8,257 research outputs found
Secrecy content of two-qubit states
We analyze the set of two-qubit states from which a secret key can be
extracted by single-copy measurements plus classical processing of the
outcomes. We introduce a key distillation protocol and give the corresponding
necessary and sufficient condition for positive key extraction. Our results
imply that the critical error rate derived by Chau, Phys. Rev. A {\bf 66},
060302 (2002), for a secure key distribution using the six-state scheme is
tight. Remarkably, an optimal eavesdropping attack against this protocol does
not require any coherent quantum operation.Comment: 5 pages, RevTe
Enantioselective Organocatalytic Singly Occupied Molecular Orbital Activation: The Enantioselective α-Enolation of Aldehydes
The first enantioselective organocatalytic α-enolation of aldehydes has been accomplished using singly occupied molecular orbital (SOMO) catalysis. Chiral secondary amines react with aldehydes to form transient enamines that undergo selective one-electron oxidation to generate electrophilic radical cations. These SOMO-activated radical cations are susceptible to attack by ketone-derived enol silanes, rendering α-substituted-γ-ketoaldehyde products with uniformly high levels of asymmetric induction. Wide latitude in both the aldehyde and enolsilane component is readily accommodated, allowing generic access to a diverse assortment of enantioenriched 1,4-dicarbonyl compounds. This report highlights the potential of SOMO catalysis to enable the development of entirely new classes of asymmetric reactions that have no traditional catalytic equivalents
Anti-oxidant and anti-hypercholesterolemic activities of Wasabia japonica
The effects of Wasabia japonica (WJ) were investigated in vitro and in vivo for their anti-oxidant and anti-hypercholesterolemic activities. It was found that the aqueous extracts of WJ leaves (WJL) had strong scavenging activities towards 1,1-Diphenyl-2-picryhydrazyl (DPPH) and nitric oxide (NO) free radicals in cell free systems. WJL also inhibited NO production and the expressions of inducible NO synthase (iNOS) mRNA and enzyme protein, determined by Griess reactions, RT-PCR or Western blotting respectively in Lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages cells. The anti-hypercholesterolemic effects of WJ diet were investigated in hypercholesterolemia rats. Sprague-Dawley rats were divided into four groups and were fed with either normal diet (Group 1), or diet containing 1%(w/w) cholesterol (Groups 2, 3 and 4). After 4 weeks, Group 2 was changed to normal diet, Groups 3 and 4 were changed to the diet containing 5% WJ leaf and or 5% WJ root, respectively. 3 weeks after WJ diets, Serum HDL-cholesterol levels were significantly increased in WJ diet groups compared with the normal diet hypercholesterolemia rats. In contrast, the serum LDL-cholesterol levels and liver xanthine oxidase (XO) activity in WJ diet groups were significantly decreased. The results indicate that the WJ extracts have significant anti-oxidant activities, and the WJ diet exhibited anti-hypercholesterolemic action in high cholesterol diet rats, which was companied with modulations of cholesterol metabolism and decrease in liver XO activity
Quantum mechanics emerges from information theory applied to causal horizons
It is suggested that quantum mechanics is not fundamental but emerges from
classical information theory applied to causal horizons. The path integral
quantization and quantum randomness can be derived by considering information
loss of fields or particles crossing Rindler horizons for accelerating
observers. This implies that information is one of the fundamental roots of all
physical phenomena. The connection between this theory and Verlinde's entropic
gravity theory is also investigated.Comment: REvtex4-1, 6pages, 2 figures, final versio
Going abroad: HR policies, national IR systems, and union activity in foreign subsidiaries of U.S. multinationals
Industrial and Labor Relations Review6651149-117
Einstein-aether theory, violation of Lorentz invariance, and metric-affine gravity
We show that the Einstein-aether theory of Jacobson and Mattingly (J&M) can
be understood in the framework of the metric-affine (gauge theory of) gravity
(MAG). We achieve this by relating the aether vector field of J&M to certain
post-Riemannian nonmetricity pieces contained in an independent linear
connection of spacetime. Then, for the aether, a corresponding geometrical
curvature-square Lagrangian with a massive piece can be formulated
straightforwardly. We find an exact spherically symmetric solution of our
model.Comment: Revtex4, 38 pages, 1 figur
How to hide a secret direction
We present a procedure to share a secret spatial direction in the absence of
a common reference frame using a multipartite quantum state. The procedure
guarantees that the parties can determine the direction if they perform joint
measurements on the state, but fail to do so if they restrict themselves to
local operations and classical communication (LOCC). We calculate the fidelity
for joint measurements, give bounds on the fidelity achievable by LOCC, and
prove that there is a non-vanishing gap between the two of them, even in the
limit of infinitely many copies. The robustness of the procedure under particle
loss is also studied. As a by-product we find bounds on the probability of
discriminating by LOCC between the invariant subspaces of total angular
momentum N/2 and N/2-1 in a system of N elementary spins.Comment: 4 pages, 1 figur
On structural physical approximations and entanglement breaking maps
Very recently a conjecture saying that the so-called structural physical
approximations (SPAa) to optimal positive maps (optimal entanglement witnesses)
give entanglement breaking (EB) maps (separable states) has been posed [J. K.
