95 research outputs found
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
New physics solutions for and
Recent measurements of have reduced tension with the Standard Model
prediction. Taking all the present data into account, we obtain the values of
the Wilson coefficients of each new physics four-fermion operator of a given
Lorentz structure. We find that the combined data rule out most of the
solutions based on scalar/pseudoscalar operators. By studying the
inter-relations between different solutions, we find that there are only four
allowed solutions, which are based on operators with , linear
combination of and , tensor and linear combination of
scalar/pseudoscalar and tensor structure. We demonstrate that the need for new
physics is driven by those measurement of and where the
lepton is not studied. Further, we show that new physics only in is not compatible with the full set of observables in the
decays and .Comment: 16 pages, 1 figure (Accepted for publication in JHEP
Study of coherence and mixedness in meson and neutrino systems
We study the interplay between coherence and mixedness in meson and neutrino
systems. The dynamics of the meson system is treated using the open quantum
system approach taking into account the decaying nature of the system. Neutrino
dynamics is studied in the context of three flavor oscillations within the
framework of a decoherence model recently used in the context of LSND (Liquid
Scintillator Neutrino Detector) experiment. For meson systems, the decoherence
effect is negligible in the limit of zero CP violation. Interestingly, the
average mixedness increases with time for about one lifetime of these
particles. For neutrino system, in the context of the model considered, the
decoherence effect is maximum for neutrino energy around 30 MeV. Further, the
effect of CP violating phase is found to decrease (increase) the coherence in
the upper (lower ) half plane.Comment: 7 Pages, 3 Figure
Quantum correlations and the neutrino mass degeneracy problem
Many facets of nonclassicality are probed in neutrino system in the context
of three flavour neutrino oscillations. The analysis is carried out for
parameters relevant to two ongoing experiments NOA and T2K, and also for
the upcoming experiment DUNE. The various quantum correlations turn out to be
sensitive to the mass-hierarchy problem in neutrinos. This sensitivity is found
to be more prominent in DUNE experiment as compared to NOA and T2K
experiments. This can be attributed to the large baseline and high energy of
the DUNE experiment. Further, we find that to probe these correlations, the
neutrino (antineutrino) beam should be preferred if the sign of mass square
difference turns out to be positive (negative).Comment: 8 pages, 3 figure
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