99,127 research outputs found
Measurement-induced nonlocality over two-sided projective measurements
Measurement-induced nonlocality (MiN), introduced by Luo and Fu [Phys. Rev.
Lett. 106(2011)120401], is a kind of quantum correlation that beyond
entanglement and even beyond quantum discord. Recently, we extended MiN to
infinite-dimensional bipartite system [arXiv:1107.0355]. MiN is defined over
one-sided projective measurements. In this letter we introduce a
measurement-induced nonlocality over two-sided projective measurements. The
nullity of this two-sided MiN is characterized, a formula for calculating
two-sided MiN for pure states is proposed, and a lower bound of (two-sided) MiN
for maximally entangled mixed states is given. In addition, we find that
(two-sided) MiN is not continuous. The two-sided geometric measure of quantum
discord (GMQD) is introduced in [Phys. Lett. A 376(2012)320--324]. We extend it
to infinite-dimensional system and then compare it with the two-sided MiN. Both
finite- and infinite-dimensional cases are considered.Comment: 12 page
One-step error correction for multipartite polarization entanglement
We present two economical one-step error-correction protocols for
multipartite polarization-entangled systems in a Greenberger-Horne-Zeilinger
state. One uses spatial entanglement to correct errors in the polarization
entanglement of an N-photon system, resorting to linear optical elements. The
other uses frequency entanglement to correct errors in the polarization
entanglement of an N-photon system. The parties in quantum communication can
obtain a maximally entangled state from each N-photon system transmitted with
one step in these two protocols, and both of their success probabilities are
100%, in principle. That is, they both work in a deterministic way, and they do
not largely consume the less-entangled photon systems, which is far different
from conventional multipartite entanglement purification schemes. These
features may make these two protocols more useful for practical applications in
long-distance quantum communication.Comment: 8 pages, 2 figure
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
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
Quantum Non-Demolition Bell State Measurement and N-party GHZ State Preparation in Quantum Dot
By exploiting the fermionic qubit parity measurement, we present a scheme to
realize quantum non-demolition (QND) measurement of Bell-states and generate
n-party GHZ state in quantum dot. Compared with the original protocol, the
required electron transfer before and after parity measurement can be
nonadiabatic, which may speed up the operation speed and make the omitting of
spin-orbit interaction more reasonable. This may help us to construct CNOT gate
without highly precise control of coupling as the way of D. Gottesman and I. L.
Chuang.Comment: some modification to introduction and some details are adde
Entanglement and quantum discord dynamics of two atoms under practical feedback control
We study the dynamics of two identical atoms resonantly coupled to a
single-mode cavity under practical feedback control, and focus on the detection
inefficiency. The entanglement is induced to vanish in finite time by the
inefficiency of detection. Counterintuitively, the asymptotic entanglement and
quantum discord can be increased by the inefficiency of detection. The noise of
detection triggers control field to create entanglement and discord when no
photon are emitted from the atoms. Furthermore, sudden change happens to the
dynamics of entanglement.Comment: 5 pages, 4 figure
From the Complete Yang Model to Snyder's Model, de Sitter Special Relativity and Their Duality
By means of Dirac procedure, we re-examine Yang's quantized space-time model,
its relation to Snyder's model, the de Sitter special relativity and their
UV-IR duality. Starting from a dimensionless dS_5-space in a 5+1-d Mink-space a
complete Yang model at both classical and quantum level can be presented and
there really exist Snyder's model, the dS special relativity and the duality.Comment: 7 papge
Secondary Rayleigh-Taylor type Instabilities in the Reconnection Exhaust Jet as a Mechanism for Supra-Arcade Downflows
Supra-arcade downflows (hereafter referred to as SADs) are low-emission,
elongated, finger-like features usually observed in active-region coronae above
post-eruption flare arcades. Observations exhibit downward moving SADs
intertwined with bright upward moving spikes. Whereas SADs are dark voids,
spikes are brighter, denser structures. Although SADs have been observed for
decades, the mechanism of formation of SADs remains an open issue. In our
three-dimensional resistive magnetohydrodynamic simulations, we demonstrate
that secondary Rayleigh-Taylor type instabilities develop in the downstream
region of a reconnecting current sheet. The instability results in the
formation of low-density coherent structures that resemble SADs, and
high-density structures that appear to be spike-like. Comparison between the
simulation results and observations suggests that secondary Rayleigh-Taylor
type instabilities in the exhaust of reconnecting current sheets provide a
plausible mechanism for observed SADs and spikes
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