33 research outputs found
Improvement of conversion efficiency of atom-molecule Bose-Einstein condensate
We investigate the stimulated Raman adiabatic passage in two-color
photoassociation for a atom-molecule Bose-Einstein condensate. By applying two
time-varying Guassian laser pulses that fulfill generalized two-photon
resonance condition, we obtain highly efficient atom-molecule conversion. The
efficiency depends on the free-bound detuning and the delay time between the
two pulses. By adjusting the parameters optimally, we achieve 92% conversion
efficiency.Comment: 4 pages, 4 figures. To be appeared in J. Korean Phys. Society (JKPS
Storage of spin squeezing in a two-component Bose-Einstein condensate
Efficient control of spin squeezing in a two-component Bose-Einstein
Condensate is studied by rapidly turning-off the external field at a time that
maximal spin squeezing appears. We show that strong reduction of spin
fluctuation can be maintained in a nearly fixed direction for a long time. We
explain the underlying physics unambiguously, and present analytical
expressions of the maximal-squeezing time.Comment: 10 pages, 5 figures. This version is slightly different from the one
published in Phys. Rev. Let
Spin squeezing and maximal-squeezing time
Spin squeezing of a nonlinear interaction model with Josephson-like coupling
is studied to obtain time scale of maximal squeezing. Based upon two exactly
solvable cases for two and three particles, we find that the maximal-squeezing
time depends on the level spacing between the ground state and its next
neighbor eigenstate.Comment: 7 pages, 5 figures, 1 table. Resubmitted to Phys. Rev.
Electromagnetically induced transparency in an atom-molecule Bose-Einstein condensate
We propose a new measurement scheme for the atom-molecule dark state by using
electromagnetically induced transparency (EIT) technique. Based on a
density-matrix formalism, we calculate the absorption coefficient numerically.
The appearance of the EIT dip in the spectra profile gives clear evidence for
the creation of the dark state in the atom-molecule Bose-Einstein condensate.Comment: 3.7pages, 4 figure
Modulational instability of two-component Bose-Einstein condensates in an optical lattice
We study modulational instability of two-component Bose-Einstein condensates
in an optical lattice, which is modelled as a coupled discrete nonlinear Schr
\"{o}dinger equation. The excitation spectrum and the modulational instability
condition of the total system are presented analytically. In the
long-wavelength limit, our results agree with the homogeneous two-component
Bose-Einstein condensates case. The discreteness effects result in the
appearance of the modulational instability for the condensates in miscible
region. The numerical calculations confirm our analytical results and show that
the interspecies coupling can transfer the instability from one component to
another.Comment: 4 pages, 3 figures (to be published in Phys. Rev. A
Collapses and revivals of exciton emission in a semiconductor microcavity: detuning and phase-space filling effects
We investigate exciton emission of quantum well embedded in a semiconductor
microcavity. The analytical expressions of the light intensity for the cases of
excitonic number state and coherent state are presented by using secular
approximation. Our results show that the effective exciton-exciton interaction
leads to the appearance of collapse and revival of the light intensity. The
revival time is twice compared the coherent state case with that of the number
state. The dissipation of the exciton-polariton lowers the revival amplitude
but does not alter the revival time. The influences of the detuning and the
phase-space filling are studied. We find that the effect of the higher-order
exciton-photon interaction may be removed by adjusting the detuning.Comment: 7 pages, 3 figure
Semiconductor-cavity QED in high-Q regimes: Detuning effect
The non-resonant interaction between the high-density excitons in a quantum
well and a single mode cavity field is investigated. An analytical expression
for the physical spectrum of the excitons is obtained. The spectral properties
of the excitons, which are initially prepared in the number states or the
superposed states of the two different number states by the resonant
femtosecond pulse pumping experiment, are studied. Numerical study of the
physical spectrum is carried out and a discussion of the detuning effect is
presented.Comment: 7 pages, 8 figure
Genome Sequencing and Comparative Transcriptomics of the Model Entomopathogenic Fungi Metarhizium anisopliae and M. acridum
Metarhizium spp. are being used as environmentally friendly alternatives to chemical insecticides, as model systems for studying insect-fungus interactions, and as a resource of genes for biotechnology. We present a comparative analysis of the genome sequences of the broad-spectrum insect pathogen Metarhizium anisopliae and the acridid-specific M. acridum. Whole-genome analyses indicate that the genome structures of these two species are highly syntenic and suggest that the genus Metarhizium evolved from plant endophytes or pathogens. Both M. anisopliae and M. acridum have a strikingly larger proportion of genes encoding secreted proteins than other fungi, while ∼30% of these have no functionally characterized homologs, suggesting hitherto unsuspected interactions between fungal pathogens and insects. The analysis of transposase genes provided evidence of repeat-induced point mutations occurring in M. acridum but not in M. anisopliae. With the help of pathogen-host interaction gene database, ∼16% of Metarhizium genes were identified that are similar to experimentally verified genes involved in pathogenicity in other fungi, particularly plant pathogens. However, relative to M. acridum, M. anisopliae has evolved with many expanded gene families of proteases, chitinases, cytochrome P450s, polyketide synthases, and nonribosomal peptide synthetases for cuticle-degradation, detoxification, and toxin biosynthesis that may facilitate its ability to adapt to heterogenous environments. Transcriptional analysis of both fungi during early infection processes provided further insights into the genes and pathways involved in infectivity and specificity. Of particular note, M. acridum transcribed distinct G-protein coupled receptors on cuticles from locusts (the natural hosts) and cockroaches, whereas M. anisopliae transcribed the same receptor on both hosts. This study will facilitate the identification of virulence genes and the development of improved biocontrol strains with customized properties