784 research outputs found
VC-dimension of short Presburger formulas
We study VC-dimension of short formulas in Presburger Arithmetic, defined to
have a bounded number of variables, quantifiers and atoms. We give both lower
and upper bounds, which are tight up to a polynomial factor in the bit length
of the formula
Are there phase transitions in information space?
The interplay between two basic quantities -- quantum communication and
information -- is investigated. Quantum communication is an important resource
for quantum states shared by two parties and is directly related to
entanglement. Recently, the amount of local information that can be drawn from
a state has been shown to be closely related to the non-local properties of the
state. Here we consider both formation and extraction processes, and analyze
informational resources as a function of quantum communication. The resulting
diagrams in information space allow us to observe phase-like transitions when
correlations become classical.Comment: 4 pages, 3 epsi figures, to appear in Phys. Rev. Let
Probing the atmosphere of a sub-Jovian planet orbiting a cool dwarf
We derive the 0.01 m binned transmission spectrum, between 0.74 and 1.0
m, of WASP-80b from low resolution spectra obtained with the FORS2
instrument attached to ESO's Very Large Telescope. The combination of the fact
that WASP-80 is an active star, together with instrumental and telluric
factors, introduces correlated noise in the observed transit light curves,
which we treat quantitatively using Gaussian Processes. Comparison of our
results together with those from previous studies, to theoretically calculated
models reveals an equilibrium temperature in agreement with the previously
measured value of 825K, and a sub-solar metallicity, as well as an atmosphere
depleted of molecular species with absorption bands in the IR ().
Our transmission spectrum alone shows evidence for additional absorption from
the potassium core and wing, whereby its presence is detected from analysis of
narrow 0.003 m bin light curves (). Further observations with
visible and near-UV filters will be required to expand this spectrum and
provide more in-depth knowledge of the atmosphere. These detections are only
made possible through an instrument-dependent baseline model and a careful
analysis of systematics in the data.Comment: 13 pages, 11 figures, 3 tables. Accepted for publication in MNRA
A Thermodynamical Approach to Quantifying Quantum Correlations
We consider the amount of work which can be extracted from a heat bath using
a bipartite state shared by two parties. In general it is less then the amount
of work extractable when one party is in possession of the entire state. We
derive bounds for this "work deficit" and calculate it explicitly for a number
of different cases. For pure states the work deficit is exactly equal to the
distillable entanglement of the state, and this is also achievable for
maximally correlated states. In these cases a form of complementarity exists
between physical work which can be extracted and distillable entanglement. The
work deficit is a good measure of the quantum correlations in a state and
provides a new paradigm for understanding quantum non-locality.Comment: 4 pages, Revtex4, title changed, caveat added to theore
Designing optimal discrete-feedback thermodynamic engines
Feedback can be utilized to convert information into useful work, making it
an effective tool for increasing the performance of thermodynamic engines.
Using feedback reversibility as a guiding principle, we devise a method for
designing optimal feedback protocols for thermodynamic engines that extract all
the information gained during feedback as work. Our method is based on the
observation that in a feedback-reversible process the measurement and the
time-reversal of the ensuing protocol both prepare the system in the same
probabilistic state. We illustrate the utility of our method with two examples
of the multi-particle Szilard engine.Comment: 15 pages, 5 figures, submitted to New J. Phy
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