34,415 research outputs found
Entangling two atoms in spatially separated cavities through both photon emission and absorption processes
We consider a system consisting of a -type atom and a V-type atom,
which are individually trapped in two spatially separated cavities that are
connected by an optical fibre. We show that an extremely entangled state of the
two atoms can be deterministically generated through both photon emission of
the -type atom and photon absorption of the V-type atom in an ideal
situation. The influence of various decoherence processes such as spontaneous
emission and photon loss on the fidelity of the entangled state is also
investigated. We find that the effect of photon leakage out of the fibre on the
fidelity can be greatly diminished in some special cases. As regards the effect
of spontaneous emission and photon loss from the cavities, we find that the
present scheme with a fidelity higher than 0.98 may be realized under current
experiment conditions.Comment: 12 pages, 4 figure
Controlled generation of field squeezing with cold atomic clouds coupled to a superconducting transmission line resonator
We propose an efficient method for controlled generation of field squeezing
with cold atomic clouds trapped close to a superconducting transmission line
resonator. It is shown that, based on the coherent strong magnetic coupling
between the collective atomic spins and microwave fields in the transmission
line resonator, two-mode or single mode field squeezed states can be generated
through coherent control on the dynamics of the system. The degree of squeezing
and preparing time can be directly controlled through tuning the external
classical fields. This protocol may offer a promising platform for implementing
scalable on-chip quantum information processing with continuous variables.Comment: accepted by Phys. Rev.
The gene expression data of Mycobacterium tuberculosis based on Affymetrix gene chips provide insight into regulatory and hypothetical genes
<p>Abstract</p> <p>Background</p> <p>Tuberculosis remains a leading infectious disease with global public health threat. Its control and management have been complicated by multi-drug resistance and latent infection, which prompts scientists to find new and more effective drugs. With the completion of the genome sequence of the etiologic bacterium, <it>Mycobacterium tuberculosis</it>, it is now feasible to search for new drug targets by sieving through a large number of gene products and conduct genome-scale experiments based on microarray technology. However, the full potential of genome-wide microarray analysis in configuring interrelationships among all genes in <it>M. tuberculosis </it>has yet to be realized. To date, it is only possible to assign a function to 52% of proteins predicted in the genome.</p> <p>Results</p> <p>We conducted a functional-genomics study using the high-resolution Affymetrix oligonucleotide GeneChip. Approximately one-half of the genes were found to be always expressed, including more than 100 predicted conserved hypotheticals, in the genome of <it>M. tuberculosis </it>during the log phase of in vitro growth. The gene expression profiles were analyzed and visualized through cluster analysis to epitomize the full details of genomic behavior. Broad patterns derived from genome-wide expression experiments in this study have provided insight into the interrelationships among genes in the basic cellular processes of <it>M. tuberculosis</it>.</p> <p>Conclusion</p> <p>Our results have confirmed several known gene clusters in energy production, information pathways, and lipid metabolism, and also hinted at potential roles of hypothetical and regulatory proteins.</p
Multiatom and resonant interaction scheme for quantum state transfer and logical gates between two remote cavities via an optical fiber
A system consisting of two single-mode cavities spatially separated and
connected by an optical fiber and multiple two-level atoms trapped in the
cavities is considered. If the atoms resonantly and collectively interact with
the local cavity fields but there is no direct interaction between the atoms,
we show that an ideal quantum state transfer and highly reliable quantum swap,
entangling, and controlled-Z gates can be deterministically realized between
the distant cavities. We find that the operation of state transfer and swap,
entangling, and controlled-Z gates can be greatly speeded up as number of the
atoms in the cavities increases. We also notice that the effects of spontaneous
emission of atoms and photon leakage out of cavity on the quantum processes can
also be greatly diminished in the multiatom case.Comment: 24 pages, 8 figures; Corrected typos in fig6(b),(c) and references;
Adding disscussion on experimental feasibility in the last section. Accepted
for PR
Branching ratios and direct CP asymmetries in decays
We propose a theoretical framework for analyzing two-body nonleptonic
meson decays, based on the factorization of short-distance (long-distance)
dynamics into Wilson coefficients (hadronic matrix elements of four-fermion
operators). The parametrization of hadronic matrix elements in terms of several
nonperturbative quantities is demonstrated for the decays,
denoting a pseudoscalar meson. We consider the evolution of Wilson coefficients
with energy release in individual decay modes, and the Glauber strong phase
associated with the pion in nonfactorizable annihilation amplitudes, that is
attributed to the unique role of the pion as a Nambu-Goldstone boson and a
quark-anti-quark bound state simultaneously. The above inputs improve the
global fit to the branching ratios involving the meson, and resolves
the long-standing puzzle from the and
branching ratios, respectively. Combining short-distance dynamics associated
with penguin operators and the hadronic parameters determined from the global
fit to branching ratios, we predict direct CP asymmetries, to which the quark
loops and the scalar penguin annihilation give dominant contributions. In
particular, we predict , lower than the LHCb and CDF data.Comment: 17 pages, 3 figures, matches published versio
Evaluation of gene importance in microarray data based upon probability of selection
BACKGROUND: Microarray devices permit a genome-scale evaluation of gene function. This technology has catalyzed biomedical research and development in recent years. As many important diseases can be traced down to the gene level, a long-standing research problem is to identify specific gene expression patterns linking to metabolic characteristics that contribute to disease development and progression. The microarray approach offers an expedited solution to this problem. However, it has posed a challenging issue to recognize disease-related genes expression patterns embedded in the microarray data. In selecting a small set of biologically significant genes for classifier design, the nature of high data dimensionality inherent in this problem creates substantial amount of uncertainty. RESULTS: Here we present a model for probability analysis of selected genes in order to determine their importance. Our contribution is that we show how to derive the P value of each selected gene in multiple gene selection trials based on different combinations of data samples and how to conduct a reliability analysis accordingly. The importance of a gene is indicated by its associated P value in that a smaller value implies higher information content from information theory. On the microarray data concerning the subtype classification of small round blue cell tumors, we demonstrate that the method is capable of finding the smallest set of genes (19 genes) with optimal classification performance, compared with results reported in the literature. CONCLUSION: In classifier design based on microarray data, the probability value derived from gene selection based on multiple combinations of data samples enables an effective mechanism for reducing the tendency of fitting local data particularities
Demonstration of Deutsch's Algorithm on a Stable Linear-Optical Quantum Computer
We report an experimental demonstration of quantum Deutsch's algorithm by
using linear-optical system. By employing photon's polarization and spatial
modes, we implement all balanced and constant functions for quantum computer.
The experimental system is very stable and the experimental data are excellent
in accordance with the theoretical results.Comment: 7 pages, 4 figure
Faithful qubit transmission against collective noise without ancillary qubits
We present a faithful qubit transmission scheme with linear optics against
collective noise, not resorting to ancillary qubits. Its set-up is composed of
three unbalanced polarization interferometers, based on a polarizing beam
splitter, a beam splitter and a half-wave plate, which makes this scheme more
feasible than others with present technology. The fidelity of successful
transmission is 1, independent of the parameters of the collective noise, and
the success probability for obtaining an uncorrupted state can be improved to
100% with some time delayers. Moreover, this scheme has some good applications
in one-way quantum communication for rejecting the errors caused by the
collective noise in quantum channel.Comment: 3 pages, 1 figur
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