17,389 research outputs found
A Foundation of Programming a Multi-Tape Quantum Turing machine
The notion of quantum Turing machines is a basis of quantum complexity
theory. We discuss a general model of multi-tape, multi-head Quantum Turing
machines with multi final states that also allow tape heads to stay still.Comment: A twelve page version is to appear in the Proceedings of the 24th
International Symposium on Mathematical Foundations of Computer Science in
September, 1999. LNC
A note on compactly generated co-t-structures
The idea of a co-t-structure is almost "dual" to that of a t-structure, but
with some important differences. This note establishes co-t-structure analogues
of Beligiannis and Reiten's corresponding results on compactly generated
t-structures.Comment: 10 pages; details added to proofs, small correction in the main
resul
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Development Of Third Harmonic Generation As A Short Pulse Probe Of Shock Heated Material
We are studying high-pressure laser produced shock waves in silicon (100). To examine the material dynamics, we are performing pump-probe style experiments utilizing 600 ps and 40 fs laser pulses from a Ti:sapphire laser. Two-dimensional interferometry reveals information about the shock breakout, while third harmonic light generated at the rear surface is used to infer the crystalline state of the material as a function of time. Sustained third harmonic generation (THG) during a similar to 100 kbar shock breakout indicate that the rear surface remains crystalline for at least 3 ns. However, a decrease in THG during a similar to 300 kbar shock breakout suggests a different behavior, which could include a change in crystalline structure.Mechanical Engineerin
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Optimization of the neutron yield in fusion plasmas produced by Coulomb explosions of deuterium clusters irradiated by a petawatt laser
The kinetic energy of hot (multi-keV) ions from the laser-driven Coulomb explosion of deuterium clusters and the resulting fusion yield in plasmas formed from these exploding clusters has been investigated under a variety of conditions using the Texas Petawatt laser. An optimum laser intensity was found for producing neutrons in these cluster fusion plasmas with corresponding average ion energies of 14 keV. The substantial volume (1-10 mm(3)) of the laser-cluster interaction produced by the petawatt peak power laser pulse led to a fusion yield of 1.6x10(7) neutrons in a single shot with a 120 J, 170 fs laser pulse. Possible effects of prepulses are discussed. DOI: 10.1103/PhysRevE.87.023106Glenn Focht Memorial FellowshipNNSA DE-FC52-08NA28512DOE Office of Basic Energy SciencesPhysic
On the role of entanglement in quantum computational speed-up
For any quantum algorithm operating on pure states we prove that the presence
of multi-partite entanglement, with a number of parties that increases
unboundedly with input size, is necessary if the quantum algorithm is to offer
an exponential speed-up over classical computation. Furthermore we prove that
the algorithm can be classically efficiently simulated to within a prescribed
tolerance \eta even if a suitably small amount of global entanglement
(depending on \eta) is present. We explicitly identify the occurrence of
increasing multi-partite entanglement in Shor's algorithm. Our results do not
apply to quantum algorithms operating on mixed states in general and we discuss
the suggestion that an exponential computational speed-up might be possible
with mixed states in the total absence of entanglement. Finally, despite the
essential role of entanglement for pure state algorithms, we argue that it is
nevertheless misleading to view entanglement as a key resource for quantum
computational power.Comment: Main proofs simplified. A few further explanatory remarks added. 22
pages, plain late
Supersymmetric Fokker-Planck strict isospectrality
I report a study of the nonstationary one-dimensional Fokker-Planck solutions
by means of the strictly isospectral method of supesymmetric quantum mechanics.
The main conclusion is that this technique can lead to a space-dependent
(modulational) damping of the spatial part of the nonstationary Fokker-Planck
solutions, which I call strictly isospectral damping. At the same time, using
an additive decomposition of the nonstationary solutions suggested by the
strictly isospectral procedure and by an argument of Englefield [J. Stat. Phys.
52, 369 (1988)], they can be normalized and thus turned into physical
solutions, i.e., Fokker-Planck probability densities. There might be
applications to many physical processes during their transient periodComment: revised version, scheduled for PRE 56 (1 August 1997) as a B
On bit-commitment based quantum coin flipping
In this paper, we focus on a special framework for quantum coin flipping
protocols,_bit-commitment based protocols_, within which almost all known
protocols fit. We show a lower bound of 1/16 for the bias in any such protocol.
We also analyse a sequence of multi-round protocol that tries to overcome the
drawbacks of the previously proposed protocols, in order to lower the bias. We
show an intricate cheating strategy for this sequence, which leads to a bias of
1/4. This indicates that a bias of 1/4 might be optimal in such protocols, and
also demonstrates that a cleverer proof technique may be required to show this
optimality.Comment: The lower bound shown in this paper is superceded by a result of
Kitaev (personal communication, 2001
Dietary transition and obesity in selected Arabic-speaking countries: a review of the current evidence
Escalating obesity rates have become a significant public health problem in the Middle East and North Africa [‎MENA]‎ region and have been associated with shifts towards a westernized diet. This integrative review aimed to examine the current dietary trends and transitions and their association with obesity in Arabic-speaking countries of the MENA region. Relevant databases were searched for studies in MENA countries between 1998 and 2014 that investigated obesity trends and changes in dietary patterns at the regional level in all age groups. A total of 39 articles fulfilled the inclusion criteria. All the articles noted that obesity was increasingly prevalent and that there was a significant dietary shift away from traditional dietary patterns; 51% reported a shift towards a westernized diet and half found that the western diet was correlated with increased obesity. Culturally relevant dietary health education and health promotion strategies are warranted to address both the dietary shifts towards the westernized diet and the increasing obesit
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