Speaker: Prof. Yuki Inoue (NCU)
Talk title: CHRONOS: Probing Gravity and Quantum Physics at Sub-Hz Frequencies
Time: 2026/09/14 (Mon.) 12:30
Place: NCTS Physics 4F Lecture Hall, Cosmology Hall, NTU

Abstract: 
The frequency band between terrestrial gravitational-wave detectors and space-based interferometers remains largely unexplored. Opening this sub-Hz window would provide access not only to new gravitational-wave sources, but also to a broader range of fundamental physics that can be probed through precision measurements of gravity and macroscopic mechanical motion.
CHRONOS is a cryogenic torsion-bar experiment being developed in Taiwan to explore this frequency regime. Its central concept combines low-frequency torsional test masses with Sagnac interferometry and quantum non-demolition measurement techniques. The experiment is designed as a platform for studying gravitational phenomena in the 0.1–10 Hz band, where seismic and gravity-gradient backgrounds, thermal fluctuations, and quantum measurement noise present fundamentally different challenges from those encountered by conventional gravitational-wave detectors.
The physics program of CHRONOS spans several complementary directions. These include gravitational waves from intermediate-mass black-hole binaries and stochastic backgrounds, searches for ultralight dark matter and deviations from Newtonian gravity, measurements of transient gravity gradients associated with earthquakes, and experimental studies of quantum measurement at macroscopic scales.
An international collaboration involving researchers from Taiwan, Japan, the Philippines, Vietnam, Thailand, and Germany has recently begun to develop this program. In this talk, I will discuss the physics accessible in the sub-Hz regime, the measurement principles and current experimental status of CHRONOS, and how the emerging international effort aims to turn this unexplored frequency band into a new laboratory for gravitational and quantum physics.