Hanbury Brown and Twiss correlations in atoms scattered from colliding condensates

Low energy elastic scattering between clouds of Bose condensed atoms leads to the well known s-wave halo with atoms emerging in all directions from the collision zone. In this paper we discuss the emergence of Hanbury Brown and Twiss coincidences between atoms scattered in nearly parallel directions. We develop a simple model that explains the observations in terms of an interference involving two pairs of atoms each associated with the elementary s wave scattering process.Comment: Minor corrections. reference update

Two-body anticorrelation in a harmonically trapped ideal Bose gas

We predict the existence of a dip below unity in the second-order coherence function of a partially condensed ideal Bose gas in harmonic confinement, signaling the anticorrelation of density fluctuations in the sample. The dip in the second-order coherence function is revealed in a canonical-ensemble calculation, corresponding to a system with fixed total number of particles. In a grand-canonical ensemble description, this dip is obscured by the occupation-number fluctuation catastrophe of the ideal Bose gas. The anticorrelation is most pronounced in highly anisotropic trap geometries containing small particle numbers. We explain the fundamental physical mechanism which underlies this phenomenon, and its relevance to experiments on interacting Bose gases.Comment: 10 pages, 5 figures. v2: Minor changes and corrections to figures and text. To appear in PR

Three-dimensional Gross-Pitaevskii solitary waves in optical lattices: stabilization using the artificial quartic kinetic energy induced by lattice shaking

In this Letter, we show that a three-dimensional Bose-Einstein solitary wave can become stable if the dispersion law is changed from quadratic to quartic. We suggest a way to realize the quartic dispersion, using shaken optical lattices. Estimates show that the resulting solitary waves can occupy as little as $\sim 1/20$-th of the Brillouin zone in each of the three directions and contain as many as $N = 10^{3}$ atoms, thus representing a \textit{fully mobile} macroscopic three-dimensional object.Comment: 8 pages, 1 figure, accepted in Phys. Lett.

Evaporative cooling in a radio-frequency trap

A theoretical investigation for implementing a scheme of forced evaporative cooling in radio-frequency (rf) adiabatic potentials is presented. Supposing the atoms to be trapped by a rf field RF1, the cooling procedure is facilitated using a second rf source RF2. This second rf field produces a controlled coupling between the spin states dressed by RF1. The evaporation is then possible in a pulsed or continuous mode. In the pulsed case, atoms with a given energy are transferred into untrapped dressed states by abruptly switching off the interaction. In the continuous case, it is possible for energetic atoms to adiabatically follow the doubly-dressed states and escape out of the trap. Our results also show that when the frequencies of the fields RF1 and RF2 are separated by at least the Rabi frequency associated with RF1, additional evaporation zones appear which can make this process more efficient.Comment: 12 pages, 11 figure

CubeSats as pathfinders for planetary detection: the FIRST-S satellite

The idea behind FIRST (Fibered Imager foR a Single Telescope) is to use single-mode fibers to combine multiple apertures in a pupil plane as such as to synthesize a bigger aperture. The advantages with respect to a pure imager are i) relaxed tolerance on the pointing and cophasing, ii) higher accuracy in phase measurement, and iii) availability of compact, precise, and active single-mode optics like Lithium Niobate. The latter point being a huge asset in the context of a space mission. One of the problems of DARWIN or SIM-like projects was the difficulty to find low cost pathfinders missions. But the fact that Lithium Niobate optic is small and compact makes it easy to test through small nanosats missions. Moreover, they are commonly used in the telecom industry, and have already been tested on communication satellites. The idea of the FIRST-S demonstrator is to spatialize a 3U CubeSat with a Lithium Niobate nulling interferometer. The technical challenges of the project are: star tracking, beam combination, and nulling capabilities. The optical baseline of the interferometer would be 30 cm, giving a 2.2 AU spatial resolution at distance of 10 pc. The scientific objective of this mission would be to study the visible emission of exozodiacal light in the habitable zone around the closest stars.Comment: SPIE 2014 -- Astronomical telescopes and instrumentation -- Montrea

Observation of atom pairs in spontaneous four wave mixing of two colliding Bose-Einstein Condensates

We study atom scattering from two colliding Bose-Einstein condensates using a position sensitive, time resolved, single atom detector. In analogy to quantum optics, the process can also be thought of as spontaneous, degenerate four wave mixing of de Broglie waves. We find a clear correlation between atoms with opposite momenta, demonstrating pair production in the scattering process. We also observe a Hanbury Brown and Twiss correlation for collinear momenta, which permits an independent measurement of the size of the pair production source and thus the size of the spatial mode. The back to back pairs occupy very nearly two oppositely directed spatial modes, a promising feature for future quantum optics experiments.Comment: A few typos have been correcte

Competing interactions in artificial spin chains

The low-energy magnetic configurations of artificial frustrated spin chains are investigated using magnetic force microscopy and micromagnetic simulations. Contrary to most studies on two-dimensional artificial spin systems where frustration arises from the lattice geometry, here magnetic frustration originates from competing interactions between neighboring spins. By tuning continuously the strength and sign of these interactions, we show that different magnetic phases can be stabilized. Comparison between our experimental findings and predictions from the one-dimensional Anisotropic Next-Nearest-Neighbor Ising (ANNNI) model reveals that artificial frustrated spin chains have a richer phase diagram than initially expected. Besides the observation of several magnetic orders and the potential extension of this work to highly-degenerated artificial spin chains, our results suggest that the micromagnetic nature of the individual magnetic elements allows observation of metastable spin configurations.Comment: 5 pages, 4 figure

