5,068 research outputs found
Isotopic composition of Murchison organic compounds: Intramolecular carbon isotope fractionation of acetic acid. Simulation studies of cosmochemical organic syntheses
Recently, in our laboratories, samples of Murchison acetic acid were decarboxylated successfully and the carbon isotopic composition was measured for the methane released by this procedure. These analyses showed significant differences in C-13/C-12 ratios for the methyl and carboxyl carbons of the acetic acid molecule, strongly suggesting that more than one carbon source may be involved in the synthesis of the Murchison organic compounds. On the basis of this finding, laboratory model systems simulating cosmochemical synthesis are being studied, especially those processes capable of involving two or more starting carbon sources
Cloning of Gaussian states by linear optics
We analyze in details a scheme for cloning of Gaussian states based on linear
optical components and homodyne detection recently demonstrated by U. L.
Andersen et al. [PRL 94 240503 (2005)]. The input-output fidelity is evaluated
for a generic (pure or mixed) Gaussian state taking into account the effect of
non-unit quantum efficiency and unbalanced mode-mixing. In addition, since in
most quantum information protocols the covariance matrix of the set of input
states is not perfectly known, we evaluate the average cloning fidelity for
classes of Gaussian states with the degree of squeezing and the number of
thermal photons being only partially known.Comment: 8 pages, 7 figure
Measurement does not always aid state discrimination
We have investigated the problem of discriminating between nonorthogonal
quantum states with least probability of error. We have determined that the
best strategy for some sets of states is to make no measurement at all, and
simply to always assign the most commonly occurring state. Conditions which
describe such sets of states have been derived.Comment: 3 page
Disseminated bacillus Calmette-Guérin (BCG): a cause of delirium in an older adult
Intra-vesical Bacillus Calmette-Guérin (BCG) immunotherapy is an effective treatment for high-risk bladder cancer. Less well known is that fewer than 1% of patients receiving BCG treatment can develop disseminated BCG. The reaction can range from a mild flu-like illness to a systemic disorder with a fulminant course which in the most severe cases can lead to death. The diagnostic yield is low and diagnosis is often made after a comprehensive exclusion of more common causes of pyrexia of unknown origin. A high level of suspicion is therefore required in those who may be at risk. We report a case of disseminated BCG in an older patient for whom early involvement of his family was pertinent to determining the precipitant for delirium
Husimi's function and quantum interference in phase space
We discuss a phase space description of the photon number distribution of non
classical states which is based on Husimi's function and does not
rely in the WKB approximation. We illustrate this approach using the examples
of displaced number states and two photon coherent states and show it to
provide an efficient method for computing and interpreting the photon number
distribution . This result is interesting in particular for the two photon
coherent states which, for high squeezing, have the probabilities of even and
odd photon numbers oscillating independently.Comment: 15 pages, 12 figures, typos correcte
Light atom quantum oscillations in UC and US
High energy vibrational scattering in the binary systems UC and US is
measured using time-of-flight inelastic neutron scattering. A clear set of
well-defined peaks equally separated in energy is observed in UC, corresponding
to harmonic oscillations of the light C atoms in a cage of heavy U atoms. The
scattering is much weaker in US and only a few oscillator peaks are visible. We
show how the difference between the materials can be understood by considering
the neutron scattering lengths and masses of the lighter atoms. Monte Carlo ray
tracing is used to simulate the scattering, with near quantitative agreement
with the data in UC, and some differences with US. The possibility of observing
anharmonicity and anisotropy in the potentials of the light atoms is
investigated in UC. Overall the observed data is well accounted for by
considering each light atom as a single atom isotropic quantum harmonic
oscillator.Comment: 10 pages, 8 figure
Non-conventional digital signatures and their implementations – A review
The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-19713-5_36The current technological scenario determines a profileration
of trust domains, which are usually defined by validating the digital
identity linked to each user. This validation entails critical assumptions
about the way users’ privacy is handled, and this calls for new methods
to construct and treat digital identities. Considering cryptography,
identity management has been constructed and managed through conventional
digital signatures. Nowadays, new types of digital signatures
are required, and this transition should be guided by rigorous evaluation
of the theoretical basis, but also by the selection of properly verified software
means. This latter point is the core of this paper. We analyse the
main non-conventional digital signatures that could endorse an adequate
tradeoff betweeen security and privacy. This discussion is focused on
practical software solutions that are already implemented and available
online. The goal is to help security system designers to discern identity
management functionalities through standard cryptographic software libraries.This work was supported by Comunidad de Madrid (Spain) under the project S2013/ICE-3095-CM (CIBERDINE) and the Spanish Government project TIN2010-19607
Unified Treatment of Heterodyne Detection: the Shapiro-Wagner and Caves Frameworks
A comparative study is performed on two heterodyne systems of photon
detectors expressed in terms of a signal annihilation operator and an image
band creation operator called Shapiro-Wagner and Caves' frame, respectively.
This approach is based on the introduction of a convenient operator
which allows a unified formulation of both cases. For the Shapiro-Wagner
scheme, where , quantum phase and amplitude
are exactly defined in the context of relative number state (RNS)
representation, while a procedure is devised to handle suitably and in a
consistent way Caves' framework, characterized by , within the approximate simultaneous measurements of
noncommuting variables. In such a case RNS phase and amplitude make sense only
approximately.Comment: 25 pages. Just very minor editorial cosmetic change
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