Squeezed state purification with linear optics and feed forward

A scheme for optimal and deterministic linear optical purification of mixed squeezed Gaussian states is proposed and experimentally demonstrated. The scheme requires only linear optical elements and homodyne detectors, and allows the balance between purification efficacy and squeezing degradation to be controlled. One particular choice of parameters gave a ten-fold reduction of the thermal noise with a corresponding squeezing degradation of only 11%. We prove optimality of the protocol, and show that it can be used to enhance the performance of quantum informational protocols such as dense coding and entanglement generation.Comment: 4 pages, 3 figure

Sub shot noise phase quadrature measurement of intense light beams

We present a setup to perform sub shot noise measurements of the phase quadrature for intense pulsed light without the use of a separate local oscillator. A Mach--Zehnder interferometer with an unbalanced arm length is used to detect the fluctuations of the phase quadrature at a single side band frequency. Using this setup, the non--separability of a pair of quadrature entangled beams is demonstrated experimentally.Comment: 9 pages, 2 figures, accepted for publication in Optics Letter

Change in intensifiers

Die vorliegende Arbeit behandelt den Wandel von englischen Gradadverbien im Rahmen der Grammatikalisierungstheorie, in einem Zeitraum von zweihundert Jahren in Amerika. Die Gruppe der Intensiva ist geprägt von Wandel und Wachstum, da die jeweiligen Begriffe mit der Zeit an Wirkungskraft verlieren und von neuen Wörtern/Begriffen ersetzt werden; so verwendet jede Generation andere Intensivadverbien. Die ausgetauschten Intensiva sterben jedoch nicht (gleich) aus, und somit steigt die Zahl der verschiedenen Gradadverbien insgesamt. Dieser stetige Wandel und Wechsel in Intensivadverbien gibt Anlass zu genauerer Beobachtung dieser Gruppe von Wörtern. Inwieweit erklärt die Grammatikalisierungstheorie diesen dynamischen Prozess der diese Gruppe auszeichnet? Was passiert mit Intensivadverbien nachdem sie ersetzt wurden, und was passiert mit ihnen wenn niemand sie mehr verwendet? Die Recherchegrundlage bildet ein Corpus, der eine Sammlung von Text(en) aus Büchern, Zeitungen und Zeitschriften zum Durchsuchen zur Verfügung stellt. Es wird gezeigt, dass Intensivadverbien, ein Produkt der Grammatikalisierung, gewisse Gemeinsamkeiten in ihrer Entwicklung aufweisen. Trotzdem stellen sie ein sehr spezielles Phänomen in der Linguistik dar und bieten sich daher an mit speziellen, und vielleicht unkonventionellen, Methoden untersucht zu werden.In this thesis an attempt is made to describe diachronic changes in frequency, usage, and category status of a group of intensifiers and intensifying adverbs in the last two centuries in American English. The study is based on a corpus-based research and on grammaticalisation theory. The group of intensifiers is characterised by constant change and steady rise in number. Frequent expressions lose their force over time and get replaced by new expression. In this sense each generation can be said to have its respective intensifiers. The constantly changing nature of intensifiers raises several questions: can grammaticalisation theory capture the dynamic processes in intensifiers?, what happens to ‘old’ intensifiers, which have been replaced, and most interestingly, what happens to them if the speakers who still use them disappear? The specified set of intensifiers is analysed according to frequencies, collocations, patterns of intensification, and extent of grammaticalisation. The analysis shows that there are, indeed, common patterns in their development. Still, intensifiers build a very distinct group of words, which might be worth considering in the frame of unconventional theories

