10,787 research outputs found
State-Dependent Approach to Entropic Measurement-Disturbance Relations
Heisenberg's intuition was that there should be a tradeoff between measuring
a particle's position with greater precision and disturbing its momentum.
Recent formulations of this idea have focused on the question of how well two
complementary observables can be jointly measured. Here, we provide an
alternative approach based on how enhancing the predictability of one
observable necessarily disturbs a complementary one. Our
measurement-disturbance relation refers to a clear operational scenario and is
expressed by entropic quantities with clear statistical meaning. We show that
our relation is perfectly tight for all measurement strengths in an existing
experimental setup involving qubit measurements.Comment: 9 pages, 2 figures. v4: published versio
Improved entropic uncertainty relations and information exclusion relations
The uncertainty principle can be expressed in entropic terms, also taking
into account the role of entanglement in reducing uncertainty. The information
exclusion principle bounds instead the correlations that can exist between the
outcomes of incompatible measurements on one physical system, and a second
reference system. We provide a more stringent formulation of both the
uncertainty principle and the information exclusion principle, with direct
applications for, e.g., the security analysis of quantum key distribution,
entanglement estimation, and quantum communication. We also highlight a
fundamental distinction between the complementarity of observables in terms of
uncertainty and in terms of information.Comment: 11 pages, 1 figure, v2: close to published versio
Solar cycle evolution of the solar wind in three dimensions
Measurements of the solar wind speed both in and out of the ecliptic are presented for 1971-82. The speed estimates, which were made with the interplanetary scintillation system at UC San Diego, have been compared to in situ for large, slowly evolving structures, and thus such structures can be studied up to 60 degrees north and south heliographic latitude. Annual average wind speeds are presented versus latitude for an entire solar cycle. Fast wind streams from the poles persisted through declining and low solar activity, but were closed off during four years of high activity. This evolution follows that of the polar coronal holes, as displayed by comparing averaged speed and coronal density over latitude and longitude. The most recent data (1982) show the reestablishment of large tilted polar holes and associated fast streams. Coronal magnetic field data show that the neutral sheet is confined to low latitudes at solar minimum and extends to high latitudes at solar maximum; thus the slow solar wind comes from the same latitude range as that of the neutral sheet
Marvin: A Heuristic Search Planner with Online Macro-Action Learning
This paper describes Marvin, a planner that competed in the Fourth
International Planning Competition (IPC 4). Marvin uses
action-sequence-memoisation techniques to generate macro-actions, which are
then used during search for a solution plan. We provide an overview of its
architecture and search behaviour, detailing the algorithms used. We also
empirically demonstrate the effectiveness of its features in various planning
domains; in particular, the effects on performance due to the use of
macro-actions, the novel features of its search behaviour, and the native
support of ADL and Derived Predicates
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