3,964 research outputs found
Probabilistic state preparation of a single molecular ion by projection measurement
We show how to prepare a single molecular ion in a specific internal quantum
state in a situation where the molecule is trapped and sympathetically cooled
by an atomic ion and where its internal degrees of freedom are initially in
thermal equilibrium with the surroundings. The scheme is based on conditional
creation of correlation between the internal state of the molecule and the
translational state of the collective motion of the two ions, followed by a
projection measurement of this collective mode by atomic ion shelving
techniques. State preparation in a large number of internal states is possible.Comment: 4 pages, 2 figures, 2 table
Global properties of Stochastic Loewner evolution driven by Levy processes
Standard Schramm-Loewner evolution (SLE) is driven by a continuous Brownian
motion which then produces a trace, a continuous fractal curve connecting the
singular points of the motion. If jumps are added to the driving function, the
trace branches. In a recent publication [1] we introduced a generalized SLE
driven by a superposition of a Brownian motion and a fractal set of jumps
(technically a stable L\'evy process). We then discussed the small-scale
properties of the resulting L\'evy-SLE growth process. Here we discuss the same
model, but focus on the global scaling behavior which ensues as time goes to
infinity. This limiting behavior is independent of the Brownian forcing and
depends upon only a single parameter, , which defines the shape of the
stable L\'evy distribution. We learn about this behavior by studying a
Fokker-Planck equation which gives the probability distribution for endpoints
of the trace as a function of time. As in the short-time case previously
studied, we observe that the properties of this growth process change
qualitatively and singularly at . We show both analytically and
numerically that the growth continues indefinitely in the vertical direction
for , goes as for , and saturates for . The probability density has two different scales corresponding to
directions along and perpendicular to the boundary. In the former case, the
characteristic scale is . In the latter case the scale
is for , and
for . Scaling functions for the probability density are given for
various limiting cases.Comment: Published versio
Hastings-Levitov aggregation in the small-particle limit
We establish some scaling limits for a model of planar aggregation. The model is described by the composition of a sequence of independent and identically distributed random conformal maps, each corresponding to the addition of one particle. We study the limit of small particle size and rapid aggregation. The process of growing clusters converges, in the sense of Caratheodory, to an inflating disc. A more refined analysis reveals, within the cluster, a tree structure of branching fingers, whose radial component increases deterministically with time. The arguments of any finite sample of fingers, tracked inwards, perform coalescing Brownian motions. The arguments of any finite sample of gaps between the fingers, tracked outwards, also perform coalescing Brownian motions. These properties are closely related to the evolution of harmonic measure on the boundary of the cluster, which is shown to converge to the Brownian web
The Prevalence of Hyperpalatable Baby Foods and Exposure During Infancy: A Preliminary Investigation
Objective: To characterize the prevalence of hyperpalatable foods (HPF) among baby foods in the U.S. and examine the prevalence of HPF exposure and consumption from both baby food and adult food sources among infants aged 9–15 months.
Methods: A U.S. baby food database as well as baby foods from three 24-h dietary recalls of 147 infants were used to identify baby foods as HPF per previous publication. HPF exposure was defined as intake of any HPF during the 3-day measurement period. To determine the extent of HFP consumption, % kilocalorie (kcal) intake from HPF was characterized.
Results: Only 12% of baby foods were HPF; however, nearly all participants (>90%) consumed HPF, primarily through exposure to adult foods. Younger infants (<12 months) consumed 38% [standard deviation (SD) = 23.6%] of their daily food kcal from HPF and older infants (≥12 months) consumed 52% (SD = 16.4%) of daily food kilocalorie from HPF. Most younger infants (68%) and older infants (88%) had repeated exposure to the same HPF across the measurement period.
Conclusions: The prevalence of HPF among baby foods in the U.S. is low. However, almost all infants were exposed to HPF, and HPF comprised a substantial percentage of daily food kilocalorie in infants' diets. Findings highlight the transition to solid food consumption during complimentary feeding period is a critical time for early HPF exposure
Generalized Borcea-Voisin Construction
C. Voisin and C. Borcea have constructed mirror pairs of families of
Calabi-Yau threefolds by taking the quotient of the product of an elliptic
curve with a K3 surface endowed with a non-symplectic involution. In this
paper, we generalize the construction of Borcea and Voisin to any prime order
and build three and four dimensional Calabi-Yau orbifolds. We classify the
topological types that are obtained and show that, in dimension 4, orbifolds
built with an involution admit a crepant resolution and come in topological
mirror pairs. We show that for odd primes, there are generically no minimal
resolutions and the mirror pairing is lost.Comment: 15 pages, 2 figures. v2: typos corrected & references adde
Coherence of qubits based on single Ca ions
Two-level ionic systems, where quantum information is encoded in long lived
states (qubits), are discussed extensively for quantum information processing.
We present a collection of measurements which characterize the stability of a
qubit based on the -- transition of single Ca ions
in a linear Paul trap. We find coherence times of 1 ms, discuss the
main technical limitations and outline possible improvements.Comment: Proceedings of "Trapped charged particles and fundamental
interactions" submitted to Journal of Physics B (IoP
Experimental and theoretical study of vibrations of a cantilevered beam using a ZnO piezoelectric sensor
Piezoelectric sensors can measure vibrations of solid structures very accurately. A model of a cantilevered beam, with a ZnO film on one side is presented. Both viscous and internal damping are considered. The output of the sensor is modeled and matched with experimental results by adjusting the damping parameters. A theoretical formulation for damage is introduced. Experimental results for a damaged beam confirm the shift in frequencies to lower values. The model is used to identify the extent of the damage
First passage times and distances along critical curves
We propose a model for anomalous transport in inhomogeneous environments,
such as fractured rocks, in which particles move only along pre-existing
self-similar curves (cracks). The stochastic Loewner equation is used to
efficiently generate such curves with tunable fractal dimension . We
numerically compute the probability of first passage (in length or time) from
one point on the edge of the semi-infinite plane to any point on the
semi-circle of radius . The scaled probability distributions have a variance
which increases with , a non-monotonic skewness, and tails that decay
faster than a simple exponential. The latter is in sharp contrast to
predictions based on fractional dynamics and provides an experimental signature
for our model.Comment: 5 pages, 5 figure
Ground state cooling, quantum state engineering and study of decoherence of ions in Paul traps
We investigate single ions of in Paul traps for quantum
information processing. Superpositions of the S electronic ground state
and the metastable D state are used to implement a qubit. Laser light
on the S D transition is used for the
manipulation of the ion's quantum state. We apply sideband cooling to the ion
and reach the ground state of vibration with up to 99.9% probability. Starting
from this Fock state , we demonstrate coherent quantum state
manipulation. A large number of Rabi oscillations and a ms-coherence time is
observed. Motional heating is measured to be as low as one vibrational quantum
in 190 ms. We also report on ground state cooling of two ions.Comment: 12 pages, 6 figures. submitted to Journal of Modern Optics, Special
Issue on Quantum Optics: Kuehtai 200
- …