7,150 research outputs found
Reducing the linewidth of an atom laser by feedback
A continuous atom laser will almost certainly have a linewidth dominated by
the effect of the atomic interaction energy, which turns fluctuations in the
condensate atom number into fluctuations in the condensate frequency. These
correlated fluctuations mean that information about the atom number could be
used to reduce the frequency fluctuations, by controlling a spatially uniform
potential. We show that feedback based on a physically reasonable quantum
non-demolition measurement of the atom number of the condensate in situ can
reduce the linewidth enormously.Comment: 5 pages, 1 figur
Effects of twin-beam squashed light on a three-level atom
An electro-optical feedback loop can make in-loop light (squashed light)
which produces a photocurrent with noise below the standard quantum limit (such
as squeezed light). We investigate the effect of squashed light interacting
with a three-level atom in the cascade configuration and compare it to the
effects produced by squeezed light and classical noise. It turns out that one
master equation can be formulated for all three types of light and that this
unified formalism can also be applied to the evolution of a two-level atom. We
show that squashed light does not mimic all aspects of squeezed light, and in
particular, it does not produce the characteristic linear intensity dependence
of the population of the upper-most level of the cascade three-level atom.
Nevertheless, it has nonclassical transient effects in the de-excitation.Comment: 12 pages, 6 figure
Control of perennial weeds based on weed biology and environmental considerations
Timing, type and duration of tillage operations and cropping practices are of importance for reducing the regeneration of perennial weeds and also for minimizing the environmental impacts of such operations. In the present work and with reference to previous publications we find that, based on the knowledge gained on growth patterns, sensitivity to competition, growth potential of roots and mechanical and management measures it is possible to coordinate control of perennial weeds with considerations of yield and reduced environmental impact
Pure-state quantum trajectories for general non-Markovian systems do not exist
Since the first derivation of non-Markovian stochastic Schr\"odinger
equations, their interpretation has been contentious. In a recent Letter [Phys.
Rev. Lett. 100, 080401 (2008)], Di\'osi claimed to prove that they generate
"true single system trajectories [conditioned on] continuous measurement". In
this Letter we show that his proof is fundamentally flawed: the solution to his
non-Markovian stochastic Schr\"odinger equation at any particular time can be
interpreted as a conditioned state, but joining up these solutions as a
trajectory creates a fiction.Comment: 4 page
Discrimination of the Healthy and Sick Cardiac Autonomic Nervous System by a New Wavelet Analysis of Heartbeat Intervals
We demonstrate that it is possible to distinguish with a complete certainty
between healthy subjects and patients with various dysfunctions of the cardiac
nervous system by way of multiresolutional wavelet transform of RR intervals.
We repeated the study of Thurner et al on different ensemble of subjects. We
show that reconstructed series using a filter which discards wavelet
coefficients related with higher scales enables one to classify individuals for
which the method otherwise is inconclusive. We suggest a delimiting diagnostic
value of the standard deviation of the filtered, reconstructed RR interval time
series in the range of (for the above mentioned filter), below
which individuals are at risk.Comment: 5 latex pages (including 6 figures). Accepted in Fractal
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