Space-based optical lattice clocks as gravitational wave detectors in search for new physics

TL;DR

This paper explores the potential of space-based optical lattice clocks to detect low-frequency gravitational waves, proposing a cross-correlation method between two detectors to improve sensitivity beyond single-detector capabilities.

Contribution

It introduces the concept of using space-based optical lattice clocks for gravitational wave detection and proposes a cross-correlation approach to enhance sensitivity in low-frequency ranges.

Findings

Space-based OLCs can respond uniquely to low-frequency GWs due to longer arm lengths.

Single OLC detectors have lower sensitivity compared to LISA.

Cross-correlation of two OLC detectors improves detection sensitivity for SGWB.

Abstract

We investigate the sensitivity and performance of space-based Optical Lattice Clocks (OLCs) in detecting gravitational waves, in particular the Stochastic Gravitational Wave Background (SGWB) at low frequencies $(10^{-4}, 1) \rm Hz$, which are inaccessible to ground-based detectors. We first analyze the response characteristics of a single OLC detector for SGWB detection and compare its sensitivity with that of Laser Interferometer Space Antenna (LISA). Due to longer arm lengths, space-based OLC detectors can exhibit unique frequency responses and enhance the capability to detect SGWB in the low-frequency range, but the sensitivity of a single OLC detector remains insufficient overall compared to LISA. Then, as a preliminary plan, we adopt a method of cross-correlation on two OLC detectors to improve the signal-to-noise ratio (SNR). This method leverages the uncorrelated origins but statistically similar properties of noise in two detectors while the SGWB signal is correlated between them, thus achieving effective noise suppression and sensitivity enhancement. Future advancements in OLC stability are expected to further enhance their detection performance. This work highlights the potential of OLC detectors as a promising platform for SGWB detection, offering complementary capabilities to LISA, and opening an observational window into more astrophysical sources and the early universe.