245 research outputs found
Flux Qubits and Readout Device with Two Independent Flux Lines
We report measurements on two superconducting flux qubits coupled to a
readout Superconducting QUantum Interference Device (SQUID). Two on-chip flux
bias lines allow independent flux control of any two of the three elements, as
illustrated by a two-dimensional qubit flux map. The application of microwaves
yields a frequency-flux dispersion curve for 1- and 2-photon driving of the
single-qubit excited state, and coherent manipulation of the single-qubit state
results in Rabi oscillations and Ramsey fringes. This architecture should be
scalable to many qubits and SQUIDs on a single chip.Comment: 5 pages, 4 figures, higher quality figures available upon request.
Submitted to PR
Genomic Data Reveal Conserved Female Heterogamety in Giant Salamanders with Gigantic Nuclear Genomes
A grant from the One-University Open Access Fund at the University of Kansas was used to defray the author's publication fees in this Open Access journal. The Open Access Fund, administered by librarians from the KU, KU Law, and KUMC libraries, is made possible by contributions from the offices of KU Provost, KU Vice Chancellor for Research & Graduate Studies, and KUMC Vice Chancellor for Research. For more information about the Open Access Fund, please see http://library.kumc.edu/authors-fund.xml.Systems of genetic sex determination and the homology of sex chromosomes in different taxa vary greatly across vertebrates. Much progress remains to be made in understanding systems of genetic sex determination in non-model organisms, especially those with homomorphic sex chromosomes and/or large genomes. We used reduced representation genome sequencing to investigate genetic sex determination systems in the salamander family Cryptobranchidae (genera Cryptobranchus and Andrias), which typifies both of these inherent difficulties. We tested hypotheses of male- or female-heterogamety by sequencing hundreds of thousands of anonymous genomic regions in a panel of known-sex cryptobranchids and characterized patterns of presence/absence, inferred zygosity, and depth of coverage to identify sex-linked regions of these 56 gigabase genomes. Our results strongly support the hypothesis that all cryptobranchid species possess homologous systems of female heterogamety, despite maintenance of homomorphic sex chromosomes over nearly 60 million years. Additionally, we report a robust, non-invasive genetic assay for sex diagnosis in Cryptobranchus and Andrias which may have great utility for conservation efforts with these endangered salamanders. Co-amplification of these W-linked markers in both cryptobranchid genera provides evidence for long-term sex chromosome stasis in one of the most divergent salamander lineages. These findings inform hypotheses about the ancestral mode of sex determination in salamanders, but suggest that comparative data from other salamander families are needed. Our results further demonstrate that massive genomes are not necessarily a barrier to effective genome-wide sequencing and that the resulting data can be highly informative about sex determination systems in taxa with homomorphic sex chromosomes.Cryptobranchid Interest GroupFresno Chaffee ZooSaint Louis Zoo WildCare InstituteUniversity of Kentucky G.F. Ribble FundNational Science Foundation (DEB-0949532 to D.W.W. and DGE-3048109801 to P.M.H.
Entangling flux qubits with a bipolar dynamic inductance
We propose a scheme to implement variable coupling between two flux qubits
using the screening current response of a dc Superconducting QUantum
Interference Device (SQUID). The coupling strength is adjusted by the current
bias applied to the SQUID and can be varied continuously from positive to
negative values, allowing cancellation of the direct mutual inductance between
the qubits. We show that this variable coupling scheme permits efficient
realization of universal quantum logic. The same SQUID can be used to determine
the flux states of the qubits.Comment: 4 pages, 4 figure
A Natural Framework for Solar and 17 keV Neutrinos
Motivated by recent experimental claims for the existence of a 17 keV
neutrino and by the solar neutrino problem, we construct a class of models
which contain in their low-energy spectrum a single light sterile neutrino and
one or more Nambu-Goldstone bosons. In these models the required pattern of
breaking of lepton-number symmetry takes place near the electroweak scale and
all mass heirarchies are technically natural. The models are compatible with
all cosmological and astrophysical constraints, and can solve the solar
neutrino problem via either the MSW effect or vacuum oscillations. The deficit
in atmospheric muon neutrinos seen in the Kamiokande and IMB detectors can also
be explained in these models.Comment: 23 page
Systematic Study of Fermion Masses and Mixing Angles in Horizontal SU(2) Gauge Theory
Despite its great success in explaining the basic interactions of nature, the
standard model suffers from an inability to explain the observed masses of the
fundamental particles and the weak mixing angles between them. We shall survey
a set of possible extensions to the standard model, employing an SU(2)
``horizontal'' gauge symmetry between the particle generations, to see what
light they can shed on this problem.Comment: 43 pages, 4 figures (available by postal mail on request), OZ-92/0
Scintillation Pulse Shape Discrimination in a Two-Phase Xenon Time Projection Chamber
The energy and electric field dependence of pulse shape discrimination in
liquid xenon have been measured in a 10 gm two-phase xenon time projection
chamber. We have demonstrated the use of the pulse shape and charge-to-light
ratio simultaneously to obtain a leakage below that achievable by either
discriminant alone. A Monte Carlo is used to show that the dominant fluctuation
in the pulse shape quantity is statistical in nature, and project the
performance of these techniques in larger detectors. Although the performance
is generally weak at low energies relevant to elastic WIMP recoil searches, the
pulse shape can be used in probing for higher energy inelastic WIMP recoils.Comment: 7 pages, 11 figure
Constraints on radiative decay of the 17-keV neutrino from COBE Measurements
It is shown that, for a nontrivial radiative decay channel of the 17-keV
neutrino, the photons would distort the microwave background radiation through
ionization of the universe. The constraint on the branching ratio of such
decays from COBE measurements is found to be more stringent than that from
other considerations. The limit on the branching ratio in terms of the Compton
parameter is for an
universe.Comment: 7 pages. (figures will be sent on request) (To appear in Phys. Rev.
D.
Planck scale effects in neutrino physics
We study the phenomenology and cosmology of the Majoron (flavon) models of
three active and one inert neutrino paying special attention to the possible
(almost) conserved generalization of the Zeldovich-Konopinski-Mahmoud lepton
charge. Using Planck scale physics effects which provide the breaking of the
lepton charge, we show how in this picture one can incorporate the solutions to
some of the central issues in neutrino physics such as the solar and
atmospheric neutrino puzzles, dark matter and a 17 keV neutrino. These
gravitational effects induce tiny Majorana mass terms for neutrinos and
considerable masses for flavons. The cosmological demand for the sufficiently
fast decay of flavons implies a lower limit on the electron neutrino mass in
the range of 0.1-1 eV.Comment: 24 pages, 1 figure (not included but available upon request), LaTex,
IC/92/196, SISSA-140/92/EP, LMU-09/9
A proposed measurement of the ß asymmetry in neutron decay with the Los Alamos Ultra-Cold Neutron Source
This article reviews the status of an experiment to study the neutron spin-electron angular correlation with the Los Alamos Ultra-Cold Neutron (UCN) source. The experiment will generate UCNs from a novel solid deuterium, spallation source, and polarize them in a solenoid magnetic field. The experiment spectrometer will consist of a neutron decay region in a solenoid magnetic field combined with several different detector possibilities. An electron beam and a magnetic spectrometer will provide a precise, absolute calibration for these detectors. An A-correlation measurement with a relative precision of 0.2% is expected by the end of 2002
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