Self-consistent theory of atomic Fermi gases with a Feshbach resonance at the superfluid transition

A self-consistent theory is derived to describe the BCS-Bose-Einstein-condensate crossover for a strongly interacting Fermi gas with a Feshbach resonance. In the theory the fluctuation of the dressed molecules, consisting of both preformed Cooper pairs and bare Feshbach molecules, has been included within a self-consistent T-matrix approximation, beyond the Nozieres and Schmitt-Rink strategy considered by Ohashi and Griffin. The resulting self-consistent equations are solved numerically to investigate the normal-state properties of the crossover at various resonance widths. It is found that the superfluid transition temperature T-c increases monotonically at all widths as the effective interaction between atoms becomes more attractive. Furthermore, a residue factor Z(m) of the molecule's Green function and a complex effective mass have been determined to characterize the fraction and lifetime of Feshbach molecules at T-c. Our many-body calculations of Z(m) agree qualitatively well with recent measurments of the gas of Li-6 atoms near the broad resonance at 834 G. The crossover from narrow to broad resonances has also been studied.

Entanglement under restricted operations: Analogy to mixed-state entanglement

We show that the classification of bipartite pure entangled states when local quantum operations are restricted yields a structure that is analogous in many respects to that of mixed-state entanglement. Specifically, we develop this analogy by restricting operations through local superselection rules, and show that such exotic phenomena as bound entanglement and activation arise using pure states in this setting. This analogy aids in resolving several conceptual puzzles in the study of entanglement under restricted operations. In particular, we demonstrate that several types of quantum optical states that possess confusing entanglement properties are analogous to bound entangled states. Also, the classification of pure-state entanglement under restricted operations can be much simpler than for mixed-state entanglement. For instance, in the case of local Abelian superselection rules all questions concerning distillability can be resolved.

Better Bell-inequality violation by collective measurements

The standard Bell-inequality experiments test for violation of local realism by repeatedly making local measurements on individual copies of an entangled quantum state. Here we investigate the possibility of increasing the violation of a Bell inequality by making collective measurements. We show that the nonlocality of bipartite pure entangled states, quantified by their maximal violation of the Bell-Clauser-Horne inequality, can always be enhanced by collective measurements, even without communication between the parties. For mixed states we also show that collective measurements can increase the violation of Bell inequalities, although numerical evidence suggests that the phenomenon is not common as it is for pure states.

Classical simulation of quantum many-body systems with a tree tensor network

We show how to efficiently simulate a quantum many-body system with tree structure when its entanglement (Schmidt number) is small for any bipartite split along an edge of the tree. As an application, we show that any one-way quantum computation on a tree graph can be efficiently simulated with a classical computer.

Coherent-state quantum key distribution without random basis switching

The random switching of measurement bases is commonly assumed to be a necessary step of quantum key distribution protocols. In this paper we present a no-switching protocol and show that switching is not required for coherent-state continuous-variable quantum key distribution. Further, this protocol achieves higher information rates and a simpler experimental setup compared to previous protocols that rely on switching. We propose an optimal eavesdropping attack against this protocol, assuming individual Gaussian attacks. Finally, we investigate and compare the no-switching protocol applied to the original Bennett-Brassard 1984 scheme.

Conditional quantum-state engineering using ancillary squeezed-vacuum states

We investigate an optical scheme to conditionally engineer quantum states using a beam splitter, homodyne detection, and a squeezed vacuum as an ancillar state. This scheme is efficient in producing non-Gaussian quantum states such as squeezed single photons and superpositions of coherent states (SCSs). We show that a SCS with well defined parity and high fidelity can be generated from a Fock state of n

Entangled-state cycles from conditional quantum evolution

A system of cascaded qubits interacting via the one-way exchange of photons is studied. While for general operating conditions the system evolves to a superposition of Bell states (a dark state) in the long-time limit, under a particular resonance condition no steady state is reached within a finite time. We analyze the conditional quantum evolution (quantum trajectories) to characterize the asymptotic behavior under this resonance condition. A distinct bimodality is observed: for perfect qubit coupling, the system either evolves to a maximally entangled Bell state without emitting photons (the dark state) or executes a sustained entangled-state cycle-random switching between a pair of Bell states while emitting a continuous photon stream; for imperfect coupling, two entangled-state cycles coexist, between which a random selection is made from one quantum trajectory to another.

