530 research outputs found
Gravitational Radiation Detection with Laser Interferometry
Gravitational-wave detection has been pursued relentlessly for over 40 years.
With the imminent operation of a new generation of laser interferometers, it is
expected that detections will become a common occurrence. The research into
more ambitious detectors promises to allow the field to move beyond detection
and into the realm of precision science using gravitational radiation. In this
article, I review the state of the art for the detectors and describe an
outlook for the coming decades.Comment: 38 pages typos, references update
Subtraction of Newtonian Noise Using Optimized Sensor Arrays
Fluctuations in the local Newtonian gravitational field present a limit to
high precision measurements, including searches for gravitational waves using
laser interferometers. In this work, we present a model of this perturbing
gravitational field and evaluate schemes to mitigate the effect by estimating
and subtracting it from the interferometer data stream. Information about the
Newtonian noise is obtained from simulated seismic data. The method is tested
on causal as well as acausal implementations of noise subtraction. In both
cases it is demonstrated that broadband mitigation factors close to 10 can be
achieved removing Newtonian noise as a dominant noise contribution. The
resulting improvement in the detector sensitivity will substantially enhance
the detection rate of gravitational radiation from cosmological sources.Comment: 29 pages, 11 figure
Quantum Limits of Interferometer Topologies for Gravitational Radiation Detection
In order to expand the astrophysical reach of gravitational wave detectors,
several interferometer topologies have been proposed to evade the thermodynamic
and quantum mechanical limits in future detectors. In this work, we make a
systematic comparison among them by considering their sensitivities and
complexities. We numerically optimize their sensitivities by introducing a cost
function that tries to maximize the broadband improvement over the sensitivity
of current detectors. We find that frequency-dependent squeezed-light injection
with a hundred-meter scale filter cavity yields a good broadband sensitivity,
with low complexity, and good robustness against optical loss. This study gives
us a guideline for the near-term experimental research programs in enhancing
the performance of future gravitational-wave detectors.Comment: grammar correcte
External quantum efficiency enhancement by photon recycling with backscatter evasion
The nonunity quantum efficiency (QE) in photodiodes (PD) causes deterioration
of signal quality in quantum optical experiments due to photocurrent loss as
well as the introduction of vacuum fluctuations into the measurement. In this
paper, we report that the external QE enhancement of a PD was demonstrated by
recycling the reflected photons. The external QE for an InGaAs PD was increased
by 0.01 - 0.06 from 0.86 - 0.92 over a wide range of incident angles. Moreover,
we confirmed that this technique does not increase backscattered light when the
recycled beam is properly misaligned
Astrophysics and cosmology with a deci-hertz gravitational-wave detector: TianGO
We present the astrophysical science case for a space-based, deci-Hz gravitational-wave (GW) detector. We particularly highlight an ability in inferring a source's sky location, both when combined with a network of ground-based detectors to form a long triangulation baseline, and by itself for the early warning of merger events. Such an accurate location measurement is the key for using GW signals as standard sirens for constraining the Hubble constant. This kind of detector also opens up the possibility of testing type Ia supernovae progenitor hypotheses by constraining the merger rates of white dwarf binaries with both super- and sub-Chandrasekhar masses separately. We will discuss other scientific outcomes that can be delivered, including the precise determination of black hole spins, the constraint of structure formation in the early Universe, and the search for intermediate-mass black holes
Towards the Fundamental Quantum Limit of Linear Measurements of Classical Signals
The quantum Cram\'er-Rao bound (QCRB) sets a fundamental limit for the
measurement of classical signals with detectors operating in the quantum
regime. Using linear-response theory and the Heisenberg uncertainty relation,
we derive a general condition for achieving such a fundamental limit. When
applied to classical displacement measurements with a test mass, this condition
leads to an explicit connection between the QCRB and the Standard Quantum Limit
which arises from a tradeoff between the measurement imprecision and quantum
backaction; the QCRB can be viewed as an outcome of a quantum non-demolition
measurement with the backaction evaded. Additionally, we show that the test
mass is more a resource for improving measurement sensitivity than a victim of
the quantum backaction, which suggests a new approach to enhancing the
sensitivity of a broad class of sensors. We illustrate these points with laser
interferometric gravitational wave detectors.Comment: revised version with supplemental materials adde
Angular instability due to radiation pressure in the LIGO gravitational-wave detector
We observed the effect of radiation pressure on the angular sensing and control system of the Laser Interferometer Gravitational-Wave Observatory (LIGO) interferometer’s core optics at LIGO Hanford Observatory. This is the first measurement of this effect in a complete gravitational-wave interferometer. Only one of the two angular modes survives with feedback control, because the other mode is suppressed when the control gain is sufficiently large. We developed a mathematical model to understand the physics of the system. This model matches well with the dynamics that we observe
Probing microplasticity in small scale FCC crystals via Dynamic Mechanical Analysis
In small-scale metallic systems, collective dislocation activity has been
correlated with size effects in strength and with a step-like plastic response
under uniaxial compression and tension. Yielding and plastic flow in these
samples is often accompanied by the emergence of multiple dislocation
avalanches. Dislocations might be active pre-yield, but their activity
typically cannot be discerned because of the inherent instrumental noise in
detecting equipment. We apply Alternate Current (AC) load perturbations via
Dynamic Mechanical Analysis (DMA) during quasi-static uniaxial compression
experiments on single crystalline Cu nano-pillars with diameters of 500 nm, and
compute dynamic moduli at frequencies 0.1, 0.3, 1, and 10 Hz under
progressively higher static loads until yielding. By tracking the collective
aspects of the oscillatory stress-strain-time series in multiple samples, we
observe an evolving dissipative component of the dislocation network response
that signifies the transition from elastic behavior to dislocation avalanches
in the globally pre-yield regime. We postulate that microplasticity, which is
associated with the combination of dislocation avalanches and slow viscoplastic
relaxations, is the cause of the dependency of dynamic modulus on the driving
rate and the quasi-static stress. We construct a continuum mesoscopic
dislocation dynamics model to compute the frequency response of stress over
strain and obtain a consistent agreement with experimental observations. The
results of our experiments and simulations present a pathway to discern and
quantify correlated dislocation activity in the pre-yield regime of deforming
crystals.Comment: 5 pages, 3 figure
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
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