5 research outputs found
Quantum precision limits of displacement noise free interferometers
Current laser-interferometric gravitational wave detectors suffer from a
fundamental limit to their precision due to the displacement noise of optical
elements contributed by various sources. Several schemes for Displacement-Noise
Free Interferometers (DFI) have been proposed to mitigate their effects. The
idea behind these schemes is similar to decoherence-free subspaces in quantum
sensing i.e. certain modes contain information about the gravitational waves
but are insensitive to the displacement noise. In this paper we derive quantum
precision limits for general DFI schemes, including optimal measurement basis
and optimal squeezing schemes. We introduce a triangular cavity DFI scheme and
apply our general bounds to it. Precision analysis of this scheme with
different noise models shows that the DFI property leads to interesting
sensitivity profiles and improved precision due to noise mitigation and larger
gain from squeezing. Further extensions of this scheme are presented
The Large-scale Coronal Structure of the 2017 August 21 Great American Eclipse: An Assessment of Solar Surface Flux Transport Model Enabled Predictions and Observations
On 2017 August 21, a total solar eclipse swept across the contiguous United States, providing excellent opportunities for diagnostics of the Sun's corona. The Sun's coronal structure is notoriously difficult to observe except during solar eclipses; thus, theoretical models must be relied upon for inferring the underlying magnetic structure of the Sun's outer atmosphere. These models are necessary for understanding the role of magnetic fields in the heating of the corona to a million degrees and the generation of severe space weather. Here we present a methodology for predicting the structure of the coronal field based on model forward runs of a solar surface flux transport model, whose predicted surface field is utilized to extrapolate future coronal magnetic field structures. This prescription was applied to the 2017 August 21 solar eclipse. A post-eclipse analysis shows good agreement between model simulated and observed coronal structures and their locations on the limb. We demonstrate that slow changes in the Sun's surface magnetic field distribution driven by long-term flux emergence and its evolution governs large-scale coronal structures with a (plausibly cycle-phase dependent) dynamical memory timescale on the order of a few solar rotations, opening up the possibility for large-scale, global corona predictions at least a month in advance