Noise thresholds for optical cluster-state quantum computation

In this paper we do a detailed numerical investigation of the fault-tolerant threshold for optical cluster-state quantum computation. Our noise model allows both photon loss and depolarizing noise, as a general proxy for all types of local noise other than photon loss noise. We obtain a threshold region of allowed pairs of values for the two types of noise. Roughly speaking, our results show that scalable optical quantum computing is possible in the combined presence of both noise types, provided that the loss probability is less than 3 X 10(-3) and the depolarization probability is less than 10(-4). Our fault-tolerant protocol involves a number of innovations, including a method for syndrome extraction known as telecorrection, whereby repeated syndrome measurements are guaranteed to agree. This paper is an extended version of Dawson.

Tense, aspect and modality in first and second language

Time after time… and aspect and mood. Over the last twenty five years, the study of time, aspect and - to a lesser extent - mood acquisition has enjoyed increasing popularity and a constant widening of its scope. In such a teeming field, what can be the contribution of this book? We believe that it is unique in several respects. First, this volume encompasses studies from different theoretical frameworks: functionalism vs generativism or function-based vs form-based approaches. It also brings together various sub-fields (first and second language acquisition, child and adult acquisition, bilingualism) that tend to evolve in parallel rather than learn from each other. A further originality is that it focuses on a wide range of typologically different languages, and features less studied languages such as Korean and Bulgarian. Finally, the book gathers some well-established scholars, young researchers, and even research students, in a rich inter-generational exchange, that ensures the survival but also the renewal and the refreshment of the discipline. The book at a glance The first part of the volume is devoted to the study of child language acquisition in monolingual, impaired and bilingual acquisition, while the second part focuses on adult learners. In this section, we will provide an overview of each chapter. The first study by Aviya Hacohen explores the acquisition of compositional telicity in Hebrew L1. Her psycholinguistic approach contributes valuable data to refine theoretical accounts. Through an innovating methodology, she gathers information from adults and children on the influence of definiteness, number, and the mass vs countable distinction on the constitution of a telic interpretation of the verb phrase. She notices that the notion of definiteness is mastered by children as young as 10, while the mass/count distinction does not appear before 10;7. However, this does not entail an adult-like use of telicity. She therefore concludes that beyond definiteness and noun type, pragmatics may play an important role in the derivation of Hebrew compositional telicity. For the second chapter we move from a Semitic language to a Slavic one. Milena Kuehnast focuses on the acquisition of negative imperatives in Bulgarian, a form that presents the specificity of being grammatical only with the imperfective form of the verb. The study examines how 40 Bulgarian children distributed in two age-groups (15 between 2;11-3;11, and 25 between 4;00 and 5;00) develop with respect to the acquisition of imperfective viewpoints, and the use of imperfective morphology. It shows an evolution in the recourse to expression of force in the use of negative imperatives, as well as the influence of morphological complexity on the successful production of forms. With Yi-An Lin’s study, we concentrate both on another type of informant and of framework. Indeed, he studies the production of children suffering from Specific Language Impairment (SLI), a developmental language disorder the causes of which exclude cognitive impairment, psycho-emotional disturbance, and motor-articulatory disorders. Using the Leonard corpus in CLAN, Lin aims to test two competing accounts of SLI (the Agreement and Tense Omission Model [ATOM] and his own Phonetic Form Deficit Model [PFDM]) that conflicts on the role attributed to spellout in the impairment. Spellout is the point at which the Computational System for Human Language (CHL) passes over the most recently derived part of the derivation to the interface components, Phonetic Form (PF) and Logical Form (LF). ATOM claims that SLI sufferers have a deficit in their syntactic representation while PFDM suggests that the problem only occurs at the spellout level. After studying the corpus from the point of view of tense / agreement marking, case marking, argument-movement and auxiliary inversion, Lin finds further support for his model. Olga Gupol, Susan Rohstein and Sharon Armon-Lotem’s chapter offers a welcome bridge between child language acquisition and multilingualism. Their study explores the influence of intensive exposure to L2 Hebrew on the development of L1 Russian tense and aspect morphology through an elicited narrative. Their informants are 40 Russian-Hebrew sequential bilingual children distributed in two age groups 4;0 – 4;11 and 7;0 - 8;0. They come to the conclusion that bilingual children anchor their narratives in perfective like monolinguals. However, while aware of grammatical aspect, bilinguals lack the full form-function mapping and tend to overgeneralize the imperfective on the principles of simplicity (as imperfective are the least morphologically marked forms), universality (as it covers more functions) and interference. Rafael Salaberry opens the second section on foreign language learners. In his contribution, he reflects on the