Proposal for demonstrating the Hong-Ou-Mandel effect with matter waves

The Hong-Ou-Mandel (HOM) effect is a striking demonstration of destructive quantum interference between pairs of indistinguishable bosons, realised so far only with massless photons. Here we propose an experiment which can realise this effect in the matter-wave regime using pair-correlated atoms produced via a collision of two Bose-Einstein condensates and subjected to two laser induced Bragg pulses. We formulate a novel measurement protocol appropriate for the multimode matter-wave field, which---unlike the typical two-mode optical case---bypasses the need for repeated measurements under different displacement settings of the beam-splitter, thus dramatically reducing the number of experimental runs required to map out the interference visibility. The protocol can be utilised in related matter-wave schemes; here we focus on condensate collisions and by simulating the entire experiment we predict a HOM-dip visibility of ~69%. By being larger than 50%, such a visibility highlights strong quantum correlations between the atoms and paves the way for a possible demonstration of a Bell inequality violation with massive particles in a related Rarity-Tapster setup.Comment: Essentially the same version as v2, except in Nature Communications style; for Supplementary Information see the source fil

Proposal for a motional-state Bell inequality test with ultracold atoms

We propose and theoretically simulate an experiment for demonstrating a motional-state Bell inequality violation for pairs of momentum-entangled atoms produced in Bose-Einstein condensate collisions. The proposal is based on realizing an atom-optics analog of the Rarity-Tapster optical scheme: it uses laser-induced Bragg pulses to implement two-particle interferometry on the underlying Bell-state for two pairs of atomic scattering modes with equal but opposite momenta. The collision dynamics and the sequence of Bragg pulses are simulated using the stochastic Bogoliubov approach in the positive-P representation. We predict values of the Clauser-Horne-Shimony-Holt (CHSH) parameter up to S~2.5 for experimentally realistic parameter regimes, showing a strong violation of the CSHS-Bell inequality bounded classically by S<2.Comment: Final published version; 11 pages, 6 figure

Quantum-Enhanced Sensing Based on Time Reversal of Nonlinear Dynamics

We experimentally demonstrate a nonlinear detection scheme exploiting time-reversal dynamics that disentangles continuous variable entangled states for feasible readout. Spin-exchange dynamics of Bose-Einstein condensates is used as the nonlinear mechanism which not only generates entangled states but can also be time reversed by controlled phase imprinting. For demonstration of a quantum-enhanced measurement we construct an active atom SU(1,1) interferometer, where entangled state preparation and nonlinear readout both consist of parametric amplification. This scheme is capable of exhausting the quantum resource by detecting solely mean atom numbers. Controlled nonlinear transformations widen the spectrum of useful entangled states for applied quantum technologies.Comment: 9 pages, 3 figures, 3 pages supplementary material, 2 supplementary figure

Statistical distribution of free water surface over a mild bed slope for extreme wavefields

This paper examines the probability density function (PDF) of free water surface elevations in coastal areas. The functional form and properties of PDFs of extreme storms propagating over a mildly sloping bathymetry are investigated. This is facilitated through comparisons between experimental measurements and a wide range of probability models; the latter including both analytical and empirical distributions. The incident wave conditions correspond to realistic storm spectra (JONSWAP) and have been simulated as long random timeseries of 60-hour duration. The length of the records is sufficient to provide an accurate description of distribution tails. Six sea-states with varying offshore steepness have been generated and measured at different cross-shore locations. The cross-shore evolution of the wavefield initially leads to the development of nonlinear harmonics, both at low and high frequencies, and a broadening of the wave spectrum. This is enhanced by wave breaking particularly at shallower water depths or steeper sea-states. These result in rapid deviations from Gaussian theory with respect to the PDFs of surface elevations. Available models are generally successful in capturing nonlinear evolution arising at a second-order of wave steepness but cannot model the probability structure once a significant proportion of waves are breaking. In comparing the deviations between experimental data and model predictions, the best performing model is identified

Bisphenol A Data in NHANES Suggest Longer than Expected Half-Life, Substantial Nonfood Exposure, or Both

Reproduced with permission from Environmental Health Perspectives. doi:10.1289/ehp.0800376It is commonly stated in the literature on human exposure to bisphenol A (BPA) that food is the predominant BPA exposure source, and that BPA is rapidly and completely cleared from the body. If this is correct, BPA levels in fasting individuals should decrease with increased fasting time. We set out to investigate the relationship between urine BPA concentration and fast¬ing time in a population-based sample. Overall, BPA levels did not decline rapidly with fasting time in this sample. This suggests substantial nonfood exposure, accumulation in body tissues such as fat, or both. Explaining these findings may require experimental pharmacokinetic studies of chronic BPA exposure, further examination of BPA levels and effects in fat, and a search for important nonfood sources.This work was supported by National Institute of Environmental Health Sciences Training Grant ES07026 and University of Rochester Environmental Health Sciences Center Grant ES01247

Frobenius Splittings

We give a gentle introduction to Frobenius splittings. Then we recall a few results that have been obtained with the method.Comment: 21 pages, typos correcte

