1,439 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
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
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
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
Characterization of GaN Nanorods Fabricated Using Ni Nanomasking and Reactive Ion Etching: A Top-Down Approach
Large thermal mismatch between GaN surface and sapphire results in compressive stress in Gallium Nitride (GaN) layer which degrades the device performance. Nanostructuring the GaN can reduce this stress leading to reduction in Quantum Confined Stark Effect. Aligned GaN nanorods based nanodevices have potential applications in electronics and optoelectronics. This paper describes the fabrication of GaN nanorods using Ni nanomasking and reactive ion etching. The morphology of GaN nanorods was studied by field emission scanning electron microscopy. The optical properties of GaN nanorods were studied by Cathodoluminescence (CL) spectroscopy. CL results revealed the existence of characteristic band-edge luminescence and yellow band luminescence.
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