difficulty L2 learners of Spanish encounter when it comes to distinguishing between iterativity (conveyed with the use of the preterite) and habituality (expressed through the imperfect). He examines in turn the theoretical views that see, on the one hand, habituality as part of grammatical knowledge and iterativity as pragmatic knowledge, and on the other hand both habituality and iterativity as grammatical knowledge. He comes to the conclusion that the use of preterite as a default past tense marker may explain the impoverished system of aspectual distinctions, not only at beginners but also at advanced levels, which may indicate that the system is differentially represented among L1 and L2 speakers. Acquiring the vast array of functions conveyed by a form is therefore no mean feat, as confirmed by the next study. Based on the prototype theory, Kathleen Bardovi-Harlig’s chapter focuses on the development of the progressive in L2 English. It opens with an overview of the functions of the progressive in English. Then, a review of acquisition research on the progressive in English and other languages is provided. The bulk of the chapter reports on a longitudinal study of 16 learners of L2 English and shows how their use of the progressive expands from the prototypical uses of process and continuousness to the less prototypical uses of repetition and future. The study concludes that the progressive spreads in interlanguage in accordance with prototype accounts. However, it suggests additional stages, not predicted by the Aspect Hypothesis, in the development from activities and accomplishments at least for the meaning of repeatedness. A similar theoretical framework is adopted in the following chapter, but it deals with a lesser studied language. Hyun-Jin Kim revisits the claims of the Aspect Hypothesis in relation to the acquisition of L2 Korean by two L1 English learners. Inspired by studies on L2 Japanese, she focuses on the emergence and spread of the past / perfective marker ¬–ess- and the progressive – ko iss- in the interlanguage of her informants throughout their third and fourth semesters of study. The data collected through six sessions of conversational interviews and picture description tasks seem to support the Aspect Hypothesis. Indeed learners show a strong association between past tense and accomplishments / achievements at the start and a gradual extension to other types; a limited use of past / perfective marker with states and an affinity of progressive with activities / accomplishments and later achievements. In addition, - ko iss– moves from progressive to resultative in the specific category of Korean verbs meaning wear / carry. While the previous contributions focus on function, Evgeniya Sergeeva and Jean-Pierre Chevrot’s is interested in form. The authors explore the acquisition of verbal morphology in L2 French by 30 instructed native speakers of Russian distributed in a low and high levels. They use an elicitation task for verbs with different models of stem alternation and study how token frequency and base forms influence stem selection. The analysis shows that frequency affects correct production, especially among learners with high proficiency. As for substitution errors, it appears that forms with a simple structure are systematically more frequent than the target form they replace. When a complex form serves as a substitute, it is more frequent only when it is replacing another complex form. As regards the use of base forms, the 3rd person singular of the present – and to some extent the infinitive – play this role in the corpus. The authors therefore conclude that the processing of surface forms can be influenced positively or negatively by the frequency of the target forms and of other competing stems, and by the proximity of the target stem to a base form. Finally, Martin Howard’s contribution takes up the challenge of focusing on the poorer relation of the TAM system. On the basis of L2 French data obtained through sociolinguistic interviews, he studies the expression of futurity, conditional and subjunctive in three groups of university learners with classroom teaching only (two or three years of university teaching) or with a mixture of classroom teaching and naturalistic exposure (2 years at University + 1 year abroad). An analysis of relative frequencies leads him to suggest a continuum of use going from futurate present to conditional with past hypothetic conditional clauses in si, which needs to be confirmed by further studies. Acknowledgements The present volume was inspired by the conference Acquisition of Tense – Aspect – Mood in First and Second Language held on 9th and 10th February 2008 at Aston University (Birmingham, UK) where over 40 delegates from four continents and over a dozen countries met for lively and enjoyable discussions. This collection of papers was double peer-reviewed by an international scientific committee made of Kathleen Bardovi-Harlig (Indiana University), Christine Bozier (Lund Universitet), Alex Housen (Vrije Universiteit Brussel), Martin Howard (University College Cork), Florence Myles (Newcastle University), Urszula Paprocka (Catholic University of Lublin), †Clive Perdue (Université Paris 8), Michel Pierrard (Vrije Universiteit Brussel), Rafael Salaberry (University of Texas at Austin), Suzanne Schlyter (Lund Universitet), Richard Towell (Salford University), and Daniel Véronique (Université d’Aix-en-Provence). We are very much indebted to that scientific committee for their insightful input at each step of the project. We are also thankful for the financial support of the Association for French Language Studies through its workshop grant, and to the Aston Modern Languages Research Foundation for funding the proofreading of the manuscript.

