21,001 research outputs found
Experimental study of one- and two-component low-turbulence confined coaxial flows
Fluid mechanics experiments to investigate methods for reducing mixing between confined coaxial flows in cylindrical chambers for application to open-cycle gaseous-core nuclear rocket
Mixedness and teleportation
We show that on exceeding a certain degree of mixedness (as quantified by the
von Neumann entropy), entangled states become useless for teleporatation. By
increasing the dimension of the entangled systems, this entropy threshold can
be made arbitrarily close to maximal. This entropy is found to exceed the
entropy threshold sufficient to ensure the failure of dense coding.Comment: 6 pages, no figure
Mass and Momentum Turbulent Transport Experiments with Confined Coaxial Jets
Downstream mixing of coaxial jets discharging in an expanded duct was studied to obtain data for the evaluation and improvement of turbulent transport models currently used in a variety of computational procedures throughout the propulsion community for combustor flow modeling. Flow visualization studies showed four major shear regions occurring; a wake region immediately downstream of the inlet jet inlet duct; a shear region further downstream between the inner and annular jets; a recirculation zone; and a reattachment zone. A combination of turbulent momentum transport rate and two velocity component data were obtained from simultaneous measurements with a two color laser velocimeter (LV) system. Axial, radial and azimuthal velocities and turbulent momentum transport rate measurements in the r-z and r-theta planes were used to determine the mean value, second central moment (or rms fluctuation from mean), skewness and kurtosis for each data set probability density function (p.d.f.). A combination of turbulent mass transport rate, concentration and velocity data were obtained system. Velocity and mass transport in all three directions as well as concentration distributions were used to obtain the mean, second central moments, skewness and kurtosis for each p.d.f. These LV/LIF measurements also exposed the existence of a large region of countergradient turbulent axial mass transport in the region where the annular jet fluid was accelerating the inner jet fluid
Thermodynamics and the Measure of Entanglement
We point out formal correspondences between thermodynamics and entanglement.
By applying them to previous work, we show that entropy of entanglement is the
unique measure of entanglement for pure states.Comment: 8 pages, RevTeX; edited for clarity, additional references, to appear
as a Rapid Communication in Phys. Rev.
An improved bound on distillable entanglement
The best bound known on 2-locally distillable entanglement is that of Vedral
and Plenio, involving a certain measure of entanglement based on relative
entropy. It turns out that a related argument can be used to give an even
stronger bound; we give this bound, and examine some of its properties. In
particular, and in contrast to the earlier bounds, the new bound is not
additive in general. We give an example of a state for which the bound fails to
be additive, as well as a number of states for which the bound is additive.Comment: 14 pages, no figures. A significant erratum in theorems 4 and 5 has
been fixe
A new class of entanglement measures
We introduce new entanglement measures on the set of density operators on
tensor product Hilbert spaces. These measures are based on the greatest cross
norm on the tensor product of the sets of trace class operators on Hilbert
space. We show that they satisfy the basic requirements on entanglement
measures discussed in the literature, including convexity, invariance under
local unitary operations and non-increase under local quantum operations and
classical communication.Comment: Revised version accepted by J Math Phys, 12 pages, LaTeX, contains
Sections 1-5 & 7 of the previous version. The previous Section 6 is now in
quant-ph/0105104 and the previous Section 8 is superseded by quant-ph/010501
Entanglement splitting of pure bipartite quantum states
The concept of entanglement splitting is introduced by asking whether it is
possible for a party possessing half of a pure bipartite quantum state to
transfer some of his entanglement with the other party to a third party. We
describe the unitary local transformation for symmetric and isotropic splitting
of a singlet into two branches that leads to the highest entanglement of the
output. The capacity of the resulting quantum channels is discussed. Using the
same transformation for less than maximally entangled pure states, the
entanglement of the resulting states is found. We discuss whether they can be
used to do teleportation and to test the Bell inequality. Finally we generalize
to entanglement splitting into more than two branches.Comment: 6 pages, 2 figures, extended version, to be published in Phys. Rev.
Building multiparticle states with teleportation
We describe a protocol which can be used to generate any N-partite pure
quantum state using Einstein-Podolsky-Rosen (EPR) pairs. This protocol employs
only local operations and classical communication between the N parties
(N-LOCC). In particular, we rely on quantum data compression and teleportation
to create the desired state. This protocol can be used to obtain upper bounds
for the bipartite entanglement of formation of an arbitrary N-partite pure
state, in the asymptotic limit of many copies. We apply it to a few
multipartite states of interest, showing that in some cases it is not optimal.
Generalizations of the protocol are developed which are optimal for some of the
examples we consider, but which may still be inefficient for arbitrary states.Comment: 11 pages, 1 figure. Version 2 contains an example for which protocol
P3 is better than protocol P2. Correction to references in version
Robust Multi-Partite Multi-Level Quantum Protocols
We present a tripartite three-level state that allows a secret sharing
protocol among the three parties, or a quantum key distribution protocol
between any two parties. The state used in this scheme contains entanglement
even after one system is traced out. We show how to utilize this residual
entanglement for quantum key distribution purposes, and propose a realization
of the scheme using entanglement of orbital angular momentum states of photons.Comment: 9 pages, 2 figure
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