13,028 research outputs found
Quantum discord and measurement-induced disturbance in the background of dilaton black holes
We study the dynamics of classical correlation, quantum discord and
measurement-induced disturbance of Dirac fields in the background of a dilaton
black hole. We present an alternative physical interpretation of single mode
approximation for Dirac fields in black hole spacetimes. We show that the
classical and quantum correlations are degraded as the increase of black hole's
dilaton. We find that, comparing to the inertial systems, the quantum
correlation measured by the one-side measuring discord is always not symmetric
with respect to the measured subsystems, while the measurement-induced
disturbance is symmetric. The symmetry of classical correlation and quantum
discord is influenced by gravitation produced by the dilaton of the black hole.Comment: 6 pages, 2 figure
Monogamy of Einstein-Podolsky-Rosen steering in the background of an asymptotically flat black hole
We study the behavior of monogamy deficit and monogamy asymmetry for
Einstein-Podolsky-Rosen steering of Gaussian states under the influence of the
Hawking effect. We demonstrate that the monogamy of quantum steering shows an
extreme scenario in the curved spacetime: the first part of a tripartite system
cannot individually steer two other parties, but it can steer the collectivity
of the remaining two parties. We also find that the monogamy deficit of
Gaussian steering, a quantifier of genuine tripartite steering, are generated
due to the influence of the Hawking thermal bath. Our results elucidate the
structure of quantum steering in tripartite quantum systems in curved
spacetime.Comment: 16 pages, 4 figure
Yangian doubles of classical types and their vertex representations
The Yangian double is introduced for the
classical types of , ,
. Via the Gauss decomposition of the generator matrix, the
Yangian double is given the Drinfeld presentation. In addition, bosonization of
level realizations for the Yangian double
of non-simply-laced types are explicitly
constructed.Comment: 50 pages, 0 figures. Revised versio
NeXtVLAD: An Efficient Neural Network to Aggregate Frame-level Features for Large-scale Video Classification
This paper introduces a fast and efficient network architecture, NeXtVLAD, to
aggregate frame-level features into a compact feature vector for large-scale
video classification. Briefly speaking, the basic idea is to decompose a
high-dimensional feature into a group of relatively low-dimensional vectors
with attention before applying NetVLAD aggregation over time. This NeXtVLAD
approach turns out to be both effective and parameter efficient in aggregating
temporal information. In the 2nd Youtube-8M video understanding challenge, a
single NeXtVLAD model with less than 80M parameters achieves a GAP score of
0.87846 in private leaderboard. A mixture of 3 NeXtVLAD models results in
0.88722, which is ranked 3rd over 394 teams. The code is publicly available at
https://github.com/linrongc/youtube-8m.Comment: ECCV 2018 worksho
Quantum metrology and estimation of Unruh effect
We study the quantum metrology for a pair of entangled Unruh-Dewitt detectors
when one of them is accelerated and coupled to a massless scalar field.
Comparing with previous schemes, our model requires only local interaction and
avoids the use of cavities in the probe state preparation process. We show that
the probe state preparation and the interaction between the accelerated
detector and the external field have significant effects on the value of
quantum Fisher information, correspondingly pose variable ultimate limit of
precision in the estimation of Unruh effect. We find that the precision of the
estimation can be improved by a larger effective coupling strength and a longer
interaction time. Alternatively, the energy gap of the detector has a range
that can provide us a better precision. Thus we may adjust those parameters and
attain a higher precision in the estimation. We also find that an extremely
high acceleration is not required in the quantum metrology process.Comment: 24 pages,3 figures, typos corrected, new references adde
The influence of Unruh effect on quantum steering for accelerated two-level detectors with different measurements
We study the dynamics of steering between two correlated Unruh-Dewitt
detectors when one of them locally interacts with external scalar field via
different quantifiers. We find that the quantum steering, either measured by
the entropic steering inequality or the Cavalcanti-Jones-Wiseman-Reid
inequality, is fragile under the influence of Unruh thermal noise. The quantum
steering is found always asymmetric and the asymmetry is extremely sensitive to
the initial state parameter. In addition, the steering-type quantum
correlations experience "sudden death" for some accelerations, which are quite
different from the behaviors of other quantum correlations in the same system.
It is worth noting that the domination value of the tight quantum steering
exists a transformation point with increasing acceleration. We also find that
the robustness of quantum steerability under the Unruh thermal noise can be
realized by choosing the smallest energy gap in the detectors.Comment: 18 pages, 3 figure
Gaussian quantum steering and its asymmetry in curved spacetime
We study Gaussian quantum steering and its asymmetry in the background of a
Schwarzschild black hole. We present a Gaussian channel description of quantum
state evolution under the influence of the Hawking radiation. We find that
thermal noise introduced by Hawking effect will destroy the steerability
between an inertial observer Alice and an accelerated observer Bob who hovers
outside the event horizon, while it generates steerability between Bob and a
hypothetical observer anti-Bob inside the event horizon. Unlike entanglement
behaviors in curved spacetime, here the steering from Alice to Bob suffers from
a "sudden death" and the steering from anti-Bob to Bob experiences a "sudden
birth" with increasing Hawking temperature. We also find that the Gaussian
steering is always asymmetric and the maximum steering asymmetry cannot exceed
, which means the state never evolves to an extremal asymmetry state.
Furthermore, we obtain the parameter settings that maximize steering asymmetry
and find that (i) is the critical
point of steering asymmetry, and (ii) the attainment of maximal steering
asymmetry indicates the transition between one-way steerability and both-way
steerability for the two-mode Gaussian state under the influence of Hawking
radiation.Comment: 7 pages, 3 figures, to appear in Phys. Rev.
Lower bounds for algebraic connectivity of graphs in terms of matching number or edge covering number
In this paper we characterize the unique graph whose algebraic connectivity
is minimum among all connected graphs with given order and fixed matching
number or edge covering number, and present two lower bounds for the algebraic
connectivity in terms of the matching number or edge covering number.Comment: arXiv admin note: substantial text overlap with arXiv:1310.853
Center of the quantum affine vertex algebra in type A
We consider the quantum vertex algebra associated with the double Yangian in
type A as defined by Etingof and Kazhdan. We show that its center is a
commutative associative algebra and construct algebraically independent
families of topological generators of the center at the critical level.Comment: 39 pages, few corrections mad
Efficient improvement of frequency-domain Kalman filter
The frequency-domain Kalman filter (FKF) has been utilized in many audio
signal processing applications due to its fast convergence speed and
robustness. However, the performance of the FKF in under-modeling situations
has not been investigated. This paper presents an analysis of the steady-state
behavior of the commonly used diagonalized FKF and reveals that it suffers from
a biased solution in under-modeling scenarios. Two efficient improvements of
the FKF are proposed, both having the benefits of the guaranteed optimal
steady-state behavior at the cost of a very limited increase of the
computational burden. The convergence behavior of the proposed algorithms is
also compared analytically. Computer simulations are conducted to validate the
improved performance of the proposed methods.Comment: 5 pages, 3 figure
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