniques, can tell us a lot about solvation dynamics, structural dynamics and energy transfer processes of solution phase molecular systems. [mehr]

Highly efficient organic devices (Prof. K. Leo)

Organic semiconductors with conjugated electron system are currently intensively investigated for (opto-) electronics. [mehr]
Hundred years after General Relativity:  Was Einstein right? [mehr]
Quantum mechanics is a foundation of physics, chemistry and materials science.  Still, there is an ongoing debate about the emergence of the classical, macroscopic world from the well-understood microscopic world of quantum mechanics.  [mehr]
Understanding the behavior of interacting electrons in solids or liquids is at the heart of modern quantum science and necessary for technological advances. [mehr]
We review the recent experimental progress on the use of quantum dots coupled to photonic-crystal waveguides [1]. [mehr]
Modern atomism evolved on the basis of observations of matter’s macroscopic features. [mehr]
Recent progress in establishing an extreme time-domain approach to condensed-matter physics and quantum optics is presented. [mehr]
The spectrum of molecular hydrogen H2 can be measured in the laboratory to very high precision using advanced laser and molecular beam techniques, as well as frequency-comb based calibration. [mehr]
The optoelectronic response of two-dimensional (2D) crystals, such as graphene and transition metal dichalcogenides (TMDs), is currently subject to intensive investigations.  [mehr]
In the talk I will review recent results on the (un-)decidability of problems in quantum many-body physics and quantum information theory. [mehr]
This talk will give a short overview of the latest insights into the promises and pitfalls of a diverse workforce on employee outcomes like respectful interactions at work, cooperation, creativity and conflict at work. [mehr]
In a recent workshop we tried to answer the very interesting question: “Attosecond science – what will it take to observe processes ‘in real time’?” [1]. [mehr]
It is more than 100 years since the battle began to determine the correct form of the momentum of light inside a material medium. [mehr]
A system of ultracold atoms in an optical lattice is an ideal quantum simulator of a strongly correlated quantum many-body system and also a topological quantum system due to the high-controllability of system parameters. [mehr]
Progress in physics and quantum information science motivates much recent study of the behavior of extensively-entangled many-body quantum systems fully isolated from their environment, and thus undergoing unitary time evolution. [mehr]
Many light-induced processes in biomolecules, such as energy relaxation, energy/charge transfer and conformational changes, occur on ultrafast timescales, ranging from 10-14 to 10-13 s. [mehr]
Ultracold atoms on optical lattices form a versatile platform for studying many-body physics, with the potential of addressing some of the most important issues in strongly correlated matter. [mehr]
Extensive research in Nano-optics over the last decade has made possible controlling optical fields on the nanometer scale. Such concentration of light, well below the limit of diffraction, opens plenty of new routes towards enhanced interaction with tiny amounts of matter down to the single molecule/atom level. [mehr]
UV-irradiation by sun-light imposes a permanent menace to live on earth. UV-radiation causes serious loss of genetic information. [mehr]
ESA's Planck mission is the third generation satellite to study the Cosmic Microwave Background. [mehr]
There has been a long-standing quest to observe chemical reactions at low temperatures where reaction rates and pathways are governed by quantum mechanical effects or long range interactions. [mehr]
We study the ground state properties of the simplest quantum link model undergoing a SU(2) lattice gauge invariance, in one spatial dimension. [mehr]
I will give an introduction to the AdS/CFT correspondence and its generalization for non-experts. [mehr]
Many applications of quantum information rely on the potentiality of quantum systems to be correlated. For pure states, these correlations coincide with entanglement. [mehr]
Quantum communications is the art of transferring a quantum state from one location to a distant one. [mehr]
Molecules cooled to ultralow temperatures provide fundamental new insights to strongly correlated quantum systems, molecular interactions and chemistry in the quantum regime, and precision measurement. [mehr]
With the announcement of the discovery of a Higgs-like particle in July 2012 by the two general-purpose experiments ATLAS and CMS at the Large Hadron Collider (LHC) at CERN particle physics has entered a new era. [mehr]
Achieving optical nonlinear interactions at the level of single photons has been the subject of extensive research in the last couple of decades. [mehr]
This talk will describe some of the physics challenges that arise in the pursuit of quantum information technology. [mehr]
Quantum systems can reach unusual states of matter when they are driven by fast time-periodic modulations. [mehr]
Multiparticle entangled quantum states, required as a resource in quantum-enhanced metrology and quantum computing, are usually generated by unitary operations exclusively, while carefully shielding the system from any coupling to the environment. [mehr]
Many body localization and the breakdown of ergodicity in quantum systems [mehr]
Time-resolved electron diffraction and electron deflectometry using femtosecond electron pulses are useful techniques for observing ultrafast changes in the atomic-scale structure of matter and in the electromagnetic fields near matter during physical phenomena. [mehr]
The physical properties of condensed matter are often caused by ultrafast phenomena involving low-energy elementary excitations, such as lattice vibrations, spin pre­ces­sion, plasmons, or superconducting energy gaps. [mehr]
"High repetition rate parametric oscillators and amplifiers (OPO, OPA) for very short optical pulses profit from the advancement in high power solid-state pump laser technology. In this talk, topical OPA and OPO systems with multi-Watt average powers and sub-10 fs pulses are presented. Employing (2+1)D nonlinear propagation simulation it is possible to reconstruct the complex spatio-temporal and spectral evolution of the interacting light fields and their mixing products in the gain crystals.Regarding the shortest pulses, challenges in pulse characterization and pulse shaping are addressed as well as some fundamental questions regarding the femtosecond response time of nonlinear phenomena." [mehr]
"The circuit-to-Hamiltonian construction translates dynamics (a quantum circuit and its output) into statics (the groundstate of a circuit Hamiltonian) by explicitly defining a quantum register for a clock. The standard Feynman-Kitaev construction uses one global clock for all qubits while we consider a different construction in which a clock is assigned to each interacting qubit. This makes it possible to capture the spatio-temporal structure of the original quantum circuit into features of the circuit Hamiltonian. The construction is inspired by the original two-dimensional interacting fermionic model (see this http URL) We prove that for one-dimensional quantum circuits the gap of the circuit Hamiltonian is appropriately lower-bounded so that the applications of this construction for QMA (and partially for quantum adiabatic computation) go through. For one-dimensional quantum circuits, the dynamics generated by the circuit Hamiltonian corresponds to diffusion of a string around the torus. See the paper at http://arxiv.org/abs/1311.6101" [mehr]