Media Baru dalam Konstruksi Jurnalis Media Cetak

Hadirnya media baru sebagai salah satu manifestasi dari kemajuan ilmu pengetahuan dan teknologi telah mengubah model komunikasi massa yang umumnya dilakukan media massa dari one to many menjadi many to many, di mana siapa pun kini bisa menjadi pembuat informasi dan melalui media baru menyebarluaskannya. Kondisi ini kemudian mengaburkan fungsi institusi pers sekaligus menimbulkan pertanyaan, apakah media massa telah terpinggirkan. Namun juga, kehadiran media baru ini secara bersamaan membantu institusi media dalam memperluas jangkauannya. Penelitian ini bermaksud untuk mencari tahu bagaimana para jurnalis media cetak sebagai media konvensional memaknai dan mengalami media baru dalam keseharian mereka sebagai jurnalis dihadapkan dengan kehadiran media baru. Melalui metode studi fenomenologi dan teori fenomenologi Alfred Schutz, hasil dari penelitian ini adalah para jurnalis memaknai media baru sebagai sumber informasi awal, tantangan yang memacu kerja, mitra yang saling melengkapi dan media informasi dan hiburan. Sementara pengalaman para jurnalis di antaranya adalah dituntut bekerja cepat serta menghasilkan laporan yang mendalam, mencari informasi melalui media sosial tanpa meninggalkan agenda liputan dan menggunakan media sosial untuk menyebarluaskan berita, mengedukasi dan partisipasi kolektif

Sensitivity to thermal noise of atomic Einstein-Podolsky-Rosen entanglement

We examine the prospect of demonstrating Einstein-Podolsky-Rosen (EPR) entanglement for massive particles using spin-changing collisions in a spinor Bose-Einstein condensate. Such a demonstration has recently been attempted by Gross et al. [Nature (London) 480, 219 (2011)] using a condensate of Rb-87 atoms trapped in an optical lattice potential. For the condensate initially prepared in the (F, m(F)) = (2,0) hyperfine state, with no population in the m(F) = +/- 1 states, we predict a significant suppression of the product of inferred quadrature variances below the Heisenberg uncertainty limit, implying strong EPR entanglement. However, such EPR entanglement is lost when the collisions are initiated in the presence of a small (currently undetectable) thermal population (n) over bar (th) in the m(F) = +/- 1 states. For condensates containing 150-200 atoms, we predict an upper bound of (n) over bar (th) similar or equal to 1 that can be tolerated in this experiment before EPR entanglement is lost

A feasibility, randomised controlled trial of a complex breathlessness intervention in idiopathic pulmonary fibrosis (BREEZE-IPF): study protocol

Introduction Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive lung disease that causes breathlessness and cough that worsen over time, limiting daily activities and negatively impacting quality of life. Although treatments are now available that slow the rate of lung function decline, trials of these treatments have failed to show improvement in symptoms or quality of life. There is an immediate unmet need for evidenced-based interventions that improve patients' symptom burden and make a difference to everyday living. This study aims to assess the feasibility of conducting a definitive randomised controlled trial of a holistic, complex breathlessness intervention in people with IPF. Methods and analysis The trial is a two-centre, randomised controlled feasibility trial of a complex breathlessness intervention compared with usual care in patients with IPF. 50 participants will be recruited from secondary care IPF clinics and randomised 1:1 to either start the intervention within 1 week of randomisation (fast-track group) or to receive usual care for 8 weeks before receiving the intervention (wait-list group). Participants will remain in the study for a total of 16 weeks. Outcome measures will be feasibility outcomes, including recruitment, retention, acceptability and fidelity of the intervention. Clinical outcomes will be measured to inform outcome selection and sample size calculation for a definitive trial. Ethics and dissemination Yorkshire and The Humber – Bradford Leeds Research Ethics Committee approved the study protocol (REC 18/YH/0147). Results of the main trial and all secondary end-points will be submitted for publication in a peer-reviewed journal

Barriers and facilitators to uptake and retention of inner-city ethnically diverse women in a postnatal weight management intervention: a mixed-methods process evaluation within a feasibility trial in England.

OBJECTIVES: To understand the barriers and facilitators to uptake and retention of postnatal women randomised to a commercial group weight management intervention using the COM-B (capability, opportunity, motivation and behaviour) behaviour change model. DESIGN: Concurrent mixed-methods (qualitative dominant) process evaluation nested within a feasibility randomised controlled trial, comprising questionnaires and interviews at 6 and 12 months postbirth. SETTING: One National Health Service maternity unit in an inner city area in the south of England. PARTICIPANTS: 98 postnatal women with body mass indices>25 kg/m2 (overweight/obese) at pregnancy commencement. INTERVENTION: Twelve-week Slimming World (SW) commercial group weight management programme, commencing anytime from 8 to 16 weeks postnatally. PRIMARY AND SECONDARY OUTCOME MEASURES: Data regarding uptake and retention from questionnaires and interviews conducted 6 and 12 months postbirth analysed thematically and mapped to the COM-B model. RESULTS: Barriers to SW uptake mostly concerned opportunity issues (eg, lack of time or childcare support) though some women also lacked motivation, not feeling that weight reduction was a priority, and a few cited capability issues such as lacking confidence. Weight loss aspirations were also a key factor explaining retention, as were social opportunity issues, particularly in relation to factors such as the extent of group identity and relationship with the group consultant; and physical opportunity such as perceived support from and fit with family lifestyle. In addition, barriers relating to beliefs and expectations about the SW programme were identified, including concerns regarding compatibility with breastfeeding and importance of exercise. Women's understanding of the SW approach, and capability to implement into their lifestyles, appeared related to level of attendance (dose-response effect). CONCLUSIONS: Uptake and retention in commercial weight management programmes may be enhanced by applying behaviour change techniques to address the barriers impacting on women's perceived capability, motivation and opportunity to participate. TRIAL REGISTRATION NUMBER: ISRCTN39186148