Wei-Tou Ni

The technological requirements and drives for gravitational-wave detection and observation are very demanding.  With these demanding requirements and drives, the achievements of the gravitational-wave detection community are fruitful. Here we discuss four applications.  The first application is to use the X-pendulum suspension and high-finesse Fabry-Perot cavity to measure the QED vacuum birefringence.  The second application is to use the high-finesse Fabry-Perot cavity to determine the gravitational constant.  The third application is to use and extend the laser space interferometry to laser astrodynamical space missions for mapping solar-system gravity and for testing relativistic gravity.  The fourth application is to use the high-finesse Fabry-Perot cavity and cryogenic suspensions with ultra high Q for monitoring and controlling the macroscopic quantum state coherence of a small suspended mirror to study the fundamentals of quantum theory.  Progress and plan for these applications will be presented.