Conceptual design and science cases of a juggled interferometer for gravitational wave detection

TL;DR

The paper proposes a novel earth-based gravitational wave detector using free-falling test masses, offering improved low-frequency sensitivity and new science opportunities in black hole and primordial black hole research.

Contribution

It introduces a phase reconstruction method for the juggled interferometer, enabling better sensitivity at low frequencies despite data discontinuities.

Findings

Significantly improves sensitivity at 0.1-2.5 Hz

Enables detection of black hole quasi-normal modes

Facilitates tests of alternative gravity theories

Abstract

The Juggled interferometer (JIFO) is an earth-based gravitational wave detector using repeatedly free-falling test masses. With no worries of seismic noise and suspension thermal noise, the JIFO can have much better sensitivity at lower frequencies than the current earth-based gravitational wave detectors. The data readout method of a JIFO could be challenging if one adopts the fringe-locking method. We present a phase reconstruction method in this paper by building up a complex function which has a fringe-independent signal-to-noise ratio. Considering the displacement noise budget of the Einstein Telescope (ET), we show that the juggled test masses significantly improve the sensitivity at 0.1-2.5$\,$Hz even with discontinuous data. The science cases brought with the improved sensitivity would include detecting quasi-normal modes of black holes with $10^4-10^5\,M_{\odot}$, testing Brans-Dicke theory with black-hole and neutron-star inspirals, and detecting primordial-black-hole-related gravitational waves.