1,924 research outputs found
Non-Markovian qubit dynamics in a circuit-QED setup
We consider a circuit-QED setup that allows the induction and control of
non-Markovian dynamics of a qubit. Non-Markovianity is enforced over the qubit
by means of its direct coupling to a bosonic mode which is controllably coupled
to other qubit-mode system. We show that this configuration can be achieved in
a circuit-QED setup consisting of two initially independent superconducting
circuits, each formed by one charge qubit and one transmission-line resonator,
which are put in interaction by coupling the resonators to a current-biased
Josephson junction. We solve this problem exactly and then proceed with a
thorough investigation of the emergent non-Markovianity in the dynamics of the
qubits. Our study might serve the context for a first experimental assessment
of non-Markovianity in a multi-element solid-state device.Comment: 8 pages, 7 figures, slightly changed titl
Degree of Quantumness in Quantum Synchronization
We introduce the concept of degree of quantumness in quantum synchronization,
a measure of the quantum nature of synchronization in quantum systems.
Following techniques from quantum information, we propose the number of
non-commuting observables that synchronize as a measure of quantumness. This
figure of merit is compatible with already existing synchronization
measurements, and it captures different physical properties. We illustrate it
in a quantum system consisting of two weakly interacting cavity-qubit systems,
which are coupled via the exchange of bosonic excitations between the cavities.
Moreover, we study the synchronization of the expectation values of the Pauli
operators and we propose a feasible superconducting circuit setup. Finally, we
discuss the degree of quantumness in the synchronization between two quantum
van der Pol oscillators
Weak -structures and one-relator groups
Motivated by the notion of boundary for hyperbolic and groups, M.
Bestvina in "Local Homology Properties of Boundaries of Groups" introduced the
notion of a (weak) -structure and (weak) -boundary for
a group of type (i.e., having a finite complex), with
implications concerning the Novikov conjecture for . Since then, some
classes of groups have been shown to admit a weak -structure (see
"Weak -structures for some classes of groups" by C.R. Guilbault for
example), but the question whether or not every group of type
admits such a structure remains open. In this paper, we show that every torsion
free one-relator group admits a weak -structure, by showing that
they are all properly aspherical at infinity; moreover, in the -ended case
the corresponding weak -boundary has the shape of either a circle
or a Hawaiian earring depending on whether the group is a virtually surface
group or not. Finally, we extend this result to a wider class of groups still
satisfying a Freiheitssatz property
Direct Olive Oil Analysis
El impacto práctico del análisis directo es tan innegable como
que el contribuye decisivamente a mejorar las denominadas características
analíticas relacionadas con la productividad como la
rapidez, la reducción de costes y la minimización de riesgos para
los analistas y el ambiente. El principal objetivo es establecer un
adecuado "bypass" a las operaciones convencionales preliminares
del proceso analítico. Este artículo ofrece una propuesta sistemática
en este contexto y resalta el gran campo de acción de las metodologías
directas en los análisis de rutina del aceite de oliva. Se analizan
los dos tipos principales de metodologías. Por una lado, se
analiza la determinación directa de los compuestos volátiles. Por el
otro, se presentan y discuten los procedimientos simples para implementar
automáticamente las operaciones preliminares del análisis
del aceite usando sistemas simples en los que la muestra se
introduce directamente con/sin una dilución simpleThe practical impact of “direct analysis” is undeniable as it
strong contributes to enhance the so-called productive analytical
features such as expeditiousness, reduction of costs and
minimisation of risks for the analysts and environment. The main
objective is to establish a reliable bypass to the conventional
preliminary operations of the analytical process. This paper offers a
systematic approach in this context and emphasises the great field
of action of direct methodologies in the routine analysis of olive oil.
Two main types of methodologies are considered. On the one hand,
the direct determination of volatile components is systematically
considered. On the other hand, simple procedures to automatically
implement the preliminary operations of the oil analysis using
simple devices in which the sample is directly introduced
with/without a simple dilution are present and discusse
Análisis directo de aceite de oliva
The practical impact of “direct analysis” is undeniable as it strong contributes to enhance the so-called productive analytical features such as expeditiousness, reduction of costs and minimisation of risks for the analysts and environment. The main objective is to establish a reliable bypass to the conventional preliminary operations of the analytical process. This paper offers a systematic approach in this context and emphasises the great field of action of direct methodologies in the routine analysis of olive oil. Two main types of methodologies are considered. On the one hand, the direct determination of volatile components is systematically considered. On the other hand, simple procedures to automatically implement the preliminary operations of the oil analysis using simple devices in which the sample is directly introduced with/without a simple dilution are present and discussed.El impacto práctico del análisis directo es tan innegable como que el contribuye decisivamente a mejorar las denominadas características analíticas relacionadas con la productividad como la rapidez, la reducción de costes y la minimización de riesgos para los analistas y el ambiente. El principal objetivo es establecer un adecuado "bypass" a las operaciones convencionales preliminares del proceso analítico. Este artículo ofrece una propuesta sistemática en este contexto y resalta el gran campo de acción de las metodologías directas en los análisis de rutina del aceite de oliva. Se analizan los dos tipos principales de metodologías. Por una lado, se analiza la determinación directa de los compuestos volátiles. Por el otro, se presentan y discuten los procedimientos simples para implementar automáticamente las operaciones preliminares del análisis del aceite usando sistemas simples en los que la muestra se introduce directamente con/sin un dilución simple
A study of local approximation for polarization potentials
We discuss the derivation of an equivalent \textit{l}-independent
polarization potential for use in the optical Schr\"{o}dinger equation that
describes the elastic scattering of heavy ions. Three diffferent methods are
used for this purpose. Application of our theory to the low energy scattering
of the halo nucleus Li from a C target is made. It is found that
the notion of \textit{l}-independent polarization potential has some validity
but can not be a good substitute for the \textit{l}-dependent local equivalent
Feshbach polarization potential.Comment: 8 pages, 4 figure
Interplay of static and dynamic effects in 6He+ 238U Fusion
We investigate the influence of the neutron halo and the breakup channel in
6He + 238U fusion at near-barrier energies. To include static effects of the
2n-halo in 6He nuclei, we use a single-folding potential obtained from an
appropriate nucleon-238U interaction and a realistic 6He density. Dynamical
effects arising from the breakup process are then included through
coupled-channel calculations. These calculations suggest that static effects
dominate the cross section at energies above the Coulomb barrier, while the
sub-barrier fusion cross section appears to be determined by coupling to the
breakup channel. This last conclusion is uncertain due to the procedure
employed to measure the fusion cross-section.Comment: 13 pages, 4 figure
Embedded Quantum Correlations in thermalized quantum Rabi systems
We study the quantum correlations embedded in open quantum Rabi systems.
Specifically, we study how the quantum correlation depends on the coupling
strength, number of qubits, and reservoir temperatures. We numerically
calculate the quantum correlations of up to three qubits interacting with a
single field mode. We find that the embedded quantum correlations exhibit a
maximum for a given coupling strength, which depends inversely on the number of
subsystems and the reservoir temperature. We explore how this feature affects
the performance of a many-qubit Otto heat engine, finding numerical evidence of
a direct correspondence between the minimum of the extractable work and the
maximum of the embedded quantum correlations in the qubit-cavity bi-partition.
Furthermore, as we increase the number of qubits, the maximum extractable work
is reached at smaller values of the coupling strength. This work could help
design more sophisticated quantum heat engines that rely on many-body systems
with embedded correlations as working substances.Comment: 12 pages and 12 figure
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