| Abstract | Gravitational wave observation has opened a new window for our universe since the first direct gravitational wave detection in 2015. Up to now, about 90 gravitational waves from compact binary coalescence have been identified and are updating our understanding ranging from particles to universe. All these discoveries have been realized through a worldwide and ground-based collaboration of laser interferometer gravitational wave detectors, including LIGO, Virgo, and KAGRA. These detectors are optimized through years to be quantum noise limited at most detection frequencies. Already in 1981, Caves proposed to use a squeezed vacuum to go beyond this limitation. After 40 years, LIGO and Virgo successfully used the squeezed vacuum to reduce quantum noise. Consequently, this brought a 50% increase in the binary neutron stars detection rate. However, due to the interferometer dynamics, the squeezed vacuum must have a proper frequency dependence to reduce quantum noise at all frequencies. Now, LIGO and Virgo are implementing this frequency dependence for the upcoming observation. Future improvement of sensitivity will come with reducing squeezing degradation sources. Other ways to go beyond the quantum noise limitation are also being explored. In this seminar, I will introduce gravitational wave detection and quantum noise in detail. Afterward, I will show how the squeezing technique can be used to reduce quantum noise. In addition, I will report on a recent understanding of the challenges of squeezing implementation. In the end, I will introduce other techniques to go beyond the quantum noise limitation and what we can do to be closer to the goal of 10dB quantum noise reduction in future gravitational wave detectors. |
