3,344 research outputs found
A Compact Source for Quantum Image Processing with Four-wave Mixing in Rubidium-85
We have built a compact light source for bright squeezed twin-beams at
795\,nm based on four-wave-mixing in atomic Rb vapor. With a total
optical power of 400\,mW derived from a free running diode laser and a tapered
amplifier to pump the four-wave-mixing process, we achieve 2.1\,dB intensity
difference squeezing of the twin beams below the standard quantum limit,
without accounting for losses. Squeezed twin beams generated by the type of
source presented here could be used as reference for the precise calibration of
photodetectors. Transferring the quantum correlations from the light to atoms
in order to generate correlated atom beams is another interesting prospect. In
this work we investigate the dispersion that is generated by the employed
four-wave-mixing process with respect to bandwidth and dependence on probe
detuning. We are currently using this squeezed light source to test the
transfer of spatial information and quantum correlations through media of
anomalous dispersion.Comment: 6 pages, 4 figure
The effect of changes in space shuttle parameters on the NASA/MSFC multilayer diffusion model predictions of surface HCl concentrations
A method for formulating these changes into the model input parameters using a preprocessor program run on a programed data processor was implemented. The results indicate that any changes in the input parameters are small enough to be negligible in comparison to meteorological inputs and the limitations of the model and that such changes will not substantially increase the number of meteorological cases for which the model will predict surface hydrogen chloride concentrations exceeding public safety levels
Minimax studies
Effect of nonzero initial conditions on selection of minimax controllers for large launch vehicles and extremal bounded amplitude bounded rate inputs to linear system
Neural-Network Quantum States, String-Bond States, and Chiral Topological States
Neural-Network Quantum States have been recently introduced as an Ansatz for
describing the wave function of quantum many-body systems. We show that there
are strong connections between Neural-Network Quantum States in the form of
Restricted Boltzmann Machines and some classes of Tensor-Network states in
arbitrary dimensions. In particular we demonstrate that short-range Restricted
Boltzmann Machines are Entangled Plaquette States, while fully connected
Restricted Boltzmann Machines are String-Bond States with a nonlocal geometry
and low bond dimension. These results shed light on the underlying architecture
of Restricted Boltzmann Machines and their efficiency at representing many-body
quantum states. String-Bond States also provide a generic way of enhancing the
power of Neural-Network Quantum States and a natural generalization to systems
with larger local Hilbert space. We compare the advantages and drawbacks of
these different classes of states and present a method to combine them
together. This allows us to benefit from both the entanglement structure of
Tensor Networks and the efficiency of Neural-Network Quantum States into a
single Ansatz capable of targeting the wave function of strongly correlated
systems. While it remains a challenge to describe states with chiral
topological order using traditional Tensor Networks, we show that
Neural-Network Quantum States and their String-Bond States extension can
describe a lattice Fractional Quantum Hall state exactly. In addition, we
provide numerical evidence that Neural-Network Quantum States can approximate a
chiral spin liquid with better accuracy than Entangled Plaquette States and
local String-Bond States. Our results demonstrate the efficiency of neural
networks to describe complex quantum wave functions and pave the way towards
the use of String-Bond States as a tool in more traditional machine-learning
applications.Comment: 15 pages, 7 figure
Modeling and Simulation of Temperature Profiles in a Reactive Distillation System for Esterification of Acetic Anhydride with Methanol
This paper pertains to an experimental and theoretical study of simulation of temperature profiles in a one- stage adiabatic batch distillation/reactor for the production of methyl acetate and acetic acid from the esterification of acetic anhydride with methanol. Basically it deals with the development of a mathematical model for temperature predictions in the reactor. The reaction kinetics of the process was modeled using information obtained from experimental temperature –time data during the esterification processes. The simulation results were then compared with the experimental data. The maximum deviation of the model –predicted temperature form the corresponding experimentally measured temperature was less than 4% which is quite within the acceptable deviation range of experimental results.. Keywords: Modeling, Simulation, Reactive distillation, Temperature, Esterification, Acetic anhydride, Methano
South African municipalities in financial distress: what can be done?
South African municipalities have been faced with financial distress for some years. In some municipalities, financial distress has intensified to the extent that local government faces a "collapse”. On the other hand, many municipalities have been in reasonably good financial shape, at least until the recent pandemic. The information National Treasury publishes can help to identify cases of real concern. The primary responsibility to address municipal financial problems lies with the municipality, but other parties also have a role to play. Financial problems have different causes and will differ in severity. Consequently, different tools are appropriate, depending on the cause, severity and aggrieved party. These tools include discretionary and mandatory financial recovery plans, debt relief and restructuring. Where a municipal financial crisis amounts to a disaster, further tools can come into play. We hope that this exploration of legal remedies will stimulate greater action to resolve financial problems in municipalities. This article addresses situations where a municipality is already faced with financial distress , and does not delve into measures aimed at preventing municipal financial distress.
Alternate route to soliton solutions in hydrogen-bonded chains
In this paper we offer an alternate route for investigating soliton solutions
in hydrogen-bonded chains. This is done by examining a class of systems of two
coupled real scalar fields. We show that this route allows investigating
several models for hydrogen-bonded chains in a unified manner. We also show how
to investigate interesting issues, in particular the one concerning classical
or linear stability of solitonic solutions.Comment: 12 pages. Late
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