"Superconducting quantum computing is now at an important crossroad, where “proof of concept” experiments involving small numbers of qubits can be transitioned to more challenging and systematic approaches that could actually lead to building a quantum computer. Our optimism is based on two recent developments: a new hardware architecture for error detection based on “surface codes”, and recent improvements in the coherence of superconducting qubits. I will explain how the surface code is a major advance for quantum computing, as it allows one to use qubits with realistic fidelities, and has a connection architecture that is compatible with integrated circuit technology. Additionally, the surface code allows quantum error detection to be understood using simple principles. I will also discuss how the hardware characteristics of superconducting qubits map into this architecture, and review recent results that show gate errors can be reduced to below that needed for the error detection threshold." [mehr]

Quantum life

"Recent experimental investigations of excitonic transport in photosynthesis indicate that quantum coherence can play an important role in enhancing energy transport in photosynthetic complexes.This talk presents a general theory of optimizing energy transport in photosynthesis and in artificial systems.Optimal energy transport takes place at the point where the timescales for dynamic and static disorder converge, a phenomenon called the quantum Goldilocks effect." [mehr]
"Recently, atom-like impurities in diamond (colour centres) have emerged as an exceptional system for quantum physics in solid state. In this talk I will discuss recent developments transforming quantum control tools into quantum technologies based on single colour centres. Specially, realization of quantum optical interface between spins and photons and scalable quantum registers in diamond will be presented. New applications of diamond qubits involving nanoscale magnetic resonance and force measurements will be shown. I will discuss single spin NMR paving the way to ultrasensitive MRI and structure determination of single biomolecules. The detection of proteins using nanodiamond sensors will be presented. I will also highlight future directions of research including combination of quantum error correction and sensing protocols and quantum enabled sensing and imaging in living cells." [mehr]

Uniform Bose gases

"For almost two decades harmonically-trapped ultracold atomic gases have been used with great success to study fundamental many-body physics in a flexible experimental setting. Recently, we achieved the first atomic Bose-Einstein condensate in an essentially uniform potential of an optical-box trap [1]. This opens unprecedented possibilities for closer connections with other many-body systems and the textbook models that rely on the translational symmetry of the system. I will present our first experiments on this new system, including the first observation of the quantum Joule-Thomson effect [2], which was theoretically predicted more than 70 years ago.[1] A. L. Gaunt et al., Phys. Rev. Lett. 110, 200406 (2013)[2] T. F. Schmidutz et al., Phys. Rev. Lett. 112, 040403 (2014)" [mehr]
"The comparison between experimental values of transition frequencies in atomic hydrogen, the most simple atomic system, and the corresponding theoretical predictions provides stringent tests of bound state QED calculations. For more than a decade, this comparison has been limited by insufficient knowledge about the size of the proton, strictly speaking its r.m.s. charge radius. In 2010, a value for the proton size has been extracted from laser spectroscopy of muonic hydrogen which is ten times more accurate than any previous determination. However, this value deviates from the value found by precision spectroscopy of regular hydrogen by four combined standard deviations. An even larger inconsistency of 7σ is obtained when including electron-proton scattering data. The muonic hydrogen value has been confirmed and improved in 2013 while the source of the discrepancy, referred to as the ‘proton size puzzle’, remains unclear.In this talk, we report on a new precision spectroscopy experiment, aiming to shed light on the regular hydrogen part of the puzzle: In contrast to previous high resolution experiments probing transition frequencies between the meta-stable 2S state and a higher lying nL state (n = 3, 4, 6, 8, 12, L = S, P, D), our measurement of the 2S – 4P transition frequency is the first experiment being performed on a cryogenic beam of hydrogen atoms in the 2S state. We will discuss how this helps to efficiently suppresses leading systematic effects of previous measurements and present preliminary results obtained so far." [mehr]
"Strongly correlated quantum many-body systems display many fascinating phenomena, but they are difficult to describe due to the huge dimension of the involved Hilbert spaces. For this reason, models that can be treated fully or partially by analytical tools are valuable guides for understanding the physics underlying the phenomena. A prominent example is the fractional quantum Hall effect (FQHE), for which much information has been obtained by use of trial wave functions. In the talk, I will present a method to construct a quite broad class of many-body models, for which both the state and Hamiltonian are known analytically. One family of states within this class constitutes FQHE-like lattice states. The FQHE was originally discovered in semiconductor devices, but in the last few years much effort has been put into investigating the possibilities for obtaining FQHE-like states in lattice systems. One motivation for this is the perspectives for simulating FQHE physics under highly controllable conditions, e.g. in ultracold atoms or molecules in optical lattices. The typical strategy for obtaining FQHE-like lattice states is to mimic the solid state setting, but the above mentioned family of models provides an alternative. It is also possible to construct critical models, which allows us to study phase transitions." [mehr]
"Non-alkali-metal atoms have recently proved to be fascinating systems to explore novel lands in ultracold quantum physics. Here, we present recent results with ultracold dipolar gases of erbium atoms. As a consequence of the strong dipole-dipole interaction and of the large anisotropy in the dispersion potential, Er shows a spectacularly high number of Fano-Feshbach resonances both in the fermionic and bosonic isotopes. The complex Er scattering behavior escapes to traditional scattering models and requires novel approaches based on statistical analysis. Following the powerful toolset provided by Random-Matrix theory, we elucidate the chaotic nature of the scattering. Finally, we report on the first degenerate Fermi gas of Er, which is realized by direct cooling of identical fermions based on dipole-dipole interaction." [mehr]

Entangled ions in an optical cavity

"Optical cavities provide a coherent interface between light and matter that can be used to link remote quantum systems. With such an interface, quantum information can be mapped from a single atom onto a photon for long-distance transport, and an atom can be entangled with a cavity photon as a resource for teleportation. However, in a future quantum network, it would be advantageous for each cavity to contain multiple atoms. These atoms could be used for local quantum information processing, error correction between network nodes, and improved quantum memories, among other tasks.I will describe the coupling of two calcium ions to the mode of a high-finesse optical cavity. When both ions are coupled with near-maximum strength to the cavity, we entangle the ions with one another, heralded by the measurement of two orthogonally polarized photons. Applications of entangled ions in a cavity will be discussed, in the context of both quantum information tasks and the investigation of open quantum systems. In particular, I will present recent measurements of enhanced quantum state transfer from a superradiant two-ion state." [mehr]
