16,763 research outputs found
Bell's theorem without inequalities and without alignments
A proof of Bell's theorem without inequalities is presented which exhibits
three remarkable properties: (a) reduced local states are immune to collective
decoherence; (b) distant local setups do not need to be aligned, since the
required perfect correlations are achieved for any local rotation of the local
setups; (c) local measurements require only individual measurements on the
qubits. Indeed, it is shown that this proof is essentially the only one which
fulfils (a), (b), and (c).Comment: REVTeX4, 4 page
Error Analysis For Encoding A Qubit In An Oscillator
In the paper titled "Encoding A Qubit In An Oscillator" Gottesman, Kitaev,
and Preskill [quant-ph/0008040] described a method to encode a qubit in the
continuous Hilbert space of an oscillator's position and momentum variables.
This encoding provides a natural error correction scheme that can correct
errors due to small shifts of the position or momentum wave functions (i.e.,
use of the displacement operator). We present bounds on the size of correctable
shift errors when both qubit and ancilla states may contain errors. We then use
these bounds to constrain the quality of input qubit and ancilla states.Comment: 5 pages, 8 figures, submitted to Physical Review
An "All Possible Steps" Approach to the Accelerated Use of Gillespie's Algorithm
Many physical and biological processes are stochastic in nature.
Computational models and simulations of such processes are a mathematical and
computational challenge. The basic stochastic simulation algorithm was
published by D. Gillespie about three decades ago [D.T. Gillespie, J. Phys.
Chem. {\bf 81}, 2340, (1977)]. Since then, intensive work has been done to make
the algorithm more efficient in terms of running time. All accelerated versions
of the algorithm are aimed at minimizing the running time required to produce a
stochastic trajectory in state space. In these simulations, a necessary
condition for reliable statistics is averaging over a large number of
simulations. In this study I present a new accelerating approach which does not
alter the stochastic algorithm, but reduces the number of required runs. By
analysis of collected data I demonstrate high precision levels with fewer
simulations. Moreover, the suggested approach provides a good estimation of
statistical error, which may serve as a tool for determining the number of
required runs.Comment: Accepted for publication at the Journal of Chemical Physics. 19
pages, including 2 Tables and 4 Figure
Treatment of multidrug-resistant tuberculosis in a remote, conflict-affected area of the Democratic Republic of Congo.
The Democratic Republic of Congo is a high-burden country for multidrug-resistant tuberculosis. Médecins Sans Frontières has supported the Ministry of Health in the conflict-affected region of Shabunda since 1997. In 2006, three patients were diagnosed with drug-resistant TB (DR-TB) and had no options for further treatment. An innovative model was developed to treat these patients despite the remote setting. Key innovations were the devolving of responsibility for treatment to non-TB clinicians remotely supported by a TB specialist, use of simplified monitoring protocols, and a strong focus on addressing stigma to support adherence. Treatment was successfully completed after a median of 24 months. This pilot programme demonstrates that successful treatment for DR-TB is possible on a small scale in remote settings
Enhanced vaccine control of epidemics in adaptive networks
We study vaccine control for disease spread on an adaptive network modeling
disease avoidance behavior. Control is implemented by adding Poisson
distributed vaccination of susceptibles. We show that vaccine control is much
more effective in adaptive networks than in static networks due to an
interaction between the adaptive network rewiring and the vaccine application.
Disease extinction rates using vaccination are computed, and orders of
magnitude less vaccine application is needed to drive the disease to extinction
in an adaptive network than in a static one
Preparation and manipulation of a fault-tolerant superconducting qubit
We describe a qubit encoded in continuous quantum variables of an rf
superconducting quantum interference device. Since the number of accessible
states in the system is infinite, we may protect its two-dimensional subspace
from small errors introduced by the interaction with the environment and during
manipulations. We show how to prepare the fault-tolerant state and manipulate
the system. The discussed operations suffice to perform quantum computation on
the encoded state, syndrome extraction, and quantum error correction. We also
comment on the physical sources of errors and possible imperfections while
manipulating the system.Comment: Typo corrected, title changed as suggested by the editors of Phys.
Rev. B, references adde
The unitary-model-operator approach to nuclear many-body problems
Microscopic nuclear structure calculations have been performed within the
framework of the unitary-model-operator approach. Ground-state and
single-particle energies are calculated for nuclei around ^{14}C, ^{16}O and
^{40}Ca with modern nucleon-nucleon interactions.Comment: 6 pages, 4 figures, Talk presented at the International Symposium on
Correlation Dynamics in Nuclei (CDN05), Jan. 1 - Feb. 4, 2005, Tokyo, Japa
The unitary-model-operator approach to nuclear many-body problems
Microscopic nuclear structure calculations have been performed within the
framework of the unitary-model-operator approach. Ground-state and
single-particle energies are calculated for nuclei around ^{14}C, ^{16}O and
^{40}Ca with modern nucleon-nucleon interactions.Comment: 6 pages, 4 figures, Talk presented at the International Symposium on
Correlation Dynamics in Nuclei (CDN05), Jan. 1 - Feb. 4, 2005, Tokyo, Japa
Time-resolved extinction rates of stochastic populations
Extinction of a long-lived isolated stochastic population can be described as
an exponentially slow decay of quasi-stationary probability distribution of the
population size. We address extinction of a population in a two-population
system in the case when the population turnover -- renewal and removal -- is
much slower than all other processes. In this case there is a time scale
separation in the system which enables one to introduce a short-time
quasi-stationary extinction rate W_1 and a long-time quasi-stationary
extinction rate W_2, and develop a time-dependent theory of the transition
between the two rates. It is shown that W_1 and W_2 coincide with the
extinction rates when the population turnover is absent, and present but very
slow, respectively. The exponentially large disparity between the two rates
reflects fragility of the extinction rate in the population dynamics without
turnover.Comment: 8 pages, 4 figure
The unitary-model-operator approach to nuclear many-body problems
Microscopic nuclear structure calculations have been performed within the
framework of the unitary-model-operator approach. Ground-state and
single-particle energies are calculated for nuclei around ^{14}C, ^{16}O and
^{40}Ca with modern nucleon-nucleon interactions.Comment: 6 pages, 4 figures, Talk presented at the International Symposium on
Correlation Dynamics in Nuclei (CDN05), Jan. 1 - Feb. 4, 2005, Tokyo, Japa
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