Raman scattering of single photons and its use for quantum networks and high-precision measurements

This work concerns the interaction of single atoms and light as a platform for quantum-communication networks, both experimentally and simulative. It treats, at its kernel, the calcium ion as a node of such a network, i. e. as storage of a quantum bit. Especially the quantum interface of this ion with the light field and its experimental implementation are addressed in detail. Thereby spontaneous Raman scattering is used to transfer the polarisation state of a single photon onto the ion’s electronic state and vice versa. On the way to this interface the Raman scattering process of single photons was investigated intensively. This led to a high-precision experiment measuring the phase shift of such photons as well as a detailed theoretical study of the spectral and temporal structure of the photons. The experiments used and expanded an existing hybrid quantum-optical set-up consisting of two identical ion traps and a light source of entangled photon pairs.Diese Arbeit behandelt die Wechselwirkung einzelner Atome mit Licht als Plattform für Quantenkommunikationsnetzwerke, sowohl experimentell als auch simulativ. Im Kern befasst sie sich mit dem Calciumion als Knotenpunkt eines solchen Netzwerks, d. h. als Speicher eines Quantenbits. Insbesondere wird die Quantenschnittstelle dieses Ions mit dem Lichtfeld und ihre experimentelle Umsetzung detailliert behandelt. Dabei wird durch spontane Raman-Streuung der Polarisationszustand eines einzelnen Photons auf den elektronischen Zustand des Ions übertragen und umgekehrt. Auf dem Weg zur Umsetzung dieser Schnittstelle wurde der Raman’sche Streuprozess einzelner Photonen genau untersucht. Dies mündete in einem Hochpräzisionsexperiment zur Messung des Phasengangs solcher Photonen sowie zu einer detaillierten theoretischen Studie der spektralen und temporalen Struktur der Photonen. Zur Verwirklichung dieser Experimente wurde ein bestehender hybrider quantenoptischer Aufbau, bestehend aus zwei identischen Ionenfallen sowie einer Lichtquelle verschränkter Photonenpaare, genutzt und erweitert.Die dò Ahwett hannelt vun de Weggselwirgung ähnselner Atome mim Licht als Arwettsplatt fa e Quandenetzwerk – unn zwar experimendell unn simmuleert. In de Hauptsach geht’s um’s Calciumion als Knibbelche vun some Netzwerk, das häßt, es dud e Quandebit speichere. Insbesonnere gebt die Quandeschnittstell vum Ion mim Lichtfeld unn die experimendell Umsetzung dòdevun genau beschrieb. Dòdebei werd mit spondaner Raman-Streiung de Polarisationszustand vumme ähnselne Phoddòn uff de elegdronische Zustand vum Ion iwwertrah odder annersch’erum. Uffem Wäh zu der dò Schnittstell is ’em Raman sei Streiprozess genau unnersucht wòr. Das hat zum ähne zuner scheen Messung vum Phasegang vun so Phodone gefihrt unn zum annere zuner deddaijiert theoredisch Ahwett iwwer die spegdral unn zeitlich Strugdur vun denne Phodone. Fa die dò Experimende ze mache, is amme voorischer Quandeobdik-Uffbau geknoddelt wòr unn aach noch meh draangebaut wòr. Bestehn duder aus zwä Ionefalle vun ähn unn de selb Sort unn’er Quell vun veschrängde Phodonepaare

Transnational Social Spaces and the Legal Status of Migrants in Ecuador

The legal status and living conditions of migrants in host countries reflect contemporary forms of inequality arising from the uneven distribution of wealth and power among states. Over the past decades, the transnational social impacts of global movements of people have raised concerns about the appropriateness of the premise of self-contained nation-states, which have led some authors and social actors to reevaluate the notion of nation-based citizenship and to consider alternative conceptions that fit better to the changing complexities of international migration. In 2008, a constitutional amendment in Ecuador introduced the concept of universal citizenship, granting citizens’ rights independently of national affiliation. This provides a valuable case study for the exploration of the real implications of a de- nationalized citizenship when adopted under the current international framework, and particularly for understanding the way normative orders and migration policies in transnational social spaces are interconnected. This article examines the way in which the rights of both emigrants and immigrants are included in the Ecuadorian Constitution and analyzes three cases that reflect the kind of interdependent limitations and constraints that Ecuador faces for its migration policy choices and constitutional rules on universal citizenship, including its unintended consequences

The Christmas Island Seamount Province, Indian Ocean: Origin of Intraplate Volcanism by Shallow Recycling of Continental Lithosphere?

The east-west-trending Christmas Island Seamount Province (CHRISP, 1800x600 km) in the northeastern Indian Ocean is elongated orthogonal to present-day plate motion, posing the question if a mantle plume formed this volcanic belt. Here we report the first age (Ar/Ar) and geochemical (Sr- Nd-Hf-Pb DS isotopic data) from the CHRISP seamount chain. A crude E-W age decrease from the Argo Basin (136 Ma), to the Eastern Wharton Basin (115-94 Ma) to the Vening-Meinesz seamounts (96-64 Ma) to the Cocos-Keeling seamounts (56-47 Ma) suggests spatial migration of melting. Christmas Island, however, yields much younger ages (44-4 Ma), inconsistent with an age progression. The isotopic compositions (e.g. 206Pb/204Pb = 17.3-19.3; 207Pb/204Pb = 15.49- 15.67; 143Nd/144Nd = 0.51220-0.51295; 176Hf/177Hf = 0.28246- 0.28319) range from enriched MORB (or “C”) to very enriched mantle (EM1) type compositions more typical of continental than oceanic volcanism. Lamproitic and kimberlitic rocks from western Australia, India and other continental areas, derived from metasomatized subcontinental lithospheric mantle, could serve as the EM1 type endmembers. The morphology, ages and chemical composition of the CHRISP, combined with plate tectonic reconstructions, cannot be easily explained within the framework of the mantle plume hypotheses. We therefore propose that the seamounts are derived through the recycling of continental lithosphere (mantle ± lower crust) delaminated during the breakup of Gondwana and brought to the surface at the former spreading centers separating Argoland (western Burma), Greater India and Australia