Korbicz {\it et al.}, Phys. Rev. A {\bf 78}, 062105 (2008)]. The main purpose
of this contribution is to explore this subject. First, we extend the set of
entanglement witnesses (EWs) supporting the conjecture. Then, we ask if SPAs
constructed from other than the depolarizing channel maps also lead to EB maps
and show that in general this is not the case. On the other hand, we prove an
interesting fact that for any positive map there exists an EB channel
such that the SPA of constructed with the aid of is
again an EB channel. Finally, we ask similar questions in the case of
continuous variable systems. We provide a simple way of construction of SPA and
prove that in the case of the transposition map it gives EB channel.Comment: 22 pages, improved version, accepted by Journal of Physics
Radion effects on unitarity in gauge-boson scattering
The scalar field associated with fluctuations in the positions of the two
branes, the ``radion'', plays an important role determining the cosmology and
collider phenomenology of the Randall-Sundrum solution to the hierarchy
problem. It is now well known that the radion mass is of order the weak scale,
and that its couplings to standard model fields are order 1/TeV to the trace of
the energy momentum tensor. We calculate longitudinal vector boson scattering
amplitudes to explore the constraints on the radion mass and its coupling from
perturbative unitarity. The scattering cross section can indeed become
non-perturbative at energies prior to reaching the TeV brane cutoff scale, but
only when some curvature-Higgs mixing on the TeV brane is present. We show that
the coefficient of the curvature-Higgs mixing operator must be less than about
3 for the 4-d effective theory to respect perturbative unitarity up to the TeV
brane cutoff scale. Mass bounds on the Higgs boson and the radion are also
discussed.Comment: 17 pages, LaTeX, 5 eps figures, uses epsf.sty and axodraw.st
using HYP-smeared staggered fermions in unquenched QCD
We present results for kaon mixing parameter calculated using
HYP-smeared improved staggered fermions on the MILC asqtad lattices. We use
three lattice spacings (, and fm), ten different
valence quark masses (), and several light sea-quark
masses in order to control the continuum and chiral extrapolations. We derive
the next-to-leading order staggered chiral perturbation theory (SChPT) results
necessary to fit our data, and use these results to do extrapolations based
both on SU(2) and SU(3) SChPT. The SU(2) fitting is particularly
straightforward because parameters related to taste-breaking and matching
errors appear only at next-to-next-to-leading order. We match to the continuum
renormalization scheme (NDR) using one-loop perturbation theory. Our final
result is from the SU(2) analysis, with the SU(3) result providing a (less
accurate) cross check. We find and ,
where the first error is statistical and the second systematic. The error is
dominated by the truncation error in the matching factor. Our results are
consistent with those obtained using valence domain-wall fermions on lattices
generated with asqtad or domain-wall sea quarks.Comment: 37 pages, 31 figures, most updated versio
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