A quadratic upper bound on the size of a synchronizing word in one-cluster automata

International audienceČerný's conjecture asserts the existence of a synchronizing word of length at most (n-1)² for any synchronized n-state deterministic automaton. We prove a quadratic upper bound on the length of a synchronizing word for any synchronized n-state deterministic automaton satisfying the following additional property: there is a letter a such that for any pair of states p, q, one has p*ar = q*as for some integers r, s (for a state p and a word w, we denote by p*w the state reached from p by the path labeled w). As a consequence, we show that for any finite synchronized prefix code with an n-state decoder, there is a synchronizing word of length O(n²). This applies in particular to Huffman codes

Variability of attitudes toward early initiation of HAART for HIV infection : a study of French prescribing physicians

This study assessed prescribing physicians' attitudes toward early initiation of HAART, three months after the dissemination of the first French official treatment guideline. Telephone interviews have been made in a national random sample of physicians with full- or part-time practice in hospital departments delivering care for HIV-infected patients. Questionnaires included hypothetical clinical cases. Logistic regression compared characteristics of respondents according to attitudes toward HAART. Among the 483 respondents (response rate = 87.0%), agreement was high with official recommendations to systematically initiate HAART with protease inhibitors (PIs) for patients with CD4+ cell counts &lt; or = 300/mm3, following a diagnosis of acute primary HIV infection, or for HIV sexual risk post-exposure prophylaxis. Confronted with a case of a naive asymptomatic patient with stable 450 CD4+/mm3, 34.6% would prescribe HAART with PIs in any case, and 29.8% only if the patient has plasma viral load &lt; or = 10,000 HIV RNA copies/ml. The remaining 35.6% would not prescribe PIs and were older, had limited activity in HIV care and expressed more interest in alternative medicines. To avoid a confusing impact of variability of clinical attitudes toward uncertainties associated with antiretroviral treatments among HIV-infected patients, shared decision-making between patient and physician should be promoted for initiation of HAART. [Authors]]]> Antiretroviral Therapy, Highly Active ; Attitude of Health Personnel ; HIV Infections ; Physician's Practice Patterns oai:serval.unil.ch:BIB_63B3A6A350EB 2022-05-07T01:19:14Z <oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> https://serval.unil.ch/notice/serval:BIB_63B3A6A350EB Logopenic syndrome and corticobasal dysfunction in a "benign" type 3 familial cortical myoclonic tremor with epilepsy. info:doi:10.1016/j.seizure.2015.01.004 info:eu-repo/semantics/altIdentifier/doi/10.1016/j.seizure.2015.01.004 info:eu-repo/semantics/altIdentifier/pmid/25645643 Magnin, E. info:eu-repo/semantics/article article 2015 Seizure, vol. 25, pp. 84-86 info:eu-repo/semantics/altIdentifier/eissn/1532-2688 urn:issn:1059-1311 eng oai:serval.unil.ch:BIB_63B3CEEF0A46 2022-05-07T01:19:14Z openaire documents urnserval <oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> https://serval.unil.ch/notice/serval:BIB_63B3CEEF0A46 Guidelines zur Behandlung von Aphasien. Schweizerische Aerztezeitung Aphasie, Suisse info:eu-repo/semantics/article article 2005 Bulletin des Médecins Suisses = Schweizerische Ärztezeitung, vol. 86, no. 40, pp. 2290-2297 urn:issn:1424-4012 ger https://serval.unil.ch/resource/serval:BIB_63B3CEEF0A46.P001/REF.pdf http://nbn-resolving.org/urn/resolver.pl?urn=urn:nbn:ch:serval-BIB_63B3CEEF0A466 info:eu-repo/semantics/altIdentifier/urn/urn:nbn:ch:serval-BIB_63B3CEEF0A466 info:eu-repo/semantics/submittedVersion info:eu-repo/semantics/openAccess Copying allowed only for non-profit organizations https://serval.unil.ch/disclaimer application/pdf oai:serval.unil.ch:BIB_63B487FEFFA8 2022-05-07T01:19:14Z openaire documents urnserval <oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> https://serval.unil.ch/notice/serval:BIB_63B487FEFFA8 Preliminary results on the postmortem measurement of 3-beta-hydroxybutyrate in liver homogenates. info:doi:10.1007/s00414-013-0870-3 info:eu-repo/semantics/altIdentifier/doi/10.1007/s00414-013-0870-3 info:eu-repo/semantics/altIdentifier/pmid/23722498 Palmiere, C. Mangin, P. Werner, D. info:eu-repo/semantics/article article 2013 International Journal of Legal Medicine, vol. 127, no. 5, pp. 943-949 info:eu-repo/semantics/altIdentifier/eissn/1437-1596 urn:issn:0937-9827 <![CDATA[The concentrations of 3-beta-hydroxybutyrate (3HB) in blood and two liver samples were retrospectively examined in a series of medicolegal autopsies. These cases included diabetic ketoacidosis, nondiabetic individuals presenting moderate to severe decompositional changes and nondiabetic medicolegal cases privy of decompositional changes. 3HB concentrations in liver sample homogenates correlate well with blood values in all examined groups. Additionally, decompositional changes were not associated with increases in blood and liver 3HB levels. These results suggest that 3HB can be reliably measured in liver homogenates when blood is not available at autopsy. Furthermore, they suggest that metabolic disturbances potentially leading or contributing to death may be objectified through liver 3HB determination even in decomposed bodies