25,876 research outputs found
If physics is an information science, what is an observer?
Interpretations of quantum theory have traditionally assumed a "Galilean"
observer, a bare "point of view" implemented physically by a quantum system.
This paper investigates the consequences of replacing such an
informationally-impoverished observer with an observer that satisfies the
requirements of classical automata theory, i.e. an observer that encodes
sufficient prior information to identify the system being observed and
recognize its acceptable states. It shows that with reasonable assumptions
about the physical dynamics of information channels, the observations recorded
by such an observer will display the typical characteristics predicted by
quantum theory, without requiring any specific assumptions about the observer's
physical implementation.Comment: 30 pages, comments welcome; v2 significant revisions - results
unchange
The identification and exploitation of almost symmetry in planning problems
Previous work in symmetry detection for planning has identified symmetries between domain objects and shown how the exploitation of this information can help reduce search at plan time. However these methods are unable to detect symmetries between objects that are almost symmetrical: where the objects must start (or end) in slightly different configurations but for much of the plan their behaviour is equivalent. In the paper we outline a method for identifying such symmetries and discuss how this symmetry information can be positively exploited to help direct search during planning we have implemented this method and integrated it with the FF-v2.3 planner and in the paper we present results of experiments with this approach that demonstrate its potential
Anonymizing Social Graphs via Uncertainty Semantics
Rather than anonymizing social graphs by generalizing them to super
nodes/edges or adding/removing nodes and edges to satisfy given privacy
parameters, recent methods exploit the semantics of uncertain graphs to achieve
privacy protection of participating entities and their relationship. These
techniques anonymize a deterministic graph by converting it into an uncertain
form. In this paper, we propose a generalized obfuscation model based on
uncertain adjacency matrices that keep expected node degrees equal to those in
the unanonymized graph. We analyze two recently proposed schemes and show their
fitting into the model. We also point out disadvantages in each method and
present several elegant techniques to fill the gap between them. Finally, to
support fair comparisons, we develop a new tradeoff quantifying framework by
leveraging the concept of incorrectness in location privacy research.
Experiments on large social graphs demonstrate the effectiveness of our
schemes
Orthogonal Wavelets via Filter Banks: Theory and Applications
Wavelets are used in many applications, including image processing, signal analysis and seismology. The critical problem is the representation of a signal using a small number of computable functions, such that it is represented in a concise and computationally efficient form. It is shown that wavelets are closely related to filter banks (sub band filtering) and that there is a direct analogy between multiresolution analysis in continuous time and a filter bank in discrete time. This provides a clear physical interpretation of the approximation and detail spaces of multiresolution analysis in terms of the frequency bands of a signal. Only orthogonal wavelets, which are derived from orthogonal filter banks, are discussed. Several examples and applications are considered
Quantum-circuit guide to optical and atomic interferometry
Atomic (qubit) and optical or microwave (modal) phase-estimation protocols
are placed on the same footing in terms of quantum-circuit diagrams. Circuit
equivalences are used to demonstrate the equivalence of protocols that achieve
the Heisenberg limit by employing entangled superpositions of Fock states, such
as N00N states. The key equivalences are those that disentangle a circuit so
that phase information is written exclusively on a mode or modes or on a qubit.
The Fock-state-superposition phase-estimation circuits are converted to use
entangled coherent-state superpositions; the resulting protocols are more
amenable to realization in the lab, particularly in a qubit/cavity setting at
microwave frequencies.Comment: To appear in Optics Communications special issue in memory of
Krzysztof Wodkiewic
Local and global gravity
Our long experience with Newtonian potentials has inured us to the view that
gravity only produces local effects. In this paper we challenge this quite
deeply ingrained notion and explicitly identify some intrinsically global
gravitational effects. In particular we show that the global cosmological
Hubble flow can actually modify the motions of stars and gas within individual
galaxies, and even do so in a way which can apparently eliminate the need for
galactic dark matter. Also we show that a classical light wave acquires an
observable, global, path dependent phase in traversing a gravitational field.
Both of these effects serve to underscore the intrinsic difference between
non-relativistic and relativistic gravity.Comment: LaTeX, 20 pages plus three figures in two postscript files. To appear
in a special issue of Foundations of Physics honoring Professor Lawrence
Horwitz on the occasion of his 65th birthday; A. van der Merwe and S. Raby,
Editors, Plenum Publishing Company, N.Y., 199
Stabilisation of Quantum Computations by Symmetrisation
We propose a method for the stabilisation of quantum computations (including
quantum state storage). The method is based on the operation of projection into
, the symmetric subspace of the full state space of redundant
copies of the computer. We describe an efficient algorithm and quantum network
effecting --projection and discuss the stabilising effect of the
proposed method in the context of unitary errors generated by hardware
imprecision, and nonunitary errors arising from external environmental
interaction. Finally, limitations of the method are discussed.Comment: 20 pages LaTeX, 2 postscript figure
Two-Domain DNA Strand Displacement
We investigate the computing power of a restricted class of DNA strand
displacement structures: those that are made of double strands with nicks
(interruptions) in the top strand. To preserve this structural invariant, we
impose restrictions on the single strands they interact with: we consider only
two-domain single strands consisting of one toehold domain and one recognition
domain. We study fork and join signal-processing gates based on these
structures, and we show that these systems are amenable to formalization and to
mechanical verification
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