Department of Physics

Postgraduate research profiles


Jiayi Qin

Phone: (+61 8) 6488 4552

Start date

Apr 2012

Submission date

Apr 2015

Jiayi Qin

Jiayi Qin profile photo


Quantum noise reduction in a table-scaled optical cavity


This proposed research aims to investigate new techniques for quantum noise reduction in laser interferometer GW detectors. I address two experiments in this proposed research: one is to achieve broadband detection by simultaneously reducing the radiation pressure noise (at low frequencies) and the shot noise (at high frequencies); the other is to realize measurements below the SQL at low frequencies dominated by quantum radiation pressure noise via back-action evasion. Not until recently have the theoretical investigations illustrated the operating principles for both two proposed experiments. However, neither has been experimentally demonstrated in an optical cavity system. Furthermore, the configuration in our proposed setup is a table-scaled coupled Fabry Perot cavity installed with a high quality Si3N4 membrane as the mechanical oscillator. This configuration can properly modulate the single cavity in GW interferometer with test masses at both ends. Therefore, this configuration, in principle, can be used as a test system for those proposed techniques to pursue future applications in laser interferometer GW detectors.

Why my research is important

The coherent interaction of laser radiation with widely spaced mirror test masses is used to measure gravitational wave induced motions in interferometric gravitational-wave detectors. The sensitivity of first generation gravitational wave (GW) detectors such as LIGO reached the quantum shot noise limit in the high frequency part of the spectrum. In the second generation detectors now under construction, quantum radiation-pressure noise is expected to dominate at low frequencies, while shot noise will dominate at high frequencies. A region around 100Hz is limited by classical test mass thermal noise, but as better optical coatings and test masses become available, future detectors should be limited mostly by quantum noise. My project aims at veritify feasibility of proposed schemes towards quantum noise reduction in a table-scaled optical cavity.


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