"On a fundamental level, chemical reactions and condensed-matter transformations are defined by the motion of atoms and electrons from initial to final conformations, typically along a complex reaction path involving ultrasmall and ultrafast dimensions. Here we report on our progress towards a full visualization of structural dynamics in space and time. After laser excitation, ultrashort electron pulses at 30-100 keV are diffracted with time delays and provide a pump-probe sequence of structural snapshots with atomic resolution. We solve the most essential problem for time resolution, Coulomb repulsion, by using single-electron pulses in combination with a microwave compressor. The so achieved 12-fs electron pulses (rms) are among the shortest worldwide and now provide access to the fastest phonons or molecular modes with atomic resolution. In order to further advance towards the regime of purely electronic motion, we apply the microwave compressor’s time-dependent fields for reshaping the single-electron phase space from the temporal into the energetic domain. The achievable pulse durations are shorter than optical light cycles, promising direct diffraction access to electronic motion with a resolution of picometers and attoseconds. We report our first proof-of-principle results and reflect on what discoveries we may expect to see." [mehr]
"All-optical switching is a technique in which a gate light pulse changes the transmission of a target light pulse without the detour via electronic signal processing. We take this to the quantum regime, where the incoming gate light pulse contains only one photon on average. The gate pulse is stored as a Rydberg excitation in an ultracold atomic gas using electromagnetically induced transparency. Rydberg blockade suppresses the transmission of the subsequent target pulse. Finally, the stored gate photon can be retrieved. A retrieved photon heralds successful storage. The corresponding postselected subensemble shows an extinction of 0.05. Recent improvements of our experiment made it possible to observe a gain of 20. The single-photon switch offers many interesting perspectives ranging from quantum communication to quantum information processing." [mehr]
"This talk discusses the ideas and goals of the Energiewende, which aims at successively decarbonizing all of the german energy supply systems, but suffers from patchwork, wild exaggerations, cost explosions, and true pitfalls due to the construction of the European Climate Program.After a general overview we have a closer look at the electrical power generation and distribution, which is strongly affected by the Energiewende. We evaluate the consequences of the intermittent power production by wind turbines and photovoltaic panels, the dynamics of the present conventional power plants and the need and potential of present or future storage systems. The role of hydrogen and synthetic fuels as a form of chemical energy storage is discussed." [mehr]
How did the field of quantum information begin? To my mind, it was when John Wheeler formed his little group of students and postdocs at the University of Texas in the early 1980s. David Deutsch, Benjamin Schumacher, William Wootters, and Wojciech Zurek were all there. Even Richard Feynman visited once. It was because Wheeler had a single-minded purpose. To every student who walked into his office---even the first year undergraduate---Wheeler would implore: “Give an information theoretic derivation of quantum theory!” He saw that as the only way to get a real understanding of “the quantum” (as he called it). In this talk, I will outline how Wheeler’s old hope is still giving technical fruit in the context of Quantum Bayesianism (or QBism). Particularly, that context points naturally to a study of a mysterious structure in Hilbert space called the Symmetric Information Complete (SIC) quantum measurement. When these structures exist (and it seems they do for all finite dimensions, though no one has yet proven it!) they give a very clean way of writing the Born rule in purely probabilistic terms. This gives the hope that all the mathematical structure of quantum theory might be derivable from one very basic physical scenario. It’s not the double-slit experiment that Feynman argued for in his Feynman Lectures, but one might still appeal to his foresight and hope, “In reality, [this new scenario] contains the only mystery [of quantum mechanics].” [mehr]
Gauge fields are ubiquitous in Physics. For example, in the context of high energy physics, they are the fundamental carrier of forces; while in condensed matter systems the associated physical fields (electrical and magnetic) are essential in creating and understanding many-body phenomena. These fields can depend on internal — spin — degrees of freedom, and in material systems these spin-dependent gauge fields are often manifest as spin-orbit coupling (SOC, but more correctly spin-crystal momentum coupling).Here I present our experimental work synthesizing SOC for ultracold neutral atoms. I will first show how we use the light-matter interaction to engineer gauge terms in the atomic Hamiltonian, and then how to make these depend on spin. Using such techniques, we created SOC in a pseudo-spin 1/2 Bose gas and observed a previously unexpected quantum phase transition. I will conclude by showing the observed phase diagram of a spin-1 spin-orbit coupled Bose gas: a context without analog in traditional condensed matter systems. [mehr]
Real-time control of electrons in the microcosm calls for electromagnetic forces confinable and tunable over sub-femtosecond time intervals. I will discuss how recent progress in lightwave technologies has enabled key steps towards this essential milestone in science and technology. With novel types of light synthesizers which can manipulate ultrawideband coherent radiation sources, spanning the visible and flanking spectral ranges, it is now possible to sculpt and trace the waveform of light with subcyclic precision opening up the route to attosecond photonics. We will focus on first representative applications that highlight the emerging capabilities. [mehr]
"Microscopic Fabry-Perot cavities built from laser-machined optical fibers offer small mode volumes and large quality factors combined with full tunability and direct access to the cavity field.In my talk I will present experiments where we harness these properties for enhanced light - matter interaction with solid-state based quantum- and nanosystems. Fiber cavities promise a route for efficient and narrow-band single-photon sources by means of Purcell enhancement of fluorescence emission. We couple colour centers in diamond nanocrystals such as the NV center to a cavity and study the scaling laws of the cavity enhancement for a large range of parameters. I will discuss our current efforts to achieve broadband enhancement with ultra-small mode volume cavities and to generate indistinguishable single photons under ambient conditions. In the context of microscopy, multiple interaction of probe light with a sample placed inside a microcavity promises an increase in sensitivity on the order of the cavity Finesse, which can reach values >10^5 for fiber cavities. We demonstrate a scheme for scanning cavity microscopy, which provides spatially and spectrally resolved maps of various optical properties of a sample with superior sensitivity. The method should enable studies of individual non-flourescent macromolecules and weakly absorbing nanoparticles." [mehr]
"Photonic systems are naturally an excellent avenue to study fundamental concepts of waves' interactions, and many times lead to new discoveries. I will discuss Anderson localization of light, its exact opposite: hyper-transport (faster than ballistic) transport driven by fluctuating spatial disorder, and finally the recent breakthrough on photonic topological insulators. The emphasis will be on fundamental concepts, that are universal to all waves systems." [mehr]
