Controlled deflection of cold atomic clouds and of Bose-Einstein condensates

We present a detailed, realistic proposal and analysis of the implementation of a cold atom deflector using time-dependent far off-resonance optical guides. An analytical model and numerical simulations are used to illustrate its characteristics when applied to both non-degenerate atomic ensembles and to Bose-Einstein condensates. Using for all relevant parameters values that are achieved with present technology, we show that it is possible to deflect almost entirely an ensemble of $^{87}$Rb atoms falling in the gravity field. We discuss the limits of this proposal, and illustrate its robustness against non-adiabatic transitions

The Problem of Purely Procedural Preemption Presented by the Federal HEAR Act

The underlying purpose of the Holocaust Expropriated Art Recovery Act of 2016 (the HEAR Act), which is to return Nazi-looted artwork to victims or their families, is undeniably laudable. Restituting Nazi-looted artwork is and has been a moral objective of this country since the conclusion of World War II. It is equally clear that victims and their families can often face obstacles to gathering evidence from the war that would demonstrate Nazi theft in court. The HEAR Act strives to address these concerns by imposing a federal statute of limitations over all state law causes of action that would enable restitution of Nazi-stolen art. Notwithstanding the important purposes that the HEAR Act aims to serve, courts should hold that the HEAR act violates the Tenth Amendment and principles of federalism because it purports to preempt state causes of action on a purely procedural basis. The HEAR Act does not itself provide a federal cause of action or remedy and does not present a basis for federal question jurisdiction. Rather, the HEAR Act purports merely to engraft a federal statute of limitations on all the various state law civil claims of general applicability that enable the restitution of alleged Nazi-stolen art (e.g., for replevin, declaratory judgment, or conversion). The purely procedural preemption imposed by the HEAR Act would appear to be an unprecedented–and unconstitutional–interference with state rights

Theoretical study of a cold atom beam splitter

A theoretical model is presented for the study of the dynamics of a cold atomic cloud falling in the gravity field in the presence of two crossing dipole guides. The cloud is split between the two branches of this laser guide, and we compare experimental measurements of the splitting efficiency with semiclassical simulations. We then explore the possibilities of optimization of this beam splitter. Our numerical study also gives access to detailed information, such as the atom temperature after the splitting

Effect of picosecond strain pulses on thin layers of the ferromagnetic semiconductor (Ga,Mn)(As,P)

The effect of picosecond acoustic strain pulses (ps-ASP) on a thin layer of (Ga,Mn)As co-doped with phosphorus was probed using magneto-optical Kerr effect (MOKE). A transient MOKE signal followed by low amplitude oscillations was evidenced, with a strong dependence on applied magnetic field, temperature and ps-ASP amplitude. Careful interferometric measurement of the layer's thickness variation induced by the ps-ASP allowed us to model very accurately the resulting signal, and interpret it as the strain modulated reflectivity (differing for $\sigma_{\pm}$ probe polarizations), independently from dynamic magnetization effects.Comment: 6 pages, 5 figure

Conceptually driven and visually rich tasks in texts and teaching practice: the case of infinite series

The study we report here examines parts of what Chevallard calls the institutional dimension of the students’ learning experience of a relatively under-researched, yet crucial, concept in Analysis, the concept of infinite series. In particular, we examine how the concept is introduced to students in texts and in teaching practice. To this purpose, we employ Duval's Theory of Registers of Semiotic Representation towards the analysis of 22 texts used in Canada and UK post-compulsory courses. We also draw on interviews with in-service teachers and university lecturers in order to discuss briefly teaching practice and some of their teaching suggestions. Our analysis of the texts highlights that the presentation of the concept is largely a-historical, with few graphical representations, few opportunities to work across different registers (algebraic, graphical, verbal), few applications or intra-mathematical references to the concept's significance and few conceptually driven tasks that go beyond practising with the application of convergence tests and prepare students for the complex topics in which the concept of series is implicated. Our preliminary analysis of the teacher interviews suggests that pedagogical practice often reflects the tendencies in the texts. Furthermore, the interviews with the university lecturers point at the pedagogical potential of: illustrative examples and evocative visual representations in teaching; and, student engagement with systematic guesswork and writing explanatory accounts of their choices and applications of convergence tests

Bose-Einstein condensation in dark power-law laser traps

We investigate theoretically an original route to achieve Bose-Einstein condensation using dark power-law laser traps. We propose to create such traps with two crossing blue-detuned Laguerre-Gaussian optical beams. Controlling their azimuthal order $\ell$ allows for the exploration of a multitude of power-law trapping situations in one, two and three dimensions, ranging from the usual harmonic trap to an almost square-well potential, in which a quasi-homogeneous Bose gas can be formed. The usual cigar-shaped and disk-shaped Bose-Einstein condensates obtained in a 1D or 2D harmonic trap take the generic form of a "finger" or of a "hockey puck" in such Laguerre-Gaussian traps. In addition, for a fixed atom number, higher transition temperatures are obtained in such configurations when compared with a harmonic trap of same volume. This effect, which results in a substantial acceleration of the condensation dynamics, requires a better but still reasonable focusing of the Laguerre-Gaussian beams

