ERC FUNDED PROJECTS

New insight into ever smaller microscopic units of matter as well as in ever faster evolving chemical, physical or atomic processes pushes the frontiers in many fields in science. Pump/probe experiments turned out to be the most direct approach to time-domain investigations of fast-evolving microscopic processes. Accessing atomic and molecular inner-shell processes directly in the time-domain requires a combination of short wavelengths in the few hundred eV range and sub-femtosecond pulse duration. The concept of light-field-controlled XUV photoemission employs an XUV pulse achieved by High-order Harmonic Generation (HHG) as a pump and the light pulse as a probe or vice versa. The basic prerequisite, namely the generation and measurement of isolated sub-femtosecond XUV pulses synchronized to a strong few-cycle light pulse with attosecond precision, opens up a route to time-resolved inner-shell atomic and molecular spectroscopy with present day sources. Studies of attosecond electronic motion (1 as = 10-18 s) in solids and on surfaces and interfaces have until now remained out of reach. The unprecedented time resolution of the aforementioned technique will enable for the first time monitoring of sub-fs dynamics of such systems in the time domain. These dynamics – of electronic excitation, relaxation, and wave packet motion – are of broad scientific interest and pertinent to the development of many modern technologies including semiconductor and molecular electronics, optoelectronics, information processing, photovoltaics, and optical nano-structuring. The purpose of this project is to investigate phenomena like the temporal evolution of direct photoemission, interference effects in resonant photoemission, fast adsorbate-substrate charge transfer, and electronic dynamics in supramolecular assemblies, in a series of experiments in order to overcome the temporal limits of measurements in solid state physics and to better understand processes in microcosm.

1 296 000 €

Start date: 2008-10-01, End date: 2013-09-30

Quantum information science and atom optics are among the most active fields in modern physics. In recent years, many theoretical efforts have been made to combine these two fields. Recent experimental progresses have shown the in-principle possibility to perform scalable quantum information processing (QIP) with linear optics and atomic ensembles. The main purpose of the present project is to use atomic qubits as quantum memory and exploit photonic qubits for information transfer and processing to achieve efficient linear optics QIP. On the one hand, utilizing the interaction between laser pulses and atomic ensembles we will experimentally investigate the potentials of atomic ensembles in the gas phase to build quantum repeaters for long-distance quantum communication, that is, to develop a new technological solution for quantum repeaters making use of the effective qubit-type entanglement of two cold atomic ensembles by a projective measurement of individual photons by spontaneous Raman processes. On this basis, we will further investigate the advantages of cold atoms in an optical trap to enhance the coherence time of atomic qubits beyond the threshold for scalable realization of quantum repeaters. Moreover, building on our long experience in research on multi-photon entanglement, we also plan to perform a number of significant experiments in the field of QIP with particular emphasis on fault-tolerant quantum computation, photon-loss-tolerant quantum computation and cluster-state based quantum simulation. Finally, by combining the techniques developed in the above quantum memory and multi-photon interference experiments, we will further experimentally investigate the possibility to achieve quantum teleportation between photonic and atomic qubits, quantum teleportation between remote atomic qubits and efficient entanglement generation via classical feed-forward. The techniques that will be developed in the present project will lay the basis for future large scale

