Observation of Motion Dependent Nonlinear Dispersion with Narrow Linewidth Atoms in an Optical Cavity

As an alternative to state-of-the-art laser frequency stabilisation using ultra-stable cavities, it has been proposed to exploit the non-linear effects from coupling of atoms with a narrow transition to an optical cavity. Here we have constructed such a system and observed non-linear phase shifts of a narrow optical line by strong coupling of a sample of strontium-88 atoms to an optical cavity. The sample temperature of a few mK provides a domain where the Doppler energy scale is several orders of magnitude larger than the narrow linewidth of the optical transition. This makes the system sensitive to velocity dependent multi-photon scattering events (Dopplerons) that affect the cavity field transmission and phase. By varying the number of atoms and the intra-cavity power we systematically study this non-linear phase signature which displays roughly the same features as for much lower temperature samples. This demonstration in a relatively simple system opens new possibilities for alternative routes to laser stabilization at the sub 100 mHz level and superradiant laser sources involving narrow line atoms. The understanding of relevant motional effects obtained here has direct implications for other atomic clocks when used in relation with ultranarrow clock transitions.Comment: 9 pages (including 4 pages of Supplemental Information), 6 figures. Updated to correspond to the published versio

Non-linear Spectroscopy of Sr Atoms in an Optical Cavity for Laser Stabilization

We study the non-linear interaction of a cold sample of strontium-88 atoms coupled to a single mode of a low finesse optical cavity in the so-called bad cavity limit and investigate the implications for applications to laser stabilization. The atoms are probed on the weak inter-combination line $\lvert 5s^{2} \, ^1 \textrm{S}_0 \rangle \,-\, \lvert 5s5p \, ^3 \textrm{P}_1 \rangle$ at 689 nm in a strongly saturated regime. Our measured observables include the atomic induced phase shift and absorption of the light field transmitted through the cavity represented by the complex cavity transmission coefficient. We demonstrate high signal-to-noise-ratio measurements of both quadratures - the cavity transmitted phase and absorption - by employing FM spectroscopy (NICE-OHMS). We also show that when FM spectroscopy is employed in connection with a cavity locked to the probe light, observables are substantially modified compared to the free space situation where no cavity is present. Furthermore, the non-linear dynamics of the phase dispersion slope is experimentally investigated and the optimal conditions for laser stabilization are established. Our experimental results are compared to state-of-the-art cavity QED theoretical calculations.Comment: 7 pages, 4 figure

Gut Microbiota Composition Modulates the Magnitude and Quality of Germinal Centers during Plasmodium Infections

Gut microbiota composition is associated with human and rodent Plasmodium infections, yet the mechanism by which gut microbiota affects the severity of malaria remains unknown. Humoral immunity is critical in mediating the clearance of Plasmodium blood stage infections, prompting the hypothesis that mice with gut microbiota-dependent decreases in parasite burden exhibit better germinal center (GC) responses. In support of this hypothesis, mice with a low parasite burden exhibit increases in GC B cell numbers and parasite-specific antibody titers, as well as better maintenance of GC structures and a more targeted, qualitatively different antibody response. This enhanced humoral immunity affects memory, as mice with a low parasite burden exhibit robust protection against challenge with a heterologous, lethal Plasmodium species. These results demonstrate that gut microbiota composition influences the biology of spleen GCs as well as the titer and repertoire of parasite-specific antibodies, identifying potential approaches to develop optimal treatments for malaria

Flimma: a federated and privacy-aware tool for differential gene expression analysis

Abstract Aggregating transcriptomics data across hospitals can increase sensitivity and robustness of differential expression analyses, yielding deeper clinical insights. As data exchange is often restricted by privacy legislation, meta-analyses are frequently employed to pool local results. However, the accuracy might drop if class labels are inhomogeneously distributed among cohorts. Flimma (https://exbio.wzw.tum.de/flimma/) addresses this issue by implementing the state-of-the-art workflow limma voom in a federated manner, i.e., patient data never leaves its source site. Flimma results are identical to those generated by limma voom on aggregated datasets even in imbalanced scenarios where meta-analysis approaches fail