"Non-classical states of light enable new modes of new modes of communications, sensing and computation. A key objective of current research is the construction of a scalable photonic quantum network that will facilitate the preparation of distributed quantum correlations among light beams, and enable new quantum-enhanced applications. Such a network can be constructed by means of pure-state quantum light sources, linear optical operations, measurement by photodetectors, and storage in a photonic quantum memory. I will discuss recent progress in developing a scalable network using such components, and describe some recent applications in quantum simulation, communication and metrology." [mehr]
"We have studied short pulse laser ionization (< 7 fs, 750 nm) and excitation with polarization-gated laser pulses. The laser pulse used is composed of a circular section at the beginning and the end of the pulse and an experimentally-defined linearly polarized central part. Due to quantum mechanics selection rules (Dm ±1), multiphoton excitation of Rydberg states with high angular momentum are only possible with linearly polarized light. We show that polarization gating allows us to study excitation and ionization with quasi sub-cycle laser pulses. The method allows us to determine the shortest temporal window needed for the excitation processes. We have used polarization gated pulses to measure non-sequential ionization as a function of the gate duration." [mehr]
"Nanomechanical resonators are freely suspended, vibrating bridges with nanoscale diameters. These nanostructures are receiving an increasing amount of attention, both in fundamental experiments addressing the foundations of quantum mechanics and in sensing applications, and show great promise as linking elements in future hybrid nanosystems. A realization of this potential is however based on the development of not only nanomechanical systems of high mechanical quality factor but also suitable control techniques. Here I will review recent progress towards these goals, focussing on dielectrically controlled pre-stressed silicon nitride string resonators. In particular I will address the dynamics of two strongly coupled nanomechanical modes which can be described as a classical two-level system, adopting the well-known Bloch sphere picture. Analogous to the coherent control of two-level systems in atoms, spin ensembles or quantum bits, electromagnetic pulse techniques are employed to demonstrate full Bloch sphere control via Rabi, Ramsey and Hahn echo experiments. Our experiments not only enable deep insights into the limiting mechanisms for decoherence in nanomechanics, but also open a pathway towards single phonon control after a series of ground-breaking experiments on ground state cooling and non-classical signatures of nanomechanical resonators in recent years." [mehr]
"We demonstrate a robust photon detector which does not rely on photon absorption. Instead, impinging light is reflected off an optical resonator containing a single atom in a superposition of two states. Upon reflection of a single photon, the phase of the superposition state is flipped, which unambiguously allows us to nondestructively detect the photon. The presented single-photon nonlinearity paves the way towards photonic quantum gates and the preparation of novel quantum states of light." [mehr]
"Rydberg atoms provide a way to achieve controlled long-range interactions in many-body systems. In our setup we implemented an optical detection technique for Rydberg atoms with sub-micron resolution, which allows for the measurement spatial correlations in strongly interacting collective states of Rydberg atoms. We prepare a two-dimensional system of ground state atoms in an optical lattice and laser couple them to a Rydberg state. The Rydberg atoms interact via the van der Waals force, which extends over approximately half the system size, thereby leading to strong correlations. Guided by numerical optimization we found laser sweeps that created self-organized many-body states with spatially ordered Rydberg excitations. The initial ground state atom configuration is crucial for the success of the sweeps. We developed a preparation technique based on local addressing in an optical lattice that allows for the preparation of sub-shot-noise initial atom numbers. The developed techniques might allow for the deterministic preparation of ordered fock states of Rydberg atoms and the investigation of their coherence properties." [mehr]
"Photonic lattices are created by the inference of light in a complex way, and therefore represent an enabling technology for diverse applications as trapping atoms or optically tweezing nanoparticles, patterning in holographic lithography, and creating artificial matter as photonic crystals. In my presentation, I will show that by tailoring complex light landscapes as e.g. nondiffracting, self-similar or vortex-bearing light fields, or by randomizing these light fields, the next generation of artificial functional materials can be created as well as novel light routing and localization schemes can take place in these optically-created structures. Moreover, these light fields open new horizons in optical micromanipulation of artificial and biophybrid nanorobots." [mehr]
"Charge relocations and atomic motions on ultrashort time scales play a key role for functional processes in condensed matter. X-ray diffraction methods with a femtosecond time resolution allow for spatially resolving transient structures and, in particular, spatial distributions of electrons, both being relevant for the structure-function relationships of crystalline materials. This talk provides an introduction into this exciting new field, combining experimental aspects with recent results on ultrafast electron and lattice motions in ionic crystals. Experiments with the photoexcited prototype material KDP (KH2PO4) reveal the interplay of lattice and charge motions which occur on distinctly different length scales. As a second example, the field-driven transfer of valence electrons between ions in a superposition of quantum states will be addressed for the materials LiBH4 and LiH. This fully reversible transfer mechanism makes a major contribution to the material’s optical polarizability." [mehr]
"Light consists of photons, mass-less particles that do not interact with one another. Recent technological developments however give rise to structures with strong interactions between light and matter in multiple nodes of a network. These devices may enable us to drive photons into novel strongly correlated quantum many-body regimes. Interestingly, these may by studied in non-equilibrium scenarios where inevitable photon losses are constantly compensated by input drives. They thus give rise to an intriguing class of quantum many-body systems where instead of ground or thermal states one is interested in the still largely unexplored stationary states of their driven and dissipative dynamics.In this talk, I will present some of our recent approaches to this physics which consider networks of superconducting circuit cavities and discuss aspects of the phase diagrams for their stationary states." [mehr]
"Ultracold atoms trapped in disordered and quasi-disordered optical potentials are a remarkable tool for the investigation of fundamental mechanisms of conduction in disordered systems. Indeed, these atomic systems offer the possibility of accurately tuning the interactions between the particles, their mobility, the system dimensionality and the kind and amount of disorder. A review of experimental results will be presented, also including very recent experiments which have provided a clear scenario for the superfluid-insulator transition in interacting disordered bosons and the observation of a mobility edge in three-dimensional Anderson localization." [mehr]
"In this talk I will discuss two topics.First, I will describe an unexpected physical mechanism of 'lasing without inversion' during filamentation of femtosecond laser pulses in the air. Importantly, realization of this mechanism requires no special effort -- it happens almost without trying.Second, I will discuss the connection between hypothetical higher order Kerr effects and the emergence of the 'Kramers-Henneberger atom' and the 'bound states of a free electron' -- stable excited electronic states dressed by a strong laser field." [mehr]
