225 research outputs found
Universal state inversion and concurrence in arbitrary dimensions
Wootters [Phys. Rev. Lett. 80, 2245 (1998)] has given an explicit formula for
the entanglement of formation of two qubits in terms of what he calls the
concurrence of the joint density operator. Wootters's concurrence is defined
with the help of the superoperator that flips the spin of a qubit. We
generalize the spin-flip superoperator to a "universal inverter," which acts on
quantum systems of arbitrary dimension, and we introduce the corresponding
concurrence for joint pure states of (D1 X D2) bipartite quantum systems. The
universal inverter, which is a positive, but not completely positive
superoperator, is closely related to the completely positive universal-NOT
superoperator, the quantum analogue of a classical NOT gate. We present a
physical realization of the universal-NOT superoperator.Comment: Revtex, 25 page
Svetlichny's inequality and genuine tripartite nonlocality in three-qubit pure states
The violation of the Svetlichny's inequality (SI) [Phys. Rev. D, 35, 3066
(1987)] is sufficient but not necessary for genuine tripartite nonlocal
correlations. Here we quantify the relationship between tripartite entanglement
and the maximum expectation value of the Svetlichny operator (which is bounded
from above by the inequality) for the two inequivalent subclasses of pure
three-qubit states: the GHZ-class and the W-class. We show that the maximum for
the GHZ-class states reduces to Mermin's inequality [Phys. Rev. Lett. 65, 1838
(1990)] modulo a constant factor, and although it is a function of the three
tangle and the residual concurrence, large number of states don't violate the
inequality. We further show that by design SI is more suitable as a measure of
genuine tripartite nonlocality between the three qubits in the the W-class
states, and the maximum is a certain function of the bipartite entanglement
(the concurrence) of the three reduced states, and only when their certain sum
attains a certain threshold value, they violate the inequality.Comment: Modified version, 5 pages, 2 figures, REVTeX
Entanglement Detection Using Majorization Uncertainty Bounds
Entanglement detection criteria are developed within the framework of the
majorization formulation of uncertainty. The primary results are two theorems
asserting linear and nonlinear separability criteria based on majorization
relations, the violation of which would imply entanglement. Corollaries to
these theorems yield infinite sets of scalar entanglement detection criteria
based on quasi-entropic measures of disorder. Examples are analyzed to probe
the efficacy of the derived criteria in detecting the entanglement of bipartite
Werner states. Characteristics of the majorization relation as a comparator of
disorder uniquely suited to information-theoretical applications are emphasized
throughout.Comment: 10 pages, 1 figur
From raw data to agent perceptions for simulation, verification, and monitoring
In this paper we present a practical solution to the problem of connecting “real world” data exchanged between sensors and actuators with the higher level of abstraction used in frameworks for multiagent systems. In particular, we show how to connect an industry-standard publish-subscribe communication protocol for embedded systems called MQTT with two Belief-Desire-Intention agent modelling and programming languages: Jason/AgentSpeak and Brahms. In the paper we describe the details of our Java implementation and we release all the code open source
Effects of virtual acoustics on dynamic auditory distance perception
Sound propagation encompasses various acoustic phenomena including
reverberation. Current virtual acoustic methods, ranging from parametric
filters to physically-accurate solvers, can simulate reverberation with varying
degrees of fidelity. We investigate the effects of reverberant sounds generated
using different propagation algorithms on acoustic distance perception, i.e.,
how faraway humans perceive a sound source. In particular, we evaluate two
classes of methods for real-time sound propagation in dynamic scenes based on
parametric filters and ray tracing. Our study shows that the more accurate
method shows less distance compression as compared to the approximate,
filter-based method. This suggests that accurate reverberation in VR results in
a better reproduction of acoustic distances. We also quantify the levels of
distance compression introduced by different propagation methods in a virtual
environment.Comment: 8 Pages, 7 figure
Forgotten Knowledge: Examining the Citational Amnesia in NLP
Citing papers is the primary method through which modern scientific writing
discusses and builds on past work. Collectively, citing a diverse set of papers
(in time and area of study) is an indicator of how widely the community is
reading. Yet, there is little work looking at broad temporal patterns of
citation. This work systematically and empirically examines: How far back in
time do we tend to go to cite papers? How has that changed over time, and what
factors correlate with this citational attention/amnesia? We chose NLP as our
domain of interest and analyzed approximately 71.5K papers to show and quantify
several key trends in citation. Notably, around 62% of cited papers are from
the immediate five years prior to publication, whereas only about 17% are more
than ten years old. Furthermore, we show that the median age and age diversity
of cited papers were steadily increasing from 1990 to 2014, but since then, the
trend has reversed, and current NLP papers have an all-time low temporal
citation diversity. Finally, we show that unlike the 1990s, the highly cited
papers in the last decade were also papers with the least citation diversity,
likely contributing to the intense (and arguably harmful) recency focus. Code,
data, and a demo are available on the project homepage.Comment: ACL 2023 Main Conferenc
Optimal Lewenstein-Sanpera Decomposition for some Biparatite Systems
It is shown that for a given bipartite density matrix and by choosing a
suitable separable set (instead of product set) on the separable-entangled
boundary, optimal Lewenstein-Sanpera (L-S) decomposition can be obtained via
optimization for a generic entangled density matrix. Based on this, We obtain
optimal L-S decomposition for some bipartite systems such as and
Bell decomposable states, generic two qubit state in Wootters
basis, iso-concurrence decomposable states, states obtained from BD states via
one parameter and three parameters local operations and classical
communications (LOCC), Werner and isotropic states, and a one
parameter state. We also obtain the optimal decomposition for
multi partite isotropic state. It is shown that in all systems
considered here the average concurrence of the decomposition is equal to the
concurrence. We also show that for some Bell decomposable states
the average concurrence of the decomposition is equal to the lower bound of the
concurrence of state presented recently in [Buchleitner et al,
quant-ph/0302144], so an exact expression for concurrence of these states is
obtained. It is also shown that for isotropic state where
decomposition leads to a separable and an entangled pure state, the average
I-concurrence of the decomposition is equal to the I-concurrence of the state.
Keywords: Quantum entanglement, Optimal Lewenstein-Sanpera decomposition,
Concurrence, Bell decomposable states, LOCC}
PACS Index: 03.65.UdComment: 31 pages, Late
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