1,781 research outputs found
Health-care district management information system plan: Review of operations analysis activities during calendar year 1975 and plan for continued research and analysis activities
Operations research activities developed to identify the information required to manage both the efficiency and effectiveness of the Veterans Administration (VA) health services as these services relate to individual patient care are reported. The clinical concerns and management functions that determine this information requirement are discussed conceptually. Investigations of existing VA data for useful management information are recorded, and a diagnostic index is provided. The age-specific characteristics of diseases and lengths of stay are explored, and recommendations for future analysis activities are articulated. The effect of the introduction of new technology to health care is also discussed
Entangling photons using a charged quantum dot in a microcavity
We present two novel schemes to generate photon polarization entanglement via
single electron spins confined in charged quantum dots inside microcavities.
One scheme is via entangled remote electron spins followed by
negatively-charged exciton emissions, and another scheme is via a single
electron spin followed by the spin state measurement. Both schemes are based on
giant circular birefringence and giant Faraday rotation induced by a single
electron spin in a microcavity. Our schemes are deterministic and can generate
an arbitrary amount of multi-photon entanglement. Following similar procedures,
a scheme for a photon-spin quantum interface is proposed.Comment: 4 pages, 4 figure
Tunneling Qubit Operation on a Protected Josephson Junction Array
We discuss a protected quantum computation process based on a hexagon
Josephson junction array. Qubits are encoded in the punctured array, which is
topologically protected. The degeneracy is related to the number of holes. The
topological degeneracy is lightly shifted by tuning the flux through specific
hexagons. We also show how to perform single qubit operation and basic quantum
gate operations in this system.Comment: 8 pages, 4 figures. The published version in Phys. Rev.,
A81(2010)01232
A New Look at the Axial Anomaly in Lattice QED with Wilson Fermions
By carrying out a systematic expansion of Feynman integrals in the lattice
spacing, we show that the axial anomaly in the U(1) lattice gauge theory with
Wilson fermions, as determined in one-loop order from an irrelevant lattice
operator in the Ward identity, must necessarily be identical to that computed
from the dimensionally regulated continuum Feynman integrals for the triangle
diagrams.Comment: 1 figure, LaTeX, 18 page
Orbits of quantum states and geometry of Bloch vectors for -level systems
Physical constraints such as positivity endow the set of quantum states with
a rich geometry if the system dimension is greater than two. To shed some light
on the complicated structure of the set of quantum states, we consider a
stratification with strata given by unitary orbit manifolds, which can be
identified with flag manifolds. The results are applied to study the geometry
of the coherence vector for n-level quantum systems. It is shown that the
unitary orbits can be naturally identified with spheres in R^{n^2-1} only for
n=2. In higher dimensions the coherence vector only defines a non-surjective
embedding into a closed ball. A detailed analysis of the three-level case is
presented. Finally, a refined stratification in terms of symplectic orbits is
considered.Comment: 15 pages LaTeX, 3 figures, reformatted, slightly modified version,
corrected eq.(3), to appear in J. Physics
A Description of Kitaev's Honeycomb Model with Toric-Code Stabilizers
We present a solution of Kitaev's spin model on the honeycomb lattice and of
related topologically ordered spin models. We employ a Jordan-Wigner type
fermionization and find that the Hamiltonian takes a BCS type form, allowing
the system to be solved by Bogoliubov transformation. Our fermionization does
not employ non-physical auxiliary degrees of freedom and the eigenstates we
obtain are completely explicit in terms of the spin variables. The ground-state
is obtained as a BCS condensate of fermion pairs over a vacuum state which
corresponds to the toric code state with the same vorticity. We show in detail
how to calculate all eigenstates and eigenvalues of the model on the torus. In
particular, we find that the topological degeneracy on the torus descends
directly from that of the toric code, which now supplies four vacua for the
fermions, one for each choice of periodic vs. anti-periodic boundary
conditions. The reduction of the degeneracy in the non-Abelian phase of the
model is seen to be due to the vanishing of one of the corresponding candidate
BCS ground-states in that phase. This occurs in particular in the fully
periodic vortex-free sector. The true ground-state in this sector is exhibited
and shown to be gapped away from the three partially anti-periodic
ground-states whenever the non-Abelian phase is gapped.Comment: 10 pages, 4 figure
Anonymous shell companies: A global audit study and field experiment in 176 countries
To test whether firms behave consistently with international law prohibiting anonymous incorporation, we conducted a global audit study and field experiment, using data from 1639 incorporation firms in 176 countries. We requested anonymous incorporation and randomly assigned references to international law, threat of penalties, norms of appropriate behavior, or a placebo. We find a substantial number of firms willing to flout international standards and show that those in OECD countries proved significantly less compliant with rules than in developing countries or tax havens. Firms in tax havens displayed significantly greater compliance and were sensitive to experimental interventions invoking international law
Age of the Peach Springs Tuff, Southeastern California and Western Arizona
Sanidine separates from pumice of the early Miocene Peach Springs Tuff are concordantly dated at 18.5 ± 0.2 Ma by two isotopic techniques. The Peach Springs Tuff is the only known unit that can be correlated between isolated outcrops of Miocene strata from the central Mojave Desert of southeastern California to the western Colorado Plateau in Arizona, across five structural provinces, a distance of 350 km. Thus the age of the Peach Springs Tuff is important to structural and paleogeographic reconstructions of a large region. Biotite and sanidine separates from bulk samples of the Peach Springs Tuff from zones of welding and vapor-phase alteration have not produced consistent ages by the K-Ar method. Published ages of mineral separates from 17 localities ranged from 16.2 to 20.5 Ma. Discordant 40Ar/39Ar incremental release spectra were obtained for one biotite and two of the sanidine separates. Ages that correspond to the last gas increments are as old as 27 Ma. The 40Ar/39Ar incremental release determinations on sanidine separated from blocks of Peach Springs Tuff pumice yield ages of 18.3 ± 0.3 and 18.6 ± 0.4 Ma. Laser fusion measurements yield a mean age of 18.51 ± 0.10. The results suggest that sanidine and biotite K-Ar ages older than about 18.5 Ma are due to inherited Ar from pre-Tertiary contaminants, which likely were incorporated into the tuff during deposition. Sanidine K-Ar ages younger than 18 Ma probably indicate incomplete extraction of radiogenic 40Ar, whereas laser fusion dates of biotite and hornblende younger than 18 Ma likely are due to postdepositional alteration. Laser fusion ages as high as 19.01 Ma on biotite grains from pumice suggest that minerals from pre-Tertiary country rocks also were incorporated in the magma chamber
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