A design methodology for soft-core platforms on FPGA with SMP Linux, OpenMP support, and distributed hardware profiling system

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The effect of a virtual reality environment on gaze behaviour and motor skill learning

Objective: Virtual reality (VR) systems hold significant potential for training skilled behaviours and are currently receiving intense interest in the sporting domain. They offer both practical and pedagogical benefits, but there are concerns about the effect that perceptual deficiencies in VR systems (e.g. reduced haptic information, and stereoscopic display distortions) may have on learning and performance. ‘Specificity of learning’ theories suggest that VR could be ineffective (or even detrimental) if important differences (e.g. perceptual deficiencies) exist between practice and real task performance conditions. Nevertheless, ‘structural learning’ theories suggest VR could be a useful training tool, despite these deficiencies, because a trainee can still learn the underlying structure of the behaviour. We explored these theoretical predictions using golf putting as an exemplar skill. Method: In Experiment 1 we used a repeated measures design to assess putting accuracy (radial error) and quiet eye duration of expert golfers (n = 18) on real putts before and after 40 VR ‘warm up’ putts. In Experiment 2, novice golfers (n = 40) were assigned to either VR or real-world putting training. Putting accuracy and quiet eye durations were then assessed on a real-world retention test. Results: Both visual guidance (quiet eye) and putting accuracy were disrupted temporarily when moving from VR to real putting (Experiment 1). However, real-world and VR practice produced comparable improvements in putting accuracy in novice golfers (Experiment 2). Conclusion: Overall, the results suggest that: (i) underlying skill structures can be learned in VR and transferred to the real-world; (ii) perceptual deficiencies will place limits on the use of VR. These findings demonstrate the challenges and opportunities for VR as a training tool, and emphasise the need to empirically test the costs and benefits of specific systems before deploying VR training

An uncharted island: searching for experimentation in Olivier Messiaen’s Île de feu 1

© 2013 David John TieriThis thesis offers a detailed examination of Olivier Messiaen’s (1908-1992) short piano work Île de feu 1 from the Quatre Études de rythme (1949-1950). Though these pieces are recognised for their radical and innovative features, their representation in the existing literature is uneven, and Île de feu 1 has been relatively neglected. Since this work is usually lumped with analytical discussions of its companion pieces, it is normally assumed to be experimental by default. This study therefore proposes to examine Île de feu 1 as a work worthy of its own analytical attention. It considers the contextual position of this piece within Messiaen’s experimental period (1949-1952) and attempts to establish a connection with the innovative quasi-serialist processes that he developed during this time. The analysis adopts the theoretical framework of Messiaen’s self-described compositional procedures, endeavouring to identify in this piece such techniques as: Greek and Indian rhythmic patterns, non-retrogradable rhythms, canonic devices, and the modes of limited transposition, in addition to the influences of theology and birdsong. The results of this technical analysis suggest that Île de feu 1 is less concerned with explicit experimentation, since it only displays an abstract association with such processes and is mainly constructed with the most fundamental features of Messiaen’s musical language. The thesis concludes that Île de feu 1 is a significant point in the evolution of Messiaen’s style, exhibiting as it does those traits that were developed in his earlier pieces, and anticipating a return to these features in the works that follow the experimental period

The Performer as Researcher, the Researcher as Performer: Articulating Arnold Schoenberg’s Connection with Johann Sebastian Bach through a Topically Informed Performance of His Complete Works for Solo Piano

