6,987 research outputs found
Laser phase modulation approaches towards ensemble quantum computing
Selective control of decoherence is demonstrated for a multilevel system by
generalizing the instantaneous phase of any chirped pulse as individual terms
of a Taylor series expansion. In the case of a simple two-level system, all odd
terms in the series lead to population inversion while the even terms lead to
self-induced transparency. These results also hold for multiphoton transitions
that do not have any lower-order photon resonance or any intermediate virtual
state dynamics within the laser pulse-width. Such results form the basis of a
robustly implementable CNOT gate.Comment: 10 pages, 4 figures, PRL (accepted
Formation of caustics in Dirac-Born-Infeld type scalar field systems
We investigate the formation of caustics in Dirac-Born-Infeld type scalar
field systems for generic classes of potentials, viz., massive rolling scalar
with potential, and inverse
power-law potentials with . We find that in the case
of\texttt{} exponentially decreasing rolling massive scalar field potential,
there are multi-valued regions and regions of likely to be caustics in the
field configuration. However there are no caustics in the case of exponentially
increasing potential. We show that the formation of caustics is inevitable for
the inverse power-law potentials under consideration in Minkowski space time
whereas caustics do not form in this case in the FRW universe.Comment: 16 pages, 14 figures, major revision, conclusions strengthen, to
appear in PR
Global oscillation analysis of solar neutrino data with helioseismically constrained fluxes
A seismic model for the Sun calculated using the accurate helioseismic data
predicts a lower neutrino flux as compared to the standard solar
model (SSM). However, there persists a discrepancy between the predicted and
measured neutrino fluxes and it seems necessary to invoke neutrino oscillations
to explain the measurements. In this work, we have performed a global, unified
oscillation analysis of the latest solar neutrino data (including the results
of SNO charged current rate) using the seismic model fluxes as theoretical
predictions. We determine the best-fit values of the neutrino oscillation
parameters and the for both
and cases and present the allowed parameter
regions in the plane for transition. The results are compared with those obtained using the
latest SSM by Bahcall and his collaborators.Comment: Version to appear in Phys. Rev.
A homomorphism theorem and a Trotter product formula for quantum stochastic flows with unbounded coefficients
We give a new method for proving the homomorphic property of a quantum
stochastic ow satisfying a quantum stochastic differential equation with
unbounded coefficients, under some further hypotheses. As an application, we
prove a Trotter product formula for quantum stochastic ows and obtain quantum
stochastic dilations of a class of quantum dynamical semigroups generalizing
results of [5
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