How does an interacting many-body system tunnel through a potential barrier to open space?

The tunneling process in a many-body system is a phenomenon which lies at the very heart of quantum mechanics. It appears in nature in the form of alpha-decay, fusion and fission in nuclear physics, photoassociation and photodissociation in biology and chemistry. A detailed theoretical description of the decay process in these systems is a very cumbersome problem, either because of very complicated or even unknown interparticle interactions or due to a large number of constitutent particles. In this work, we theoretically study the phenomenon of quantum many-body tunneling in a more transparent and controllable physical system, in an ultracold atomic gas. We analyze a full, numerically exact many-body solution of the Schr\"odinger equation of a one-dimensional system with repulsive interactions tunneling to open space. We show how the emitted particles dissociate or fragment from the trapped and coherent source of bosons: the overall many-particle decay process is a quantum interference of single-particle tunneling processes emerging from sources with different particle numbers taking place simultaneously. The close relation to atom lasers and ionization processes allows us to unveil the great relevance of many-body correlations between the emitted and trapped fractions of the wavefunction in the respective processes.Comment: 18 pages, 4 figures (7 pages, 2 figures supplementary information

From Principles to Disease:Functions and Deficiencies of the Synaptic Release Machinery

This thesis had two general aims: 1) understanding the role of tomosyns in synaptic transmission, and 2) furthering our knowledge on specific and general disease mechanisms of STXBP1-related disorders. Chapter 2 was dedicated to uncovering tomosyn’s mode of action. A new mouse model in which both tomosyn paralogues can be conditionally removed allowed us to study the effect of complete knockout of tomosyns on synaptic transmission using a single-cell electrophysiology assay. This revealed strongly increased spontaneous as well as evoked synaptic vesicle fusion, and application of hypertonic sucrose further demonstrated that tomosyns reduce vesicular release probability by adding to the energy barrier for fusion. Tomosyn knockout could be rescued by full-length tomosyn but not by truncation mutants as well as a mutant in which the tomosyn SNARE domain was replaced by the VAMP2 SNARE domain. In addition, single molecule optical tweezer experiments showed that tomosyns interact with the template complex of Munc18-1, syntaxin-1 and VAMP2, blocking entry of SNAP25. These results together demonstrate that tomosyns do not simply replace VAMP2 and sequester the other SNARE proteins, but that they inhibit vesicle fusion by preventing the formation of the SNARE complex via the template complex. In chapter 3, we focused on the disease associated STXBP1 variant L446F. We engineered iPSCs derived from a healthy donor to introduce this mutation on both alleles, mimicking the situation in patients who are homozygous for this mutation. In contrast to wildtype controls, induced neurons harboring the mutation showed reduced depression upon multiple stimuli in electrophysiological experiments. The mutation also partially prevented binding of an antibody, as shown by immunocytochemistry and Western blot analysis. Together these results confirmed a gain-of-function of this variant on MUNC18-1 function in synaptic transmission, and indicate that protein-protein interactions may underlie this effect. In chapter 4, we compared neurons derived from multiple patients with STXBP1-related disorders to neurons derived from multiple healthy donors functionally using calcium imaging and electrophysiology, and molecularly using proteomics and immunocytochemistry. All patient neurons had reduced MUNC18-1 expression levels compared to the controls and showed disturbed network but not single-cell activity. Proteomics revealed disturbed synaptic and RNA-processing proteomes. Two clusters of patients were discernible, but clustering occurred independent of mutation type. Together, these results demonstrate unique and common disease mechanisms between patients. Finally, in chapter 5 we introduced STXBP1 haploinsufficiency in neurons from multiple healthy donors and repaired a mutation in one patient line. We found that network activity patterns were affected by STXBP1 haploinsufficiency but to different extents between different donor cell lines. Moreover, we showed that the phenotypes change over time, also to different extents between different donor cell lines. Phenotype severity correlated with the reduction of MUNC18-1 expression levels, and baseline expression levels differed between cell lines. These results reveal cell line-specific characteristics of STXBP1 haploinsufficiency which may contribute to understanding the symptomatic heterogeneity of patients

Resolving photon number states in a superconducting circuit

Electromagnetic signals are always composed of photons, though in the circuit domain those signals are carried as voltages and currents on wires, and the discreteness of the photon's energy is usually not evident. However, by coupling a superconducting qubit to signals on a microwave transmission line, it is possible to construct an integrated circuit where the presence or absence of even a single photon can have a dramatic effect. This system is called circuit quantum electrodynamics (QED) because it is the circuit equivalent of the atom-photon interaction in cavity QED. Previously, circuit QED devices were shown to reach the resonant strong coupling regime, where a single qubit can absorb and re-emit a single photon many times. Here, we report a circuit QED experiment which achieves the strong dispersive limit, a new regime of cavity QED in which a single photon has a large effect on the qubit or atom without ever being absorbed. The hallmark of this strong dispersive regime is that the qubit transition can be resolved into a separate spectral line for each photon number state of the microwave field. The strength of each line is a measure of the probability to find the corresponding photon number in the cavity. This effect has been used to distinguish between coherent and thermal fields and could be used to create a photon statistics analyzer. Since no photons are absorbed by this process, one should be able to generate non-classical states of light by measurement and perform qubit-photon conditional logic, the basis of a logic bus for a quantum computer.Comment: 6 pages, 4 figures, hi-res version at http://www.eng.yale.edu/rslab/papers/numbersplitting_hires.pd

