13,908 research outputs found
Decoherence of number states in phase-sensitive reservoirs
The non-unitary evolution of initial number states in general Gaussian
environments is solved analytically. Decoherence in the channels is quantified
by determining explicitly the purity of the state at any time. The influence of
the squeezing of the bath on decoherence is discussed. The behavior of coherent
superpositions of number states is addressed as well.Comment: 5 pages, 2 figures, minor changes, references adde
Modification of EMS-induced reversion frequencies in Neurospora with enriched plating media
Modification of EMS-induced reversion frequencies in Neurospora with enriched plating medi
Reducing iron loss in interior PM machines under field-weakening conditions
Field-weakening in interior PM machines is performed by using negative rf-axis current to oppose the magnet flux and hence reduce the total fundamental rf-axis flux at high speeds. Due to the rotor saliency, the rf-axis current produces large amplitude harmonic airgap flux density components which can cause large harmonic stator iron losses. Reducing the magnet flux density reduces the required rf-axis stator mmf to oppose it and hence reduces the field-weakening iron losses. However reducing the magnet flux density also reduces the magnet torque and hence increases the stator current requirement, particularly at lower speeds. This paper examines this trade-off for an automotive integrated starter/alternator using a graphical interior PM machine parameter plane approach.W.L. Soong, S.H. Han, T.M. Jahns and N. Ertugru
Spontaneous emission and teleportation in cavity QED
In this work, we consider atomic spontaneous emission in a system consisting
of two identical two-level atoms interacting dispersively with the quantized
electromagnetic field in a high-Q cavity. We investigate the destructive effect
of the atomic decay on the generation of maximally entangled states, following
the proposal by Zheng S B and Guo G C (2000 Phys. Rev. Lett. 85 2392). In
particular, we analyze the fidelity of teleportation performed using such a
noisy channel and calculatethe maximum spontaneous decay rate we may have in
order to realize teleportation.Comment: 11 pages, 6 figures, LaTe
Decoherence due to three-body loss and its effect on the state of a Bose-Einstein condensate
A Born-Markov master equation is used to investigate the decoherence of the
state of a macroscopically occupied mode of a cold atom trap due to three-body
loss. In the large number limit only coherent states remain pure for times
longer than the decoherence time: the time it takes for just three atoms to be
lost from the trap. For large numbers of atoms (N>10^4) the decoherence time is
found to be much faster than the phase collapse time caused by intra-trap
atomic collisions
Large-uncertainty intelligent states for angular momentum and angle
The equality in the uncertainty principle for linear momentum and position is
obtained for states which also minimize the uncertainty product. However, in
the uncertainty relation for angular momentum and angular position both sides
of the inequality are state dependent and therefore the intelligent states,
which satisfy the equality, do not necessarily give a minimum for the
uncertainty product. In this paper, we highlight the difference between
intelligent states and minimum uncertainty states by investigating a class of
intelligent states which obey the equality in the angular uncertainty relation
while having an arbitrarily large uncertainty product. To develop an
understanding for the uncertainties of angle and angular momentum for the
large-uncertainty intelligent states we compare exact solutions with analytical
approximations in two limiting cases.Comment: 20 pages, 9 figures, submitted to J. Opt. B special issue in
connection with ICSSUR 2005 conferenc
Optimal discrimination of quantum operations
We address the problem of discriminating with minimal error probability two
given quantum operations. We show that the use of entangled input states
generally improves the discrimination. For Pauli channels we provide a complete
comparison of the optimal strategies where either entangled or unentangled
input states are used.Comment: 4 pages, no figure
Universality of Regge and vibrational trajectories in a semiclassical model
The orbital and radial excitations of light-light mesons are studied in the
framework of the dominantly orbital state description. The equation of motion
is characterized by a relativistic kinematics supplemented by the usual funnel
potential with a mixed scalar and vector confinement. The influence of finite
quark masses and potential parameters on Regge and vibrational trajectories is
discussed. The case of heavy-light mesons is also presented.Comment: 12 page
Assessing Information Technology Use over Time with Growth Modeling and Hierarchical Linear Modeling: A Tutorial
Time is an important factor in the use of information technology. However, traditional information systems research methods cannot adequately account for the dynamic nature of time-based relationships often found in longitudinal data. This shortcoming is problematic when investigating volatile relationships that evolve over time (e.g., information technology use across users, departments, and organizations). Educational, sociological, and management researchers study the influence of time using a rigorous multilevel method called growth modeling. We demonstrate the use of growth modeling in this tutorial, which is based on a semester-long study of an actual web-based university-level course content delivery system. The tutorial provides guidance on preliminary data tests, the construction and analysis of growth models using hierarchical linear modeling, and the interpretation of final results. The tutorial also describes other unique advantages of using growth modeling for IS research
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