Decoherence as a resource for quantum information

The field of quantum information develops rapidly as it promises to solve various computational problems that are intractable for classical computers. However, building a functional quantum computer turns out to be a challenging task as its performance suffers from unavoidable decoherence. Decoherence removes the quantum nature of matter and hence the source of the quantum advantage over classical computing. However, for specific applications, some carefully engineered decoherence assisting the unitary quantum evolution can be beneficial. In this thesis, I discuss two such examples: Quantum stochastic walks (QSWs) and hybrid quantum-classical annealing (HQCA). QSWs generalize the concept of unitary quantum walks to additional non-unitary evolution. This gives rise to directed walks. QSWs can either be continuous-time or discrete-time. In the first part of this work, I present two algorithms to simulate specific QSWs on a coherent quantum computer. The first one applies to continuous-time QSWs and the second one applies to discrete-time QSWs. In the second part of this work, I present a method called hybrid quantum-classical annealing to improve the performance of adiabatic quantum computing (AQC), which is supposed to find the ground state of some target Hamiltonian. HQCA is supposed to increase the final ground state probability by coupling the qubit system to an engineered heat bath. The performance of HQCA is numerically tested for a single qubit and for two qubits.Die Quanteninformationstheorie entwickelt sich rapide, da sie verspricht verschiedene Rechenaufgaben zu lösen, die für klassische Rechner nicht handhabbar sind. Doch ist es eine Herausforderung einen Quantenrechner zu bauen, weil dessen Performanz von unvermeidbarer Dekohärenz eingeschränkt wird. Durch diese verliert Materie ihre quantenmechanischen Eigenschaften und damit die Quelle der Vorteile eines Quantenrechners. Für bestimmte Anwendungen kann gesteuerte, die unitären Zeitentwicklung begleitende Dekohärenz allerdings von Vorteil sein. In dieser Arbeit diskutiere ich zwei solcher Fälle: stochastische Quanten-Walks (QSWs) und hybrides quanten-klassisches Ausglühen (HQCA). QSWs sind eine Verallgemeinerung der Quanten-Walks auf zusätzliche nicht-unitäre Zeitentwicklung. Damit ermöglichen sie gerichtete Walks. Wie ihre unitären Analoga können QSWs sowohl stetig als auch diskret in der Zeit sein. Im ersten Teil dieser Arbeit präsentiere ich zwei Algorithmen, die QSWs auf einem Quantenrechner simulieren. Der erste Algorithmus simuliert stetige und der zweite diskrete QSWs. Im zweiten Teil dieser Arbeit präsentiere ich eine Methode, die wir vorgeschlagen haben um adiabatisches Quantencomputing (AQC) zu verbessern. Das Ziel von AQC ist es den Grundzustand eines gewünschten Hamiltonoperators zu finden. HQCA soll die Grundzustandsbesetzung erhöhen, indem man die Qubits an ein künstliches Wärmebad ankoppelt. Der Effekt von HQCA wird numerisch für ein und für zwei Qubits getestet

Automated glycan assembly of xyloglucan oligosaccharides

We report the automated glycan assembly of oligosaccharide fragments related to the hemicellulose xyloglucan (XG). Iterative addition of monosaccharide and disaccharide building blocks to a solid support provided seven cellulose and xyloglucan fragments including XXGG- and XXXG-type oligosaccharides

Active Site Mapping of Xylan-Deconstructing Enzymes with Arabinoxylan Oligosaccharides Produced by Automated Glycan Assembly

