1,742 research outputs found
String Effective Action and Two Dimensional Charged Black Hole
Graviton-dilaton background field equations in three space-time dimensions,
following from the string effective action are solved when the metric has only
time dependence. By taking one of the two space dimensions as compact, our
solution reproduces a recently discovered charged black hole solution in two
space-time dimensions. Solutions in presence of nonvanishing three dimensional
background antisymmetric tensor field are also discussed.Comment: 11 page
Multiple charge beam dynamics in Alternate Phase Focusing structure
Asymmetrical Alternate Phase (A-APF) focusing realized in a sequence of 36
Superconducting Quarter Wave Resonators has been shown to accelerate almost 81
% of input Uranium beam before foil stripper to an energy of 6.2 MeV/u from 1.3
MeV/u. Ten charge states from 34+ to 43+ could be simultaneously accelerated
with the phase of resonators tuned for 34+. A-APF structure showed unique
nature of large potential bucket for charge states higher than that of tuned
one. Steering inherent to QWRs can be mitigated by selecting appropriate phase
variation of the APF periods and optimization of solenoid field strengths
placed in each of the periods. This mitigation facilitates multiple charge
state acceleration schemeComment: 10 pages, 8 figure
Quantum Fisher and Skew information for Unruh accelerated Dirac qubit
We develop a Bloch vector representation of Unruh channel for a Dirac field
mode. This is used to provide a unified, analytical treatment of quantum Fisher
and Skew information for a qubit subjected to the Unruh channel, both in its
pure form as well as in the presence of experimentally relevant external noise
channels. The time evolution of Fisher and Skew information is studied along
with the impact of external environment parameters such as temperature and
squeezing. The external noises are modelled by both purely dephasing phase
damping as well as the squeezed generalized amplitude damping channels. An
interesting interplay between the external reservoir temperature and squeezing
on the Fisher and Skew information is observed, in particular, for the action
of the squeezed generalized amplitude damping channel. It is seen that for some
regimes, squeezing can enhance the quantum information against the
deteriorating influence of the ambient environment. Similar features are also
observed for the analogous study of Skew information, highlighting the similar
origin of the Fisher and Skew information.Comment: 12 pages, 10 figure
Re-examining sin(2beta) and Delta m(d) from evolution of B(d) mesons with decoherence
In the time evolution of neutral meson systems, a perfect quantum coherence
is usually assumed. The important quantities of the B(d) system, such as sin
(2beta) and Delta m(d), are determined under this assumption. However, the
meson system interacts with its environment. This interaction can lead to
decoherence in the mesons even before they decay. In our formalism this
decoherence is modelled by a single parameter lambda. It is desirable to
re-examine the procedures of determination of sin(2beta) and Delta m(d) in
meson systems with decoherence. We find that the present values of these two
quantities are modulated by lambda. Re-analysis of B(d) data from B-factories
and LHCb can lead to a clean determination of lambda, sin(2beta) and Delta
m(d).Comment: Version accepted for publication in Physics Letters
Swapping path-spin intraparticle entanglement onto spin-spin interparticle entanglement
Based on a scheme that produces an entanglement between the spin and the path
variables of a single spin-1/2 particle (qubit) using a beam-splitter and a
spin-flipper, we formulate a procedure for transferring this intraparticle
hybrid entanglement to an interparticle entanglement between the spin variables
of two other spatially separated spin-1/2 particles which never interact with
each other during the entire process. This procedure of entanglement swapping
is accomplished by a Mach-Zehnder setup in conjunction with the Stern-Gerlach
measuring device, using suitable unitary operations. The proposed protocol,
thus, enables the use of intraparticle entanglement as a resource - a feature
that has remained unexplored.Comment: 5 pages, 1 Figur
Characterization of Unruh Channel in the context of Open Quantum Systems
We show through the Choi matrix approach that the effect of Unruh
acceleration on a qubit is similar to the interaction of the qubit with a
vacuum bath, despite the finiteness of the Unruh temperature. Thus, rather
counterintuitvely, from the perspective of decoherence in this framework, the
particle experiences a vacuum bath with a temperature-modified interaction
strength, rather than a thermal bath. We investigate how this "relativistic
decoherence" is modified by the presence of environmentally induced
decoherence, by studying the degradation of quantum information, as quantified
by parameters such as nonlocality, teleportation fidelity, entanglement,
coherence and quantum measurement-induced disturbance (a discord-like measure).
Also studied are the performance parameters such as gate and channel fidelity.
We highlight the distinction between dephasing and dissipative environmental
interactions, by considering the actions of quantum non-demolition and squeezed
generalized amplitude damping channels, respectively, where, in particular,
squeezing is shown to be a useful quantum resource.Comment: 15 pages, 19 figure
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