© 2022 David John TieriThe music of Arnold Schoenberg (1874–1951) can be difficult for listeners and performers, who often find it cerebral and hard to understand. In this project, I take up the challenge of how pianists can present an eloquent performance—comprehensible and emotionally appealing to listeners—of Schoenberg’s complete works for solo piano. I seek the inspiration behind the music, contending that a listener can see past the image of Schoenberg as a controversial and intellectual composer, and better appreciate and connect with his compositions, if a performer makes artistic choices to emphasise his continuity with the past. I narrow down the problem to Schoenberg’s connection with one composer: Johann Sebastian Bach (1685–1750). I face this challenge as a performer as well as a scholar. The project consists of a thesis and a folio of performances. In the thesis, I substantiate the Schoenberg-Bach connection with a close reading of Schoenberg’s comments on Bach in his writings and a topical analysis of references to Baroque conventions in his piano works; in the folio, I demonstrate this connection through my recording of these works. I argue that the connection with Bach, which is explicit in Schoenberg’s writings, should also be implicit in his music, at both deeper and surface levels. The connection between the composers can, therefore, be illuminated in a topically informed performance of Schoenberg’s piano music. The performance folio features my recordings of Schoenberg’s complete published works for solo piano. This folio also includes my recordings of a selection of Bach’s works for solo keyboard, some of which illustrate the connection between the composers. The criterion for this selection of Bach pieces is that Schoenberg mentioned them in his writings. The first chapter of the thesis provides a literature review of existing scholarship on Schoenberg’s connection with Bach, his works for solo piano, and his use of topics. The second chapter outlines my theory and methods: three guiding ideas (haptic knowledge, Schoenberg’s perception of Bach, and musical topics) and three strategies (practice-led research, close reading, and topical analysis). This chapter also presents an original music-specific and performance-related methodology: the artistic-research interaction model. Chapter 3 offers a close reading of Schoenberg’s comments on Bach in the totality of his writings. Chapters 4, 5, 6, and 7 present a topical analysis of musical figures in Schoenberg’s piano music that can be connected to Baroque conventions. These include Baroque dance, the learned style, the Baroque improvisatory keyboard style, and the pianto. In the conclusion, I outline and anticipate further research into Schoenberg’s piano music, his connections with previous composers, and his use of topics. The thesis concludes with a reflection on the contribution of this project to the field of artistic research, as well as the potential of the interaction model developed and applied here for performer-scholars

Open Quantum Systems with Applications to Precision Measurements

A spectrally pure coherent light source is an important component in precision measurement applications, such as an atomic clock. The more spectrally pure the coherent light source, or the narrower the linewidth of its power spectrum, the better for atomic clock experiments. A coherent light light source, such as a laser, is intrinsically an open quantum system, meaning that it gains and loses energy from an external environment. The aim of this thesis is to study various open quantum systems in an attempt to discover a scheme in which an extremely spectrally pure coherent light source might be realized. Therefore, this thesis begins by introducing the two main approaches to treating open quantum systems, the quantum master equation approach, and the quantum Langevin equation approach. In addition to deriving these from first principles, many of the solution methods to these approaches are given and then demonstrated using computer simulations. These include the quantum jump algorithm, the quantum state diffusion algorithm, the cumulant expansion method, and the method of c-number Langevin equations. Using these methods, the theory of the crossover between lasing and steady state superradiance is presented. It is shown that lasing and steady state superradiance might be demonstrated in the same physical system, but in different parameter regimes. The parameter space between these two extreme limits is explored, and the benefits and drawbacks of operating a system at a given set of parameters, i.e. to achieve the most spectrally pure light source, are discussed. We also consider the phase stability of a laser that is locked to a cavity QED system comprised of atoms with an ultra-narrow optical transition. Although the atomic motion introduces Doppler broadening, the standing wave nature of the cavity causes saturated absorption, which can be used to achieve an extremely high degree of phase stabilization. The inhomogeneity introduced by finite atomic velocities can also cause optical bistability to disappear, resulting in no regions of dynamic instability that would otherwise restrict operational parameters in the experiment to be tuned outside of the optimum region where the minimum linewidth occurs