Using Recurrent Neural Networks to Optimize Dynamical Decoupling for Quantum Memory

We utilize machine learning models which are based on recurrent neural networks to optimize dynamical decoupling (DD) sequences. DD is a relatively simple technique for suppressing the errors in quantum memory for certain noise models. In numerical simulations, we show that with minimum use of prior knowledge and starting from random sequences, the models are able to improve over time and eventually output DD-sequences with performance better than that of the well known DD-families. Furthermore, our algorithm is easy to implement in experiments to find solutions tailored to the specific hardware, as it treats the figure of merit as a black box.Comment: 18 pages, comments are welcom

Neural-Network Quantum States, String-Bond States, and Chiral Topological States

Neural-Network Quantum States have been recently introduced as an Ansatz for describing the wave function of quantum many-body systems. We show that there are strong connections between Neural-Network Quantum States in the form of Restricted Boltzmann Machines and some classes of Tensor-Network states in arbitrary dimensions. In particular we demonstrate that short-range Restricted Boltzmann Machines are Entangled Plaquette States, while fully connected Restricted Boltzmann Machines are String-Bond States with a nonlocal geometry and low bond dimension. These results shed light on the underlying architecture of Restricted Boltzmann Machines and their efficiency at representing many-body quantum states. String-Bond States also provide a generic way of enhancing the power of Neural-Network Quantum States and a natural generalization to systems with larger local Hilbert space. We compare the advantages and drawbacks of these different classes of states and present a method to combine them together. This allows us to benefit from both the entanglement structure of Tensor Networks and the efficiency of Neural-Network Quantum States into a single Ansatz capable of targeting the wave function of strongly correlated systems. While it remains a challenge to describe states with chiral topological order using traditional Tensor Networks, we show that Neural-Network Quantum States and their String-Bond States extension can describe a lattice Fractional Quantum Hall state exactly. In addition, we provide numerical evidence that Neural-Network Quantum States can approximate a chiral spin liquid with better accuracy than Entangled Plaquette States and local String-Bond States. Our results demonstrate the efficiency of neural networks to describe complex quantum wave functions and pave the way towards the use of String-Bond States as a tool in more traditional machine-learning applications.Comment: 15 pages, 7 figure

On the diversity of T cell receptors in the genus Mus

The diversity of T cell receptors (TCRs) is one of the backbones of an effective adaptive immune system. This diversity is generated by somatic rearrangements of gene segments in two separate peptide chains that dimerize to form a unique receptor that can specifically recognize antigens. The generative process of TCR repertoire formation is largely defined by stochastic events that can theoretically give rise to more than 10^15 unique receptors. Strikingly, immune responses to common pathogens are frequently driven by identical or very similar TCRs. Consequently, there is significant non-random sharing of such “public” receptors between individuals. This has invoked the idea that genetically encoded factors contribute to the shaping of an individual’s TCR repertoire, but experimental validation of such factors has been lacking due to the technical challenge of capturing the sheer size of diverse TCR repertoires. I have developed a single-cell and high-throughput TCR sequencing protocol capable of generating paired TCR sequencing data from millions of CD8+ T cells. To reveal the contribution of genetic factors in the generation of TCRs, I generated TCR repertoires from 32 mice representing the reference lab mouse and three sister species, as well as F1 hybrids between them. Collectively, these mice span an evolutionary divergence time of approximately three million years and represent an exceptional model to study germline determinants of TCR repertoire formation. By conducting a comprehensive comparison of the variable, diversity and joining gene segments across the different species, I showed that the TCR alpha variable gene segment locus has undergone a major locus expansion. Following this observation, I was able to show that the usage frequencies of gene segments of TCRs varied significantly across species but were remarkably conserved in intra-species repertoires. Using F1 hybrids, I demonstrated genetic control in usage for specific gene segments, because individual parental alleles retain differential usage frequencies despite a shared heterozygous genetic background. Further, I have evaluated the impact of thymic selection on the shaping of an individual’s repertoire. TCR repertoire diversity reduction caused by thymic selection is mostly defined by rejection of variable gene segments in TCR beta chains and occurs strictly through direct protein-protein interaction with antigen-presenting major histocompatibility complexes. This has significant consequences for the sharing of identical and similar TCRs across several individuals. Further, by comparing the frequencies of short amino acid motifs of TCRs, I showed that even in those regions, arising from seemingly random fusion of gene segments, abundances of particular amino acids motifs are remarkably dependent of the respective genotype of an individual. This work not only provides an approach to analyze TCR repertoires at unprecedented scale but also reveals a surprising extent of genetic contribution to the shaping of an individual’s TCR repertoire

