455 research outputs found
Phase Control of Squeezed Vacuum States of Light in Gravitational Wave Detectors
Quantum noise will be the dominant noise source for the advanced laser
interferometric gravitational wave detectors currently under construction.
Squeezing-enhanced laser interferometers have been recently demonstrated as a
viable technique to reduce quantum noise. We propose two new methods of
generating an error signal for matching the longitudinal phase of squeezed
vacuum states of light to the phase of the laser interferometer output field.
Both provide a superior signal to the one used in previous demonstrations of
squeezing applied to a gravitational-wave detector. We demonstrate that the new
signals are less sensitive to misalignments and higher order modes, and result
in an improved stability of the squeezing level. The new signals also offer the
potential of reducing the overall rms phase noise and optical losses, each of
which would contribute to achieving a higher level of squeezing. The new error
signals are a pivotal development towards realizing the goal of 6 dB and more
of squeezing in advanced detectors and beyond
Direct Drive Wave Energy Array with Offshore Energy Storage Supplying Off-Grid Residential Load
Lubrication and Tribological Performance Optimizations for Micro-Electro-Mechanical Systems
Ph.DNUS-ICL JOINT PH.D. (FoE
Analysis of Tower Shadow Effects on Battery Lifetime in Standalone Hybrid Wind-Diesel-Battery Systems
Skin perfusion assessed by contrast ultrasound predicts tissue survival in a free flap model
High power and ultra-low-noise photodetector for squeezed-light enhanced gravitational wave detectors
Current laser-interferometric gravitational wave detectors employ a self-homodyne
readout scheme where a comparatively large light power (5–50 mW) is detected per photosensitive
element. For best sensitivity to gravitational waves, signal levels as low as the quantum
shot noise have to be measured as accurately as possible. The electronic noise of the detection
circuit can produce a relevant limit to this accuracy, in particular when squeezed states of light
are used to reduce the quantum noise. We present a new electronic circuit design reducing the
electronic noise of the photodetection circuit in the audio band. In the application of this circuit at
the gravitational-wave detector GEO 600 the shot-noise to electronic noise ratio was permanently
improved by a factor of more than 4 above 1 kHz, while the dynamic range was improved by
a factor of 7. The noise equivalent photocurrent of the implemented photodetector and circuit
is about 5 µA/
√\ud
Hz above 1 kHz with a maximum detectable photocurrent of 20 mA. With the
new circuit, the observed squeezing level in GEO 600 increased by 0.2 dB. The new circuit also
creates headroom for higher laser power and more squeezing to be observed in the future in
GEO 600 and is applicable to other optics experiments
Big Bang Nucleosynthesis Constraints on Brane Cosmologies
We examine constraints from Big Bang nucleosynthesis on type II
Randall-Sundrum brane cosmologies with both a dark radiation component and a
quadratic term that depends on the 5-dimensional Planck mass, M_5. Using limits
on the abundances of deuterium and helium-4, we calculate the allowed region in
the M_5-dark radiation plane and derive the precise BBN bound on M_5 alone with
no dark radiation: M_5 > 13 TeV.Comment: 3 pages, 1 figure, references added, to appear in Phys. Lett.
- …