"In this talk we will review the recent advances within density-functional and many-body based schemes to describe spectroscopic properties of complex systems with special emphasis to modelling time and spatially resolved electron spectroscopies (including transient pump-probe techniques). Pros and cons of present functionals will be highlighted and provide insight in how to overcome those limitations by merging concepts from many-body perturbation theory and time-dependent density functional theory. We will discuss some of the theoretical approaches developed in the group (and under development) for the characterisation of matter out of equilibrium, the control material processes at the electronic level and tailor material properties, and master energy and information on the nanoscale to propose new devices with capabilities. We will focus on examples linked to the efficient conversion of light into electricity or chemical fuels ("artificial photosynthesis") and the design on new nanostructured based optoelectronic devices based on inorganic nanotubes, among others. The goal of the group activities in the long-run is to provide a detailed, efficient, and at the same time accurate microscopic approach for the ab-initio description and control of the dynamics of decoherence and dissipation in quantum many-body systems. With the help of quantum optimal control (QOC) theory and the mastery over spectroscopy we could direct the movement of electrons, selectively trigger chemical reactions and processes, and create new materials." [mehr]
"Kilometer scale free-electron lasers will reach their full potential in providing molecular movies if all laser and rf-sources involved in the facility can be timed and synchronized to at least 10-fs precision with scalability to potentially 100 attoseconds in the future. A set of ultrafast optical techniques for long-term stable femtosecond synchronization of large-scale X-ray free-electron lasers will be presented and performance scaling towards sub-femtsecond precision will be demonstrated. Sub-cycle optical waveforms with spectra spanning multiple octaves are desired for efficient attosecond pulse generation and multi-wavelength spectroscopy. It turns out that some of the techniques invented for large scale timing distribution can be used to coherently stich few-cycle optical pulses together. Progress towards a multi-Joule optical waveform synthesizer covering 500 Nanometer – 2.5 micrometers will be presented and potential applications are discussed." [mehr]
"The pursuit of increasingly sensitive interferometric measurement of mechanical motion has played an important role in the history of quantum optics. In a continuous position measurement, one must ultimately confront the effect of quantum measurement backaction. The requirement to balance measurement imprecision with backaction forces results in a lower bound on sensitivity, the ‘standard quantum limit’. Decades ago many ideas for avoiding this 'limit' were studied in the context of the ultimate sensitivity of gravitational wave detection. However, it has proven difficult to realize interferometers actually limited by quantum backaction, which physically stems from the shot noise of radiation pressure. In recent years, there has been considerable progress in manipulating low-mass, high-frequency, and mechanically-isolated objects with radiation pressure. In our group we have developed a cryogenically-compatible Fabry-Perot cavity incorporating a millimeter-scale silicon-nitride membrane. In this talk, I present work in which we subject the membrane to a strong continuous position measurement and observe the shot noise of radiation pressure. Further, we demonstrate correlations between quantum fluctuations of the optical field and the mechanical motion and use these correlations to observe ponderomotive squeezing of light. Mechanical objects at quantum limits also hold promise for connecting disparate quantum resources, for example microwave and optical photons; I will describe initial work, in conjunction with Konrad Lehnert’s group at JILA, to combine our optomechanical device with an electromechanical interface. I will end with a brief update on our work to control motion at another scale, namely experiments with single neutral atoms in optical tweezers laser-cooled to their ground state." [mehr]
"Casimir forces are macroscopic manifestations of QED and can be designed by altering the shape and material of the interacting bodies. In addition to experiments on attractive and repulsive forces that emphasize this dependence, I will discuss a number of exotic yet –to-be-observed effects such as the vacuum torque, vacuum radiation from oscillating cavities and related phenomena. Casimir forces offer both limits and exciting opportunities for the operation of future Nano-ElectroMechanical-Systems (NEMS)." [mehr]
"A new class of plasmonic interfaces is presented which greatly expands the capability of plasmonics for science and technology. I will discuss: polarization controlled tunable directional coupling of surface plasmons (SP); holographic metasurfaces that generate broadband radially polarized beams, holographic vortex detectors and the generation for the first time of straight propagating diffraction less SP beams (cosine-Gauss beams and bottle beams). These findings have potential applications in quantum information processing, chip interconnects and nanoparticle trapping." [mehr]
"Acceleration of particles at high gradient is an intense research topic. Without new acceleration methods allowing for future accelerators to be of reasonable size and cost, accelerator-based high-energy physics may reach an end. Plasmas can sustain very large longitudinal electric fields that can travel at velocities close to the speed of light. Large energy gains where demonstrated for electrons in plasma-based accelerators driven by intense laser pulses or short electron bunches. Research on the beam-driven, plasma wakefield accelerator (PWFA) scheme is experiencing an increasing interest. This is motivated by the 42GeV energy gain in 85 cm of plasma (50GeV/m accelerating gradient) demonstrated at SLAC [Blumenfeld, Nature 445, 741 (2007)]. Current PWFA experiments focus on two aspects: first, on the production of high quality accelerated bunches (narrow energy spread, low emittance, etc.) for example at SLAC FACET; second, on a new scheme based on the transverse self-modulation of long particle bunches in dense plasmas to resonantly drive wakefields [Kumar, Phys. Rev. Lett. 104, 255003 (2010)]. After briefly introducing the PWFA and the recent results I will focus on the second aspect and begin by introducing the physics of the self-modulation instability (SMI). I will discuss initial experiments at the Brookhaven National Laboratory Accelerator Test Facility that have shown that long electron bunches do indeed drive multiple period wakefields. They also suggest that the seeding of the self-modulation instability is possible. After presenting these results, I will describe experiments that we are planning at SLAC-FACET to study the physics of the SMI of electron and positron bunches. This experimental program is known as E209. Then I will describe the AWAKE project that was recently approved at CERN. AWAKE will use the long SPS, 400GeV bunch with 3x10^11 protons and a 10m-long plasma to address the issues related to driving GeV/m accelerating gradients over large distances to accelerate electrons to high energies in a single plasma section. This experiment will operate at lower gradient than other plasma-based accelerators, but aims at avoiding the staged-acceleration necessary when using drivers (laser pulse or particle bunch) carrying small amounts of energy. The SPS bunch carries ~20kJ, while LHC bunches carry more than 100kJ, more than necessary to produce an ILC-like electron bunch (2x10^10 e -500GeV or ~1.6kJ)! Operating at lower plasma density and therefore with a larger accelerating structure also eases the injection process and the beams generation and alignment tolerances. The purpose of the presentation is to give an overview of the experimental programs we are developing while explaining the basic concepts." [mehr]
