685 research outputs found
Remote State Preparation
Quantum teleportation uses prior entanglement and forward classical
communication to transmit one instance of an unknown quantum state. Remote
state preparation (RSP) has the same goal, but the sender knows classically
what state is to be transmitted. We show that the asymptotic classical
communication cost of RSP is one bit per qubit - half that of teleportation -
and becomes even less when transmitting part of a known entangled state. We
explore the tradeoff between entanglement and classical communication required
for RSP, and discuss RSP capacities of general quantum channels.Comment: 4 pages including 1 epsf figure; v3 has an additional author and
discusses relation to work of Devetak and Berger (quant-ph/0102123); v4
improves low-entanglement protocols without back communication to perform as
well as low-entanglement protocols with back communication; v5 (journal
version) has a few small change
Purification of Noisy Entanglement and Faithful Teleportation via Noisy Channels
Two separated observers, by applying local operations to a supply of
not-too-impure entangled states ({\em e.g.} singlets shared through a noisy
channel), can prepare a smaller number of entangled pairs of arbitrarily high
purity ({\em e.g.} near-perfect singlets). These can then be used to faithfully
teleport unknown quantum states from one observer to the other, thereby
achieving faithful transfrom one observer to the other, thereby achieving
faithful transmission of quantum information through a noisy channel. We give
upper and lower bounds on the yield of pure singlets ()
distillable from mixed states , showing if
\bra{\Psi^-}M\ket{\Psi^-}>\half.Comment: 4 pages (revtex) plus 1 figure (postscript). See also
http://vesta.physics.ucla.edu/~smolin/ . Replaced to correct interchanged
and near top of column 2, page
Quantum Nonlocality without Entanglement
We exhibit an orthogonal set of product states of two three-state particles
that nevertheless cannot be reliably distinguished by a pair of separated
observers ignorant of which of the states has been presented to them, even if
the observers are allowed any sequence of local operations and classical
communication between the separate observers. It is proved that there is a
finite gap between the mutual information obtainable by a joint measurement on
these states and a measurement in which only local actions are permitted. This
result implies the existence of separable superoperators that cannot be
implemented locally. A set of states are found involving three two-state
particles which also appear to be nonmeasurable locally. These and other
multipartite states are classified according to the entropy and entanglement
costs of preparing and measuring them by local operations.Comment: 27 pages, Latex, 6 ps figures. To be submitted to Phys. Rev. A.
Version 2: 30 pages, many small revisions and extensions, author added.
Version 3: Proof in Appendix D corrected, many small changes; final version
for Phys. Rev. A Version 4: Report of Popescu conjecture modifie
Streptokinase thrombolysis in experimental coronary artery thrombosis: pattern of reflow and effect of a stenosis
We studied recanalization of an obstructed left circumflex coronary artery by streptokinase in open-chest anesthetized dogs. Thrombotic occlusion was induced by a 100 [mu]A anodal current selectively delivered to the intimal surface of the vessel. Intracoronary streptokinase (50,000 U) or saline was infused over a 50-min period beginning at either 30 min or 90 min after occlusion. Continous recordings were made of antegrade circumflex flow and regional myocardial function, which was quantitated using sonomicrometer crystals in the regions of the left anterior descending and circumflex coronary arteries. In some experiments a fixed stenosis, having no effect on mean circumflex coronary artery blood flow, was placed at the site of subsequent thrombus formation. The presence of a stenosis decreased the weight of occlusive thrombi obtained from nonreperfused saline controls by 40% and increased the proportion of animals successfully reperfused by streptokinase from 13 to 76%. Streptokinase reduced thrombus mass by 44% in animals recanalized in the presence of the stenosis. On the average, reflow was established after 26 min of streptokinase infusion, was less in magnitude than pre-occlusion flow, and was unstable and intermittent, being marked by frequent reocclusions. Initiating treatment at 30 min or 90 min post-occlusion did not influence characteristics of the reflow. Return of myocardial contractility in the ischemic bed was not detected during the immediate reperfusion period in the majority of these experiments.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24656/1/0000069.pd
Mixed State Entanglement and Quantum Error Correction
Entanglement purification protocols (EPP) and quantum error-correcting codes
(QECC) provide two ways of protecting quantum states from interaction with the
environment. In an EPP, perfectly entangled pure states are extracted, with
some yield D, from a mixed state M shared by two parties; with a QECC, an arbi-
trary quantum state can be transmitted at some rate Q through a
noisy channel without degradation. We prove that an EPP involving one-
way classical communication and acting on mixed state (obtained
by sharing halves of EPR pairs through a channel ) yields a QECC on