2 kirja Karl Morgensternile, Gotha

http://tartu.ester.ee/record=b1806423~S1*es

Beiträge zur Geschichte des Landkreises Regensburg 6

Das Donautal zwischen Regensburg und Wörth - Beschreibungen und Bilder aus fünf Jahrhunderten; darin: Fendl, Josef: Kaufmannszüge, Treidelpferde und Ordinarischiffe / Zur Verkehrsgeschichte des Regensburger Südostens (S. 3); Arndt, Ernst Moritz: Dem Mäandrischen Strome nach (S. 9); Zur Beruhigung der Reisenden (S. 9); Weber, Carl Julius: Die Nymphen der Donau (S. 9); Bundschue, Johann: So gut wie im Wirtshause (S. 10); Schultes, Joseph August: Herrliche Landschaftsstücke (S. 10); Schultes, Joseph August: Eine sonderbare Erscheinung (S. 10); Schindler, Herbert, Ein Bau aus dem Tagen Barbarossas (S. 11); Schindler, Herbert: Ein Treffpunkt der Romantiker (S. 12); Schindler, Herbert: Dieses lyrische Land (S. 13); Dielhelm, Johann Hermann: Auf einem ziemlich hohen Berg (S. 13); Bepanzert bis zum Scheitel (S. 14); Schultes, Joseph August: Eine der schönsten Punkte (S. 14); Dem Deutschen Ruhme (S. 16); Fürst von Metternich, Clemens: Ein Wald von abgeschnittenen Köpfen (S. 17); Donner, Jos. Alex.: Unheimlich aussehende Donaustaufer (S. 17); Fendl, Josef: Eine verzauberte romantische Landschaft (S. 18); Schultes, Joseph August: In mineralogischer Hinsicht merkwürdig (S. 20); Schultes, Joseph August: Ein Jägersteig am Scheuchen (S. 20); Schultes, Joseph August: Der gefürchtete Baierwein (S. 21); Schultes, Joseph August: Unbedeutende alte Dörfer (S. 22); Ein stattliches Kirchdorf (S. 22); Kaiser Joseph II.: Eine Messe auf dem Donauufer (S. 23); Schindler, Herbert: Wie ein Wachauer Weindorf (S. 23); J.H.: Die Donau bei Wiesent (S. 24); Schultes, Joseph August: Eine Art von Tantalischer Fahrt (S. 24); Der Wein hat viel Schneide (S. 25); Roedig, Michael: Spiegelwellen nach Deutscher Art (S. 25); Roedig, Michael: Etwas von süßer Wehmuth (S. 26); Arndt, Ernst Moritz: Wir landeten im Dorfe Pater (S. 26); Dielhelm, Johann Hermann: Ein feiner Marktflecken (S. 26); Schultes, Joseph August: Ein alter römischer Waffenplatz (S. 28); Berühmt durch die Bayerischen Rüben (S. 28); Fendl, Josef: St. Nikola in Pfatter (S. 28); Schultes, Joseph August: Das schöne, uralte Wörth (S. 29); Eine glückliche Lage (S. 29); Dunzinger, Franz Xaver: Die hehrste der Burgen (S. 30); Schindler, Herbert: Herbes Mittelalter und heitere Renaissance (S. 31); Freyberger, Laurentius: Magie der Donaulandschaft (S. 31); Bauer, Josef Martin: Ein Strom im Strom (S. 33); Britting, Georg: Wie ein silberner Fisch (S. 33