"New degrees of freedom in optical design can be attained by introducing in the optical path phase discontinuities in addition to the usual propagation phase. This enables wavefront engineering with unprecedented flexibility, including a generalization of the classical laws of reflection and refraction and a wide variety of new planar optical components. These include aberration-free flat lenses and axicons, background free broadband wave platesand flat phase plates that create optical vortices." [mehr]
"A revision of our system of units, the SI, is currently discussed and may be implemented as early as 2018. The new SI is a logical extension of an argument made in 1983 when the meter was redefined to be based on the exact value of the speed of light. In the new SI all units will be derived from seven fundamental reference constants, thus replacing the seven base units of the current system.For example, the unit of mass, the kilogram, is currently defined by an artifact called the International Prototype of the Kilogram (IPK). In the future we will be able to realize the unit of mass, not just at the kilogram level, from a fixed value of the Planck constant, which has units of kg m^2/s.One condition for redefinition is agreement between different measurements of the Planck constant. Currently two measurement strategies lead to values with relative uncertainties less than 100 parts per billion (ppb): (1) Avogadro’s number can be determined by estimating the number of atoms in a well characterized crystal. From Avogadro’s number h can be calculated using the Rydberg constant, which is known with much smaller uncertainty (2) A watt balance can be used to measure mechanical power in units of electrical power. Electrical power can be measured as the product of the Planck constant and two frequencies by utilizing the Josephson effect and the Quantum Hall effect.NIST has carried out measurements of h with watt balances for over 20 years. In the past 18 months a new team has performed a largely independent determination of h. I will describe this measurement and measurements from other laboratories." [mehr]
"Cold molecules are useful for doing science that ranges from fundamental particle physics to commercially important applications. I will discuss two experiments, the search for the electric dipole moment of the electron and determination of molecular identity within a mixture.We have developed methods for trace detection of molecules in mixtures, in both the optical and microwave regime. The cooling of the molecules leads to dramatic increase in the inverse of the internal molecular ro-vibrational partition function.In addition to species identification, we have also devised a method to measure the absolute chirality of the molecular species, and enantiomeric excess. We have recently demonstrated true sum-frequency generation, a type of three-wave mixing, on a chiral sample in the microwave regime. We use two orthogonally polarized resonant applied electric fields to induce a third mutually orthogonal field at their sum frequency. The phase of this induced field changes sign with enantiomer, and its amplitude provides a sensitive, quantitative measure of enantiomeric excess. The narrow rotational resonances used make this measure of enantiomeric excess fundamentally mixture compatible.In separate work, we have devised a new kind of high flux molecular beam and used it with ThO to perform a sensitive search for the electron EDM. Measurement of a non-zero electric dipole moment (EDM) of the electron within a few orders of magnitude of the current best limit[1] of |de|<1.05*10-27 e*cm would be an indication of CP violation beyond the Standard Model.The ACME Collaboration is searching for an electron EDM by performing a precision measurement of electron spin precession signals from the metastable H state of thorium monoxide (ThO). I will provide a brief update on the current status of the experiment. Based on a data set acquired from 50 hours of running time over a period of two days, we have achieved a one-sigma statistical uncertainty of 6*10-29 e*cm/√T, where T is the running time in days." [1] JJ Hudson et al., "Improved measurement of the shape of the electron." Nature 473, 493 (2011) [mehr]
"Pitch is a complex hearing phenomenon that results from elicited and self-generated cochlear vibrations. Read-off vibrational information is relayed up the auditory pathway, where it is then condensed into pitch sensation. How this can adequately be described in terms of physics has largely remained an open question. We have developed a peripheral hearing system (in hardware and software) that reproduces with great accuracy all salient pitch features known from biophysical and psychoacoustic experiments. At the level of the auditory nerve, the system exploits stochastic resonance to achieve this performance, which may explain the large amount of noise observed in the working auditory nerve. The work is a rare example of how starting from a general principle of physics, biological processes can be understood, and, moreover, lean and efficient sensory designs can be achieved by navigating close to the biophysical example. This in contrast to often-taken reverse engineering approaches that focus on modeling the resulting signal rather than asking on what physical grounds the resulting signal dwells." [mehr]
"Resonant optical excitation of semiconductors creates an interband polarization that can decay via re-radiation or interaction-induced conversion into quasi-particle excitations such as electron-hole plasma and/or excitons. With the help of time-delayed pulses with central frequencies in the terahertz (THz) range, one can induce transitions between the eigenstates of the temporally developing many-body system. Besides the characterization of the momentary excitation state, this combined optical and THz time-domain scheme allows for deliberate quantum-state manipulation, excitation shelving into optically dark states, transient exciton ionization, as well as high-harmonic generation." [mehr]
After the full characterization of the tools for attosecond spectroscopy by the attosecond streaking technique [1], first experiments have been carried out to measure sub-femtosecond behavior of matter. Recently, the dynamics of the photoionization process on solids has been studied [2,3]. Not only that attosecond metrology now enables clocking on surface dynamics, but also the individual behaviour of electrons of different type (core electrons vs. conduction band electrons) can be resolved. We measured different time delays in the emission of the aforemention two types of electrons in different solids. Recent experiments towards an absolute measurement of the travel time of electron inside solids and through layered systems are discussed.On the other hand, experiments with molecules in the gas phase and on surfaces are carried out. UV pump / XUV probe experiments to investigate ultrafast electron dynamics in these molecules are introduced. [1] R. Kienberger et al., Nature 427, 817 (2004)[2] A. Cavalieri et al., Nature 449, 1029 (2007)[3] S. Neppl et al., PRL 109 (8), 087401 (2012) [mehr]
"The regular pulse train of a mode-locked femtosecond laser can give rise to a comb spectrum of millions of laser modes with a spacing precisely equal to the pulse repetition frequency. Laser frequency combs were conceived a decade ago as tools for the precision spectroscopy of atomic hydrogen. They are now becoming enabling tools for an increasing number of applications, including molecular spectroscopy. 