with rate , and vice versa. We compare the amount of entanglement
E(M) required to prepare a mixed state M by local actions with the amounts
and that can be locally distilled from it by EPPs using one-
and two-way classical communication respectively, and give an exact expression
for when is Bell-diagonal. While EPPs require classical communica-
tion, QECCs do not, and we prove Q is not increased by adding one-way classical
communication. However, both D and Q can be increased by adding two-way com-
munication. We show that certain noisy quantum channels, for example a 50%
depolarizing channel, can be used for reliable transmission of quantum states
if two-way communication is available, but cannot be used if only one-way com-
munication is available. We exhibit a family of codes based on universal hash-
ing able toachieve an asymptotic (or ) of 1-S for simple noise models,
where S is the error entropy. We also obtain a specific, simple 5-bit single-
error-correcting quantum block code. We prove that {\em iff} a QECC results in
high fidelity for the case of no error the QECC can be recast into a form where
the encoder is the matrix inverse of the decoder.Comment: Resubmission with various corrections and expansions. See also
http://vesta.physics.ucla.edu/~smolin/ for related papers and information. 82
pages latex including 19 postscript figures included using psfig macro
Entangled Rings
Consider a ring of N qubits in a translationally invariant quantum state. We
ask to what extent each pair of nearest neighbors can be entangled. Under
certain assumptions about the form of the state, we find a formula for the
maximum possible nearest-neighbor entanglement. We then compare this maximum
with the entanglement achieved by the ground state of an antiferromagnetic ring
consisting of an even number of spin-1/2 particles. We find that, though the
antiferromagnetic ground state does not maximize the nearest-neighbor
entanglement relative to all other states, it does so relative to other states
having zero z-component of spin.Comment: 19 pages, no figures; v2 includes new results; v3 corrects a
numerical error for the case N=
The anaphylatoxins C3a and C5a are vasodilators in the canine coronary vasculature in vitro and in vivo
The effect of complement fragments on coronary blood flow in vivo and the contraction of coronary arteries in vitro was determined. In pentobarbital anesthetized dogs, intraarterial bolus injection of C3a and C5a, zymosan-activated serum and methylcholine in the coronary vascular bed caused transient and dose-dependent increases in coronary blood flow. Similar increases were obtained with 25 μg of C3a (104±13%, n =5) and 0.1 μg of methylcholine (102±4%, n =3). Smaller, increases in blood flow were elicited by 25 μg of C5a (41±18%, n =4) and 0.2 ml, of zymosan-activated serum (48±5%, n =4). None of these responses were associated, with significant changes in left ventricular contractile force measured with a strain gauge, arterial blood pressure, and heart rate. C3a dilated the coronary vascular bed in conscious dogs with an activity equal to or greater than that observed in anesthetized dogs. Isolated canine coronary arteries that were precontracted with serotonin relaxed in response to C3a, whether or not the endothelium was intact. Overall these data suggest that physiologically high doses of anaphylactic complement fragments vasodilate the canine coronary circulation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45056/1/11_2005_Article_BF01988727.pd
Colorectal cancer linkage on chromosomes 4q21, 8q13, 12q24, and 15q22
A substantial proportion of familial colorectal cancer (CRC) is not a consequence of known susceptibility loci, such as mismatch repair (MMR) genes, supporting the existence of additional loci. To identify novel CRC loci, we conducted a genome-wide linkage scan in 356 white families with no evidence of defective MMR (i.e., no loss of tumor expression of MMR proteins, no microsatellite instability (MSI)-high tumors, or no evidence of linkage to MMR genes). Families were ascertained via the Colon Cancer Family Registry multi-site NCI-supported consortium (Colon CFR), the City of Hope Comprehensive Cancer Center, and Memorial University of Newfoundland. A total of 1,612 individuals (average 5.0 per family including 2.2 affected) were genotyped using genome-wide single nucleotide polymorphism linkage arrays; parametric and non-parametric linkage analysis used MERLIN in a priori-defined family groups. Five lod scores greater than 3.0 were observed assuming heterogeneity. The greatest were among families with mean age of diagnosis less than 50 years at 4q21.1 (dominant HLOD = 4.51, α = 0.84, 145.40 cM, rs10518142) and among all families at 12q24.32 (dominant HLOD = 3.60, α = 0.48, 285.15 cM, rs952093). Among families with four or more affected individuals and among clinic-based families, a common peak was observed at 15q22.31 (101.40 cM, rs1477798; dominant HLOD = 3.07, α = 0.29; dominant HLOD = 3.03, α = 0.32, respectively). Analysis of families with only two affected individuals yielded a peak at 8q13.2 (recessive HLOD = 3.02, α = 0.51, 132.52 cM, rs1319036). These previously unreported linkage peaks demonstrate the continued utility of family-based data in complex traits and suggest that new CRC risk alleles remain to be elucidated. © 2012 Cicek et al
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