1,415 research outputs found
Inefficiency of classically simulating linear optical quantum computing with Fock-state inputs
Aaronson and Arkhipov recently used computational complexity theory to argue
that classical computers very likely cannot efficiently simulate linear,
multimode, quantum-optical interferometers with arbitrary Fock-state inputs
[Aaronson and Arkhipov, Theory Comput. 9, 143 (2013)]. Here we present an
elementary argument that utilizes only techniques from quantum optics. We
explicitly construct the Hilbert space for such an interferometer and show that
its dimension scales exponentially with all the physical resources. We also
show in a simple example just how the Schr\"odinger and Heisenberg pictures of
quantum theory, while mathematically equivalent, are not in general
computationally equivalent. Finally, we conclude our argument by comparing the
symmetry requirements of multiparticle bosonic to fermionic interferometers
and, using simple physical reasoning, connect the nonsimulatability of the
bosonic device to the complexity of computing the permanent of a large matrix.Comment: 7 pages, 1 figure Published in PRA Phys. Rev. A 89, 022328 (2014
Computerized system for translating a torch head
The system provides a constant travel speed along a contoured workpiece. It has a driven skate characterized by an elongated bed, with a pair of independently pivoted trucks connected to the bed for support. The trucks are mounted on a contoured track of arbitrary configuration in a mutually spaced relation. An axially extensible torch head manipulator arm is mounted on the bed of the carriage and projects perpendicular from the midportion. The torch head is mounted at its distal end. A real-time computerized control drive subsystem is used to advance the skate along the track of a variable rate for maintaining a constant speed for the torch head tip, and to position the torch axis relative to a preset angle to the workpiece
Phase sensitivity at the Heisenberg limit in an SU(1,1) interferometer via parity detection
We theoretically investigate the phase sensitivity with parity detection on
an SU(1,1) interferometer with a coherent state combined with a squeezed vacuum
state. This interferometer is formed with two parametric amplifiers for beam
splitting and recombination instead of beam splitters. We show that the
sensitivity of estimation phase approaches Heisenberg limit and give the
corresponding optimal condition. Moreover, we derive the quantum Cram\'er-Rao
bound of the SU(1,1) interferometer.Comment: 9 pages, 2 figures, 3 table
Prenatal Smoke Exposure Predicts Hyperactive/Impulsive but Not Inattentive ADHD Symptoms in Adolescent and Young Adult Girls
We examined the longitudinal associations between prenatal tobacco smoke exposure (PSE) and attention‐deficit hyperactivity disorder (ADHD) symptom domains in adolescence and young adulthood. A sample of girls with ADHD combined presentation (N = 93), ADHD predominantly inattentive presentation (N = 47), and matched comparisons (N = 88) was assessed prospectively. Symptoms of hyperactivity/impulsivity (HI), inattention (IA), and oppositionality (oppositional defiant disorder) were measured via multiple informants 5 (M age = 14 years; retention rate = 92%) and 10 years (M age = 20 years; retention rate = 95%) following childhood ascertainment. PSE was captured via maternal self‐report. We used linear regressions to examine the prediction from PSE to both HI and IA in adolescence and early adulthood after stringent control of relevant confounding variables. PSE significantly predicted HI during adolescence and young adulthood across multiple informants but did not predict IA at either wave. Symptoms of HI may have partial etiological independence from IA symptoms. Copyright © 2015 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/133536/1/icd1943_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/133536/2/icd1943.pd
Reduction and reconstruction of stochastic differential equations via symmetries
An algorithmic method to exploit a general class of infinitesimal symmetries
for reducing stochastic differential equations is presented and a natural
definition of reconstruction, inspired by the classical reconstruction by
quadratures, is proposed. As a side result the well-known solution formula for
linear one-dimensional stochastic differential equations is obtained within
this symmetry approach. The complete procedure is applied to several examples
with both theoretical and applied relevance
Rapidly driven nanoparticles: Mean first-passage times and relaxation of the magnetic moment
We present an analytical method of calculating the mean first-passage times
(MFPTs) for the magnetic moment of a uniaxial nanoparticle which is driven by a
rapidly rotating, circularly polarized magnetic field and interacts with a heat
bath. The method is based on the solution of the equation for the MFPT derived
from the two-dimensional backward Fokker-Planck equation in the rotating frame.
We solve these equations in the high-frequency limit and perform precise,
numerical simulations which verify the analytical findings. The results are
used for the description of the rates of escape from the metastable domains
which in turn determine the magnetic relaxation dynamics. A main finding is
that the presence of a rotating field can cause a drastic decrease of the
relaxation time and a strong magnetization of the nanoparticle system. The
resulting stationary magnetization along the direction of the easy axis is
compared with the mean magnetization following from the stationary solution of
the Fokker-Planck equation.Comment: 24 pages, 4 figure
Sterilization of lung matrices by supercritical carbon dioxide
Lung engineering is a potential alternative to transplantation for patients with end-stage pulmonary failure. Two challenges critical to the successful development of an engineered lung developed from a decellularized scaffold include (i) the suppression of resident infectious bioburden in the lung matrix, and (ii) the ability to sterilize decellularized tissues while preserving the essential biological and mechanical features intact. To date, the majority of lungs are sterilized using high concentrations of peracetic acid (PAA) resulting in extracellular matrix (ECM) depletion. These mechanically altered tissues have little to no storage potential. In this study, we report a sterilizing technique using supercritical carbon dioxide (ScCO(2)) that can achieve a sterility assurance level 10(−6) in decellularized lung matrix. The effects of ScCO(2) treatment on the histological, mechanical, and biochemical properties of the sterile decellularized lung were evaluated and compared with those of freshly decellularized lung matrix and with PAA-treated acellular lung. Exposure of the decellularized tissue to ScCO(2) did not significantly alter tissue architecture, ECM content or organization (glycosaminoglycans, elastin, collagen, and laminin), observations of cell engraftment, or mechanical integrity of the tissue. Furthermore, these attributes of lung matrix did not change after 6 months in sterile buffer following sterilization with ScCO(2), indicating that ScCO(2) produces a matrix that is stable during storage. The current study's results indicate that ScCO(2) can be used to sterilize acellular lung tissue while simultaneously preserving key biological components required for the function of the scaffold for regenerative medicine purposes
Cognitive-enhancing effects of angiotensin IV
Angiotensin IV is a derivative of the potent vasoconstrictor angiotensin II and it has been shown to enhance acquisition, consolidation and recall in animal models of learning and memory when administered centrally or peripherally. Whether changes in angiotensin IV activity underlie the cognitive effects of those cardiovascular drugs designed to disrupt the peripheral renin-angiotensin system in humans remains undetermined, but angiotensin IV appears to be a worthy candidate for consideration in drug development programmes. The mechanism of action of angiotensin IV is still debated, although its AT4 receptor has been convincingly identified as being insulin-regulated amino peptidase, which is also known as oxytocinase and placental leucine aminopeptidase. It is speculated that angiotensin IV may interact with insulin-regulated amino peptidase to enhance neuronal glucose uptake, prevent metabolism of other neuroactive peptides, induce changes in extracellular matrix molecules, or induce release of acetylcholine and/or dopamine. All of these things may be responsible for the beneficial effects on cognition, but none of them are yet proven. Importantly, strain differences in murine responses to angiotensin IV suggest that some individuals may benefit from drugs targeted to the AT4 receptor whilst others may be refractory. At present it thus appears that those individuals with the poorest baseline cognition may receive greatest benefit, but possible genetic differences in responses to angiotensin IV cannot be ruled-out
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