The Hong-Ou-Mandel effect with atoms

Controlling light at the level of individual photons has led to advances in fields ranging from quantum information and precision sensing to fundamental tests of quantum mechanics. A central development that followed the advent of single photon sources was the observation of the Hong-Ou- Mandel (HOM) effect, a novel two-photon path interference phenomenon experienced by indistinguishable photons. The effect is now a central technique in the field of quantum optics, harnessed for a variety of applications such as diagnosing single photon sources and creating probabilistic entanglement in linear quantum computing. Recently, several distinct experiments using atomic sources have realized the requisite control to observe and exploit Hong-Ou-Mandel interference of atoms. This article provides a summary of this phenomenon and discusses some of its implications for atomic systems. Transitioning from the domain of photons to atoms opens new perspectives on fundamental concepts, such as the classification of entanglement of identical particles. It aids in the design of novel probes of quantities such as entanglement entropy by combining well established tools of AMO physics - unity single-atom detection, tunable interactions, and scalability - with the Hong-Ou-Mandel interference. Furthermore, it is now possible for established protocols in the photon community, such as measurement-induced entanglement, to be employed in atomic experiments that possess deterministic single-particle production and detection. Hence, the realization of the HOM effect with atoms represents a productive union of central ideas in quantum control of atoms and photons.Comment: 19 pages, 7 figure

An extremely top-heavy initial mass function in the galactic center stellar disks

Composite armors, having two or more different materials, contain a ceramic layer in the front face and a metallic or polymer matrix composite as support on the back side backing. The function of the ceramic layer is to erode and break up the projectile and to increase the contact surface of the metallic plate by forming a hard cone. The role of the metallic backing layer is to absorb the kinetic energy of the projectile and support the fragmented ceramic. The most impportant advantage of these materials over monolithic metallic armors is to reduce the thickness by using the ceramic layer in front of the metallic layer. This provides reducing the weight of armor. In this study, experiments have been conducted to describe ballistic performance of polymer matrix composites having different geometrical shapes. To do these experiments, aramid and polyethilen composite specimens were first fabricated as laminates in different geometrical shapes. Then, these composite plates at charpy harms were investigeted in varios speed bullet to cover the impact damageKompozit zırhlar iki veya daha fazla farklı malzemeden oluşan, yüzeyde seramik katman ile arkada metal veya polimer matrisli kompozit destek içeren malzemelerdir. Seramik katmanın işlevi mermiyi aşındırma ve parçalamanın yanısıra sert koni oluşturarak metal katmanın temas yüzeyini artırmaktır. Metal destek katmanının görevi ise merminin kinetik enerjisini emmek ve darbe sonrası oluşacak seramik parçaları tutmaktır. Bu malzemelerin, tamamen metalik olan zırhlara göre en önemli avantajı, metalik katmandan önce seramik katmanın kullanılması yoluyla zırh kalınlığının, dolayısı ile zırhın ağırlığının azalmasını sağlamaktadır. Bu çalışmada değişik geometriye sahip, polimer matrisli kompozitlerin, balistik performansını ölçmek için deneyler yapılmıştır. Bunun için önce Aramid ve polietilen numuneler düz, iki değişik çapta silindirik ve küre plakalar halinde üretilmiştir. Bu kompozit plakalara atış poligonunda atışlar yapılmış ve oluşan darbe hasarları incelenmiştir

motilitAI: a machine learning framework for automatic prediction of human sperm motility

In this article, human semen samples from the Visem dataset are automatically assessed with machine learning methods for their quality with respect to sperm motility. Several regression models are trained to automatically predict the percentage (0–100) of progressive, non-progressive, and immotile spermatozoa. The videos are adopted for unsupervised tracking and two different feature extraction methods—in particular custom movement statistics and displacement features. We train multiple neural networks and support vector regression models on the extracted features. Best results are achieved using a linear Support Vector Regressor with an aggregated and quantized representation of individual displacement features of each sperm cell. Compared to the best submission of the Medico Multimedia for Medicine challenge, which used the same dataset and splits, the mean absolute error (MAE) could be reduced from 8.83 to 7.31. We provide the source code for our experiments on GitHub (Code available at: https://github.com/EIHW/motilitAI)

Nichtlineares Verhalten von Spiralseilen unter Zug und Torsion

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Emotion and themes recognition in music with convolutional and recurrent attention-blocks

Emotion is an essential aspect of music, and its recognition is a prevalent research topic in the field of computer audition. Machine learning-based Music Emotion Recognition ( MER) systems could boost the accessibility of music collections by providing standardised methodologies of music categorisation. In this paper, we introduce our (team name: AugsBurger) machine learning architecture sequentially composed of a convolutional feature extractor with block attention modules and a recurrent stack with self-attention for automatic MER. We train 5 models and conduct various late fusion experiments. Utilising a Convolutional Recurrent Neural Network ( CRNN ) with convolutional block attention applied throughout a 18-layer ResNet and a single recurrent layer with a Gated Recurrent Unit cell, a ROC-AUC of 73.9 % can be achieved on the test partition of the MediaEval 2020 Emotion & Themes in Music task. Applying late fusion on the individual model predictions and another challenge submission, this result is further increased to 75.3 % ROC-AUC