6,077 research outputs found
Observation of sub-Poisson photon statistics in the cavity-QED microlaser
We have measured the second-order correlation function of the cavity-QED
microlaser output and observed a transition from photon bunching to
antibunching with increasing average number of intracavity atoms. The observed
correlation times and the transition from super- to sub-Poisson photon
statistics can be well described by gain-loss feedback or enhanced/reduced
restoring action against fluctuations in photon number in the context of a
quantum microlaser theory and a photon rate equation picture. However, the
theory predicts a degree of antibunching several times larger than that
observed, which may indicate the inadequacy of its treatment of atomic velocity
distributions.Comment: 4 pages, 4 figure
Qudit Quantum State Tomography
Recently quantum tomography has been proposed as a fundamental tool for
prototyping a few qubit quantum device. It allows the complete reconstruction
of the state produced from a given input into the device. From this
reconstructed density matrix, relevant quantum information quantities such as
the degree of entanglement and entropy can be calculated. Generally orthogonal
measurements have been discussed for this tomographic reconstruction. In this
paper, we extend the tomographic reconstruction technique to two new regimes.
First we show how non-orthogonal measurement allow the reconstruction of the
state of the system provided the measurements span the Hilbert space. We then
detail how quantum state tomography can be performed for multi qudits with a
specific example illustrating how to achieve this in one and two qutrit
systems.Comment: 6 pages, 4 figures, submitted to PR
The mixing of two-pion and vector-meson states using staggered fermions
In this study we employ staggered fermions to calculate the two-pion taste
singlet states at rest. Leveraging the Clebsch-Gordan coefficients of the
symmetry group associated with staggered fermions, we effectively compute the
contributions to the resting -meson correlator. To discern the
distinct energy states involved, we adopt a generalized eigenvalue
problem-solving approach. This work will provide insight into the important
role played by the two-pion contribution to the anomalous magnetic moment of
the muon.
In this paper we present our group theoretic considerations and preliminary
results on the contribution of two-pion states to the rho meson correlation
function.Comment: 8 pages, 2 tables, 5 figure
Epistasis with HLA DR3 implicates the P2X7 receptor in the pathogenesis of primary Sjögren's syndrome
Introduction: The aim of this study was to examine the association between functional polymorphisms in the proinflammatory P2X7 receptor and the Ro/La autoantibody response in primary Sjögren's syndrome (pSS). Methods: Twelve functional P2RX7 polymorphisms were genotyped in 114 pSS patients fulfilling the Revised American-European Consensus Criteria for pSS, and 136 controls. Genotyping of the A1405G (rs2230912) polymorphism was performed on a replication cohort consisting of 281 pSS patients and 534 controls. P2X7 receptor function in lymphocytes and monocytes was assessed by measurement of ATP-induced ethidium+ uptake. Serum IL-18 levels were determined by ELISA. Results: The minor allele of P2RX7 A1405G is a tag for a common haplotype associated with gain in receptor function, as assessed by ATP-induced ethidium+ uptake. A positive association between 1405G and anti-Ro±La seropositive pSS patients was observed in Cohort 1. Although not replicated in Cohort 2, there was a consistent, significant, negative epistatic interaction effect with HLA-DR3 in seropositive pSS patients from both cohorts, thereby implicating this gain of function variant in the pathogenesis of pSS. Serum IL-18 was elevated in seropositive pSS patients, but was not influenced by P2RX7 A1405G. Conclusions: The P2RX7 1405G gain-of-function haplotype may be a risk factor for seropositive pSS in a subset of subjects who do not carry HLA risk alleles, but has no effect in subjects who do (epistasis). Potential mechanisms relate to autoantigen exposure and inflammatory cytokine expression. The observed elevation of IL-18 levels is consistent with P2X7 receptor activation in seropositive pSS patients. Collectively these findings implicate P2X7 receptor function in the pathogenesis of pSS
Improving Effective Surgical Delivery in Humanitarian Disasters: Lessons from Haiti
Kathryn Chu and colleagues describe the experiences of Médecins sans Frontières after the 2010 Haiti earthquake, and discuss how to improve delivery of surgery in humanitarian disasters
Effect of Strain on the Growth of InAs/GaSb Superlattices: An X-Ray Study
We present a detailed x-ray diffraction study of the strain in InAs/GaSb
superlattices grown by molecular beam epitaxy. The superlattices were grown
with either InSb or GaAs interfaces. We show that the superlattice morphology,
either planar or nanostructured, is dependent on the chemical bonds at the
heterointerfaces. In both cases, the misfit strain has been determined for the
superlattice layers and the interfaces. We also determined how the magnitude
and sign of this strain is crucial in governing the morphology of the
superlattice. Our analysis suggests that the growth of self-assembled
nanostructures may be extended to many systems generally thought to have too
small a lattice mismatch.Comment: 40 pages, 14 figures, 2 tables. Submitted to Journal of Applied
Physics in November 200
Witnessing effective entanglement in a continuous variable prepare&measure setup and application to a QKD scheme using postselection
We report an experimental demonstration of effective entanglement in a
prepare&measure type of quantum key distribution protocol. Coherent
polarization states and heterodyne measurement to characterize the transmitted
quantum states are used, thus enabling us to reconstruct directly their
Q-function. By evaluating the excess noise of the states, we experimentally
demonstrate that they fulfill a non-separability criterion previously presented
by Rigas et al. [J. Rigas, O. G\"uhne, N. L\"utkenhaus, Phys. Rev. A 73, 012341
(2006)]. For a restricted eavesdropping scenario we predict key rates using
postselection of the heterodyne measurement results.Comment: 12 pages, 12 figures, 2 table
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