1 435 000 €

Start date: 2008-07-01, End date: 2013-12-31

Epigenetic gene regulation is of central importance for development and disease. Despite dramatic progress in epigenetics during the past decade, DNA demethylation remains one of the last big frontiers and very little is known about it. DNA demethylation is a widespread phenomenon and occurs in plants as well as in animals, during development, in the adult, and during somatic cell reprogramming of pluripotency genes. The molecular identity of the DNA demethylase in animal cells remained unresolved and has hampered progress in the field for decades. In 2007 we published that Growth Arrest and DNA Damage 45 a (Gadd45a) is a key player in active DNA demethylation, which opened new avenues in the study of this elusive process. The goal of this project is to further analyze the mechanism of DNA demethylation as well as the role played by Gadd45 in development. Given the many unresolved questions in this burgeoning field, our work promises to be ground-breaking and therefore have a profound impact in unraveling one of the least understood processes of gene regulation. Specifically we will address the following points. I) The biological role of Gadd45 mediated DNA demethylation in mouse embryos and adults is unknown. We have obtained mouse mutants for Gadd45a,b, and g and we will analyze them for developmental defects and dissect the methylation regulation of relevant genes. II) The targeting mechanism by which Gadd45 is binding to and demethylating specific sites in the genome is a central unresolved issue. We have identified a candidate DNA binding protein interacting with Gadd45 and we will analyze its role in site specific targeting of DNA demethylation in vitro and in mouse. III) We found that Gadd45 is an RNA binding protein and we will therefore analyze how non-coding RNAs are involved in targeting and/or activating Gadd45 during DNA demethylation.

2 376 000 €

Start date: 2010-06-01, End date: 2015-05-31

Equal segregation of chromosomes during cell division is vital to all life. Using a unique combination of cell biological and biochemical techniques, I will show how an essential set of enzymes promotes error-free chromosome segregation. During each cell division, genetically identical daughter cells are generated by accurate partitioning of the duplicated chromosomes. This relies on proper spatio-temporal execution of various highly dynamic processes. The activity of a small group of enzymes is crucial for at least two of these processes: correct chromosome positioning on the cell's equator prior to cell division and the ability to prevent cell division until every chromosome is thus positioned. The molecular fundamentals of signalling to and from these enzymes will be uncovered by chemical genetics, quantitative (phospho)proteomics, rapid affinity purifications and live-cell deconvolution microscopy. The resulting insights will open research avenues that will ultimately contribute to comprehensive models of how biochemical networks manage to prevent chromosome mis-segregation.

1 572 000 €

Start date: 2009-11-01, End date: 2014-10-31

Wnt proteins dictate critical cell growth and lineage decisions during development and in adult tissue homeostasis. Inappropriate activation of Wnt signalling is a frequent cause of cancer. The earliest events that occur after Wnts bind their receptors at the cell surface, such as receptor endocytosis and recruitment of cytoplasmic effectors, are decisive for downstream gene activation but the underlying mechanisms by which these events process and tune the Wnt signal remain poorly understood. The key objective of this proposal is to resolve critical molecular events that drive initiation of the Wnt cascade by focusing on two central questions: How does protein trafficking control Wnt signalling initiation? What molecular mechanisms underlie Wnt-induced formation and activation of multiprotein complexes? I will take a unique approach combining advanced live cell imaging and high resolution immuno-electron microscopy with sophisticated peptide chemistry, gene silencing and biochemistry to dissect early Wnt signalling events at the level of isolated molecules, in cultured cells and in complex tissues of living animals. With the proposed interdisciplinary work I expect to uncover where key Wnt signalling steps occur, which proteins are involved, how they direct protein complex assembly, trafficking and turnover and how these events control transmission of the Wnt signal. Mechanistic insight in how Wnt signals are transmitted is vital to understand how pathway specificity and sensitivity is controlled. Basic insight in these processes will be of utmost importance for the design of strategies to interfere with Wnt signalling in cancer.

