7,978 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
Charged scalar gravitational collapse in de Sitter spacetime
We study the charged scalar collapse in de Sitter spacetimes. With the
electric charge, there is one more competitor to join the competition of
dynamics in the gravitational collapse. We find that two factors can influence
the electric charge. If we just adjust the charge conjugation, the electric
charge effect is always perturbative at the black hole threshold. The electric
charge can also be influenced by the initial conditions of perturbations. These
initial parameters can be tuned to control the competition in dynamics and
present us new and rich physics in the process of gravitational collapse. We
give physical explanations on these phenomena found in dynamics. Furthermore we
show that the properties of the gravitational collapse are universal and do not
depend on spacetime dimensions.Comment: 16pages, 8 figures. Accepted by PR
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
The Generation and Exchange of Entanglement via Zeeman Effect
In this paper we show a new way to generate entanglement via two identical
three-level atoms splitting in the magnetic field interacting with the cavity
field. By the system we investigate, We can acquire the EPR state,
multi-dimensional entangled states etc. which are more stable than usual
realization by high-energy-level Rydberg atoms and we can realize the local
exchange operator too. We also achieve the goal of maintaining long- time
entanglement between atoms. At last, by using the procedure of local exchange,
we put forward an experimental scheme for quantum feedback.Comment: 9 pages, 1 figur
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
Multibrane DGP model: Our universe as a stack of -dim branes
We consider scenario in which our -dim universe is actually a dense
stack of multiple parallel -dim branes. For this purpose, we generalize
the DGP model to a multi-brane case. We solve for the propagation of the scalar
field and gravity in this setup. At short distances (high momenta) along the
branes interactions follow the -dim laws, while at large distances (low
momenta) interactions follow the usual -dim laws. This feature is
inherited from the original DGP model. In the direction perpendicular to the
brane, we show that interactions become -dim at low momenta which are
unable to resolve the interbrane separation. Thus, this is one of the explicit
constructs of the "vanishing dimensions" scenario where high energy physics
appears to be lower dimensional rather than higher dimensional.Comment: updated references, published in Phys. Rev. D90, 064031 (2014
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
Properties of Geometric Potential in the Invariant Adiabatic Theory
We concentrate on the geometric potential in the invariant perturbation
theory of quantum adiabatic process which is presented in our recent papers. It
is found out to be related to the geodesic curvature of the spherical curve in
2-dimension quantum systems. We also show that the geometric potential may
affect adiabatic approximation remarkably.Comment: 4 pages, 6 figure
Adiabatic Approximation Condition
In this paper, we present an invariant perturbation theory of the adiabatic
process based on the concepts of U(1)-invariant adiabatic orbit and
U(1)-invariant adiabatic expansion. As its application, we propose and discuss
new adiabatic approximation conditions.Comment: 4 pages, no figure
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