Xylan-degrading enzymes are crucial for the deconstruction of hemicellulosic biomass, making the hydrolysis products available for various industrial applications such as the production of biofuel. To determine the substrate specificities of these enzymes, we prepared a collection of complex xylan oligosaccharides by automated glycan assembly. Seven differentially protected building blocks provided the basis for the modular assembly of 2-substituted, 3-substituted, and 2-/3-substituted arabino- and glucuronoxylan oligosaccharides. Elongation of the xylan backbone relied on iterative additions of C4-fluorenylmethoxylcarbonyl (Fmoc) protected xylose building blocks to a linker-functionalized resin. Arabinofuranose and glucuronic acid residues have been selectively attached to the backbone using fully orthogonal 2-(methyl)naphthyl (Nap) and 2-(azidomethyl)benzoyl (Azmb) protecting groups at the C2 and C3 hydroxyls of the xylose building blocks. The arabinoxylan oligosaccharides are excellent tools to map the active site of glycosyl hydrolases involved in xylan deconstruction. The substrate specificities of several xylanases and arabinofuranosidases were determined by analyzing the digestion products after incubation of the oligosaccharides with glycosyl hydrolases.Fil: Senf, Deborah. Max Planck Institut für Kolloid und Grenzflächenforschung; Alemania. Freie Universität; AlemaniaFil: Ruprecht, Colin. Max Planck Institut für Kolloid und Grenzflächenforschung; AlemaniaFil: de Kruijff, Goswinus H. M.. Max Planck Institut für Kolloid und Grenzflächenforschung; Alemania. Freie Universität; Alemania. University Mainz. Institute of Institute of Organic Chemistry, Johannes Gutenberg; AlemaniaFil: Simonetti, Sebastián Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina. Max Planck Institut für Kolloid und Grenzflächenforschung; AlemaniaFil: Schuhmacher, Frank. Max Planck Institut für Kolloid und Grenzflächenforschung; Alemania. Freie Universität; AlemaniaFil: Seeberger, Peter H.. Max Planck Institut für Kolloid und Grenzflächenforschung; Alemania. Freie Universität; AlemaniaFil: Pfrengle, Fabian. Max Planck Institut für Kolloid und Grenzflächenforschung; Alemania. Freie Universität; Alemani

Second WAW Quantum Computing: Introductory Talk

This talk sketches how quantum computers are build and the current state of the art. In a second part we discuss possibilities and limitations of quantum computers

Second WAW Quantum Computing: Introductory Talk

This talk sketches how quantum computers are build and the current state of the art. In a second part we discuss possibilities and limitations of quantum computers

Modular automated solid phase synthesis of dermatan sulfate oligosaccharides

Dermatan sulfates are glycosaminoglycan polysaccharides that serve a multitude of biological roles as part of the extracellular matrix. Orthogonally protected D-galactosamine and L-iduronic acid building blocks and a photo- cleavable linker are instrumental for the automated synthesis of dermatan sulfate oligosaccharides. Conjugation-ready oligosaccharides were obtained in good yield

DAOA/G72 predicts the progression of prodromal syndromes to first episode psychosis

The genetic factors determining the progression of prodromal syndromes to first episode schizophrenia have remained enigmatic to date. In a unique prospective multicentre trial, we assessed whether variants at the d-amino acid oxidase activator (DAOA)/G72 locus influence progression to psychosis. Young subjects with a prodromal syndrome were observed prospectively for up to 2 years to assess the incidence of progression to schizophrenia or first episode psychosis. Of the 82 probands with a prodromal syndrome, 21 probands experienced progression to psychosis within the observation period. Assessment of nine common variants in the DAOA/G72 locus yielded two variants with the predictive value for symptom progression: all four probands with the rs1341402 CC genotype developed psychosis compared with 17 out of 78 probands with the TT or CT genotypes (χ2 = 12.348; df = 2; p = 0.002). The relative risk for progression to psychosis was significantly increased in the CC genotype: RR = 4.588 (95% CI = 2.175–4.588). Similarly, for rs778294, 50% of probands with the AA genotype, but only 22% of probands with a GG or GA genotype progressed to psychosis (χ2 = 7.027; df = 2; p = 0.030). Moreover, haplotype analysis revealed a susceptibility haplotype for progression to psychosis. This is one of the first studies to identify a specific genetic factor for the progression of prodromal syndromes to schizophrenia, and further underscores the importance of the DAOA/G72 gene for schizophrenia