1 513 800 €

Start date: 2009-12-01, End date: 2014-11-30

In a recent series of experiments, it has been shown that polar molecules can be decelerated, bunched, cooled, and trapped using time-varying electric fields. These experiments demonstrate an unprecedented level of control over molecules, which enables a variety of applications of great scientific interest. Here, I propose to use these techniques to create a molecular fountain. In this fountain, the first of its kind, polar molecules are decelerated, cooled, and subsequently launched upwards some 10-50 cm before falling back under gravity, thereby passing a microwave cavity or laser beam twice – as they fly up and as they fall back down. The effective interrogation time in such a Ramsey type measurement scheme includes the entire flight time between the two traversals through the driving field, which can be up to a second. This long interrogation time will allow for extreme precision measurements on molecular structure to a level at which fundamental physics theories can be tested. I will use the inversion frequency in ammonia around 23 GHz as a test case. This transition is very well studied and was used in the first ‘atomic’ clock and the first demonstration of a MASER. The fountain should make it possible to measure the inversion frequency with a relative accuracy of 10^{-12}–10^{-14}; that is more than a thousand fold improvement as compared to the best previous measurement. Besides serving as a proof-of-principle, this measurement may be used as a test of the time-variation of fundamental constants – an issue that has profound implications on how we understand the universe. The inversion frequency in ammonia is determined by the tunneling rate of the protons through the barrier between the two equivalent configurations of the molecule, and is exponentially dependent on the proton mass. By monitoring the inversion frequency over a period of a few years, a possible variation of the proton-electron mass ratio can be constrained or measured.

1 100 000 €

Start date: 2008-08-01, End date: 2013-07-31

Hadrons, the building blocks of all matter in Nature, are not fundamental but composed of quarks and gluons. Up to now we do not know HOW NATURE MAKES HADRONS one of the most important questions of contemporary structure-of-matter physics. Major breakthroughs are to be expected with new experimental facilities such as FAIR. Most studies in hadron physics at HESR/FAIR will employ beams of unpolarized antiprotons, but the most spectacular opportunities will arise for polarized antiprotons the physics case is exceptional. The flag-ship experiment, Drell-Yan production in double polarized proton-antiproton scattering, gives direct access to transversity , the terra incognita of nucleon spin structure. The provision of such beams presents enormous scientific / technological challenges and has never been achieved with intensities sufficient for the crucial experiments. State-of-the-art techniques are capable of producing intensities less than ~10^5 s-1, which cannot be efficiently accumulated. It is the aim of this project to develop an efficient method for POLARIZING ANTIPROTON BEAMS by in-situ build-up in a storage ring. The only viable method to do this effectively is through "spin-filtering" by the repeated interaction of an antiproton beam with a polarized hydrogen gas target in a cooler storage ring. This technique works with protons, but it is not clear how the polarization build-up happens in detail. Spin-filtering needs to be optimized and, in particular, it must be extended to antiprotons. Within the framework of this project, the aim is to provide polarized antiproton beams in a storage ring with at least WITH 10 ORDERS OF MAGNITUDE higher intensity than previously possible. A very experienced team of scientists and engineers is needed, and this is available within my group. We will also strongly benefit from our collaboration partners. Thus, it is a "now or never" opportunity. If successful, a new era will open with fascinating experiments.

2 448 376 €

Start date: 2010-05-01, End date: 2016-04-30

Supersymmetry provides an invaluable tool for quantitatively exploring a large variety of non-perturbative phenomena arising in gauge theories and gravitation. This proposal intends to exploit this fact to make significant progress on three important topics in theoretical physics, namely, black holes, strongly-coupled gauge fields, and instantons and supersymmetry breaking. Besides supersymmetry, there is a variety of cross-links between these topics, as well as joint applications. The specific objectives of the proposal are as follows. The first objective concerns the determination of supersymmetric black hole entropy for finite electric and magnetic charges, improving our understanding of critical aspects of the field-theoretic description of the entropy, in direct confrontation with the results based on the counting of microscopic states. The second objective is a construction of the exact spectrum of quantum strings moving in an anti-de Sitter space-time, which, according to the gauge-string correspondence, yields the spectrum of a corresponding dual supersymmetric gauge theory. Deforming the anti-de Sitter space will then lead to stringy descriptions of non-perturbative phenomena in a generic gauge theory with a confining phase. The third objective pertains to instantons and their implications for phenomenologically viable string compactifications on spaces with generalized geometries, which include background electric and magnetic fields. An instanton calculus will be developed to improve the understanding of non-perturbative string theory and its implication for moduli stabilization and supersymmetry breaking.

1 910 093 €

Start date: 2010-09-01, End date: 2016-08-31