10,149 research outputs found
Two-Photon Beatings Using Biphotons Generated from a Two-Level System
We propose a two-photon beating experiment based upon biphotons generated
from a resonant pumping two-level system operating in a backward geometry. On
the one hand, the linear optical-response leads biphotons produced from two
sidebands in the Mollow triplet to propagate with tunable refractive indices,
while the central-component propagates with unity refractive index. The
relative phase difference due to different refractive indices is analogous to
the pathway-length difference between long-long and short-short in the original
Franson interferometer. By subtracting the linear Rayleigh scattering of the
pump, the visibility in the center part of the two-photon beating interference
can be ideally manipulated among [0, 100%] by varying the pump power, the
material length, and the atomic density, which indicates a Bell-type inequality
violation. On the other hand, the proposed experiment may be an interesting way
of probing the quantum nature of the detection process. The interference will
disappear when the separation of the Mollow peaks approaches the fundamental
timescales for photon absorption in the detector.Comment: to appear in Phys. Rev. A (2008
Bell inequalities for three particles
We present tight Bell inequalities expressed by probabilities for three four-
and five-dimensional systems. The tight structure of Bell inequalities for
three -dimensional systems (qudits) is proposed. Some interesting Bell
inequalities of three qubits reduced from those of three qudits are also
studied.Comment: 8 pages, 3 figures. Accepted for publication in Phys. Rev.
Detecting Full N-Particle Entanglement in Arbitrarily High-Dimensional Systems with Bell-Type Inequality
We derive a set of Bell-type inequalities for arbitrarily high-dimensional
systems, based on the assumption of partial separability in the hybrid
local-nonlocal hidden variable model. Partially entangled states would not
violate the inequalities, and thus upon violation, these Bell-type inequalities
are sufficient conditions to detect the full -particle entanglement and
validity of the hybrid local-nonlocal hidden variable description.Comment: 6 page
Greenberger-Horne-Zeilinger paradoxes from qudit graph states
One fascinating way of revealing the quantum nonlocality is the
all-versus-nothing test due to Greenberger, Horne, and Zeilinger (GHZ) known as
GHZ paradox. So far genuine multipartite and multilevel GHZ paradoxes are known
to exist only in systems containing an odd number of particles. Here we shall
construct GHZ paradoxes for an arbitrary number (greater than 3) of particles
with the help of qudit graph states on a special kind of graphs, called as GHZ
graphs. Based on the GHZ paradox arising from a GHZ graph, we derive a Bell
inequality with two -outcome observables for each observer, whose maximal
violation attained by the corresponding graph state, and a Kochen-Specker
inequality testing the quantum contextuality in a state-independent fashion
Isolated and non-isolated dwarfs in terms of modified Newtonian dynamics
Within the framework of modified Newtonian dynamics (MOND) we investigate the
kinematics of two dwarf spiral galaxies belonging to very different
environments, namely KK 246 in the Local Void and Holmberg II in the M81 group.
A mass model of the rotation curve of KK 246 is presented for the first time,
and we show that its observed kinematics are consistent with MOND. We re-derive
the outer rotation curve of Holmberg II, by modelling its HI data cube, and
find that its inclination should be closer to face-on than previously derived.
This implies that Holmberg II has a higher rotation velocity in its outer
parts, which, although not very precisely constrained, is consistent with the
MOND prediction.Comment: Accepted in A&A as a Research Note. 6 pages, 3 figure
Testing tripartite Mermin inequalities by spectral joint-measurements of qubits
It is well known that Bell inequality supporting the local realism can be
violated in quantum mechanics. Numerous tests of such a violation have been
demonstrated with bipartite entanglements. Using spectral jointmeasurements of
the qubits, we here propose a scheme to test the tripartite Mermin inequality
(a three-qubit Bell-type inequality) with three qubits dispersively-coupled to
a driven cavity. First, we show how to generate a three-qubit
Greenberger-Horne-Zeilinger (GHZ) state by only one-step quantum operation.
Then, spectral joint-measurements are introduced to directly confirm such a
tripartite entanglement. Assisted by a series of single-qubit operations, these
measurements are further utilized to test the Mermin inequality. The
feasibility of the proposal is robustly demonstrated by the present numerical
experiments.Comment: 7pages,3figure
Gisin's Theorem for Three Qubits
We present a Theorem that all generalized Greenberger-Horne-Zeilinger states
of a three-qubit system violate a Bell inequality in terms of probabilities.
All pure entangled states of a three-qubit system are shown to violate a Bell
inequality for probabilities; thus, one has Gisin's theorem for three qubits.Comment: 5 pages, 2 figures. v2: journal-ref is added and some corrections are
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Quantum Separability of Thermal Spin One Boson Systems
Using the temperature Green's function approach we investigate entanglement
between two non-interacting spin 1 bosons in thermal equilibrium. We show that,
contrary to the fermion case, the entanglement is absent in the spin density
matrix. Separability is demonstrated using the Peres-Horodecki criterion for
massless particles such as photons in black body radiation. For massive
particles, we show that the density matrix can be decomposed with separable
states.Comment: References & comments related to AQFT added. no figure, revtex4, to
be published in Phys. Lett.
Multi-Component Bell Inequality and its Violation for Continuous Variable Systems
Multi-component correlation functions are developed by utilizing d-outcome
measurements. Based on the multi-component correlation functions, we propose a
Bell inequality for bipartite d-dimensional systems. Violation of the Bell
inequality for continuous variable (CV) systems is investigated. The violation
of the original Einstein-Podolsky-Rosen state can exceed the Cirel'son bound,
the maximal violation is 2.96981. For finite value of squeezing parameter,
violation strength of CV states increases with dimension d. Numerical results
show that the violation strength of CV states with finite squeezing parameter
is stronger than that of original EPR state.Comment: 5 pages and 1 figure, rewritten version, accepted by Phys. Rev.
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