Extending Ground-Based Gravitational-Wave Sensitivity to 5 Hz

TL;DR

This paper demonstrates advanced inertial isolation and position sensing technologies that significantly improve low-frequency sensitivity of ground-based gravitational-wave detectors, enabling detection of signals down to 10 mHz and extending the observable range for intermediate-mass black hole binaries.

Contribution

The authors introduce ultra-high-vacuum compatible inertial sensors and laser position sensors that achieve active stabilization down to 10 mHz, representing a major technological advancement for gravitational-wave detection.

Findings

Achieved active platform stabilization down to 10 mHz

Sub-picometer per root Hz laser position sensing sensitivity

At least fivefold improvement in low-frequency sensitivity over commercial seismometers

Abstract

Extending the sensitivity of terrestrial gravitational-wave detectors below 20 Hz is a long-standing challenge, limited by ground motion and inertial sensing noise. In this letter, we demonstrate ultra-high-vacuum compatible inertial isolation and position sensing technologies that achieve active platform stabilization down to 10 mHz. Our laser position sensors reach a sub-pm/$\sqrt{\rm Hz}$ sensitivity above 10 mHz, independent of the input light polarization, representing a 100-fold improvement over the current LIGO position sensors. In addition, our inertial sensors provide at least a factor of 5 improvement in low-frequency sensitivity compared to state-of-the-art commercial seismometers. We integrate these technologies into a LIGO-like interferometer model and predict a low-frequency sensitivity improvement of up to an order of magnitude at 10 Hz, with enhanced linearity and calibration stability. This extension increases the detection horizon for intermediate-mass black hole binaries of mass $10^3 M_\odot$ by a factor of 3. Our results provide the first experimental demonstration of a practical pathway to sub-10 Hz operation of terrestrial gravitational-wave detectors and establish key technologies for next-generation observatories such as Cosmic Explorer and Einstein Telescope.