Sexuelle Gewalt im Religionsunterricht zur Sprache bringen

Die vorliegende Arbeit untersucht das Thema der sexuellen Gewalt aus religionspädagogischer Perspektive und bettet dieses in die präventive Arbeit mit Kinder- und Jugendliteratur ein. Der Fokus wird dabei auf folgende Forschungsfrage gerichtet: Was gilt es zu beachten, wenn das Thema der sexuellen Gewalt im Religionsunterricht zur Sprache gebracht wird und wie kann dabei die Kinder- und Jugendliteratur hilfreich sein? Es soll die These überprüft werden, dass das Jugendbuch „Wofür die Worte fehlen“ von Carolin Philipps hilfreich sein kann, damit das Thema der sexuellen Gewalt nicht mehr als ein Tabuthema betrachtet wird, sondern dass das Schweigen darüber auch im Religionsunterricht gebrochen werden kann. Der erste Teil der Arbeit verortet das Thema der sexuellen Gewalt im religionspädagogischen Kontext und stellt die Frage nach neuen Wegen, die es angesichts der bekannt gewordenen Fälle von sexueller Gewalt zu bestreiten gilt. Dabei wird von der christlichen Erinnerungsarbeit als religionspädagogischer Leitkategorie ausgegangen und diese mit Kinder- und Jugendliteratur verknüpft. Anschließend werden diese Aspekte in einen didaktischen Kontext gesetzt, wobei hier die Frage leitend ist, welche zentralen didaktischen Momente beachtet werden müssen, wenn das Thema der sexuellen Gewalt im Religionsunterricht anhand von Kinder- und Jugendliteratur behandelt wird. Wie festgestellt werden kann, ob sich ein Kinder- und Jugendbuch für den schulischen Einsatz zum Thema der sexuellen Gewalt eignet, wird im abschließenden Kapitel dargestellt. Hier werden Analysekriterien, die sich vor allem auf die wissenschaftlichen Erkenntnisse der Präventionsforschung stützen, entwickelt und beispielhaft anhand der Analyse des Jugendbuches „Wofür die Worte fehlen“ dargestellt. Bezüglich der Forschungsfrage kann gesagt werden, dass trotz der aufgezeigten Risiken literarischen Texten gelingen kann, was christliche Erinnerungsarbeit leisten will: ein Bewusstsein für das Leid der Opfer zu schaffen und sich präventiv gegen Gewalt einzusetzen. Des Weiteren hat die Analyse zusammenfassend ergeben, dass „Wofür die Worte fehlen“ den wissenschaftlichen Erkenntnissen zum Thema der sexuellen Gewalt entspricht und somit einen informativen wie auch präventiven Charakter besitzt.This thesis analyses the topic of sexual violence from a religious education perspective and embeds it into the preventive work with literature for children and adolescents. The focus is put on the following research question: What should be paid attention to when the topic of sexual violence is raised in the religious education classroom and how can literature for children and adolescents are helpful for this purpose? The assumption is, that the book “Wofür die Worte fehlen” by Carolin Phillips can be helpful for breaking the silence about sexual violence even in the religious education classroom. The first part of the thesis locates the issue of sexual violence in the context of religious education and asks for new ways which have to be found in the face of the cases of sexual violence which have recently come to light. The “Christian memory work” is the starting point and will be connected with aspects of the literature for children and adolescents. Afterwards, these aspects will be placed into a didactic context. In the last step, several analysis criteria will be presented, which can help to find out if a book for children and adolescents is suitable for being used in a classroom. The analysis criteria are based on scientific facts of the preventive research and are illustrated with the help of the analysis of “Wofür die Worte fehlen”. Regarding the research question it can be said that literary texts can be helpful to realize the intentions of “Christian memory work” in context of sexual abuse in a classroom, because they can create an awareness of the suffering of victims and they can help to work preventively against sexual abuse. Furthermore, the analysis showed that “Wofür die Worte fehlen” equates to the scientific insights concerning sexual abuse and has therefore an informative as well as a preventive effect

Verifying continuous variable entanglement of intense light pulses

Three different methods have been discussed to verify continuous variable entanglement of intense light beams. We demonstrate all three methods using the same set--up to facilitate the comparison. The non--linearity used to generate entanglement is the Kerr--effect in optical fibres. Due to the brightness of the entangled pulses, standard homodyne detection is not an appropriate tool for the verification. However, we show that by using large asymmetric interferometers on each beam individually, two non-commuting variables can be accessed and the presence of entanglement verified via joint measurements on the two beams. Alternatively, we witness entanglement by combining the two beams on a beam splitter that yields certain linear combinations of quadrature amplitudes which suffice to prove the presence of entanglement.Comment: 11 pages, 7 figures, to appear in Phys. Rev.

3D phase-matching conditions for the generation of entangled triplets by chi(2) interlinked interactions

An analytical calculation of the interaction geometry of two interlinked second-order nonlinear processes fulfilling phase-matching conditions is presented. The method is developed for type-I uniaxial crystals and gives the positions on a screen beyond the crystal of the entangled triplets generated by the interactions. The analytical results are compared to experiments realized in the macroscopic regime. Preliminary tests to identify the triplets are also performed based on intensity correlations.Comment: 6 pages, 3 figures, 1 movie (extension of fig. 2

Quantum study of information delay in electromagetically induced transparency

Using electromagnetically induced transparency (EIT), it is possible to delay and store light in atomic ensembles. Theoretical modelling and recent experiments have suggested that the EIT storage mechanism can be used as a memory for quantum information. We present experiments that quantify the noise performance of an EIT system for conjugate amplitude and phase quadratures. It is shown that our EIT system adds excess noise to the delayed light that has not hitherto been predicted by published theoretical modelling. In analogy with other continuous-variable quantum information systems, the performance of our EIT system is characterised in terms of conditional variance and signal transfer.Comment: 4 pages, 4 figure

Erratum : Squeezing and entanglement delay using slow light

An inconsistency was found in the equations used to calculate the variance of the quadrature fluctuations of a field propagating through a medium demonstrating electromagnetically induced transparency (EIT). The decoherence term used in our original paper introduces inconsistency under weak probe approximation. In this erratum we give the Bloch equations with the correct dephasing terms. The conclusions of the original paper remain the same. Both entanglement and squeezing can be delayed and preserved using EIT without adding noise when the decoherence rate is small.Comment: 1 page, no figur

Polarization-squeezed light formation in a medium with electronic Kerr nonlinearity

We analyze the formation of polarization-squeezed light in a medium with electronic Kerr nonlinearity. Quantum Stokes parameters are considered and the spectra of their quantum fluctuations are investigated. It is established that the frequency at which the suppression of quantum fluctuations is the greatest can be controlled by adjusting the linear phase difference between pulses. We shown that by varying the intensity or the nonlinear phase shift per photon for one pulse, one can effectively control the suppression of quantum fluctuations of the quantum Stokes parameters.Comment: final version, RevTeX, 10 pages, 5 eps figure

Systematic analysis of SNR in bipartite Ghost Imaging with classical and quantum light

We present a complete and exhaustive theory of signal-to-noise-ratio in bipartite ghost imaging with classical (thermal) and quantum (twin beams) light. The theory is compared with experiment for both twin beams and thermal light in a certain regime of interest