912 research outputs found
Some rules of good scientific writing
A non-native English speaking physics professor formulates obvious yet useful
rules for writing research papers.Comment: 1 page, no figure
Gyroscopes based on nitrogen-vacancy centers in diamond
We propose solid-state gyroscopes based on ensembles of negatively charged
nitrogen-vacancy () centers in diamond. In one scheme, rotation of
the nitrogen-vacancy symmetry axis will induce Berry phase shifts in the electronic ground-state coherences proportional to the solid angle
subtended by the symmetry axis. We estimate sensitivity in the range of
in a 1 sensor volume using
a simple Ramsey sequence. Incorporating dynamical decoupling to suppress
dipolar relaxation may yield sensitivity at the level of . With a modified Ramsey scheme, Berry phase shifts in the
hyperfine sublevels would be employed. The projected sensitivity
is in the range of , however the smaller
gyromagnetic ratio reduces sensitivity to magnetic-field noise by several
orders of magnitude. Reaching would represent
an order of magnitude improvement over other compact, solid-state gyroscope
technologies.Comment: 3 figures, 5 page
How do you know if you ran through a wall?
Stable topological defects of light (pseudo)scalar fields can contribute to
the Universe's dark energy and dark matter. Currently the combination of
gravitational and cosmological constraints provides the best limits on such a
possibility. We take an example of domain walls generated by an axion-like
field with a coupling to the spins of standard-model particles, and show that
if the galactic environment contains a network of such walls, terrestrial
experiments aimed at detection of wall-crossing events are realistic. In
particular, a geographically separated but time-synchronized network of
sensitive atomic magnetometers can detect a wall crossing and probe a range of
model parameters currently unconstrained by astrophysical observations and
gravitational experiments.Comment: 5 pages, 2 figure; to appear in the PR
Nonlinear magneto-optical rotation of frequency-modulated light resonant with a low-J transition
A low-light-power theory of nonlinear magneto-optical rotation of
frequency-modulated light resonant with a J=1->J'=0 transition is presented.
The theory is developed for a Doppler-free transition, and then modified to
account for Doppler broadening and velocity mixing due to collisions. The
results of the theory are shown to be in qualitative agreement with
experimental data obtained for the rubidium D1 line.Comment: 11 pages, 5 figures, v.2 edited for clarit
Hyperfine-interaction- and magnetic-field-induced Bose-Einstein-statistics suppressed two-photon transitions
Two-photon transitions between atomic states of total electronic angular
momentum and are forbidden when the photons are of the same
energy. This selection rule is analogous to the Landau-Yang theorem in particle
physics that forbids decays of vector particle into two photons. It arises
because it is impossible to construct a total angular momentum
quantum-mechanical state of two photons that is permutation symmetric, as
required by Bose-Einstein statistics. In atoms with non-zero nuclear spin, the
selection rule can be violated due to hyperfine interactions. Two distinct
mechanisms responsible for the hyperfine-induced two-photon transitions are
identified, and the hyperfine structure of the induced transitions is
evaluated. The selection rule is also relaxed, even for zero-nuclear-spin
atoms, by application of an external magnetic field. Once again, there are two
similar mechanisms at play: Zeeman splitting of the intermediate-state
sublevels, and off-diagonal mixing of states with different total electronic
angular momentum in the final state. The present theoretical treatment is
relevant to the ongoing experimental search for a possible
Bose-Einstein-statistics violation using two-photon transitions in barium,
where the hyperfine-induced transitions have been recently observed, and the
magnetic-field-induced transitions are being considered both as a possible
systematic effect, and as a way to calibrate the measurement
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