A hybrid metal/semiconductor electron pump for quantum metrology

Electron pumps capable of delivering a current higher than 100pA with sufficient accuracy are likely to become the direct mise en pratique of the possible new quantum definition of the ampere. Furthermore, they are essential for closing the quantum metrological triangle experiment which tests for possible corrections to the quantum relations linking e and h, the electron charge and the Planck constant, to voltage, resistance and current. We present here single-island hybrid metal/semiconductor transistor pumps which combine the simplicity and efficiency of Coulomb blockade in metals with the unsurpassed performances of silicon switches. Robust and simple pumping at 650MHz and 0.5K is demonstrated. The pumped current obtained over a voltage bias range of 1.4mV corresponds to a relative deviation of 5e-4 from the calculated value, well within the 1.5e-3 uncertainty of the measurement setup. Multi-charge pumping can be performed. The simple design fully integrated in an industrial CMOS process makes it an ideal candidate for national measurement institutes to realize and share a future quantum ampere

In Our Country, but Outside Our Homeland: Identity and Diaspora Among Ukraine’s Internally Displaced Crimeans

In response to Russia’s annexation of the Crimean Peninsula in 2014, tens of thousands of Crimean residents have relocated to mainland Ukraine as Internally Displaced Persons (IDPs), including many ethnic Ukrainians, Russians, and indigenous Crimean Tatars. Deliberately choosing to remain Ukrainian rather than Russian citizens, Crimean IDPs have become emblematic of new discourses of Ukrainian civic and multicultural nationalism emerging in the wake of the 2013-2014 Euromaidan protests. While they are proud Ukrainian patriots, most Crimean IDPs also maintain a strong sense of regional identity tied to Crimea itself, and therefore understand themselves to be simultaneous “in place” and “out of place” within the Ukrainian mainland. This disjunctive sense of territorial belonging bears most of the hallmarks of a diasporic condition, except for the presumption of international migration that undergirds normative “transnational” theories of diaspora. Showcasing Crimean IDPs as a salient case study, this dissertation advances an alternative “translocal” theory of diaspora that is attentive to discourses of belonging and exclusion whether or not migrants have crossed an international border. Relying on ethnographic fieldwork conducted within Crimean IDP communities in the cities of Kyiv and Lviv, this dissertation traces the motivating factors driving internal displacement from occupied Crimea, unpacks the Ukrainian and Crimean identities that dialectically animate IDPs’ schismatic senses of territorial belonging, and analytically situates their varied experiences within a diasporic framework, disrupting the problematic epistemological binary of internal/international migration that hampers theories of diaspora

Ice Hockey Goaltender Physiology Profile and Physical Testing: A Systematic Review and Meta-Analysis

International Journal of Exercise Science 14(6): 855-875, 2021. This review aims to 1) be the first systematic review and meta-analysis of the literature examining the physiology and assessment of goaltenders, and 2) present a physiological profile of ice-hockey goaltenders. It will 1) highlight physiological differences between goaltenders and players at other positions, 2) determine strengths and weaknesses of ice hockey goaltenders, and 3) offer possible guidelines for strength and conditioning coaches. Six electronic databases were systematically searched in October 2019 using the PRISMA model. A total of twelve scientific articles published in peer-reviewed journals were included. Professional male (PM) goaltenders had the following profile for age (A) 26.8 ± 2.5 years, body weight (BW) 85.64 ± 3.79 kg, height (H) 184.38 ± 2.79 cm, body fat % (BF%) 11.9 ± 2.22, VO2max 49.9 ± 4.45 ml/kg/min, anaerobic power (AP) 12.78 ± 1.63 W/kg, and combined hand grip strength (GS) 120.7 ± 15 kg. Amateur male (AM) goaltenders presented the following: A: 18.2 ± 0.75, BW: 83.85 ± 4.51, H: 184.96 ± 2.06, BF%: 10.51 ± 1.61, VO2max: 55.73 ± 4.57, AP: 10.9 ± 1.2 and GS: 109.08 ± 14.06. Amateur female (AF) goaltenders presented the following: A: 21.04 ± 1.84, BW: 63.4 ± 5.14, H: 164.86 ± 5.73, BF%: 22.12 ± 2.27 and VO2max: 42.84 ± 3.59. Overall, PM goaltenders are heavier, have a higher BF%, and exhibit greater GS and abdominal muscular endurance than AM, while AM goaltenders are heavier, taller, leaner, and can generate greater lower-body muscular power than AF goaltenders. In the current literature, there were a small number of studies on women players and a lack of distinction between player position in reported results. Specific physiological assessments during NHL Combines should be developed for goaltenders in accordance with their specific positional demands

Theoretical analysis of the implementation of a quantum phase gate with neutral atoms on atom chips

We present a detailed, realistic analysis of the implementation of a proposal for a quantum phase gate based on atomic vibrational states, specializing it to neutral rubidium atoms on atom chips. We show how to create a double--well potential with static currents on the atom chips, using for all relevant parameters values that are achieved with present technology. The potential barrier between the two wells can be modified by varying the currents in order to realize a quantum phase gate for qubit states encoded in the atomic external degree of freedom. The gate performance is analyzed through numerical simulations; the operation time is ~10 ms with a performance fidelity above 99.9%. For storage of the state between the operations the qubit state can be transferred efficiently via Raman transitions to two hyperfine states, where its decoherence is strongly inhibited. In addition we discuss the limits imposed by the proximity of the surface to the gate fidelity.Comment: 9 pages, 5 color figure