282,034 research outputs found
First-order coherence versus entanglement in a nano-mechanical cavity
The coherence and correlation properties of effective bosonic modes of a
nano-mechanical cavity composed of an oscillating mirror and containing an
optical lattice of regularly trapped atoms are studied. The system is modeled
as a three-mode system, two orthogonal polariton modes representing the coupled
optical lattice and the cavity mode, and one mechanical mode representing the
oscillating mirror. We examine separately the cases of two-mode and three-mode
interactions which are distinguished by a suitable tuning of the mechanical
mode to the polariton mode frequencies. In the two-mode case, we find that the
occurrence of entanglement between one of the polariton modes and the
mechanical mode is highly sensitive to the presence of the first-order
coherence between the modes. In particular, the creation of the first-order
coherence among the modes is achieved at the expense of entanglement between
the modes. In the three-mode case, we show that no entanglement is created
between the independent polariton modes if both modes are coupled to the
mechanical mode by the parametric interaction. There is no entanglement between
the polaritons even if the oscillating mirror is damped by a squeezed vacuum
field. The interaction creates the first-order coherence between the polaritons
and the degree of coherence can, in principle, be as large as unity. This
demonstrates that the oscillating mirror can establish the first-order
coherence between two independent thermal modes. A further analysis shows that
two independent thermal modes can be made entangled in the system only when one
of the modes is coupled to the intermediate mode by a parametric interaction
and the other is coupled by a linear-mixing interaction.Comment: Published versio
Global well-posedness for the Gross-Pitaevskii equation with an angular momentum rotational term in three dimensions
In this paper, we establish the global well-posedness of the Cauchy problem
for the Gross-Pitaevskii equation with an angular momentum rotational term in
which the angular velocity is equal to the isotropic trapping frequency in the
space \Real^3.Comment: 11 page
Universal contact and collective excitations of a strongly interacting Fermi gas
We study the relationship between Tan's contact parameter and the macroscopic
dynamic properties of an ultracold trapped gas, such as the frequencies of the
collective oscillations and the propagation of sound in one-dimensional (1D)
configurations. We find that the value of the contact, extracted from the most
recent low-temperature measurements of the equation of state near unitarity,
reproduces with accuracy the experimental values of the collective frequencies
of the radial breathing mode at the lowest temperatures. The available
experiment results for the 1D sound velocities near unitarity are also
investigated.Comment: 5 pages, 3 figure
The Precise Formula in a Sine Function Form of the norm of the Amplitude and the Necessary and Sufficient Phase Condition for Any Quantum Algorithm with Arbitrary Phase Rotations
In this paper we derived the precise formula in a sine function form of the
norm of the amplitude in the desired state, and by means of he precise formula
we presented the necessary and sufficient phase condition for any quantum
algorithm with arbitrary phase rotations. We also showed that the phase
condition: identical rotation angles, is a sufficient but not a necessary phase
condition.Comment: 16 pages. Modified some English sentences and some proofs. Removed a
table. Corrected the formula for kol on page 10. No figure
Sexually transmitted infection testing and self-reported diagnoses among a community sample of men who have sex with men, in Scotland
Introduction To examine sexually transmitted infection (STI) testing and self-reported diagnoses among men who have sex with men (MSM), in Scotland.
Methods Cross-sectional survey of seven Glasgow gay bars in July 2010 (n=822, 62% response rate); 693 are included in the analyses.
Results 81.8% reported ever having had an STI test; 37.4% had tested in the previous 6 months; 13.2% reported having an STI in the previous 12 months. The adjusted odds of having ever tested were significantly higher for men who had 6+ sexual partners in the previous 12 months (adjusted OR=2.66), a maximum sexual health knowledge score (2.23), and had talked to an outreach worker/participated in counselling (1.96), and lower for men reporting any high-risk unprotected anal intercourse (UAI) in the previous 12 months (0.51). Adjusted odds of recent testing were higher for men who had 6+ sexual partners (2.10), talked to an outreach worker/participated in counselling (1.66), maximum sexual health knowledge (1.59), and higher condom use knowledge (1.04), and lower for men aged ≥25 years (0.46). Adjusted odds of having had an STI in the previous 12 months were higher for men who had 6+ sexual partners (3.96) and any high-risk UAI in the previous 12 months (2.24) and lower for men aged ≥25 years (0.57).
Conclusions STI testing rates were relatively high, yet still below the minimum recommended for MSM at high risk. Consideration should be given to initiating recall systems for men who test positive for STIs, and to developing behavioural interventions which seek to address STI transmission
Ratcheting Heat Flux against a Thermal Bias
Merely rocking the temperature in one heat bath can direct a steady heat flux
from cold to hot against a non-zero thermal bias in stylized nonlinear lattice
junctions that are sandwiched between two heat baths. Likewise, for an average
zero-temperature difference between the two contacts a net, ratchet-like heat
flux emerges. Computer simulations show that this very heat flux can be
controlled and reversed by suitably tailoring the frequency ( 100
MHz) of the alternating temperature field.Comment: 5 pages, 6 figure
Cusp Summations and Cusp Relations of Simple Quad Lenses
We review five often used quad lens models, each of which has analytical
solutions and can produce four images at most. Each lens model has two
parameters, including one that describes the intensity of non-dimensional mass
density, and the other one that describes the deviation from the circular lens.
In our recent work, we have found that the cusp and the fold summations are not
equal to 0, when a point source infinitely approaches a cusp or a fold from
inner side of the caustic. Based on the magnification invariant theory, which
states that the sum of signed magnifications of the total images of a given
source is a constant, we calculate the cusp summations for the five lens
models. We find that the cusp summations are always larger than 0 for source on
the major cusps, while can be larger or smaller than 0 for source on the minor
cusps. We also find that if these lenses tend to the circular lens, the major
and minor cusp summations will have infinite values, and with positive and
negative signs respectively. The cusp summations do not change significantly if
the sources are slightly deviated from the cusps. In addition, through the
magnification invariants, we also derive the analytical signed cusp relations
on the axes for three lens models. We find that both on the major and the minor
axes the larger the lenses deviated from the circular lens, the larger the
signed cusp relations. The major cusp relations are usually larger than the
absolute minor cusp relations, but for some lens models with very large
deviation from circular lens, the minor cusp relations can be larger than the
major cusp relations.Comment: 8 pages, 4 figures, accepted for publication in MNRA
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