2,698 research outputs found
Abrupt and gradual changes of information through the Kane solid state computer
The susceptibility of the transformed information to the filed and system
parameters is investigated for the Kane solid state computer. It has been
shown, that the field polarization and the initial state of the system play the
central roles on the abrupt and gradual quench of the purity and the fidelity.
If the field and the initial state are in different polarizations, then the
purity and the fidelity decrease abruptly, while for the common polarization
the decay is gradual and smooth. For some class of initial states one can send
the information without any loss. Therefore, by controlling on the devices one
can increase the time of safe communication, reduce the amount of exchange
information between the state and its environment and minimize the purity
decrease rate
Characteristics of versatile buildings
Thesis (M. Arch)--Massachusetts Institute of Technology, Dept. of Architecture, 1983.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCHText on even numbered pages runs from back to front.Includes bibliographical references (p. 81).If a building is to maintain its life-long usefulness it must be possible to alter it to accommodate different programmatic demands. This thesis investigates the spatial and material character that facilitates this architectural accommodation of diversity and change: Framed New England houses are compared with contemporary office buildings for their adaptability. A program of office and residential space is presented for a small valley near Brownsville Vermont. A building type is planned for this context and inhabited several ways to test its capabilities.by Stephen N. Mahler.M.Arc
Multipartite entanglement in fermionic systems via a geometric measure
We study multipartite entanglement in a system consisting of
indistinguishable fermions. Specifically, we have proposed a geometric
entanglement measure for N spin-1/2 fermions distributed over 2L modes (single
particle states). The measure is defined on the 2L qubit space isomorphic to
the Fock space for 2L single particle states. This entanglement measure is
defined for a given partition of 2L modes containing m >= 2 subsets. Thus this
measure applies to m <= 2L partite fermionic system where L is any finite
number, giving the number of sites. The Hilbert spaces associated with these
subsets may have different dimensions. Further, we have defined the local
quantum operations with respect to a given partition of modes. This definition
is generic and unifies different ways of dividing a fermionic system into
subsystems. We have shown, using a representative case, that the geometric
measure is invariant under local unitaries corresponding to a given partition.
We explicitly demonstrate the use of the measure to calculate multipartite
entanglement in some correlated electron systems. To the best of our knowledge,
there is no usable entanglement measure of m > 3 partite fermionic systems in
the literature, so that this is the first measure of multipartite entanglement
for fermionic systems going beyond the bipartite and tripartite cases.Comment: 25 pages, 8 figure
Quantum dense coding over Bloch channels
Dynamics of coded information over Bloch channels is investigated for
different values of the channel's parameters. We show that, the suppressing of
the travelling coded information over Bloch channel can be increased by
decreasing the equilibrium absolute value of information carrier and
consequently decreasing the distilled information by eavesdropper. The amount
of decoded information can be improved by increasing the equilibrium values of
the two qubits and decreasing the ratio between longitudinal and transverse
relaxation times. The robustness of coded information in maximum and partial
entangled states is discussed. It is shown that the maximum entangled states
are more robust than the partial entangled state over this type of channels
Violation of Heisenberg's Measurement-Disturbance Relationship by Weak Measurements
While there is a rigorously proven relationship about uncertainties intrinsic
to any quantum system, often referred to as "Heisenberg's Uncertainty
Principle," Heisenberg originally formulated his ideas in terms of a
relationship between the precision of a measurement and the disturbance it must
create. Although this latter relationship is not rigorously proven, it is
commonly believed (and taught) as an aspect of the broader uncertainty
principle. Here, we experimentally observe a violation of Heisenberg's
"measurement-disturbance relationship", using weak measurements to characterize
a quantum system before and after it interacts with a measurement apparatus.