Recent experiments of multi-heterodyne frequency comb Fourier transform spectroscopy (also called dual-comb spectroscopy) have demonstrated that the spectral lines of a laser frequency comb can be harnessed for new techniques of linear absorption spectroscopy. The first proof-of-principle experiments have demonstrated a very exciting potential of dual-comb spectroscopy without moving parts for ultra-rapid and ultra-sensitive recording of complex broad spectral bandwidth molecular spectra. Compared to conventional Michelson-based Fourier transform spectroscopy, recording times could be shortened from seconds to microseconds, with intriguing prospects for spectroscopy of short lived transient species. The resolution improves proportionally to the measurement time. Therefore longer recordings allow high resolution spectroscopy of molecules with extreme precision, since the absolute frequency of each comb line can be known with the accuracy of an atomic clock.
Moreover, since laser frequency combs involve intense ultrashort laser pulses, nonlinear interactions can be harnessed. Broad spectral bandwidth ultra-rapid nonlinear spectroscopy and imaging with two laser frequency combs is demonstrated with coherent Raman effects and two-photon excitation. Real-time multiplex accessing of hyperspectral images may dramatically expand the range of applications of nonlinear microscopy." [mehr]
"Applications of actuators have increased in various fields. In industry, precise and high speed positioning is one of the most important technologies. Especially in the production of semiconductors and flat panel displays, dust-free transporting and precise positioning systems for wafers and thin glass plates are needed to avoid generation of dusts. In peripheral machines for computers like disc memories, small and thin linear actuators are necessary to satisfy the demand of reduction of thickness and weight of the products.Conventional motors driven by the electromagnetic force will play the most important roles. However, in some cases these conventional actuators seem to be difficult to satisfy the new and advanced demands in the near future. Therefore, seeking for new actuators has been activated.Our laboratory in the University of Tokyo has been enrolled to develop new actuators of various kinds in order to cope with severe demands of coming production systems and future automated machines. In our laboratory, a number of unique actuators and drive technologies were invented and realized. Among them, first, the following two actuators using piezoelectric materials, impact drive mechanism and surface acoustic wave motor, are introduced with applications. Impact drive method can move an object with a step of several nm to micrometers for a long distance by using rapid deformation of a piezoelectric element. The surface acoustic wave motor is a very thin ultrasonic motor with promising properties like large thrust, high velocity, and quick response. Then, as applications of electrostatic force, powerful electrostatic motor and new technologies of electrostatic transportation of particles, powder and droplets, sheets and films, and thin plates, are presented respectively with their principles and devices. And combining the technologies of electrostatic suspension without mechanical contact and electrostatic drives, super clean transportation devices for 300 mm and 400 mm silicon wafers and thin plates of glass for flat displays are introduced." [mehr]
"Precisely controlling the dynamics of real-world open quantum systems is a central challenge across quantum science and technology, with implications ranging from quantum to condensed-matter physics and fault-tolerant quantum information processing. While overcoming the effect of uncontrolled decoherence and dissipation mechanisms is essential to meet this challenge, engineering the coupling to a dissipative environment can likewise be instrumental to a number of quantum control applications, notably open-system quantum simulators. In this talk, I will describe recent advances in pursuing these two complementary approaches. In particular, I will focus on two representative problems: using dynamical decoupling methods for non-Markovian error suppression to achieve high-fidelity quantum memory for long times, while minimizing access latency and sequencing complexity; and designing Markovian dissipative dynamics to drive a many-qubit system to an entangled steady-state of interest, while respecting physical locality constraints." [mehr]
"Chiral topological states are exotic quantum phases of matter in two dimensions with broken time-reversal symmetry (e.g. fractional quantum Hall states). These states support topological ground state degeneracy, stable gapless edge excitations, and quasiparticles carrying fractional charges and fractional statistics. In this talk, I will discuss the bulk-edge correspondence as a powerful tool for modeling and characterizing chiral topological phases in 2D lattices. In the first part, I will describe how chiral topological wave functions and their parent Hamiltonians can be constructed by using the chiral correlators of the edge conformal field theory. In the second part, I will introduce a new quantity named as momentum polarization, which allows extracting topological spin and chiral central charge from the ground-state wave functions and provides an efficient approach to identify 2D chiral topological states from finite-size numerics." [mehr]
"Ultracold-atom experiments are suitable to study out-of-equilibrium dynamics of quantum many-body systems. Here I will present the quantum dynamics of deterministically and locally created mobile spin impurities in the one-dimensional bosonic atoms in optical lattices. First, we investigate the dynamics of a single-spin impurity. In the Mott-insulating regime, the coherent propagation of a magnetic excitation, or a magnon, in the Heisenberg model can be observed. Extending the study to the superfluid regime of the bath, we quantitatively determine how the bath affects the motion of the impurity, showing evidence of polaronic behavior. Second, we observe bound states of two magnons in a Heisenberg chain by tracking their dynamics. Such bound states were pointed out theoretically by H. Bethe in 1931, and our novel microscopic study of quantum magnets can directly confirm their existence." [mehr]
"Direct frequency comb spectroscopy (DFCS) is a powerful application of frequency combs that is increasing in importance rapidly. In my talk I will discuss two new methods related to DFCS that we developed in our pursuit of precision spectroscopy of the ground states of helium and the helium-ion. The first method is spatial coherent control with comb laser pulses, which enables complex pattern formation and background elimination with two-photon DFCS. Secondly, I will discuss Ramsey-comb spectroscopy, which combines high pulse energies at the mJ level with the accuracy and resolution of frequency combs. It is based on a new laser system that can selectively and phase coherently amplify two frequency comb pulses at widely different time delays. The high pulse energy provides straightforward access to multi-photon transitions and nonlinear wavelength conversion, while the original frequency comb laser accuracy and resolution is fully recovered from a series of Ramsey-like measurements. The special properties of this approach, such as a cancelation of optical light-shift effects, are demonstrated by improving the accuracy of several weak two-photon transitions in atomic rubidium and cesium up to thirty times." [mehr]

"Superfluid atom circuits".

