4,382 research outputs found
Easy Monitored Entangled States
We discuss the generation and monitoring of durable atomic entangled state
via Raman-type process, which can be used in the quantum information
processing.Comment: 9 pages, 2 figures, the previous title "Durable Entanglement in
Atomic Systems" is replaced by new title, accepted to Appl. Phys. Let
Teleporting a rotation on remote photons
Quamtum remote rotation allows implement local quantum operation on remote
systems with shared entanglement. Here we report an experimental demonstration
of remote rotation on single photons using linear optical element. And the
local dephase is also teleported during the process. The scheme can be
generalized to any controlled rotation commutes with .Comment: 5 pages, 4 figure
Methods for linear optical quantum Fredkin gate
We consider the realization of quantum Fredkin gate with only linear optics
and single photons. First we construct a heralded Fredkin gate using four
heralded controlled-not (CNOT) gates. Then we simplify this method to a
post-selected one utilizing only two CNOT gates. We also give a possible
realization of this method which is feasible with current experimental
technology. Another post-selected scheme requires time entanglement of the
input photons but needs no ancillary photons.Comment: 5 pages, 5 figure
Vector and axial-vector couplings of D and D* mesons in 2+1 flavor Lattice QCD
Using the axial-vector coupling and the electromagnetic form factors of the D
and D* mesons in 2+1 flavor Lattice QCD, we compute the D*D\pi, DD\rho and
D*D*\rho coupling constants, which play an important role in describing the
charm hadron interactions in terms of meson-exchange models. We also extract
the charge radii of D and D* mesons and determine the contributions of the
light and charm quarks separately.Comment: 19 pages, 3 figures; added references and comments, published versio
Entanglement measurement based on two-particle interference
We propose a simple and realizable method using a two-particle interferometer
for the experimental measurement of pairwise entanglement, assuming some prior
knowledge about the quantum state. The basic idea is that the properties of the
density matrix can be revealed by the single- and two-particle interference
patterns. The scheme can easily be implemented with polarized entangled
photons.Comment: 5 pages, 1 figur
Generation of a High-Visibility Four-Photon Entangled State and Realization of a Four-Party Quantum Communication Complexity Scenario
We obtain a four-photon polarization-entangled state with a visibility as
high as (95.35\pm 0.45)% directly from a single down-conversion source. A
success probability of (81.54\pm 1.38)% is observed by applying this entangled
state to realize a four-party quantum communication complexity scenario (QCCS),
which comfortably surpass the classical limit of 50%. As a comparison, two
Einstein-Podolsky-Rosen (EPR) pairs are shown to implement the scenario with a
success probability of (73.89\pm 1.33)%. This four-photon state can be used to
fulfill decoherence-free quantum information processing and other advanced
quantum communication schemes.Comment: REVTEX 4.0, 4 pages, 4 figures, 1 tabl
Remote Preparation of Mixed States via Noisy Entanglement
We present a practical and general scheme of remote preparation for pure and
mixed state, in which an auxiliary qubit and controlled-NOT gate are used. We
discuss the remote state preparation (RSP) in two important types of decoherent
channel (depolarizing and dephaseing). In our experiment, we realize RSP in the
dephaseing channel by using spontaneous parametric down conversion (SPDC),
linear optical elements and single photon detector.Comment: 10 pages, 5 figures, submitted to PR
Local Operations in qubit arrays via global but periodic Manipulation
We provide a scheme for quantum computation in lattice systems via global but
periodic manipulation, in which only effective periodic magnetic fields and
global nearest neighbor interaction are required. All operations in our scheme
are attainable in optical lattice or solid state systems. We also investigate
universal quantum operations and quantum simulation in 2 dimensional lattice.
We find global manipulations are superior in simulating some nontrivial many
body Hamiltonians.Comment: 5 pages, 2 figures, to appear in Phys. Rev.
Stability of Pairwise Entanglement in a Decoherent Environment
Consider the dynamics of a two-qubit entangled system in the decoherence
environment, we investigate the stability of pairwise entanglement under
decoherence. We find that for different decoherence models, there exist some
special class of entangled states of which the pairwise entanglement is the
most stable. The lifetime of the entanglement in these states is larger than
other states with the same initial entanglement. In addition, we also
investigate the dynamics of pairwise entanglement in the ground state of spin
models such as Heisenberg and XXY models.Comment: accepted by Physical Review A, references updated and minor change
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