3,478 research outputs found
On Series of Multiqubit Bell's Inequalities
We overview series of multiqubit Bell's inequalities which apply to
correlation functions. We present conditions that quantum states must satisfy
to violate such inequalities.Comment: 10 page
Detection of N-particle entanglement with generalized Bell inequalities
We show that the generalized Bell-type inequality, explicitly involving
rotational symmetry of physical laws, is very efficient in distinguishing
between true N-particle quantum correlations and correlations involving less
particles. This applies to various types of generalized partial separabilities.
We also give a rigorous proof that the new Bell inequalities are maximally
violated by the GHZ states, and find a very handy description of the N-qubit
correlation function.Comment: 5 pages, minor typos corrected, journal versio
Magnetic groundstate and Fermi surface of bcc Eu
Using spin-spiral technique within the full potential linearized
augmented-plane-waves (LAPW) electronic structure method we investigate the
magnon spectrum and N\'eel temperature of bcc Eu. Ground state corresponding to
an incommensurate spin-spiral is obtained in agreement with experiment and
previous calculations. We demonstrate that the magnetic coupling is primarily
through the intra-atomic and exchange and
Ruderman-Kittel-Kasuya-Yosida mechanism. We show that the existence of this
spin-spiral is closely connected to a nesting feature of the Fermi surface
which was not noticed before.Comment: 6 pages 8 figure
Bell inequality with an arbitrary number of settings and its applications
Based on a geometrical argument introduced by Zukowski, a new multisetting
Bell inequality is derived, for the scenario in which many parties make
measurements on two-level systems. This generalizes and unifies some previous
results. Moreover, a necessary and sufficient condition for the violation of
this inequality is presented. It turns out that the class of non-separable
states which do not admit local realistic description is extended when compared
to the two-setting inequalities. However, supporting the conjecture of Peres,
quantum states with positive partial transposes with respect to all subsystems
do not violate the inequality. Additionally, we follow a general link between
Bell inequalities and communication complexity problems, and present a quantum
protocol linked with the inequality, which outperforms the best classical
protocol.Comment: 8 pages, To appear in Phys. Rev.
THE ROLE OF WALKING AND RUNNING VELOCITY ON OSTEOGENIC POTENTIAL
This study assessed the ground reaction forces (GRF) associated with walking and running at a variety of speeds and compared these kinetic values to the landing after a maximum counter-movement jump in order to understand the osteogenic potential for these activities. Twenty-four women walked and ran over a force platform at slow, medium, and fast walking and running speeds, which were assessed using Doppler radar. Landing vertical peak GRF and rate of force development (RFD) were analyzed for all movements using a force platform. In almost all cases, higher walking or running speeds resulted in statistically significant increases in GRF and RFD. Based on the findings of this study, moderate to fast sprints should be prescribed in the training programs for those who seek to maximize their bone health
ProFunc: a server for predicting protein function from 3D structure
ProFunc () is a web server for predicting the likely function of proteins whose 3D structure is known but whose function is not. Users submit the coordinates of their structure to the server in PDB format. ProFunc makes use of both existing and novel methods to analyse the protein's sequence and structure identifying functional motifs or close relationships to functionally characterized proteins. A summary of the analyses provides an at-a-glance view of what each of the different methods has found. More detailed results are available on separate pages. Often where one method has failed to find anything useful another may be more forthcoming. The server is likely to be of most use in structural genomics where a large proportion of the proteins whose structures are solved are of hypothetical proteins of unknown function. However, it may also find use in a comparative analysis of members of large protein families. It provides a convenient compendium of sequence and structural information that often hold vital functional clues to be followed up experimentally
Rotational invariance as an additional constraint on local realism
Rotational invariance of physical laws is a generally accepted principle. We
show that it leads to an additional external constraint on local realistic
models of physical phenomena involving measurements of multiparticle spin 1/2
correlations. This new constraint rules out such models even in some situations
in which standard Bell inequalities allow for explicit construction of such
models. The whole analysis is performed without any additional assumptions on
the form of local realistic models.Comment: 4 page
Nonclassicality of pure two-qutrit entangled states
We report an exhaustive numerical analysis of violations of local realism by
two qutrits in all possible pure entangled states. In Bell type experiments we
allow any pairs of local unitary U(3) transformations to define the measurement
bases. Surprisingly, Schmidt rank-2 states, resembling pairs of maximally
entangled qubits, lead to the most noise-robust violations of local realism.
The phenomenon seems to be even more pronounced for four and five dimensional
systems, for which we tested a few interesting examples.Comment: 6 pages, journal versio
Salient signatures of entanglement in the surrounding environment
We develop a model in which presence of entanglement in a quantum system can
be confirmed through coarse observations of the environment surrounding the
system. This counter-intuitive effect becomes possible when interaction between
the system and its environment is proportional to an observable being an
entanglement witness. While presenting intuitive examples we show that: i) a
cloud of an ideal gas, when subject to a linear potential coupled with the
entanglement witness, accelerates in the direction dictated by the sign of the
witness; ii) when the environment is a radiation field, the direction of
dielectric polarization depends on the presence of entanglement; iii)
quadratures of electromagnetic field in a cavity coupled with two qubits (or a
four-level atom) are displaced in the same manner
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