18,516 research outputs found
Fiber glass reinforced structural materials for aerospace application
Evaluation of fiber glass reinforced plastic materials concludes that fiber glass construction is lighter than aluminum alloy construction. Low thermal conductivity and strength makes the fiber glass material useful in cryogenic tank supports
Applications of ISES for coastal zone studies
In contrast to the discipline- and process-oriented topics addressed, coastal zone studies are defined geographically by the special circumstances inherent in the interface between land and water. The characteristics of coastal zones which make them worthy of separate consideration are: (1) the dynamic nature of natural and anthropogenic processes taking place; (2) the relatively restricted spatial domain of the narrow land/water interface; and (3) the large proportion of the Earth's population living within coastal zones, and the resulting extreme pressure on natural and human resources. These characteristics place special constraints and priorities on remote sensing applications, even though the applications themselves bear close relation to those addressed by other elements of this report (e.g., oceans, ice, vegetation/land use). The discussion which follows first describes the suite of remote sensing activities relevant to coastal zone studies. Potential Information Sciences Experiment System (ISES) experiments will then be addressed within two general categories: applications of real-time data transmission and applications of onboard data acquisition and processing
Symmetry-protected self-correcting quantum memories
A self-correcting quantum memory can store and protect quantum information
for a time that increases without bound with the system size and without the
need for active error correction. We demonstrate that symmetry can lead to
self-correction in 3D spin-lattice models. In particular, we investigate codes
given by 2D symmetry-enriched topological (SET) phases that appear naturally on
the boundary of 3D symmetry-protected topological (SPT) phases. We find that
while conventional on-site symmetries are not sufficient to allow for
self-correction in commuting Hamiltonian models of this form, a generalized
type of symmetry known as a 1-form symmetry is enough to guarantee
self-correction. We illustrate this fact with the 3D "cluster-state" model from
the theory of quantum computing. This model is a self-correcting memory, where
information is encoded in a 2D SET-ordered phase on the boundary that is
protected by the thermally stable SPT ordering of the bulk. We also investigate
the gauge color code in this context. Finally, noting that a 1-form symmetry is
a very strong constraint, we argue that topologically ordered systems can
possess emergent 1-form symmetries, i.e., models where the symmetry appears
naturally, without needing to be enforced externally.Comment: 39 pages, 16 figures, comments welcome; v2 includes much more
explicit detail on the main example model, including boundary conditions and
implementations of logical operators through local moves; v3 published
versio
Optimizing qubit Hamiltonian parameter estimation algorithms using PSO
We develop qubit Hamiltonian single parameter estimation techniques using a
Bayesian approach. The algorithms considered are restricted to projective
measurements in a fixed basis, and are derived under the assumption that the
qubit measurement is much slower than the characteristic qubit evolution. We
optimize a non-adaptive algorithm using particle swarm optimization (PSO) and
compare with a previously-developed locally-optimal scheme.Comment: 3 pages, 2 figures, presented at 2012 IEEE Congress on Evolutionary
Computation, to be published in the proceeding
Non-additivity of pair interactions in charged colloids
It is general wisdom that the pair potential of charged colloids in a liquid
may be closely approximated by a Yukawa interaction, as predicted by the
classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. We experimentally
determine the effective forces in a binary mixture of like-charged particles,
of species 1 and 2, with blinking optical tweezers. The measured forces are
consistent with a Yukawa pair potential but the (12) cross-interaction is not
equal to the geometric mean of the (11) and (22) like-interactions, as expected
from DLVO. The deviation is a function of the electrostatic screening length
and the size ratio, with the cross-interaction measured being consistently
weaker than DLVO predictions. The corresponding non-additivity parameter is
negative and grows in magnitude with increased size asymmetry.Comment: Final versio
Comparison of ERTS-1 and Skylab-EREP for interdisciplinary coastal investigations
The author has identified the following significant results. NASA's ERTS-1 satellite and Skylab EREP have both provided imagery suitable for investigating coastal vegetation, land use, current circulation, water turbidity, waste disposal, and sea state. Based on high contrast targets, such as piers and breakwaters, the ERTS-1 MSS seems to have a resolution of 70-100 meters, Skylab's S190A about 30-70 meters, and its S190B about 10-30 meters. Important coastal land use details can be more readily mapped using Skylab's imagery. On the other hand, the regular eighteen day cycle of ERTS-1 allows observation of important manmade and natural changes, and facilitates collection of ground truth. The Skylab/EREP multispectral scanner offers 13 spectral bands as compared to 4 bands on ERTS-1. However, EREP scanner tapes require special filtering to remove several types of noise and their conical line scan pattern must be linearized before one can identify small targets based on spatial features
Quantum methods for clock synchronization: Beating the standard quantum limit without entanglement
We introduce methods for clock synchronization that make use of the adiabatic
exchange of nondegenerate two-level quantum systems: ticking qubits. Schemes
involving the exchange of N independent qubits with frequency give a
synchronization accuracy that scales as , i.e., as the
standard quantum limit. We introduce a protocol that makes use of N coherent
exchanges of a single qubit at frequency , leading to an accuracy that
scales as . This protocol beats the standard quantum
limit without the use of entanglement, and we argue that this scaling is the
fundamental limit for clock synchronization allowed by quantum mechanics. We
analyse the performance of these protocols when used with a lossy channel.Comment: 9 pages, 1 figure, published versio
Bell's theorem without inequalities and without alignments
A proof of Bell's theorem without inequalities is presented which exhibits
three remarkable properties: (a) reduced local states are immune to collective
decoherence; (b) distant local setups do not need to be aligned, since the
required perfect correlations are achieved for any local rotation of the local
setups; (c) local measurements require only individual measurements on the
qubits. Indeed, it is shown that this proof is essentially the only one which
fulfils (a), (b), and (c).Comment: REVTeX4, 4 page
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