Serrated yielding and the localized shear failure mode in aluminium alloys

A study has been made of serrated yielding in two commercial Al-Zn-Mg alloys in the as-quenched condition. The different serration types produced in the two alloys and the shear failure mechanism observed in both notched-bend and tensile testing are related to the mechanisms of dynamic strain ageing occurring during the test. An estimate of 19.7 kJ/mole for the activation energy for exchange of a solute atom and a vacancy in Al-6.2 wt% Zn, 2.5 wt% Mg has been made. © 1981.

Quantifying Aflatoxin B1 in peanut oil using fabricating fluorescence probes based on upconversion nanoparticles

Rare earth doped upconversion nanoparticles convert near-infrared excitation light into visible emission light. Compared to organic fluorophores and semiconducting nanoparticles, upconversion nanoparticles (UCNPs) offer high photochemical stability, sharp emission bandwidths, and large anti-Stokes shifts. Along with the significant light penetration depth and the absence of autofluorescence in biological samples under infrared excitation, these UCNPs have attracted more and more attention on toxin detection and biological labelling. Herein, the fluorescence probe based on UCNPs was developed for quantifying Aflatoxin B₁ (AFB₁) in peanut oil. Based on a specific immunity format, the detection limit for AFB₁ under optimal conditions was obtained as low as 0.2 ng·ml^{- 1}, and in the effective detection range 0.2 to 100 ng·ml^{- 1}, good relationship between fluorescence intensity and AFB₁ concentration was achieved under the linear ratios up to 0.90. Moreover, to check the feasibility of these probes on AFB₁ measurements in peanut oil, recovery tests have been carried out. A good accuracy rating (93.8%) was obtained in this study. Results showed that the nanoparticles can be successfully applied for sensing AFB₁ in peanut oil.

Charge migration induced by attosecond pulses in bio-relevant molecules

After sudden ionization of a large molecule, the positive charge can migrate throughout the system on a sub-femtosecond time scale, purely guided by electronic coherences. The possibility to actively explore the role of the electron dynamics in the photo-chemistry of bio-relevant molecules is of fundamental interest for understanding, and perhaps ultimately controlling, the processes leading to damage, mutation and, more generally, to the alteration of the biological functions of the macromolecule. Attosecond laser sources can provide the extreme time resolution required to follow this ultrafast charge flow. In this review we will present recent advances in attosecond molecular science: after a brief description of the results obtained for small molecules, recent experimental and theoretical findings on charge migration in bio-relevant molecules will be discussed.

Absolute cross sections for dissociative electron attachment to HCCCN

New absolute cross sections for dissociative electron attachment to HCCCN (cyanoacetylene or propiolonitrile) in the range of 0-10 eV electron energy are presented here, which have been determined from a new analysis of previously reported data (Graupner et al 2006 New J. Phys. 8 117). The highest cross sections are observed for the formation of CN^- at 5.3 eV and CCCN^- at 5.1 eV; approximately 0.06 Ų and 0.05 Ų respectively. As part of the re-analysis, it was necessary to determine absolute cross sections for electron-impact ionization of HCCCN with the binary-encounter Bethe method. These electron-impact ionization absolute cross sections for HCCCN are also presented here; the maximum value was found to be ∼6.6 Ų at ∼80 eV.

A transport beamline solution to control optically accelerated proton beams

Laser-target interaction represents a very promising field for several potential applications,
from the nuclear physics to the radiobiology. However optically accelerated particle beams are
characterized by some extreme features, not suitable for many applications. Therefore, beyond
the improvements at the laser-target interaction level, many researchers are spending their efforts
for the development of specific beam transport devices in order to obtain controlled and
reproducible output beams.In this background, the ELIMED (ELI-Beamlines MEDical applications)
project was born. Within 2017, a dedicated transport beam-line coupled with dosimetric
systems, named ELIMED, will be installed at the Extreme Light Infrastructure Beamlines
(ELI-Beamlines) facility in Prague (CZ),as a part of the ELIMAIA (ELI Multidisciplinary Applications
of laserâA ¸SIon Acceleration) beamline