1,691 research outputs found
Quantum state engineering using conditional measurement on a beam splitter
State preparation via conditional output measurement on a beam splitter is
studied, assuming the signal mode is mixed with a mode prepared in a Fock state
and photon numbers are measured in one of the output channels. It is shown that
the mode in the other output channel is prepared in either a photon-subtracted
or a photon-added Jacobi polynomial state, depending upon the difference
between the number of photons in the input Fock state and the number of photons
in the output Fock state onto which it is projected. The properties of the
conditional output states are studied for coherent and squeezed input states,
and the probabilities of generating the states are calculated. Relations to
other states, such as near-photon-number states and squeezed-state-excitations,
are given and proposals are made for generating them by combining the scheme
with others. Finally, effects of realistic photocounting and Fock-state
preparation are discussed.Comment: 8 figures using a4.st
Estimating Electric Fields from Vector Magnetogram Sequences
Determining the electric field (E-field) distribution on the Sun's
photosphere is essential for quantitative studies of how energy flows from the
Sun's photosphere, through the corona, and into the heliosphere. This E-field
also provides valuable input for data-driven models of the solar atmosphere and
the Sun-Earth system. We show how Faraday's Law can be used with observed
vector magnetogram time series to estimate the photospheric E-field, an
ill-posed inversion problem. Our method uses a "poloidal-toroidal
decomposition" (PTD) of the time derivative of the vector magnetic field. The
PTD solutions are not unique; the gradient of a scalar potential can be added
to the PTD E-field without affecting consistency with Faraday's Law. We present
an iterative technique to determine a potential function consistent with ideal
MHD evolution; but this E-field is also not a unique solution to Faraday's Law.
Finally, we explore a variational approach that minimizes an energy functional
to determine a unique E-field, similar to Longcope's "Minimum Energy Fit". The
PTD technique, the iterative technique, and the variational technique are used
to estimate E-fields from a pair of synthetic vector magnetograms taken from an
MHD simulation; and these E-fields are compared with the simulation's known
electric fields. These three techniques are then applied to a pair of vector
magnetograms of solar active region NOAA AR8210, to demonstrate the methods
with real data.Comment: 41 pages, 10 figure
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