1,899 research outputs found
Spin-1/2 geometric phase driven by decohering quantum fields
We calculate the geometric phase of a spin-1/2 system driven by a one and two
mode quantum field subject to decoherence. Using the quantum jump approach, we
show that the corrections to the phase in the no-jump trajectory are different
when considering an adiabatic and non-adiabatic evolution. We discuss the
implications of our results from both the fundamental as well as quantum
computational perspective.Comment: 4 page
Direct measurement of finite-time disentanglement induced by a reservoir
We propose a method for directly probing the dynamics of disentanglement of
an initial two-qubit entangled state, under the action of a reservoir. We show
that it is possible to detect disentanglement, for experimentally realizable
examples of decaying systems, through the measurement of a single observable,
which is invariant throughout the decay. The systems under consideration may
lead to either finite-time or asymptotic disentanglement. A general
prescription for measuring this observable, which yields an operational meaning
to entanglement measures, is proposed, and exemplified for cavity quantum
electrodynamics and trapped ions.Comment: 4 pages, 2 figure
Ion backflow studies with a triple-GEM stack with increasing hole pitch
Gas Electron Multipliers have undergone a very consistent development since
their invention in 1997. Their production procedures have been tuned in such a
way that nowadays it is possible to produce foils with areas of the order of
the square meter that can operate at a reasonable gain, uniform over large
areas and with a good stability in what concerns electrical discharges. For the
third run of LHC, they will be included in the CMS and ALICE experiments after
significant upgrades of the detectors, confirming that these structures are
suitable for very large experiments. In the special case of Time Projection
Chambers, the ion backflow and the energy resolution are sensitive issues that
must be addressed and the GEM has shown to be able to deal with both of them.
In this work, a stack of three GEMs with different pitches has been studied
as a possible future approach for ion-backflow suppression to be used in TPCs
and other detection concepts. With this approach, an ion backflow of 1 % with
an energy resolution of 12 % at 5.9 keV has been achieved with the detector
operating in an Ar/CO2 (90/10) mixture at a gain of ~ 2000.Comment: 15 pages, 11 figure
Coherent evolution via reservoir driven holonomy
We show that in the limit of strongly interacting environment a system
initially prepared in a Decoherence Free Subspace (DFS) coherently evolves in
time, adiabatically following the changes of the DFS. If the reservoir cyclicly
evolves in time, the DFS states acquire an holonomy.Comment: 4 page
Controlling the dynamics of a coupled atom-cavity system by pure dephasing : basics and potential applications in nanophotonics
The influence of pure dephasing on the dynamics of the coupling between a
two-level atom and a cavity mode is systematically addressed. We have derived
an effective atom-cavity coupling rate that is shown to be a key parameter in
the physics of the problem, allowing to generalize the known expression for the
Purcell factor to the case of broad emitters, and to define strategies to
optimize the performances of broad emitters-based single photon sources.
Moreover, pure dephasing is shown to be able to restore lasing in presence of
detuning, a further demonstration that decoherence can be seen as a fundamental
resource in solid-state cavity quantum electrodynamics, offering appealing
perspectives in the context of advanced nano-photonic devices.Comment: 10 pages, 7 figure
Otimização de protocolo para o enraizamento in vitro de jalapa (Mandevilla illustris) (Vell.) R. E. Woodson.
Suplemento. Edição dos Trabalhos do 49 Congresso Brasileiro de Olericultura, Águas de Lindóia, ago. 2009
Emergence of classicality in small number entangled systems
We show the transition from a fully quantized interaction to a semiclassical
one in entangled small number quantum systems using the quantum trajectories
approach. In particular, we simulate the microwave Ramsey zones used in Rydberg
atom interferometry, filling in the gap between the strongly entangling Jaynes
Cummings evolution and the semiclassical rotation of the atomic internal
states. We also correlate the information flowing with leaking photons to the
entanglement generation between cavity field and flying atom and detail the
roles played by the strong dissipation and the external driving force in
preserving atomic coherence through the interaction.Comment: 4 pages, 6 figure
Cultivo de mangueira Tommy Atkins com diferentes compostos orgânicos.
bitstream/item/29170/1/Alineaurea.pd
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