Impact of Flow Conditions and Geometrical Parameters on the Separation of Two Immiscible Liquids in Helical Pipes

The separation of two immiscible liquids was studied in helical pipes with different flow and geometrical conditions. The main objective is to investigate the impact of the geometrical dimensions on the phase separation in helical pipes. The Volume Of Fluid (VOF) method was used to model the two-phase flow. The separation performance was quantified and compared using the average mixing coefficient of the two liquids. A perfect mixture of two liquids (water and amine) was always assumed at the inlet. Comparing different flow orientations, proper separation could only be obtained when the helical pipe is oriented horizontally. A laminar flow at the optimal range of Reynolds number for separation was considered (approximately Re = 225-563), where Re = 225 leads to a slightly better separation. The three key geometrical dimensions of helical pipes; the coil pitch, the pipe diameter, and the coil diameter were studied within the ranges of 16-60 mm, 5-15 mm, and 70-150 mm, respectively. The results show that changing the coil pitch has no significant effect on the separation behavior, while high enough pipe and coil diameters are needed to preserve an efficient separation of immiscible liquids and easier extraction of the lighter phase

Synthetic communication signals influence wild harbour porpoise (Phocoena phocoena) behaviour

We used our novel and programmable Porpoise Alarm (PAL, patd.) to synthesize life-like, electronic harbour porpoise communication signals based on those described for captive animals. In the Little Belt, Denmark, we employed PAL (source level 158 ± 1 dB p–p re 1 μPa@1 m; centroid frequency 133 ± 8.5 kHz) to synthesize three aggressive click train types termed “A”, “F3” and “M1” to naive, free-living harbour porpoises. Via theodolite tracking (372 h of total visual effort spread over 10 expeditions) we found that, depending on signal type, porpoises either avoid or become attracted to PAL: Signal types “A” and “F3” are slight deterrents, porpoises increasing minimum range (+23 to 32 m, respectively), whereas “M1” attracts porpoises, reducing range (by − 29 m). As determined via archival acoustic detectors (AADs), both signals “F3” and “M1” led the animals to significantly intensify their click rate (by +10% and 68%, respectively) while signal “A” led to a significant reduction ( − 59%). We propose that equipping fishing gear with PAL emitting signal “F3” could potentially reduce porpoise by-catch by increasing (1) awareness through enhanced echolocation and (2) distance to the nets. Detection probability and radius of PAL/AAD tandems could be improved by emitting signal “M1” to focus porpoise echolocation signals on the AAD. The signal may also be useful in luring animals away from hazards, which may be helpful for conservation measures prior to the onset of harmful acoustic activities such as pile-driving, seismic exploration or ammunition clearance

Designer rhamnolipid production

Rhamnolipids are biosurfactants featuring surface-active properties that render them suitable for a broad range of applications, e.g., in detergents, food, bioremediation, medicine/pharmacology, and crop science. These properties include their emulsification and foaming capacities and their ability to lower the surface tension. Further, aspects like biocompatibility and environmental friendliness, both features of rhamnolipids [1] are becoming increasingly important. Rhamnolipids thus constitute suitable substitutes for synthetic surfactants produced from fossil resources. Native producers of rhamnolipids are mainly pathogenic bacteria like Pseudomonas aeruginosa. We previously designed and constructed a recombinant Pseudomonas putida KT2440, which synthesizes rhamnolipids by decoupling production from host-intrinsic regulations and cell growth [2]. As most biosurfactants, rhamnolipids are synthesized in mixtures. We here show our approach to alter the native mixture of surfactant molecules to produce specific new-to-nature combinations. The molecular structure (Figure 1) can on the one hand be altered in the hydrophilic moiety by changing the number of rhamnose molecules. We achieved this by using only distinct genes from the native rhamnolipid synthesis pathway. On the other hand, we were also able to change the length of the fatty acids in the hydrophobic part. This chain length is determined by the acyl-transferase (RhlA). Using rhlA genes from different organisms enables our microbial cell factory to synthesize molecules with different chain lengths [3]. The different molecular structures have further been shown to feature diverse physico-chemical properties [4]. Exploiting the natural structural diversity will thus allow for the synthesis of designer rhamnolipids tailormade for specific applications. We thus present a novel approach to use biochemical engineering to create tailormade products for a more sustainable future. Please click Additional Files below to see the full abstract

High-Resolution Replication Profiles Define the Stochastic Nature of Genome Replication Initiation and Termination

Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.Peer reviewedPublisher PD

A global profile of replicative polymerase usage

Three eukaryotic DNA polymerases are essential for genome replication. Polymerase (Pol) α–primase initiates each synthesis event and is rapidly replaced by processive DNA polymerases: Polɛ replicates the leading strand, whereas Polδ performs lagging-strand synthesis. However, it is not known whether this division of labor is maintained across the whole genome or how uniform it is within single replicons. Using Schizosaccharomyces pombe, we have developed a polymerase usage sequencing (Pu-seq) strategy to map polymerase usage genome wide. Pu-seq provides direct replication-origin location and efficiency data and indirect estimates of replication timing. We confirm that the division of labor is broadly maintained across an entire genome. However, our data suggest a subtle variability in the usage of the two polymerases within individual replicons. We propose that this results from occasional leading-strand initiation by Polδ followed by exchange for Polɛ