500 research outputs found
Homodyne Measurements on a Bose-Einstein Condensate
We investigate a non-destructive measurement technique to monitor
Josephson-like oscillations between two spatially separated neutral atom
Bose-Einstein condensates. One condensate is placed in an optical cavity, which
is strongly driven by a coherent optical field. The cavity output field is
monitored using a homodyne detection scheme. The cavity field is well detuned
from an atomic resonance, and experiences a dispersive phase shift proportional
to the number of atoms in the cavity. The detected current is modulated by the
coherent tunneling oscillations of the condensate. Even when there is an equal
number of atoms in each well initially, a phase is established by the
measurement process and Josephson-like oscillations develop due to measurement
back-action noise alone.Comment: 8 pages, 12 figures to appear in PR
Natural Language Processing for Drug Discovery Knowledge Graphs: promises and pitfalls
Building and analysing knowledge graphs (KGs) to aid drug discovery is a
topical area of research. A salient feature of KGs is their ability to combine
many heterogeneous data sources in a format that facilitates discovering
connections. The utility of KGs has been exemplified in areas such as drug
repurposing, with insights made through manual exploration and modelling of the
data. In this article, we discuss promises and pitfalls of using natural
language processing (NLP) to mine unstructured text typically from scientific
literature as a data source for KGs. This draws on our experience of initially
parsing structured data sources such as ChEMBL as the basis for data within a
KG, and then enriching or expanding upon them using NLP. The fundamental
promise of NLP for KGs is the automated extraction of data from millions of
documents a task practically impossible to do via human curation alone.
However, there are many potential pitfalls in NLP-KG pipelines such as
incorrect named entity recognition and ontology linking all of which could
ultimately lead to erroneous inferences and conclusions.Comment: 17 pages, 7 figure
Weak force detection using a double Bose-Einstein condensate
A Bose-Einstein condensate may be used to make precise measurements of weak
forces, utilizing the macroscopic occupation of a single quantum state. We
present a scheme which uses a condensate in a double well potential to do this.
The required initial state of the condensate is discussed, and the limitations
on the sensitivity due to atom collisions and external coupling are analyzed.Comment: 12 pages, 2 figures, Eq.(41) has been correcte
Rapid identification of some Leptospira isolates from cattle by random amplified polymorphic DNA fingerprinting
We compared random amplified polymorphic DNA (RAPD) fingerprinting with cross-absorption agglutination and restriction enzyme analysis for typing bovine leptospires. Using RAPD fingerprinting, we examined a number of Leptospira serovars, namely, hardjo genotypes bovis and prajitno, pomona, balcanica, tarassovi, swajizak, kremastos, australis, and zanoni, which are likely to be isolated from Australian cattle. Each serovar and genotype had a unique RAPD profile. Of 26 field isolates of Leptospira, 23 were identified as hardjo genotype bovis subtype A, 2 were identified as zanoni, and 1 was identified as pomona by RAPD fingerprinting, and their types were confirmed by cross-absorption agglutination and restriction enzyme analysis
Two-dimensional Nanolithography Using Atom Interferometry
We propose a novel scheme for the lithography of arbitrary, two-dimensional
nanostructures via matter-wave interference. The required quantum control is
provided by a pi/2-pi-pi/2 atom interferometer with an integrated atom lens
system. The lens system is developed such that it allows simultaneous control
over atomic wave-packet spatial extent, trajectory, and phase signature. We
demonstrate arbitrary pattern formations with two-dimensional 87Rb wavepackets
through numerical simulations of the scheme in a practical parameter space.
Prospects for experimental realizations of the lithography scheme are also
discussed.Comment: 36 pages, 4 figure
Covariant spinor representation of and quantization of the spinning relativistic particle
A covariant spinor representation of is constructed for the
quantization of the spinning relativistic particle. It is found that, with
appropriately defined wavefunctions, this representation can be identified with
the state space arising from the canonical extended BFV-BRST quantization of
the spinning particle with admissible gauge fixing conditions after a
contraction procedure. For this model, the cohomological determination of
physical states can thus be obtained purely from the representation theory of
the algebra.Comment: Updated version with references included and covariant form of
equation 1. 23 pages, no figure
A quantitative study of spin noise spectroscopy in a classical gas of K atoms
We present a general derivation of the electron spin noise power spectrum in
alkali gases as measured by optical Faraday rotation, which applies to both
classical gases at high temperatures as well as ultracold quantum gases. We
show that the spin-noise power spectrum is determined by an electron spin-spin
correlation function, and we find that measurements of the spin-noise power
spectra for a classical gas of K atoms are in good agreement with the
predicted values. Experimental and theoretical spin noise spectra are directly
and quantitatively compared in both longitudinal and transverse magnetic fields
up to the high magnetic field regime (where Zeeman energies exceed the
intrinsic hyperfine energy splitting of the K ground state)
Quantum Dynamics of Three Coupled Atomic Bose-Einstein Condensates
The simplest model of three coupled Bose-Einstein Condensates (BEC) is
investigated using a group theoretical method. The stationary solutions are
determined using the SU(3) group under the mean field approximation. This
semiclassical analysis using the system symmetries shows a transition in the
dynamics of the system from self trapping to delocalization at a critical value
for the coupling between the condensates. The global dynamics are investigated
by examination of the stable points and our analysis shows the structure of the
stable points depends on the ratio of the condensate coupling to the
particle-particle interaction, undergoes bifurcations as this ratio is varied.
This semiclassical model is compared to a full quantum treatment, which also
displays the dynamical transition. The quantum case has collapse and revival
sequences superposed on the semiclassical dynamics reflecting the underlying
discreteness of the spectrum. Non-zero circular current states are also
demonstrated as one of the higher dimensional effects displayed in this system.Comment: Accepted to PR
An Improved Experimental Limit on the Electric Dipole Moment of the Neutron
An experimental search for an electric-dipole moment (EDM) of the neutron has
been carried out at the Institut Laue-Langevin (ILL), Grenoble. Spurious
signals from magnetic-field fluctuations were reduced to insignificance by the
use of a cohabiting atomic-mercury magnetometer. Systematic uncertainties,
including geometric-phase-induced false EDMs, have been carefully studied. Two
independent approaches to the analysis have been adopted. The overall results
may be interpreted as an upper limit on the absolute value of the neutron EDM
of |d_n| < 2.9 x 10^{-26} e cm (90% CL).Comment: 5 pages, 2 figures. The published PRL is slightly more terse (e.g. no
section headings) than this version, due to space constraints. Note a small
correction-to-a-correction led to an adjustment of the final limit from 3.0
to 2.9 E-26 e.cm compared to the first version of this preprin
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