Our experiment implements a 2010 proposal of Lund and Wiseman to confirm a
revised measurement-disturbance relationship derived by Ozawa in 2003. Its
results have broad implications for the foundations of quantum mechanics and
for practical issues in quantum mechanics.Comment: 5 pages, 4 figure
On the set of zero coefficients of a function satisfying a linear differential equation
Let be a field of characteristic zero and suppose that satisfies a recurrence of the form
for sufficiently large, where are polynomials in
. Given that is a nonzero constant polynomial, we show that the
set of for which is a union of finitely many
arithmetic progressions and a finite set. This generalizes the
Skolem-Mahler-Lech theorem, which assumes that satisfies a linear
recurrence. We discuss examples and connections to the set of zero coefficients
of a power series satisfying a homogeneous linear differential equation with
rational function coefficients.Comment: 11 page
On the Stability and the Approximation of Branching Distribution Flows, with Applications to Nonlinear Multiple Target Filtering
We analyse the exponential stability properties of a class of measure-valued
equations arising in nonlinear multi-target filtering problems. We also prove
the uniform convergence properties w.r.t. the time parameter of a rather
general class of stochastic filtering algorithms, including sequential Monte
Carlo type models and mean eld particle interpretation models. We illustrate
these results in the context of the Bernoulli and the Probability Hypothesis
Density filter, yielding what seems to be the first results of this kind in
this subject
Modelling CO emission from Mira's wind
We have modelled the circumstellar envelope of {\it o} Ceti (Mira) using new
observational constraints. These are obtained from photospheric light scattered
in near-IR vibrational-rotational lines of circumstellar CO molecules at 4.6
micron: absolute fluxes, the radial dependence of the scattered intensity, and
two line ratios. Further observational constraints are provided by ISO
observations of far-IR emission lines from highly excited rotational states of
the ground vibrational state of CO, and radio observations of lines from
rotational levels of low excitation of CO. A code based on the Monte-Carlo
technique is used to model the circumstellar line emission.
We find that it is possible to model the radio and ISO fluxes, as well as the
highly asymmetric radio-line profiles, reasonably well with a spherically
symmetric and smooth stellar wind model. However, it is not possible to
reproduce the observed NIR line fluxes consistently with a `standard model' of
the stellar wind. This is probably due to incorrectly specified conditions of
the inner regions of the wind model, since the stellar flux needs to be larger
than what is obtained from the standard model at the point of scattering, i.e.,
the intermediate regions at approximately 100-400 stellar radii (2"-7") away
from the star. Thus, the optical depth in the vibrational-rotational lines from
the star to the point of scattering has to be decreased. This can be
accomplished in several ways. For instance, the gas close to the star (within
approximately 2") could be in such a form that light is able to pass through,
either due to the medium being clumpy or by the matter being in radial
structures (which, further out, developes into more smooth or shell-like
structures).Comment: 18 pages, 3 figures, accepted for publication in Ap
Spatially Resolved Outflows in a Seyfert Galaxy at z = 2.39
We present the first spatially resolved analysis of rest-frame optical and UV
imaging and spectroscopy for a lensed galaxy at z = 2.39 hosting a Seyfert
active galactic nucleus (AGN). Proximity to a natural guide star has enabled
high signal-to-noise VLT SINFONI + adaptive optics observations of rest-frame
optical diagnostic emission lines, which exhibit an underlying broad component
with FWHM ~ 700 km/s in both the Balmer and forbidden lines. Measured line
ratios place the outflow robustly in the region of the ionization diagnostic
diagrams associated with AGN. This unique opportunity - combining gravitational
lensing, AO guiding, redshift, and AGN activity - allows for a magnified view
of two main tracers of the physical conditions and structure of the
interstellar medium in a star-forming galaxy hosting a weak AGN at cosmic noon.
By analyzing the spatial extent and morphology of the Ly-alpha and
dust-corrected H-alpha emission, disentangling the effects of star formation
and AGN ionization on each tracer, and comparing the AGN induced mass outflow
rate to the host star formation rate, we find that the AGN does not
significantly impact the star formation within its host galaxy.Comment: 16 pages, 5 figures, accepted for publication in Ap
Struggling to a monumental triumph : Re-assessing the final stages of the smallpox eradication program in India, 1960-1980
The global smallpox program is generally presented as the brainchild of a handful of actors from the WHO headquarters in Geneva and at the agency's regional offices. This article attempts to present a more complex description of the drive to eradicate smallpox. Based on the example of India, a major focus of the campaign, it is argued that historians and public health officials should recognize the varying roles played by a much wider range of participants. Highlighting the significance of both Indian and international field officials, the author shows how bureaucrats and politicians at different levels of administration and society managed to strengthen—yet sometimes weaken—important program components. Centrally dictated strategies developed at WHO offices in Geneva and New Delhi, often in association with Indian federal authorities, were reinterpreted by many actors and sometimes changed beyond recognition
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