"We have created a superfluid atom circuit using a toroidal Bose-Einstein Condensate. Just as a current in a superconducting circuit will flow forever, if a current is created in our superfluid circuit, the flow will not decay as long as the current is below a critical value. A repulsive optical barrier across one side of the torus creates the tunable weak link in the condensate circuit and can be used to control the current around the loop. By rotating the weak link at low rotation rates, we have observed phase slips between well-defined persistent current states. This behavior is analogous to that of a weak link in a superconducting loop. A feature of our system is the ability to dynamically vary the weak link, which in turn varies the critical current, a feature that is difficult to implement in superconducting circuits. For higher rotation rates, we observe a transition to a regime where vortices penetrate the bulk of the condensate. These results demonstrate an important step toward realizing an atomic SQUID analog." [mehr]
"I will describe three insights into the transition from quantum to classical. I will start with (i) a minimalist (decoherence-free) derivation of preferred states. Such pointer states define events (e.g., measurement outcomes) without appealing to Born's rule . Probabilities and; (ii) Born’s rule can be then derived from the symmetries of entangled quantum states. Derivation of Born’s rule will be the focus of my presentation. With probabilities at hand one can analyze information flows from the system to the environment in course of decoherence. They explain how (iii) robust “classical reality” arises from the quantum substrate by accounting for objective existence of pointer states of quantum systems through redundancy of their records in the environment. Taken together, and in the right order, these three advances elucidate quantum origins of the classical." *W. H. Zurek, Nature Physics 5, 181-188 (2009) [mehr]
"Historically, two paradigms competed to explain superconductivity (i) Bose Einstein Condensation (BEC) of weakly interacting Charge 2e pairs (Schafroth), and (ii) Pairing instability of the Fermi liquid (BCS). BCS theory was the unquestionable winner until the late 80's. BCS approximations however, have suffered major setbacks in the advent of high temperature, short coherence length superconductors, such as cuprates, pnictides, and granular superconducting films. A third paradigm has offered itself for understanding some properties of unconventional superconductors: Strongly Interacting Lattice Bosons (LB). LB behave less like in BEC's or or BCS theory, but (strangely) more like localized quantum spins. Their static correlations are very well understood by theories of quantum antiferromagnets. Their dynamics have only recently been explored. Near commensurate fillings they exhibit the condensed matter version of the Higgs mode. Conductivity of Lattice Bosons exhibit strange metallic properties which may explain phenomenology of unconventional superconductors in their "normal" state. LB also exhibit interesting vortex dynamics and Hall conductivity sign reversals." [mehr]
"There has been remarkable progress on using the combination of short pulse, high spatial coherence and large flux from x-ray free electron lasers (FEL) for nonperiodic imaging and nanocrystallography. The possibility of atomic-scale imaging remains a primary motivation for the construction of FELSs. Their unprecedented properties also motivate the study the dynamics of atomic-scale fluctuations directly in the time-domain. However, an important open question is under what conditions the textbook picture of linear, x-ray–matter interactions holds. In this colloquium, I will describe evidence for coherent nonlinear interactions at LCLS and SACLA FELs as well as the first direct time-domain measurements of the dispersion relation for lattice vibrations in photo-excited materials." [mehr]
"Liberation of an electron is the first step of the recollision model describing high order harmonic generation and attosecond pulse generation. Orbital tomography and electron self-diffraction imaging furthermore intimately rely on a firm grasp of electron dynamics in the Coulomb field of their parent molecular ion. These strong field effects all rely on tunneling dynamics which we study with true mid-IR waveforms. I will show unexpected electron dynamics, and first 3D momentum measurements, when probed, without the ubiquitous ambiguities at the Ti:Sa range, in the non-perturbative tunneling regime. The availability of intense ultrashort pulses at 3100 nm permits exploitation of nonlinear pulse propagation in the anomalous dispersion regime leading to interesting X-wave dynamics, unprecedentedly large supercontinua and stable pulse self-compression in bulk media." [mehr]
"We will review successes and limitations of the variational method in quantum many-body physics; both the time-independent and the time dependent variational method will be illustrated. Special attention will be paid to the role of entanglement in strongly correlated systems and quantum field theory, to classes of wavefunctions that naturally encompass the required entanglement, and to Ansätze for describing elementary excitations and particles on top of the strongly correlated vacuum." [mehr]
"Achieving better control and ability to manipulate molecules by decelerating and cooling them is important for various fields of research, such as, many-body physics, quantum information science, cold chemistry, investigation of the fundamental properties of matter, etc. Towards this end, here we present the concept of and demonstrate the first experimental results from a novel and versatile decelerator for continuous beams of neutral polar molecules, which employs the centrifugal potential in a rotating frame. With this technique, deceleration of continuous supersonic beams from a cryogenic source is conceivable. This is expected to provide large samples of slow and internally cold molecules amenable to further cooling down to quantum degenerate regimes." [mehr]
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