5,679 research outputs found
Quantum and Classical in Adiabatic Computation
Adiabatic transport provides a powerful way to manipulate quantum states. By
preparing a system in a readily initialised state and then slowly changing its
Hamiltonian, one may achieve quantum states that would otherwise be
inaccessible. Moreover, a judicious choice of final Hamiltonian whose
groundstate encodes the solution to a problem allows adiabatic transport to be
used for universal quantum computation. However, the dephasing effects of the
environment limit the quantum correlations that an open system can support and
degrade the power of such adiabatic computation. We quantify this effect by
allowing the system to evolve over a restricted set of quantum states,
providing a link between physically inspired classical optimisation algorithms
and quantum adiabatic optimisation. This new perspective allows us to develop
benchmarks to bound the quantum correlations harnessed by an adiabatic
computation. We apply these to the D-Wave Vesuvius machine with revealing -
though inconclusive - results
The U.S. trade deficit: made in China?
Rapid growth of the U.S. bilateral trade deficit with China has promoted a widespread view that the overall trade deficit is "made in China." The authors examine the probable consequences of increased protection directed toward U.S. imports from China. Their appraisal of recent and prospective U.S. trade policy focuses on textiles and apparel—sectors where the growth of imports from China has been prominent. They also consider the likely effects of yuan appreciation on the bilateral and overall trade deficits.Balance of trade ; Balance of trade - China
Construction of an instrument for the measurement of educational philosophy
Thesis (M.Ed.)--Boston Universit
Travelling waves in a drifting flux lattice
Starting from the time-dependent Ginzburg-Landau (TDGL) equations for a type
II superconductor, we derive the equations of motion for the displacement field
of a moving vortex lattice without inertia or pinning. We show that it is
linearly stable and, surprisingly, that it supports wavelike long-wavelength
excitations arising not from inertia or elasticity but from the
strain-dependent mobility of the moving lattice. It should be possible to image
these waves, whose speeds are a few \mu m/s, using fast scanning tunnelling
microscopy.Comment: 4 pages, revtex, 2 .eps figures imbedded in paper, title shortened,
minor textual change
A tradeoff in simultaneous quantum-limited phase and loss estimation in interferometry
Interferometry with quantum light is known to provide enhanced precision for
estimating a single phase. However, depending on the parameters involved, the
quantum limit for the simultaneous estimation of multiple parameters may not
attainable, leading to trade-offs in the attainable precisions. Here we study
the simultaneous estimation of two parameters related to optical
interferometry: phase and loss, using a fixed number of photons. We derive a
trade-off in the estimation of these two parameters which shows that, in
contrast to single-parameter estimation, it is impossible to design a strategy
saturating the quantum Cramer-Rao bound for loss and phase estimation in a
single setup simultaneously. We design optimal quantum states with a fixed
number of photons achieving the best possible simultaneous precisions. Our
results reveal general features about concurrently estimating Hamiltonian and
dissipative parameters, and has implications for sophisticated sensing
scenarios such as quantum imaging.Comment: 9 pages, 6 figure
Research and investigation of geology, mineral, and water resources of Maryland
The authors have identified the following significant results. Field work in Baltimore County revealed that the signature returns of serpentinitic and nonserpentinitic rocks correlates with the vegetation cover and land use pattern. In Maryland Piedmont, bedrock lithology and structure are enhanced only to the extent that land use is geologically dictated. Two prominent sets of linear features are detected on ERTS-1 imagery at N 45 deg E and N 20 deg E. Beaches of Chesapeake Bay are classified as broad and narrow beaches based on the width of the backshore zone. It is shown by comparing historical shorelines of Ocean City, from the inlet to the Maryland-Delaware line that reversal zones of erosion and accretion occur at different locations for different periods. High reflectance levels (high marsh-high topographic areas) for the lower Eastern Shore are found to be distributed as two distinct trending linear ridge systems. Observations of MSS band 5 dated 9 April 1974 exhibited an unique sedimentation pattern for Chesapeake Bay. Following a 1.5 inch rainfall, heavy concentration of suspended sediments is observed on the imagery, particularly in the area of the turbidity maximum
Genetic Variation in Clinical Varicella-Zoster Virus Isolates Collected in Ireland Between 2002 and 2003
Analysis of genetic variation in 16 varicella-zoster
virus (VZV) isolates selected at random and circulating in the Irish population between March 2002 and February 2003 was carried out. A 919 bp fragment of the glycoprotein E gene (open reading frame 68) encompassing codon 150, at which a non-synonymous mutation defines the escape
mutant VZV-MSP, and including two other epitope
regions e1 and c1, was sequenced. No new single nucleotide polymorphisms (SNPs) were detected, indicating stability of these epitopes in clinical isolates of VZV. However, when four informative polymorphic markers consisting of
defined regions from genes 1, 21, 50, and 54 were sequenced 14 variable nucleotide positions were identified. Phylogenetic analysis showed the presence of three highly supported clades A, B, and C circulating in the Irish population.
Approximately one third (6/16; 37.5%) of the Irish
VZV isolates in this study belonged to genotype
C, 4/16 (25%) to genotype A, and 4/16 (25%) to genotype B. A smaller number 2/16 (12.5%) belonged to genotype J1. This indicates remarkable heterogeneity in the Irish population given the small sample size. No evidence was found to
suggest any of the 16 isolates was a recombinant. These findings have implications for the model of geographic isolation of VZV clades to certain regions as the circulating Irish VZV population appears to comprise approximately equal numbers of each of the main genotypes. This data is inconsistent with a model of strict geographical separation of VZV genotypes and suggests that
VZVdiversity ismorepronounced in certain areas than had been thought previously
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