Magnetic noise spectrum measurement by an atom laser in gravity

Bose-Einstein condensates of ultracold atoms can be used to sense fluctuations of the magnetic field by means of transitions into untrapped hyperfine states. It has been shown recently that counting the outcoupled atoms can yield the power spectrum of the magnetic noise. We calculate the spectral resolution function which characterizes the condensate as a noise measurement device in this scheme. We use the description of the radio-frequency outcoupling scheme of an atom laser which takes into account the gravitational acceleration. Employing both an intuitive and the exact three-dimensional and fully quantum mechanical approach we derive the position-dependent spectral resolution function for condensates of different size and shape

In situ characterization of an optical cavity using atomic light shift

We report the precise characterization of the optical potential obtained by injecting a distributed-feedback erbium-doped fiber laser (DFB EDFL) at 1560 nm to the transversal modes of a folded optical cavity. The optical potential was mapped in situ using cold rubidium atoms, whose potential energy was spectrally resolved thanks to the strong differential light shift induced by the 1560 nm laser on the two levels of the probe transition. The optical potential obtained in the cavity is suitable for trapping rubidium atoms, and eventually to achieve all-optical Bose-Einstein condensation directly in the resonator.Comment: 3 pages, 4 figure

Dynamical Coupling between a Bose-Einstein Condensate and a Cavity Optical Lattice

A Bose-Einstein condensate is dispersively coupled to a single mode of an ultra-high finesse optical cavity. The system is governed by strong interactions between the atomic motion and the light field even at the level of single quanta. While coherently pumping the cavity mode the condensate is subject to the cavity optical lattice potential whose depth depends nonlinearly on the atomic density distribution. We observe bistability already below the single photon level and strong back-action dynamics which tunes the system periodically out of resonance.Comment: 5 pages, 4 figure

Ethnic differences in the prevalence of inherited thrombophilic polymorphisms in an asymptomatic Australian prenatal population

Differences in the prevalence of thrombophilias in different ethnic populations have been demonstrated. Because the Australian population includes many different ethnic groups, we sought to assess the effect of ethnicity in our Australian prenatal population on the prevalence of thrombophilic polymorphisms. Asymptomatic, nulliparous women (n = 1,129) recruited for a large prospective study were included in this analysis. These women had no personal or family history of venous thromboembolism and were not known to be carrying an inherited or acquired thrombophilia. Ethnicity was determined at recruitment, and women were categorized as being of Northern European, Southern European, Middle Eastern, Asian, or Other ethnicity. These women underwent genotyping for the following polymorphisms: factor V Leiden G1691A, prothrombin gene A20210G mutation, methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C, and thrombomodulin C1418T. The factor V Leiden allele was seen significantly more frequently in patients of Middle Eastern background compared to those of Northern European and Asian ethnicity (p < 0.05). The prothrombin gene mutation was seen significantly more frequently in patients of Southern European ethnicity compared to those of Northern European or Asian ethnicity (p < 0.05). The MTHFR C677T allele (mutant) was significantly less common in those of Asian ethnicity compared to patients of Northern European and Southern European ethnicity (p < 0.0005). There were no significant differences seen with the MTHFR A1298C polymorphism. The mutant thrombomodulin allele was seen significantly more frequently in Asian women compared to Northern European, Southern European, or Middle Eastern women (p < 0.005). There are important ethnic differences in the prevalence of thrombophilic polymorphisms in the Australian prenatal population

A single Hox locus in Drosophila produces functional microRNAs from opposite DNA strands

MicroRNAs (miRNAs) are approximately 22-nucleotide RNAs that are processed from characteristic precursor hairpins and pair to sites in messages of protein-coding genes to direct post-transcriptional repression. Here, we report that the miRNA iab-4 locus in the Drosophila Hox cluster is transcribed convergently from both DNA strands, giving rise to two distinct functional miRNAs. Both sense and antisense miRNA products target neighboring Hox genes via highly conserved sites, leading to homeotic transformations when ectopically expressed. We also report sense/antisense miRNAs in mouse and find antisense transcripts close to many miRNAs in both flies and mammals, suggesting that additional sense/antisense pairs exist

Collapse and revival of oscillations in a parametrically excited Bose-Einstein condensate in combined harmonic and optical lattice trap

In this work, we study parametric resonances in an elongated cigar-shaped BEC in a combined harmonic trap and a time dependent optical lattice by using numerical and analytical techniques. We show that there exists a relative competition between the harmonic trap which tries to spatially localize the BEC and the time varying optical lattice which tries to delocalize the BEC. This competition gives rise to parametric resonances (collapse and revival of the oscillations of the BEC width). Parametric resonances disappear when one of the competing factors i.e strength of harmonic trap or the strength of optical lattice dominates. Parametric instabilities (exponential growth of Bogoliubov modes) arise for large variations in the strength of the optical lattice.Comment: 9 pages, 20 figure

Dynamics of a bistable Mott insulator to superfluid phase transition in cavity optomechanics

We study the dynamics of the many-body state of ultracold bosons trapped in a bistable optical lattice in an optomechanical resonator controlled by a time-dependent input field. We focus on the dynamics of the many-body system following discontinuous jumps of the intracavity field. We identify experimentally realizable parameters for the bistable quantum phase transition between Mott insulator and superfluid.Comment: 6 pages, 5 figure

Kinematically complete experimental study of Compton scattering at helium atoms near the ionization threshold

Compton scattering is one of the fundamental interaction processes of light with matter. Already upon its discovery [1] it was described as a billiard-type collision of a photon kicking a quasi-free electron. With decreasing photon energy, the maximum possible momentum transfer becomes so small that the corresponding energy falls below the binding energy of the electron. Then ionization by Compton scattering becomes an intriguing quantum phenomenon. Here we report a kinematically complete experiment on Compton scattering at helium atoms below that threshold. We determine the momentum correlations of the electron, the recoiling ion, and the scattered photon in a coincidence experiment finding that electrons are not only emitted in the direction of the momentum transfer, but that there is a second peak of ejection to the backward direction. This finding links Compton scattering to processes as ionization by ultrashort optical pulses [2], electron impact ionization [3,4], ion impact ionization [5,6], and neutron scattering [7] where similar momentum patterns occur.Comment: 7 pages, 4 figure

Generalised quantum weakest preconditions

Generalisation of the quantum weakest precondition result of D'Hondt and Panangaden is presented. In particular the most general notion of quantum predicate as positive operator valued measure (POVM) is introduced. The previously known quantum weakest precondition result has been extended to cover the case of POVM playing the role of a quantum predicate. Additionally, our result is valid in infinite dimension case and also holds for a quantum programs defined as a positive but not necessary completely positive transformations of a quantum states.Comment: 7 pages, no figures, added references, changed conten