arXiv subjects

R. L. Ward

Publications and source records attributed to R. L. Ward.

4 recordsLinked to original sources

arXiv2026

LIGO A$^\sharp$: Detector Design and Science Prospects Beyond A+

We present the LIGO A$^\sharp$ detector concept, an upgrade for the LIGO observatories based on room-temperature interferometers beyond the fifth observing run (O5). Building on the A+ sensitivity, A$^\sharp$ targets broadband sensitivity improvements through heavier test masses, improved suspensions and seismic isolation, increased arm-cavity power, enhanced frequency-dependent squeezing, reduced coating thermal noise considering two scenarios, and improved control of mechanical motion and optical modes. We describe the principal design choices, projected noise performance, and corresponding astrophysical prospects. LIGO A$^\sharp$ substantially increases compact-binary detection rates, strengthens population inference, and improves both early-warning times and localization for binary neutron star mergers. The improved sensitivity enables more detailed studies of compact-binary coalescences, including higher-order multipoles, intermediate-mass black holes, remnant black hole ringdown, and the neutron star equation of state. It also broadens the discovery potential for new gravitational-wave sources such as continuous waves and bursts, should enable detection of the stochastic background from compact binary mergers if it remains undetected after O5, and strengthens the role of gravitational-wave detectors as probes of fundamental physics. We discuss key technical challenges and the role of A$^\sharp$ as both a major scientific upgrade for the 2030s and a technology pathfinder for next-generation gravitational-wave observatories, such as Cosmic Explorer.

astro-ph.IM↗

arXiv2025

Loss-tolerant detection of squeezed states in the 2 um region

Squeezed states of light enable quantum-enhanced measurements but are limited by optical loss, particularly at 2 um where photodiode efficiency is low. We report the first loss-tolerant, audio-band squeezed light detection at 1984 nm by using a phase-sensitive amplifier to amplify the squeezed vacuum prior to detection. This technique increases the effective detection efficiency from 74% to 95% and increases the observed squeezing from 4 dB to 8 dB, the highest level of squeezing observed at this wavelength. Additionally, the shot-to-dark-noise clearance increases, extending the effective measurement bandwidth toward lower frequencies. This approach is largely wavelength-independent, extending high-fidelity quantum measurements to future gravitational-wave detectors and related quantum technologies.

quant-ph↗

arXiv2021

LIGOs Quantum Response to Squeezed States

Gravitational Wave interferometers achieve their profound sensitivity by combining a Michelson interferometer with optical cavities, suspended masses, and now, squeezed quantum states of light. These states modify the measurement process of the LIGO, VIRGO and GEO600 interferometers to reduce the quantum noise that masks astrophysical signals; thus, improvements to squeezing are essential to further expand our gravitational view of the universe. Further reducing quantum noise will require both lowering decoherence from losses as well more sophisticated manipulations to counter the quantum back-action from radiation pressure. Both tasks require fully understanding the physical interactions between squeezed light and the many components of km-scale interferometers. To this end, data from both LIGO observatories in observing run three are expressed using frequency-dependent metrics to analyze each detector's quantum response to squeezed states. The response metrics are derived and used to concisely describe physical mechanisms behind squeezing's simultaneous interaction with transverse-mode selective optical cavities and the quantum radiation pressure noise of suspended mirrors. These metrics and related analysis are broadly applicable for cavity-enhanced optomechanics experiments that incorporate external squeezing, and -- for the first time -- give physical descriptions of every feature so far observed in the quantum noise of the LIGO detectors.

physics.ins-det↗

arXiv2018

Early Earthquake Detection with a Dual Torsion-Beam Gravimeter

Ground mass is redistributed during an earthquake causing the local gravitational potential to change. These gravitational fluctuations travel at the speed of light meaning they will arrive at a remote location significantly earlier than the fastest seismic waves. If these gravitational signals are measured by a gravimeter then early warning can be provided for an imminent earthquake. Earlier detection of earthquakes could be used to protect crucial infrastructure and save lives. The Torsion Pendulum Dual Oscillator (TorPeDO) is a gravity gradient sensor that has been constructed at the Australian National University. In this article we investigate the feasibility of measuring prompt gravitational transients from earthquakes with the TorPeDO. We simulated the response of the sensor to these signals and inserted these responses into scaled TorPeDO strain data to test their detection using a matched filter search. This simulation allows us to estimate the signal-to-noise ratio and detection time of the sensor to these transient signals, along with the influence of different detection thresholds on range and detection time. This article also proposes a method of earthquake localisation using TorPeDO sensors without the need for accurate signal timing. A real-time estimate of earthquake magnitude can be produced by combining this calculated location with TorPeDO strain data. We find that a TorPeDO system operating at design sensitivity would measure a moment magnitude 7.1 earthquake, 200~km away, reaching a signal-to-noise ratio of 5 at 15.7~s after the event starts. This will provide roughly 50.96~s of warning before the arrival of the first S waves.

physics.ins-det↗