28,217 research outputs found
Violations of Locality Beyond Bell's Theorem
Locality and realism are two main assumptions in deriving Bell's
inequalities. Though the experimentally demonstrated violations of Bell's
inequalities rule out local realism, it is, however, not clear what role each
of the two assumptions solely plays in the observed violations. Here we show
that two testable inequalities for the statistical predictions of two-qubit
systems can be derived by assuming either locality or realism. It turns out
that quantum mechanics respects a nonlocal classical realism, and it is
locality that is incompatible with experimental observations and quantum
mechanics.Comment: 4 pages, 1 figure; comments are welcom
Numerical solution to the Bloch equations, paramagnetic solutions under wideband continuous radio frequency irradiation in a pulsed magnetic field
A novel NMR experimental scheme, called wide band continuous wave NMR, is
presented in this article
Linear Optics Quantum Communication over Long Distances
We propose a feasible scheme for teleporting an arbitrary polarization state
or entanglement of photons by requiring only single-photon (SP) sources, simple
linear optical elements and SP quantum non-demolition measurements. An unknown
SP polarization state can be faithfully teleported either to a duplicate
polarization state or to an entangled state. Our proposal can be used to
implement long-distance quantum communication in a simple way. The scheme is
within the reach of current technology and significantly simplifies the
realistc implementation of long-distance high-fidelity quantum communication
with photon qubits.Comment: 4 pages, no figure; comments are welcome / with refs. added and other
change
Feasible Linear-optics Generation of Polarization-entangled Photons Assisted with Single-photon Quantum Non-demolition Measurement
We propose a feasible scheme to create -party ()
polarization-entangled photon states in a controllable way. The scheme requires
only single-photon sources, single-photon quantum non-demolition measurement
(SP-QNDM) and simple linear optical elements, usually with high perfections.
The SP-QNDM acts as a non-destructive projection measurement onto the wanted
entangled states and filters out the unwanted terms. Our scheme in fact
realizes entanglement of non-interacting photons; the interaction occurs only
implicitly in the optical elements and SP-QNDM. We also briefly consider
purification of mixed single-photon states within our scheme.Comment: 4 pages, no figur
Holographic thermalization and gravitational collapse in the spacetime dominated by quintessence dark energy
In this paper, the thermalization has been studied holographically.
Explicitly in the gravity side, we consider the gravitational collapse of a
thin shell of dust in a spacetime dominated by quintessence dark energy. With
the thermalization probes such as the normalized geodesic length and minimal
area surface, we study the effect of the state parameter for the quintessence
dark energy on the thermalization. Our results show that the smaller the state
parameter of quintessence is, the harder the plasma to thermalize. We also
investigate the thermalization velocity and thermalization acceleration. We
hope our results here can shed light on the nature of the quintessence dark
energy.Comment: minor modifications. arXiv admin note: text overlap with
arXiv:1407.526
Exact solution to an extremal problem on graphic sequences with a realization containing every -tree on vertices
A simple graph is an {\it 2-tree} if , or has a vertex of
degree 2, whose neighbors are adjacent, and is an 2-tree. Clearly, if
is an 2-tree on vertices, then . A non-increasing sequence
of nonnegative integers is a {\it graphic sequence} if
it is realizable by a simple graph on vertices. Yin and Li (Acta
Mathematica Sinica, English Series, 25(2009)795--802) proved that if ,
and is a graphic
sequence with , then has a realization
containing every 1-tree (the usual tree) on vertices. Moreover, the lower
bound is the best possible. This is a variation of a conjecture due to
Erd\H{o}s and S\'{o}s. In this paper, we investigate an analogue problem for
-trees and prove that if is an integer with k\equiv i(\mbox{mod
}3), and
is a graphic sequence with , then
has a realization containing every 2-tree on vertices. Moreover, the
lower bound is the
best possible. This result implies a conjecture due to Zeng and Yin (Discrete
Math. Theor. Comput. Sci., 17(3)(2016), 315--326).Comment: 31 pag
Unifying Entanglement and Nonlocality as a Single Concept: Quantum Wholeness
Although entanglement is widely recognized as one of the most fascinating
characteristics of quantum mechanics, nonlocality remains to be a big
labyrinth. The proof of existence of nonlocality is as yet not much convincing
because of its strong reliance on Bell's theorem where the assumption of
realism weakens the proof. We demonstrate that entanglement and quantum
nonlocality are two equivalent aspects of the same quantum wholeness for
spacelike separated quantum systems. This result implies that quantum mechanics
is indeed a nonlocal theory and lays foundation of understanding quantum
nonlocality beyond Bell's theorem.Comment: 5 pages, one figure; comments are welcom
Violation of Locality Without Inequalities for Multiparticle Perfect Correlations
We prove that for a three-qubit system in the Greenberger-Horne-Zeilinger
(GHZ) state, locality per se is in conflict with the perfect GHZ correlations.
The proof does not in any way use the realism assumption and can lead to a
refutation of locality. We also provide inequalities that are imposed by
locality. The experimental confirmation of the present reasoning may imply a
genuine quantum nonlocality and will deepen our understanding of nonlocality of
nature.Comment: 4 pages, 1 figure; comments are welcom
Constructing quantum circuits for maximally entangled multi-qubit states using the genetic algorithm
Numerical optimization methods such as hillclimbing and simulated annealing
have been applied to search for highly entangled multi-qubit states. Here the
genetic algorithm is applied to this optimization problem -- to search not only
for highly entangled states, but also for the corresponding quantum circuits
creating these states. Simple quantum circuits for maximally (highly) entangled
states are discovered for 3, 4, 5, and 6-qubit systems; and extension of the
method to systems with more qubits is discussed. Among other results we have
found explicit quantum circuits for maximally entangled 5 and 6-qubit circuits,
with only 8 and 13 quantum gates respectively. One significant advantage of our
method over previous ones is that it allows very simple construction of quantum
circuits based on the quantum states found.Comment: 15 pages, 4 figure
Calculation of entanglement for continious variable states
In this paper, we present a general formula for obtaining the reduced density
opeator for any biparticle pure entangled state. Using this formula, we derive,
in a compact form, the explicit formula of the entanglement for any bipartical
pure entangled Gaussian state. In the case of Gaussian states, the criteria of
separabelity can be naturely obtained by the formula. For non-Gaussian states,
we also show the usefulness of the method presented in this paper.Comment: 4 pages, no figur
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